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Old 11-20-2011, 19:35   #1
DanaT
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Loads and Spring Rates

I know its a little off-topic, but I am trying to get some data on different loads that you use and what you believe is the optimum spring rates for glock pistols.


Some background: I have been doing some computational modeling with the slide-springs on Glock pistols and seem to have found values that work very well to predict recoil springs needed for a certain load or to predict stovepiping with under-powered loads.

So, far the data matches well with G17, G19, G20, G21, G34 data.

I have read that many people feel the 17lb factory recoil spring is undersprung on the G22 (and possibly G23). Has anyone played with the recoil spring and determined if there one that works better for factory ammo (around 400ft-lbs energy).

If you have favorite spring / ammo combinations, it would be great if you could post the data (need spring rate, bullet weight, and velocity, what pistol).

Also, does anyone the actual mass of a G22 slide/barrel/recoil spring assembly? I am estimating the combined mass at 546 grams.

Once I get some data to make sure the model works well, I will share results.

-Dana
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Old 11-20-2011, 20:05   #2
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I can only give you anecdotal info. In the G17, I loaded 115 grainers down as low as possible. When they were too low, the stock spring wouldn't cycle. I tired a 15# IMSI spring and it helped a bit, but when I went any lower on the charge of Bullseye, the cases didn't obdurate and the pressure would drop dramatically to the point that I could see the bullet travel down range. Basically I would get BANG, BANG, pop, BANG. So with the G17, a lighter spring didn't really help me out. Also, with the IMSI 13# spring, the firing pin spring would hold the action out of battery, so I never actually fired it like that.

In the G27, I have the heaviest Wolff spring setup, 22# I think, and it will run all but the lightest loads. I only use it on the range to make empties easier to find. I like to keep things OEM for carry use.
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Old 11-20-2011, 20:07   #3
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Why don't you just make life easier and buy a 1911.


Jack
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Old 11-20-2011, 20:45   #4
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Why don't you just make life easier and buy a 1911.


Jack
Because then I would have not had the please of reading and going through the math in the following book last night and this morning:

Engineering Design Handbook Automatic Weapons

What is even worse is my wife wanted me to come to bed at 10 last night and did I stay up looking at naughty pictures? Nope. I was up until after midnight working on bolt timing calculations. Why? Because I couldn't get it to work.

The problem. Damn engineering books that aren't in metric. I was having issues with 386.4. WTF is that? Damn slugs. Now-a-days it is 9.8m/s and kg don't have gravity added into the mass.


I think what this is really telling me is that I need to get some more exicting entertainment in my life.

-Dana
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Old 11-20-2011, 21:38   #5
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http://www.custom-glock.com/springtech.html
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Old 11-21-2011, 08:05   #6
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Very Interesting.

I put some "normal" loads (i.e. 9mm NATO, 230gr 45) into the model and changed the force constant use to hold the slide closed. The numbers in those recommendations seemed to model well (full power 10mm does not model well).

When looking at the automatic weapon design book (this is public domain from US govt so no copyright infringment) it says:

"A reasonable by adsorbing 75% of the recoil energy before the buffer [spring] is reached.."

This means a good starting point if that the spring should adsorb 25% of the energy. The custom glock spring rates (in the link) are spot on formost loads at 25% of recoil energy. The glock spring all come in (with exception of 40SW and full power 10mm) at 33.5% of the recoil energy.

-Dana
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Old 11-21-2011, 10:06   #7
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I have had this link bookmarked for years... the following to me it the most invaluable.
"Effects of a Heavier spring:

Recoil is transferred to the shooter over a longer duration of time due to lower slide velocities.

Slower slides equal a longer recovery time for the shooter.

The shooter does more work, as there is more force to counteract. This often causes and increase in muzzle flip.

The chances of a limp wrist style jam are increased, as there is more force working to unlock your wrists.

The chance of the slide short stroking and causing a feed jam is increased.

Increased muzzle dip when the slide closes for a slower follow-up shot."

I run my G34 with 13# ISMI that has 2 coils cut. There is a significant difference in sight tracking with the faster slide for me. I run 135g 1000 fps reloads.
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Old 11-21-2011, 10:30   #8
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I run my G34 with 13# ISMI that has 2 coils cut. There is a significant difference in sight tracking with the faster slide for me. I run 135g 1000 fps reloads.
Is that factory ammo? If not, what load are you using?

