Cut the barrel on a 6920? [Archive] - Glock Talk

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samuse
01-25-2011, 00:21
I keep hearing that the 16" bbl is really not optimal for the carbine length gas system.

Would cutting the barrel down to 14 1/2" and pinning the flash hider be a better setup than the 16"?

Or not matter?

RMTactical
01-25-2011, 00:56
If you feel like you are up to the job...

I prefer my 16" AR's to be midlengths and the 14.5" AR's to be carbine length. I find that I just prefer the 14.5" w/ a permanently attached flash hider above anything else...

http://i166.photobucket.com/albums/u87/RMTactical/IMG_6608.jpg

samuse
01-25-2011, 02:59
Cool. Who did those?

jdodd
01-25-2011, 05:51
It just comes down to personal preference. You are not losing anything real world with a 16" carbine.

My go to shop is ADCO, they have a quick turn around and do top quality work. I just had them re-work my newest AR and I couldn't be more pleased. Ill have to post up pictures sometime today.

http://adcofirearms.com/shopservices/

I can provide other shop names...but thats who I would go to.

-J

RMTactical
01-25-2011, 10:37
Cool. Who did those?

I did one and BCM did the other. They were 14.5" barrel from the factory though. I didn't cut it down (I pinned and welded the flash hider though), although my brother and I did one like that with a superlight barrel once.

K. Foster
01-25-2011, 15:52
I keep hearing that the 16" bbl is really not optimal for the carbine length gas system.

Would cutting the barrel down to 14 1/2" and pinning the flash hider be a better setup than the 16"?

Or not matter?

Cutting your barrel just to optimize your gas system is not a good idea. If you want an optimized gas system with either a 14 or 16" barrel, you should get a mid length upper. A mid length does provide a slightly softer recoil impulse but the difference is minor. If you were buying a new upper...yes, get a middy. But I recommend leaving the Colt as is.

thisaway
01-26-2011, 08:06
I do not recommend that you cut the barrel on your Colt upper. Try buying a BCM 14.5-inch mid-gas-length upper to better match your performance requirements, and keep the Colt as a spare.

glock22357
01-26-2011, 09:09
OP; Why do you think it's necessary to cut the barrel on your 6920? What do you think you will gain in doing that?

samuse
01-26-2011, 15:34
OP; Why do you think it's necessary to cut the barrel on your 6920? What do you think you will gain in doing that?


I didn't think that it was necessary, I was just wondering if a 14.5" barrel is a better match for the carbine length gas system.

RMTactical
01-26-2011, 17:40
I didn't think that it was necessary, I was just wondering if a 14.5" barrel is a better match for the carbine length gas system.

The short answer is yes.

mvician
01-26-2011, 19:43
16" barrels with carbine gas systems has worked for years. Leave your 6920 alone.

glock22357
01-28-2011, 05:29
I didn't think that it was necessary, I was just wondering if a 14.5" barrel is a better match for the carbine length gas system.

The short answer is yes.


Let's be clear about what the OP is really asking about. This isn't a question on aesthetics or preference.

The OP has gotten some bad info from somewhere, and has been lead to believe that there is a mechanical ratio or "match" between barrel length and gas system length, to the point where he believes he needs to chop his barrel to "match" his gas system.

No, cutting the barrel on your 6920 down will not make any difference in the operation of your rifle, other than losing you some velocity. It's not like there is some mechanical "match" relationship between barrel lenth and gas system, it's just which length gas system you have on your AR. The length of the barrel is not the issue, it's just that the shorter length gas system is slightly harsher on the operation of the rifle. Unless you shoot tens of thousands of rounds a month, and want your AR to last five life times, there's no practical difference in gas system lengths.

