G20, factory length, 200gr at 1200FPS, Lowest Pressure [Archive] - Glock Talk

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7.62FMJ
12-09-2009, 00:26
Looking to achieve 1200FPS with a 200gr from a factory length Glock 20 barrel and with the lowest pressure. I know you can push beyond this but am looking to keep to this as a consistency. I am running a 24lb spring w/LWD barrel. Would like to hear about your favorite loads to achieve this, easiest metering for consistency, and your results.


Thanks,

7.62FMJ

Waffentomas
12-09-2009, 10:19
I use 8.5gr of Longshot over a CCI 350 primer to get +/- 200@1200, that wonderful 10mm formula. I don't know if it's the lowest pressure load for this or not. 800x is pretty forgiving in the pressure dept, but I have not worked up a load for this because is meters poorly. Though Longshot is a flake shotgun powder, it is "slick", and meters well.

Someone will come along and give you a #9 load, I'd imagine. I've always had pressure issues with #9, I don't know why, so I don't push it. But lots of guys, who have reloaded a long time and know what they are talking about, use it for just this load.

Tom

7.62FMJ
12-09-2009, 13:47
I got a friend locally who loads and I have the Glock set up for punishment. Just looking for a tried and true pet load that someone else has ventured. We plan on working it up. My G20 has an LWD barrel with a 22lb spring, now going to 24lb with this venture. We just want to try some different full house spec loads that maybe others have tried.

The AA#9 is what we thought of using but like you say, it is a high pressure game there. Just looking for something that would meter well in combination with building a viable round close to a 200gr at 1200FPS with a 5" barrel.

Taterhead
12-09-2009, 16:00
I have a load that averages 1205 fps (shot @ 15' from the chrony and not corrected to the muzzle) for the DT 200gr WFNGC Hardcast. I shoot that in a Gen 3 G20 with a 22# spring. This round is probably at max pressure +/- so work up cautiously. I see case expansion and primer conditions consistent with those of other max or near max loads.

Here is the data:

Case: New Starline
Primer: CCI 350
Powder: 13.8 gr A9
Projectile: Double Tap 200gr WFNGC Hardcast
COAL: 1.26"
medium-firm crimp

The same projectile with 800X only yielded about 1050 fps before excess pressure signs began to emerge. I believe that was with 8.0 gr of 800X.

A quick note of caution. There has been discussion about the safety of shooting hardcast loads from a stock Glock barrel. I have had good results, but I do not shoot many at a time and I keep my barrel clean. The Canyon Man posted recently (and many of you may have read his post) that he believes that lead buildup contributed to the G20 Ka-boom that he experienced last year. He stated that he had shot quite a few hardcast loads between cleanings. One factory Silvertip and... I'm sure you've seen the pictures. The bottom line, you might want to keep your cleaning kit handy if you choose to shoot these projectiles.

MSgt Dotson
12-14-2009, 09:16
Loads that are safe with a GLock barrel will likely be too hot in a tighter LWD barrel...(As the GLock barrel has an extra thousandth of an inch of slop in all directions, some pressure is bled off simply expanding the case to fill the factory barrel's chamber; this situation does not occur with an LWD barrel)

7.62FMJ
12-14-2009, 10:09
Loads that are safe with a GLock barrel will likely be too hot in a tighter LWD barrel...(As the GLock barrel has an extra thousandth of an inch of slop in all directions, some pressure is bled off simply expanding the case to fill the factory barrel's chamber; this situation does not occur with an LWD barrel)

I'd say that's a bit of a stretch and probably the opposite is true. If anything the fully supported chamber on the LWD barrel allows much higher pressures than can be used on a stock Glock barrel. The LWD is also not so tight as to not allow any expansion, it does allow some- just not the slop found in the Glock stock barrel. We tested rounds side by side and the LWD barrel could definitely handle far hotter loads than the stock barrel.

alwaysshootin
12-14-2009, 11:22
I decided to go with Longshot, and have been pleased from the start that I did. My books recommend 8.2 as the max load, and although have not choreographed factory length barrel, with the 6" LW, I am achieving 1250 FPS. I would imagine the 1200 fps threshold is met with the standard length aftermarket LW barrel. One of the reasons I decided to go with Longshot, is velocity comparisons between powders, Longshot gave lower chamber pressures then the other powder varieties. It also meters quite nicely.

also,

I'd say that's a bit of a stretch and probably the opposite is true. If anything the fully supported chamber on the LWD barrel allows much higher pressures than can be used on a stock Glock barrel. The LWD is also not so tight as to not allow any expansion, it does allow some- just not the slop found in the Glock stock barrel. We tested rounds side by side and the LWD barrel could definitely handle far hotter loads than the stock barrel.