Richard
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Old 11-21-2011, 10:34   #9
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so... a ligther spring will make the felt recoil less? on a G21 ?
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Old 11-21-2011, 11:01   #10
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Is that factory ammo? If not, what load are you using?

Richard
135g Bear Creek moly RN, 4.0g WST at 1.150 OAL just started running this load out of the G34 since getting a a KKM barrel for it. Been using the same in my Spartan 9mm 1911for a over year. I run a 124g fmj at 130pf with the stock barrel. Standardizing my loads forall my game guns for cost reasons.
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Old 11-21-2011, 12:03   #11
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so... a ligther spring will make the felt recoil less? on a G21 ?
I kind of think there is more to it.

Suppose you used a 1# spring. The slide would move very fast (to the rear) and the pulse would be sharp but very fast - the perception of lower recoil. When it comes time to close the slide, that wimpy spring can't even get a cartridge out of the magazine. Even if it did, the spring would have a hard time getting the slide to move foreward. Force, mass and acceleration; that kind of thing. Not enough energy was stored in the spring and, very probably, something banged together inside the gun.

Suppose you had a 50# spring. The slide would move rearward very slowly. The pulse would be spread out in time - perhaps the perception of more felt recoil. However, the slide might not fully retract and there would be no chance of feeding a cartridge. However, the slide would close quickly. All of the energy was stored in the spring, nothing banged together but the slide didn't move far enough.

So, in my view, the idea is to size the spring so that it totally absorbs the recoil energy that remains after the barrel unlocks. If it is too small, the slide bangs into the frame (or the coils bind, or something else absorbs the energy, but not the spring). If it is too stiff, the slide doesn't open all the way. In a perfect world, the spring would max out exactly when the slide was fully rearward. The spring will have been sized to store exactly the recoil energy remaining after the barrel unlocks.

Variations have been tried like having multiple spring rates. A light spring rate until the slide is nearly open and then a heavy spring rate to keep things from banging together.

The other side of the story: if you want the spring to absorb all of the remaining energy, the frame itself can't be allowed to move. Limp-wristing would not allow the spring to store all the energy; some of it would be lost in moving the frame.

So, we size the spring a little lighter than necessary to allow for the spring to absorb most of the energy (but the slide moves fully rearward) and allow the remainder to go into moving the frame.

These are my 'broad brush' thoughts on how springs should work. I have no expectation that they are correct.

Richard
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Old 11-21-2011, 14:14   #12
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I like a #13 spring in my 34 with match loads - 124gr at ~125PF. That setup feels balanced to me. Match loads run fine with an #11 spring, but I can't feel much difference between that and the #13, so I use the stronger spring. Basically the thinking is to use the strongest spring that feels balanced.

I've played around a bit with 115gr weanie loads for steel at ~117-120PF. The #13 spring still runs OK with these, but the difference in ejection is evident.

A #15 spring felt pretty good to me when experimenting with loads more in the 135PF range, so that might be a consideration for factory ammo, but not a huge difference from #17.

Getting the load down under 130PF and a bit slower powder makes a lot more difference than just the spring. The weaker spring is more of a compensatory change to balance the lesser energy.
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Old 11-21-2011, 16:10   #13
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The glock is a short recoil operated weapon.

A spring is a linear force item. When the slide is closed, it exerts the least force. As the slide goes back the amount of force increases.

For the most part, when the cartridge is fired most of the energy of the cartdige is transferred to the slide/barrel/spring assembly (they move as a unit at first).

Just looking at a 9mm Nato round, it will have about ft-lbs energy. The slide/barrel/spring in a G17 will have about 6.2 ft-lbs energy. By the design rules (due to increasing weight on the spring) and using that the slide travels about 1.7 inches to rear a spring rate to limit this can be calculated.

Like wise, if you know the energy of the bullet, you can calculate how far the slide will open with a given spring.

For example, my calculation show with the G17 17lb spring, a reduced load with a 147gr bullet at 875ft/sec and a stock 17# spring would open the slide 1.46 inches. This starts getting close to OAL length of the cartridge and can have ejection problems.

It is a balance.

-Dana
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Old 11-21-2011, 17:02   #14
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I have tried every spring from 12# - 18# in my G22. I am running a 180 gn bullet at about a 140 PF. I finally settled on a 4# striker spring with a 14# recoil spring. Shoots very flat and the slide isn't sluggish
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Old 11-21-2011, 17:15   #15
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Originally Posted by Shadyscott69 View Post
I have tried every spring from 12# - 18# in my G22. I am running a 180 gn bullet at about a 140 PF. I finally settled on a 4# striker spring with a 14# recoil spring. Shoots very flat and the slide isn't sluggish
Thanks for the info.