The only way to make an actual change is to get a new barrel, mid-(or rifle) length gas system, spring, buffer, hand guards, and front sight/gas block installed. This is just shy of pointless, a bit expensive, and won't reap the OP any practical benefits. The OP would be far better off just getting an entire mid-length gas system upper, and even then the difference would hardly be noticeable.

samuse
01-28-2011, 07:43
So I think the answer is clear. Since there is no real good reason to cut my barrel, I'm gonna leave the 6920 totally unmolested and buy a BCM A4 rifle.

That's what ya'll said right?:-)

glock22357
01-28-2011, 07:59
So I think the answer is clear. Since there is no real good reason to cut my barrel, I'm gonna leave the 6920 totally unmolested and buy a BCM A4 rifle.

That's what ya'll said right?:-)

Lotsa answers.........all over the board, right?:rofl::rofl:

Yeah, just either get a new BCM upper (a good, cost effective answer) and put it on your Colt's lower, or get another rifle.

One cool thing is that getting an upper is just a question of ordering and having shipped to your home. If you get an entire rifle, ya gotta do your forms and such.

Is an M16A4 what you're looking to get?

surf
01-28-2011, 12:19
Just to clarify, the Colt CAR length gas system on a 14.5" barrel will have the same gas port size as does the 16" version. The 2 will run slightly different however since both will work well it might be a moot point of which actually works better. So in essence one may be more "optimal" than the other however since both work well no one really notices, but there is a technical difference in a few aspects. Also with non milspec rifle types, you may have variances when talking barrel lengths in relation to gas port sizing so there is no real "standard" to go by.

It's not like there is some mechanical "match" relationship between barrel lenth and gas system, it's just which length gas system you have on your AR. The length of the barrel is not the issue....This statement however is not true. Just to clarify so that someone does not think that they can cut their CAR length barrel from 16.1" to 10" and be OK, well they will not be OK. SBR legal considerations in mind, the barrel length will directly affect how the weapon functions. Or more importantly the relationship of the length of the barrel after the gas port and the actual diameter of the gas port itself. So there is a "match" relationship in barrel length and gas system. Do it yourself and you had best understand gas port sizing and perhaps altering other aspects of the rifles systems. However when you purchase off the rack, it has usually been done by the manufacturer. However you may still need to alter or change some components to optimize your rifles performance or to ensure that it runs period.

So yes there is a technical difference in what may be "optimal" in your original question, however from a user standpoint, you will not notice a difference. I do however prefer a shorter barrel in a carbine, even if it is only 1.5". Of course shorter is better for most of my carbine needs and 10"-12" is my preferred barrel length on a carbine.

12131
01-28-2011, 13:59
16" barrels with carbine gas systems has worked for years. Leave your 6920 alone.
Exactly!
If you have shot your 6920, and it's fine (and I suspect it is, just like millions of 16 in. ARs out there, already), stop messing up your fine rifle, based on what you read on the internet.

RMTactical
01-28-2011, 19:10
You don't need to cut the barrel. No. However the 14.5" barrel on a carbine gas system is a better fit than the 16".

Its not a big deal. I prefer the 14.5" for other reasons.

However I wouldn't cut a 6920. Id just sell it and get a 14.5"

Alaskapopo
01-29-2011, 01:49
I keep hearing that the 16" bbl is really not optimal for the carbine length gas system.

Would cutting the barrel down to 14 1/2" and pinning the flash hider be a better setup than the 16"?

Or not matter?

I would not. I have a 14.5 inch Noveske with a perm muzzle brake and while it is a good shooter I am stuck with that muzzle device and I have wanted to switch it out. But doing so would ruin the current expensive brake and if done wrong could hurt the barrel as well. I would get a 16 inch mid length instead.
Carbine gas system is not as good. It kicks more and has a shorter service life.
Pat

glock22357
01-30-2011, 03:53
Just to clarify, the Colt CAR length gas system on a 14.5" barrel will have the same gas port size as does the 16" version. The 2 will run slightly different however since both will work well it might be a moot point of which actually works better. So in essence one may be more "optimal" than the other.....