I agree wholeheartedly!

SDGlock23
12-14-2009, 12:04
I haven't tried 200gr and Longshot yet, but I have tried to get around 1200 fps using 800x and the stock G20 barrel. I didn't get the velocity I was wanting and the brass was beginning to bulge pretty badly. I've not tried AA #9 yet either.

Let me add, 9grs on 800x averaged 1182 from the G20, but as I said above, brass was a bit bulgy for my liking.

7.62FMJ
12-14-2009, 13:16
I haven't tried 200gr and Longshot yet, but I have tried to get around 1200 fps using 800x and the stock G20 barrel. I didn't get the velocity I was wanting and the brass was beginning to bulge pretty badly. I've not tried AA #9 yet either.

Let me add, 9grs on 800x averaged 1182 from the G20, but as I said above, brass was a bit bulgy for my liking.


That is why you have to use an aftermarket barrel. The stock Glock barrels are poorly made for full spec 10mm, .357 SIG, or .40 S&W. Hence their reputation for KaBoom!!! I was running a LWD barrel with a 24lb spring and was able to step up at least another 10% on the power band to full spec 10mm loads before showing signs of pressure found with the stock barrel.

I tried one relatively mild load with my stock barrel and was showing signs of pressure.

Maxed to the 9.5gr vv 3N38 with a stock barrel and had some smileys stepped up into 10gr of vv 3N38 with the aftermarket tuned LWD set up and feel it could handle another grain. Was getting around 1185FPS average out of a stock barrel pushing the 200 grainers, many over 1200FPS.

SDGlock23
12-14-2009, 15:15
Good deal, I do have a LWD barrel for the G20, but I like to see what the stock barrel can do. I'll have to say, the newer .40's have pretty good chamber support.

MSgt Dotson
12-15-2009, 09:38
I'd say that's a bit of a stretch and probably the opposite is true. If anything the fully supported chamber on the LWD barrel allows much higher pressures than can be used on a stock Glock barrel. The LWD is also not so tight as to not allow any expansion, it does allow some- just not the slop found in the Glock stock barrel. We tested rounds side by side and the LWD barrel could definitely handle far hotter loads than the stock barrel.

I'm not discussing the factory bbl's 6 oclock support, or the ability of either bbl to contain normal Ten mm 35k psi pressures...

There have been a few posters using max loads with Longshot or 800x (loads safe in GLock bbl) that then experienced blown/ruptured primers with the LWD bbl...

The pressure will be higher in a tighter LWD bbl, with no pressure being 'wasted' expanding the brass to fit the factory bbl's generous dimensions.

For those of you already at max charges, feel free of course to use the LWD bbl without any charge reduction if you wish..

Kegs
12-15-2009, 10:35
Loads that are safe with a GLock barrel will likely be too hot in a tighter LWD barrel...(As the GLock barrel has an extra thousandth of an inch of slop in all directions, some pressure is bled off simply expanding the case to fill the factory barrel's chamber; this situation does not occur with an LWD barrel)

Not even close to being accurate...WAY more than 1/1000" tolerance relative to a fully supported barrel, and because the case is not as well supported on the stock barrel, the brass does not last as long (you are correct about the pressure expanding the case alright), because it is stretched more - and the bullets do not move out to their intended velocities.

Fully supported barrels can withstand MUCH higher loads than stock barrels - as everyone who has had both and reloads has experienced.

Kegs
12-15-2009, 10:42
I'm not discussing the factory bbl's 6 oclock support, or the ability of either bbl to contain normal Ten mm 35k psi pressures...

There have been a few posters using max loads with Longshot or 800x (loads safe in GLock bbl) that then experienced blown/ruptured primers with the LWD bbl...