A 140PF with a 180gr = 780ft/sec.

Putting this into my "magical" formula for the duplication of "stock function" for a glock a 14.448# spring should be used.

I like info like this because it shows the model is working well with real life observations.

On a side note, if I take like a buffalo bore (I am afraid to say double tap) heavy 10mm load (claimed 180gr @1350), with a G20 it should have a 28.9lb spring. It is well known that erratic results occur with hot 10mm with velocities because the slide is moving too fast. Of course, the CORRECT way to compensate would be to add mass to the slide and use a spring closer to stock but it much harder to add mass to a slide than change a spring.

-Dana
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Old 11-21-2011, 17:21   #16
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Originally Posted by DanaT View Post
The glock is a short recoil operated weapon.

A spring is a linear force item. When the slide is closed, it exerts the least force. As the slide goes back the amount of force increases.

For the most part, when the cartridge is fired most of the energy of the cartdige is transferred to the slide/barrel/spring assembly (they move as a unit at first).

Just looking at a 9mm Nato round, it will have about ft-lbs energy. The slide/barrel/spring in a G17 will have about 6.2 ft-lbs energy. By the design rules (due to increasing weight on the spring) and using that the slide travels about 1.7 inches to rear a spring rate to limit this can be calculated.

Like wise, if you know the energy of the bullet, you can calculate how far the slide will open with a given spring.

For example, my calculation show with the G17 17lb spring, a reduced load with a 147gr bullet at 875ft/sec and a stock 17# spring would open the slide 1.46 inches. This starts getting close to OAL length of the cartridge and can have ejection problems.

It is a balance.

-Dana
I can understand what you are trying to accomplish, but in all honesty I think it's all in vain. you can calculate the force / slide weight / travel etc. however one thing you will never be able to do is account for the Glock's polymer slide construction. They are all a little bit different and all flex slightly differently. Trial and error is really only way to fine tune your gun. Of course, YMMV.
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Old 11-21-2011, 17:23   #17
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Originally Posted by DanaT View Post
Thanks for the info.

A 140PF with a 180gr = 780ft/sec.

Putting this into my "magical" formula for the duplication of "stock function" for a glock a 14.448# spring should be used.

I like info like this because it shows the model is working well with real life observations.

On a side note, if I take like a buffalo bore (I am afraid to say double tap) heavy 10mm load (claimed 180gr @1350), with a G20 it should have a 28.9lb spring. It is well known that erratic results occur with hot 10mm with velocities because the slide is moving too fast. Of course, the CORRECT way to compensate would be to add mass to the slide and use a spring closer to stock but it much harder to add mass to a slide than change a spring.

-Dana
That's cool. Now making the gun actually run with the right spring rate is an entirely different bag of biscuits.

When I tried the 12 # spring I got a lot of muzzle rise as the slide slammed back against the frame causing my second shots to go high. The 15 and up springs were the opposite. Second shots would be low due to the slide slamming shut with too much force,
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Old 11-21-2011, 17:28   #18
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Originally Posted by Boxerglocker View Post
I can understand what you are trying to accomplish, but in all honesty I think it's all in vain. you can calculate the force / slide weight / travel etc. however one thing you will never be able to do is account for the Glock's polymer slide construction. They are all a little bit different and all flex slightly differently. Trial and error is really only way to fine tune your gun. Of course, YMMV.
I kind of agree. Before the WWW. what Dana is trying to accomplish would have been awesome. Now-a-days, you can figure out +/- 1lb what spring you should run in about 5 minutes on Benos or one of the other competition oriented forums. Still a cool experiment.
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Old 11-21-2011, 18:20   #19
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You really don't want to try and figure out why I do what I do. That will drive you insane. In fact, look at me.

What I am trying to do is mathematically model something I know (and compare it to real data), substantiate the model, and then use the model to build unknown configuration with minimal trial and error.

-Dana
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Old 11-21-2011, 18:26   #20
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You really don't want to try and figure out why I do what I do. That will drive you insane. In fact, look at me.

What I am trying to do is mathematically model something I know (and compare it to real data), substantiate the model, and then use the model to build unknown configuration with minimal trial and error.

-Dana
I don't understand why people like you do what you do. But I sure do appreciate it.
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