......the barrel length will directly affect how the weapon functions. Or more importantly the relationship of the length of the barrel after the gas port and the actual diameter of the gas port itself. So there is a "match" relationship in barrel length and gas system.

So yes there is a technical difference in what may be "optimal" in your original question,

You're writting is not very clear on what point you are trying to convey in an effort to actually answer the OP's question. You are discussing 2 variables, gas port size and barrel length, when that has not been the discussion at hand. What has been discussed (up to your post) is the relationship between barrel length and gas system length (i.e. carbine vrs. mid vrs. rifle length.) Then, you further muddy the waters of what is being discussed by bring SBRs into the picture, in an apparent attempt to rationalize discussing gas port size.

O.K., we'll hang in there with ya.......but.....

You're stating as fact that there is a difference in the operation of otherwise identical 6920s, one having a 14.5" barrel and one having a 16" barrel, due to the 1.5" difference in barrel length after the gas port.

Please provide some emperical evidence to support this claim.

Captains1911
01-30-2011, 10:09
I don't see anything wrong with chopping your Colt barrel if that's what you want and you don't mind losing some of the barrel markings and resale value. I would use ADCO for this type of work.

ETA: if you do go for it, I would consider chopping the barrel to 14.7" and permanently attaching a standard A2 suppressor, rather than going 14.5" with an extended A2X. Both options will bring the overall length to 16". Just a thought.

Captains1911
01-30-2011, 10:16
OP; Why do you think it's necessary to cut the barrel on your 6920? What do you think you will gain in doing that?

Weight savings and manuverability. And for those who care about aesthetics, it gives the rifle the M4 "look"

glock22357
01-30-2011, 15:03
Weight savings and manuverability. And for those who care about aesthetics, it gives the rifle the M4 "look"


The OP already answered the question I asked him. These are not the reasons he was looking at the barrel length reduction.

surf
01-30-2011, 22:07
For the OP - In simple terms, the correct answer is YES, there IS an optimal barrel length for a particular rifle and its related gas system. Barrel length, gas port sizing and gas system length are direct mathematical correlations. Which is why the midlength system was developed to optimize the direct restrictions of the 16" civvy barrel length.

However a carbine length system will work well in both a 14.5" barrel as well as a 16" barrel. Also in a midlength gas system a 16" barrel and a 14.5" barrel works well. This does not mean that one is not more "optimal" or "efficient" than the other.

Bottom line is I would not chop a 14.5" barrel because of the efficiency of the rifles operation, however a shorter barrel for me, has numerous other advantages.

Please provide some emperical evidence to support this claim.So your saying please now?

Again you don't know, what you don't know. To think that there is no relationship to barrel length in regards to gas system length and how this direct impingement rifle system operates is pure ignorance.

After the lack of class and use of profanity in your last set of PM's to me, I neither have the inclination nor desire to answer your questions. I might suggest you do your own research on topics such as "dwell time", "gas port sizing", "unlock timing", "barrel length", "gas system length", "extractor float", "stronger extractor spring", "buffer weight differences" and how the relationship of all of these affect, or "Optimize" how the direct impingement system in the M16/M4/AR rifles function. Google is your friend. I am not.

Edit - don't waste your time by sending more rude PM's to me either.

Alaskapopo
01-30-2011, 23:23
For the OP - In simple terms, the correct answer is YES, there IS an optimal barrel length for a particular rifle and its related gas system. Barrel length, gas port sizing and gas system length are direct mathematical correlations. Which is why the midlength system was developed to optimize the direct restrictions of the 16" civvy barrel length.

However a carbine length system will work well in both a 14.5" barrel as well as a 16" barrel. Also in a midlength gas system a 16" barrel and a 14.5" barrel works well. This does not mean that one is not more "optimal" or "efficient" than the other.

Bottom line is I would not chop a 14.5" barrel because of the efficiency of the rifles operation, however a shorter barrel for me, has numerous other advantages.

So your saying please now?