The pressure will be higher in a tighter LWD bbl, with no pressure being 'wasted' expanding the brass to fit the factory bbl's generous dimensions.

For those of you already at max charges, feel free of course to use the LWD bbl without any charge reduction if you wish..

I'd suggest you have a second look at the numbers on this reloading forum as well as read the words on several reloading guides that specifically say "these loads are meant for fully supported chambers" and warn against trying the loads on "certain firearms" (e.g. this means Glocks) that don't include fully supported chambers in their barrels.
All of the information I've EVER read CONTRADICTS what you are stating (except the case expansion issue).

O.P.:

As for 1200 fps/200xtp, I've got to believe based on what I have read that the 2 best choices of powders to run are going to be #9 (which you said you don't want to use) or 800x.

Have a very close look at the published data above in the different mfgr. powders - I know you've already been there 'cause I saw your post (I'm checking this forum quite often) - keep looking. The answer is in the text.

Ignore anyone attempting you tell you that a stock barrel is better - I think we all know that's a load of horse poo.

Taterhead
12-16-2009, 19:33
Ignore anyone attempting you tell you that a stock barrel is better - I think we all know that's a load of horse poo.

I won't ague that one is "better." Because one should select the appropriate setup according to one's needs, but let's not toss out the stock barrel as a load of horse poo. Glock engineers are not dumb and they designed their barrel with certain priorities in mind. There are a number of positives about the Glock barrel that come to mind. Here is my short list.

1) My single top priority is having a weapon that I can rely on. My stock barrel has yet to have a failure to feed or extract. Not once in thousands of rounds. GT is peppered with questions about how to get load X to feed right in aftermarket barrel Y. I have no such issues. Some folks do have great results with aftermarket barrels, but I doubt that I could improve feeding reliability with the tighter clearances of a "fully-supported" chamber. One may get great feeding results with an aftermarket barrel, and one may approach the reliability of a Glock barrel - but I doubt that I could improve on my perfect results.

2) You mentioned in an earlier post that velocities are wasted in energies used to expand the case. While that may be the case, my emperical ovservations lead me to conclude that the factory barrel is effecient in terms of velocities. My chronied results for handloads exceed the velocities of those in published manuals - usually significantly. Component manufacturers typically use test firearms with traditional barrels that are marginally longer than the Glock, yet I get faster velocities. So there may be some logic to polygonal rifling. Want to shoot a bunch of lead? Well there may be a trade-off. I don't, so non-issue.

I have shot thousands of max and near-max loads without excess case bulging or other troubling symptoms. I am not a believer that if one chooses to shoot DT, BB, or handloads within published guidelines; that an aftermarket barrel is a requirement. To read some posts, you'd think that one round of Double Tap in a stock barrel and... hand grenade. It is hard to imagine that Glock would knowingly design a barrel that was unsafe to shoot factory-spec loads. It is hard to imagine that Mike McNett would make a living selling 10mm loads to G20 owners without a disclaimer if he felt them to be unsafe in your G29.

I understand that you are recently getting into loading for 10mm and have been considering an aftermarket barrel for your G29, so your results may vary. I would never advise slapping a "fully supported" barrel into your G29 and feeling that it is now safe to go nuclear. I would not exceed 37,500 psi - even with a "fully-supported" barrel.

The argument for me distills down to this. I don't feel deprived of chamber support so the flawless feeding, reasonable accuracy, and demonstrable velocities of the stock barrel have won me over.

Taterhead
12-16-2009, 19:36
Quick note to the OP: for those who still have some Speer 200 gr TMJs laying around, Accurate has some older data listing that projectile over A9 at 1200 fps. It can be found in Loadbooks. I'm pretty sure that projectile has been discontinued though. If anyone wants the recipe, I can look it up.

MSgt Dotson
12-18-2009, 20:14
All of the information I've EVER read CONTRADICTS what you are stating (except the case expansion issue).

.

No one said the stock bbl is 'better' for max loads...; it isn't.

No one said the LWD bbl does not have better case support. (It does)

What i said was, or implied, that some max loads that are safe in even a glock bbl may result in blown/ruptured PRIMERS in a tighter LWD bbl...

SInce the case can't fireform to the larger Glock chamber dimensions, obviously pressures will be higher just after ignition with a smaller match grade chamber....

Oddly enough, this may result in blown out primers. Typically, better velocity can be clocked out of the LWD bbl with a few tenths less powder.

The case or barrel containing the peak pressure are not the only issues;the primer /primer pocket must also contain these pressures.

7.62FMJ
12-21-2009, 04:45
Quick note to the OP: for those who still have some Speer 200 gr TMJs laying around, Accurate has some older data listing that projectile over A9 at 1200 fps. It can be found in Loadbooks. I'm pretty sure that projectile has been discontinued though. If anyone wants the recipe, I can look it up.


If you don't mind, please look it up and post back here. All the newer load data is basically .40 +P.

Taterhead
12-21-2009, 21:28
If you don't mind, please look it up and post back here. All the newer load data is basically .40 +P.

Here is The Accurate Powders' recipe found in Loadbooks:

Projectile: SPR 200 TMJ
Primer: CCI 300
Case: HDY
Barrel length: 5"
COAL: 1.25"
Powder: A9
Starting load: 12.2 gr @ 1056 fps
Max load: 13.5 gr @ 1200 fps; pressure: 36,300 psi

This load is not part of the current data issued by AA. I imagine it is because this projectile has been discontinued.

It seems like the "bonded" Speer bullets obturate with a bit less pressure for a given charge than others, so this might be a bit hot for some other 200 gr bullets. AA lists a max charge for the 200 gr XTP as one grain less @ 12.5 gr. (1170 fps).

7.62FMJ
12-22-2009, 05:56
No one said the stock bbl is 'better' for max loads...; it isn't.

No one said the LWD bbl does not have better case support. (It does)

What i said was, or implied, that some max loads that are safe in even a glock bbl may result in blown/ruptured PRIMERS in a tighter LWD bbl...

SInce the case can't fireform to the larger Glock chamber dimensions, obviously pressures will be higher just after ignition with a smaller match grade chamber....

Oddly enough, this may result in blown out primers. Typically, better velocity can be clocked out of the LWD bbl with a few tenths less powder.

The case or barrel containing the peak pressure are not the only issues;the primer /primer pocket must also contain these pressures.



Your entire argument for coming here, ****ting on my thread to somehow show that a stock barrel is superior to an aftermarket barrel when we are discussing load data, is pointless. Everyone on this forum will disagree with you, and these are individuals who actually load ammo and test proof loads that cannot be tolerated in a stock configuration. Sure there are some of us who load specifically for stock barrel configurations but most of us are past this. A stock Glock barrel cannot handle the same pressures as a LWD, KKM, Storm Lake or any other barrel with a fully supported chamber. Saying otherwise is reckless and outright stupid, as this is the 10mm reloading forum, where someone could actually believe you and get themselves hurt- I mean seriously hurt. Second, the dimensional differences of a stock Glock barrel vs an aftermarket barrel are minimal at best, so this crap about primers blowing out prematurely on an aftermarket barrel versus a stock Glock barrel- is again reckless. I'm not sure what your motivation is, or if you simply just talk out your ass, but some of us have actually tested high pressure loads and clearly know that pushing a stock barrel with anything close to full Norma spec is asking for problems. Please go troll someplace else.


7.62

7.62FMJ
12-22-2009, 06:01
Here is The Accurate Powders' recipe found in Loadbooks:

Projectile: SPR 200 TMJ
Primer: CCI 300
Case: HDY
Barrel length: 5"
COAL: 1.25"
Powder: A9
Starting load: 12.2 gr @ 1056 fps
Max load: 13.5 gr @ 1200 fps; pressure: 36,300 psi

This load is not part of the current data issued by AA. I imagine it is because this projectile has been discontinued.

It seems like the "bonded" Speer bullets obturate with a bit less pressure for a given charge than others, so this might be a bit hot for some other 200 gr bullets. AA lists a max charge for the 200 gr XTP as one grain less @ 12.5 gr. (1170 fps).


The 12.5gr for XTP is what I'm looking to run with the AA# 9 may push it up to around 12.8 or even 13 to see what kind of pressure specs I'm getting. I'd be happy with 1170 out of a stock length configuration but since the specs are likely for a 5" barrel, then the 12.5 might be pushed a little. We're using 200gr HAP bullets, similiar to the XTP enough that it shouldn't make a difference. Nice part, having the chronograph in the next room next to the reloading bench, load up 5 rounds, take an average, check for pressure, then load 5 more- in a matter of minutes.