Again you don't know, what you don't know. To think that there is no relationship to barrel length in regards to gas system length and how this direct impingement rifle system operates is pure ignorance.

After the lack of class and use of profanity in your last set of PM's to me, I neither have the inclination nor desire to answer your questions. I might suggest you do your own research on topics such as "dwell time", "gas port sizing", "unlock timing", "barrel length", "gas system length", "extractor float", "stronger extractor spring", "buffer weight differences" and how the relationship of all of these affect, or "Optimize" how the direct impingement system in the M16/M4/AR rifles function. Google is your friend. I am not.

Edit - don't waste your time by sending more rude PM's to me either.

Its amazing how people get so caught up in these topics as to resort to profanity and other childish behavior. Don't let it get you down Surf. But I imagine you won't lose any sleep over it.
Pat

glock22357
01-31-2011, 13:19
For the OP - In simple terms, the correct answer is YES, there IS an optimal barrel length for a particular rifle and its related gas system. Barrel length, gas port sizing and gas system length are direct mathematical correlations. Which is why the midlength system was developed to optimize the direct restrictions of the 16" civvy barrel length.

However a carbine length system will work well in both a 14.5" barrel as well as a 16" barrel. Also in a midlength gas system a 16" barrel and a 14.5" barrel works well. This does not mean that one is not more "optimal" or "efficient" than the other.

Bottom line is I would not chop a 14.5" barrel because of the efficiency of the rifles operation, however a shorter barrel for me, has numerous other advantages.

So your saying please now?

Again you don't know, what you don't know. To think that there is no relationship to barrel length in regards to gas system length and how this direct impingement rifle system operates is pure ignorance.

After the lack of class and use of profanity in your last set of PM's to me, I neither have the inclination nor desire to answer your questions. I might suggest you do your own research on topics such as "dwell time", "gas port sizing", "unlock timing", "barrel length", "gas system length", "extractor float", "stronger extractor spring", "buffer weight differences" and how the relationship of all of these affect, or "Optimize" how the direct impingement system in the M16/M4/AR rifles function. Google is your friend. I am not.

Edit - don't waste your time by sending more rude PM's to me either.

I was wrong stating that there wasn't a match between gas system and barrel length. I made those statements stupidly, without qualifying them with "as far as the OPs question is concerned." I'll be more careful in the future not to make statements without important qualifications.

There is most definitely a match between barrel lengths and gas systems, but not as far as the OP's question is concerned. A 1.5" longer barrel on a carbine length (14.5" barrel) gas system, or on a mid length (16" barrel) gas system, will not make any real difference.

The OP already has the worst type of gas systemv (aside from SBRs and AR pistols), as far as punishment on the operating system, highest gas system pressures, etc. Unless he were to switch to a mid or rifle-length gas system somewhow (new upper), there is no way to "improve" his rifle by cutting his barrel 1.5"

Were my previous statements worded poorly, to the point of being incorrect without qualifications? Yes, very.

Should the OP cut his barrel down? No.

As far as all of the personal stuff goes, you should steer well clear of using the word "class." I PM'd you to keep our dialogue private. Your decision to air dirty laundry here in this thread is the absolute opposite of class.

mstennes
02-01-2011, 16:25
I was wrong stating that there wasn't a match between gas system and barrel length. I made those statements stupidly, without qualifying them with "as far as the OPs question is concerned." I'll be more careful in the future not to make statements without important qualifications.

There is most definitely a match between barrel lengths and gas systems, but not as far as the OP's question is concerned. A 1.5" longer barrel on a carbine length (14.5" barrel) gas system, or on a mid length (16" barrel) gas system, will not make any real difference.

The OP already has the worst type of gas systemv (aside from SBRs and AR pistols), as far as punishment on the operating system, highest gas system pressures, etc. Unless he were to switch to a mid or rifle-length gas system somewhow (new upper), there is no way to "improve" his rifle by cutting his barrel 1.5"

Were my previous statements worded poorly, to the point of being incorrect without qualifications? Yes, very.