Taterhead
12-23-2009, 13:25
The 12.5gr for XTP is what I'm looking to run with the AA# 9 may push it up to around 12.8 or even 13 to see what kind of pressure specs I'm getting. I'd be happy with 1170 out of a stock length configuration but since the specs are likely for a 5" barrel, then the 12.5 might be pushed a little. We're using 200gr HAP bullets, similiar to the XTP enough that it shouldn't make a difference. Nice part, having the chronograph in the next room next to the reloading bench, load up 5 rounds, take an average, check for pressure, then load 5 more- in a matter of minutes.

See below

Taterhead
12-23-2009, 13:36
The 12.5gr for XTP is what I'm looking to run with the AA# 9 may push it up to around 12.8 or even 13 to see what kind of pressure specs I'm getting. I'd be happy with 1170 out of a stock length configuration but since the specs are likely for a 5" barrel, then the 12.5 might be pushed a little. We're using 200gr HAP bullets, similiar to the XTP enough that it shouldn't make a difference. Nice part, having the chronograph in the next room next to the reloading bench, load up 5 rounds, take an average, check for pressure, then load 5 more- in a matter of minutes.

The AA data is from a 5" barrel. I tend to get chronied velocities a bit higher than published velocities (from my stock 4.6" poly).

It may be of interest to note that Hornady's max charge for a 200 gr XTP or FMJ-FP ENC is 13.2 gr @ 1150 fps (5" Delta Elite).

All this time I was thinking how nice it would be to be able to bring my loading bench to the range. I had it all wrong. I need to figure out how to bring the range to the loading bench! That must be very nice indeed! Some day, some day.

gator378
12-23-2009, 22:29
I use 8.5gr of Longshot over a CCI 350 primer to get +/- 200@1200, that wonderful 10mm formula. I don't know if it's the lowest pressure load for this or not. 800x is pretty forgiving in the pressure dept, but I have not worked up a load for this because is meters poorly. Though Longshot is a flake shotgun powder, it is "slick", and meters well.

Someone will come along and give you a #9 load, I'd imagine. I've always had pressure issues with #9, I don't know why, so I don't push it. But lots of guys, who have reloaded a long time and know what they are talking about, use it for just this load.

Tom 12.5 grains of AA#9, mag primer, col 1.26 inch, glock 20 with barstow barrel. No Smiley problems

mmomn
12-25-2009, 20:00
Not even close to being accurate...WAY more than 1/1000" tolerance relative to a fully supported barrel, and because the case is not as well supported on the stock barrel, the brass does not last as long (you are correct about the pressure expanding the case alright), because it is stretched more - and the bullets do not move out to their intended velocities.

Fully supported barrels can withstand MUCH higher loads than stock barrels - as everyone who has had both and reloads has experienced.

After reading this I fired some Doubletap 200 gr XTP's through a stock G20 barrel and some through a stock length G20 KKM barrel. The stock barrel averaged 1070 fps and the KKM averaged 1105 fps for a gain of 35 fps.

Taterhead
12-26-2009, 13:47
After reading this I fired some Doubletap 200 gr XTP's through a stock G20 barrel and some through a stock length G20 KKM barrel. The stock barrel averaged 1070 fps and the KKM averaged 1105 fps for a gain of 35 fps.

Interesting reports about velocities. Double Tap touts velocities of 1250 fps from a G20. Your measurements are more in line with those claimed by Hornady in their loaded ammo.

mmomn
12-26-2009, 22:41
Interesting reports about velocities. Double Tap touts velocities of 1250 fps from a G20. Your measurements are more in line with those claimed by Hornday.
I am going to load my own with 200 gr XTP's and longshot . I'm hoping to get 1150 fps.

FlyBoy007
01-10-2010, 13:31
AA #9 at 12.5 gr gives me 1180fps with just slight pressure signs (primer, no similes) it is under max pressure at 37000 psi. AA #9 is my first choice with heavy 10mm. G20 stock with a 20# recoil spring

It needs a tight, firm crimp for consistency.

#9 is actually safer when used with heavy and near max as it has less peak pressure then BD (another favorite of mine) or even #7.

I use #7 for loads using bullets less then 180gr.

http://www.accuratepowder.com/data/Accurate%20v322%20web%20publication.pdf


Some good points, from another thread, not mine but I agree with them 100% and I have found this to be true in my 10mm reloading experience.

"In the Complete Reloading Manual for 10mm/.40 S&W, the hottest Blue Dot load for a 180 grain bullet is 10.4 grains. This yields 1220fps at 35,800 psi".

"In the 2008 Hodgdon Reloading Manual, the hottest Longshot load for a 180 grain bullet is 9.5 grains. This yields 1287fps at 34,600 psi."

"In the Complete Reloading Manual for 10mm/.40 S&W, the hottest Accurate #9 load for a 180 grain bullet is 14.5 grains. This yields 1290 fps at 32,600 psi."

"The Blue Dot load you attached achieves 1295 fps with 11 grains. Remember that the Blue Dot load of 10.4 grains hit 35,800 psi. If the 11 grain load isn't at 37,500 SAAMI max, it is just as close as Alliant can stand. With the Accurate #9 load of 14.5 grains, you'll hit 1290 fps at 32,600 psi. This gives you plenty of space to get your load well into the 1300's fps. Indeed, I have loaded this up to 15.3 grains, which achieved a median speed of 1353 fps. Using a PressureTrace II system, the strain gauge indicated a median pressure of 37,230 psi. If a Blue Dot load were to achieve 1353fps with a 180 grain bullet, it would certainly be in the 40,000-45,000 psi range, perhaps even more."

From...

http://www.thehighroad.org/showthread.php?t=417315

MakeMineA10mm
01-14-2010, 16:56
Loads that are safe with a GLock barrel will likely be too hot in a tighter LWD barrel...(As the GLock barrel has an extra thousandth of an inch of slop in all directions, some pressure is bled off simply expanding the case to fill the factory barrel's chamber; this situation does not occur with an LWD barrel)

Guys, PLEASE go back and re-read what MSgt Dotson wrote VERY slowly. You are ALL missing his point. MSgt Dotson is 1000% CORRECT.

He is NOT saying that factory barrels are better than aftermarket barrels for high-pressure loads.

He is NOT saying (nor implying, though I could see how you could mis-interpret what he is saying) that aftermarket barrels cannot handle loads that a stock barrel can.



What he IS saying is that when you work-up a load in a firearm with a LOOSE CHAMBER, there are interior ballistic qualities that would make that load DANGEROUS in a tight chamber, namely, that the mechanical action of the brass expanding greater PLUS the dynamic action that by expanding farther it actually increases the combustion area that the powder is expanding in.

These actions LOWER PRESSURE. This results in lower velocities AND lower pressures, all other things being equal. Therefore, if you shoot these exact same loads in a tighter-chambered barrel, it very likely can and will be dangerously high-pressured.

Now, all things are usually not equal, and the 6 o'clock feedramp issue is the primary difference. What this means is that loads developed in the Glock bbl will not ever be able to reach the load development levels of a custom chamber.

Also keep in mind that the interior ballistic issues I pointed out above work inversely when you have a tight chamber. THEREFORE: with the tight barrel you should be able to load hotter than with the Glock bbl, BUT you will not have to and probably not be able to go a LOT higher (as much as you would think) than the factory barrel because of PRESSURE. HOWEVER, you will get higher VELOCITY, because the pressure is contained better and so acts on the only moveable part of the machine - the bullet's base.

So, don't be too quick to jump on MSgt Dotson. It's been my experience with him to never have been wrong in his postings here yet that I've seen. He's as knowledgeable and experienced as anyone I know, and I plan on listening to him in the future as I have in the past.

There's a LOT more to ballistics than we sometimes want to admit to ourselves. (We like to think we've got a solid handle on it.) Don't forget to always be open-minded and prepared to learn.

Snapper2
01-16-2010, 15:10
Guys, PLEASE go back and re-read what MSgt Dotson wrote VERY slowly. You are ALL missing his point. MSgt Dotson is 1000% CORRECT.

He is NOT saying that factory barrels are better than aftermarket barrels for high-pressure loads.