Should the OP cut his barrel down? No.

As far as all of the personal stuff goes, you should steer well clear of using the word "class." I PM'd you to keep our dialogue private. Your decision to air dirty laundry here in this thread is the absolute opposite of class.

So your saying my old 16 Bushy bought back in the 80's still shouldnt be functioning still? Granted the middy setup is superior, and not just the 16", but also the 14.5, but lets face it, most AR shooters, who own carbines, will never see problems caused by the gas system, unless their shooting 1000 upon 1000s of rounds, or shooting in full auto allot. My Bushy has close to 10,000 rounds through it will only a extrator failure, and that was from reloads. Is the carbine optimal, no, and SURF spelled it out, heck, I dont even use that old Bushy anymore, all my builds are middys on mt REECE's, and my SPR is a rifle action, which isnt supposed to work well in the cold, its shot up until I couldnt take it any more. To the OP, you sound like your not super knowlegeable on AR's, no sweat, go shoot and have fun. Dont cut your Colt, just shoot it and dont worry, I would be you will not shoot enough through it to see the problems of carbine vs middy. Allot of what you hear or read about those gas length's are from those who really dont know, and they read it on the internet or heard it so it has to be true, but like I said, dont worry go shoot, your Colt is not going to blow up on you, you have 99.9% more chance of having a failure brought on by bad mags, or ammo than a gas length action problem.

glock22357
02-01-2011, 16:48
So your saying my old 16 Bushy bought back in the 80's still shouldnt be functioning still?.....................

You'd really need to read the entire thread to understand that I'm not picking on your Bushy, or any other AR brand.

surf
02-01-2011, 16:50
As far as all of the personal stuff goes, you should steer well clear of using the word "class." I PM'd you to keep our dialogue private. Your decision to air dirty laundry here in this thread is the absolute opposite of class.Airing dirty laundry? I have no dirty laundry to air. It is your dirty laundry not mine. You PM'd me and I asked you more than once to stop waisting my time.

So let me get this straight, you want to use PM's to be a rude ******* and expect people to keep it private? I will gladly keep sensitive information private but I do not feel that your PM's qualifies for any favors. I also mentioned nothing of what you wrote, just the demeanor in which you wrote it. You should be happy with that. Or think better next time about sending people rude messages.

glock22357
02-01-2011, 16:55
Airing dirty laundry? I have no dirty laundry to air. It is your dirty laundry not mine. You PM'd me and I asked you more than once to stop waisting my time.

So let me get this straight, you want to use PM's to be a rude ******* and expect people to keep it private? I will gladly keep sensitive information private but I do not feel that your PM's qualifies for any favors. I also mentioned nothing of what you wrote, just the demeanor in which you wrote it. You should be happy with that. Or think better next time about sending people rude messages.

:rofl::rofl:

Baby don't be so mean!!

It's a beautiful evening, go out and enjoy it. Stop wasting your time continuing being upset over a little GT tift, there's more important things in life.

mstennes
02-01-2011, 17:45
You'd really need to read the entire thread to understand that I'm not picking on your Bushy, or any other AR brand.
Oh I know you were not, as I want it known my Bushy, is a total POS. It was bought as a test mule, to test loads, see how minimal of maintainace is required before jamming starts(I didnt want to ruin a good AR:whistling: and it was cheap). My point was that is had been abused, trashed still works fine with a carbine gas system. Jeeze its a mid teir 2 at best, just above DPMS imo, just think what a good teir one will do. I just think the OP is to worried about something he wont see, sorta like 1911's and MIM.

ETA, I in no way endorse or like Bushys, but why ruin a good rifle, by abusing it?

glock22357
02-01-2011, 17:54
Oh I know you were not, as I want it known my Bushy, is a total POS. It was bought as a test mule, to test loads, see how minimal of maintainace is required before jamming starts(I didnt want to ruin a good AR:whistling:). My point was that is had been abused, trashed still works fine with a carbine gas system. Jeeze its a mid teir 2 at best, just above DPMS imo, just think what a good teir one will do. I just think the OP is to worried about something he wont see, sorta like 1911's and MIM.