He is NOT saying (nor implying, though I could see how you could mis-interpret what he is saying) that aftermarket barrels cannot handle loads that a stock barrel can.



What he IS saying is that when you work-up a load in a firearm with a LOOSE CHAMBER, there are interior ballistic qualities that would make that load DANGEROUS in a tight chamber, namely, that the mechanical action of the brass expanding greater PLUS the dynamic action that by expanding farther it actually increases the combustion area that the powder is expanding in.

These actions LOWER PRESSURE. This results in lower velocities AND lower pressures, all other things being equal. Therefore, if you shoot these exact same loads in a tighter-chambered barrel, it very likely can and will be dangerously high-pressured.

Now, all things are usually not equal, and the 6 o'clock feedramp issue is the primary difference. What this means is that loads developed in the Glock bbl will not ever be able to reach the load development levels of a custom chamber.

Also keep in mind that the interior ballistic issues I pointed out above work inversely when you have a tight chamber. THEREFORE: with the tight barrel you should be able to load hotter than with the Glock bbl, BUT you will not have to and probably not be able to go a LOT higher (as much as you would think) than the factory barrel because of PRESSURE. HOWEVER, you will get higher VELOCITY, because the pressure is contained better and so acts on the only moveable part of the machine - the bullet's base.

So, don't be too quick to jump on MSgt Dotson. It's been my experience with him to never have been wrong in his postings here yet that I've seen. He's as knowledgeable and experienced as anyone I know, and I plan on listening to him in the future as I have in the past.

There's a LOT more to ballistics than we sometimes want to admit to ourselves. (We like to think we've got a solid handle on it.) Don't forget to always be open-minded and prepared to learn.

Not putting anyone's arguments down because thats how we learn. If I understand this right glocks barrel has a looser chamber but tighter rifling(more bearing space for bullet to ride on). Most aftermarket barrels have a tighter chamber and (looser) rifling or less bearing space on bullet to rifling. More pressure can escape around bullet? I've been using 8.2 gr longshot with 350 primers in a stormlake g20 barrel and a 22lb spring. This seems like a max loading and is accurate enough with 200gr XTPs, but I've been afraid to go this high in my factory barrel with the stronger recoil spring. I've read(buffalo bore's website) where a strronger spring holds the barrel in lockup a little longer and allowing pressures to build up also.As for high pressures, it might not be all about chamber/cartridge fit, but also chamber wall thickness. It seems the best way to protect against primer flow or rupture would be to use a magnum primer which is thicker or use a weaker recoil spring which allows pressure to escape earlier but also allows the slide to slam the frame harder.

MakeMineA10mm
01-17-2010, 00:45
You've brought up a LOT of questions.

First off, your take on the Glock Factory bbl being loose-chambered and tight-bored is for the most part correct. Basically, the factory barrel gets to the tight end of tolerances at the neck/throat area and then on towards the muzzle.

Most aftermarket bbls, being conventionally-rifled, have a different profile. I'd hesitate to call it "tighter" or "looser" than the factory barrel, because it's really an issue of the cross-sectional area of the bore, which would be very complicated to measure.

As far as blow-by, yes, the aftermarket's conventional rifling will allow more of this than polygonal. (Basically, the bullet does not deform as nicely in the conventional rifling and seal all the little corners at the bottom of the rifling - where the land meets the bore.) How significant this is to the pressure equation is again something I don't know. Making it even more complicated, is that bullet construction/resistance to deformation will have an effect on this. (Compare in your mind the Barnes XPB vs. a soft-lead swaged bullet.)

It is true that a heavier spring will keep the breach closed FRACTIONALLY longer than a lighter spring, but the difference is so small, it should be discounted, IMO. This is something that has been hotly debated for years. The springs MAIN function is to make sure the slide goes CLOSED, NOT to resist it opening. In the Browning lock-up system, the slide and barrel remain locked together as the slide moves back for a short distance. The spring does happen to resist this, but the weight of the slide and barrel set (recoil overcoming the inertia of those parts) applies more resistance to unlocking than the difference between a 17-lb spring and a 22-lb spring. By the time the spring begins to compress, the majority of the pressure should be gone, as the bullet will have already left the bore. By that time, the weight of the spring has only effect on the residual pressure left in the bore. (Can't discount this entirely, but the spring is not as big of a factor as some make it out to be.) Also, your last statement about a weaker spring allowing the pressure to drop earlier/faster is just in error. This is the problem with Buffalo Bore giving the impression that the spring plays a large role in this. It leads people to surmise that the spring can effect pressures in the opposite direction, which is totally untrue. If the weaker spring allows pressures to drop sooner/faster, it's because it let the breach open while the pressures were too high, and the case blew over the feedramp, providing a second exit point for the pressure!!

Chamber wall thickness is only part of the equation. Raw stainless steel that is thicker (aftermarket bbl.) can be much weaker than thinner-walled, custom-alloyed, heat-treated steel (factory barrel). But the issue is gone by then, because the web of the brass will have let-go over the feed ramp before you get to the point of testing chamber wall's ability to withstand hot loads.

Kegs
03-13-2010, 10:51
What an excellent discussion and FINALLY some intelligence on this forum.

Bravo, MMA10!

_The_Shadow
03-13-2010, 18:06
WellI have my pet loading for the Hornady 200XTP this based on a Speer publication for their 200FMJ thru a Delta Elite @ 1175 fps.

I have worked this load up in 0.1 grain increments but these are from my S&W1006 5" so use caution if you try...

Hornady 200XTP, 10.5 grains of Blue Dot, 300 CCI primers, COAL of 1.260" and the velocity runs 1180fps-1200fps from my S&W 1006 5" with wolf 22# recoil spring. The primers are starting to flatten slightly, extraction/ejecton is clean, brass is not bulged. Thes same rounds from my G-29 stock are running 1120fps-1140fps.

This is my carry ammo untill someone produces a better 10mm/40 cal 200 grain bullet! I wish Speer made the 200 grain in their Gold Dot line up.

gator378
03-14-2010, 14:20
I'd say that's a bit of a stretch and probably the opposite is true. If anything the fully supported chamber on the LWD barrel allows much higher pressures than can be used on a stock Glock barrel. The LWD is also not so tight as to not allow any expansion, it does allow some- just not the slop found in the Glock stock barrel. We tested rounds side by side and the LWD barrel could definitely handle far hotter loads than the stock barrel.

Concur. My Barstow barrel will handle a lot hotter rounds than the OEM Glock barrel due to the smileys or bulges.

hill billy
03-15-2010, 09:34
Not that I recommend this, but a 200 gr over 14 (or more) grains of #9 is a consistent 1200 fps load. I am scared to go much over 14.3 grains. I think DT's claim of 1250 is baloney. I barely got 1175 shooting those.

Mountain10mm
03-17-2010, 14:28
Not that I recommend this, but a 200 gr over 14 (or more) grains of #9 is a consistent 1200 fps load. I am scared to go much over 14.3 grains. I think DT's claim of 1250 is baloney. I barely got 1175 shooting those.

I agree. I get about 1180fps from a factory Glock barrel with a Hornady 200gr FMJ over 14.0 grains of #9. This used to be a published load, but I can not find a current listing for it...probably because Hornady no longer makes the 200gr. FMJ. The primer is just barely deformed...but ironically it looks the same as when bullet is used over 12.5 grains of #9. No case buldging, no black steaks, cracks, stuck cases, etc. I have even tried up to 14.3 grains with no addition pressure signs. My goal was 1200fps and 14.0 grains was close enough to that goal that stopped there.

hill billy
03-17-2010, 14:33
I agree. I get about 1180fps from a factory Glock barrel with a Hornady 200gr FMJ over 14.0 grains of #9. This used to be a published load, but I can not find a current listing for it...probably because Hornady no longer makes the 200gr. FMJ. The primer is just barely deformed...but ironically it looks the same as when bullet is used over 12.5 grains of #9. No case buldging, no black steaks, cracks, stuck cases, etc. I have even tried up to 14.3 grains with no addition pressure signs. My goal was 1200fps and 14.0 grains was close enough to that goal that stopped there.

I've been up to 14.5. Things look fine to me but AA's highest published load is something like 13.2 and I started to get really nervous.

Dave T
03-18-2010, 09:43
I will second the support of MSgt Dotson's posts. You people are not reading carefully enough or you don't understand internal ballistics.

Dave