Some people get to shoot waaaay more than others, and a top tier rifle is a necessity. Most people, however, can get along just fine with a mid-level AR. I wonder what practical difference an average shooter would see between, say, my M&P15T, and a Colt 6940 or BCM.

As far as the OP goes, yeah, he had a bird in his ear telling him to worry over nothing. I actually called Colt because my curiosity was killing me, and asked if there would be any benefit to cutting the barrel on a 6920 down to 14.5". I was given a number to a company called Advanced Armorment (who does work on Colt rifles for LEOs and .Mil) to get the question answered, and the guy from Advanced Armorment said it would be pointless.

surf
02-01-2011, 17:56
:rofl::rofl:

Baby don't be so mean!!

It's a beautiful evening, go out and enjoy it. Stop wasting your time continuing being upset over a little GT tift, there's more important things in life.You will know if I am ever mean to you. I could have jumped on you from the start about your usual arrogant ignorance on this weapon platform but I didn't. I am not 10 years old and I will continue to remain professional in my replies. As I have told you in the past I will not be drawn into a pissing match with you, no matter how hard you try and I am done here.

Sorry to the OP for where this thread has gone. There is some very good technical info in this thread that I elude to in regards to this weapon system and if you wish to know any more about those topics feel free to let me know or start a new thread with any questions. There are a few very knowledgeable people here who can correctly explain those topics.

glock22357
02-01-2011, 17:57
.....I will not be drawn into a pissing match with you, no matter how hard you try and I am done here.

Thank you.

Alaskapopo
02-01-2011, 18:02
Thank you.

A simple apology would have ended this drama several posts back. I have not always agreed with Surf. We totally disagree on triggers. But he has always been polite and professional.
Pat

glock22357
02-01-2011, 18:19
A simple apology would have ended this drama several posts back. I have not always agreed with Surf. We totally disagree on triggers. But he has always been polite and professional.
Pat

Simply put, Surf and I have interacted differently than you and he. Simple personality differences, that's all. And keep in mind, it always takes two to tango, there are no innocent parties.

I'm sure that Surf is very far from an apology, as am I.

Let's just let this go, and move forward with the thread.

NeverMore1701
02-01-2011, 18:22
The main difference in interactions that I see is that Surf an Alaskapopo are both knowledgeable about the AR platform.

Glockdude1
02-01-2011, 18:24
I do not recommend that you cut the barrel on your Colt upper. Try buying a BCM 14.5-inch mid-gas-length upper to better match your performance requirements, and keep the Colt as a spare.

:agree:

mstennes
02-01-2011, 18:49
Some people get to shoot waaaay more than others, and a top tier rifle is a necessity. Most people, however, can get along just fine with a mid-level AR. I wonder what practical difference an average shooter would see between, say, my M&P15T, and a Colt 6940 or BCM.

As far as the OP goes, yeah, he had a bird in his ear telling him to worry over nothing. I actually called Colt because my curiosity was killing me, and asked if there would be any benefit to cutting the barrel on a 6920 down to 14.5". I was given a number to a company called Advanced Armorment (who does work on Colt rifles for LEOs and .Mil) to get the question answered, and the guy from Advanced Armorment said it would be pointless.

True, some do shoot way more, some shoot maybe a couple a hundred a year. I agree with teir one if your going to depend 100% on it, that said though, the POS Bushy has amazed me, also, like I said my AR's are BCM, a couple LMT's, but mostly home built, using teir one parts. I was trained by the goverment to rebuild these, and my homebuilts have yet to fail, even in high round courses. The OP just needs to go ut shoot the ***** out of it and enjoy it, quit worry, what "might" happen at the 10,000 plus round count. Sure some fail earlier, but allot of those failures stem back to cheap parts.