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Posted: 8/5/2017 2:49:18 PM EST
Other than length what's the difference? Is one considered more reliable?
Seems most run a rail over gas block, but I want to do a stock A2.
Link Posted: 8/5/2017 3:10:55 PM EST
[Last Edit: 8/5/2017 3:13:56 PM EST by LV1976]
Originally Posted By bigkracka:
Other than length what's the difference? Is one considered more reliable?
Seems most run a rail over gas block, but I want to do a stock A2.
View Quote


The shorter the barrel/gas system length, the shorter the dwell time. Shorter dwell time can cause extraction problems if the rifle is running too fast. This can be controlled with an adjustable gas block, but since you want to have an A2 look, you'll have to use a heavier buffer to slow it down.

If you're looking for something a little more classic looking,

Del-Ton 11.5 kit

This kit comes with an H1 buffer, but you might have to play around with buffer weights to get it right.
Link Posted: 8/5/2017 5:45:22 PM EST
I have a 10.5" from LMT and it has been nothing but reliable for a few thousand rounds. Some of which has been several hundred round multi day courses with no cleaning and just daily lubing. 

It also has been reliable with all ammo too. From Tula and Wolf to good NATO spec stuff. 
Link Posted: 8/5/2017 6:23:07 PM EST
A bit of velocity. A user did a great comparison over on the ar15 ammo sub-board recently. 12.5" in many loads chrono'd much more like a 14.5" and 11.5" in a lot of loads had minimal difference from a 10.5"; that was my take away at least.

As far as the reliability; while it should technically be true that the longer barrels are more reliable than a 10" gun with good components I've had great luck with 10" guns and never seen or known of anyone with reliability issues with good 10" setups.
Link Posted: 8/5/2017 9:27:58 PM EST
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Originally Posted By FiveToOne:
A bit of velocity. A user did a great comparison over on the ar15 ammo sub-board recently. 12.5" in many loads chrono'd much more like a 14.5" and 11.5" in a lot of loads had minimal difference from a 10.5"; that was my take away at least.

As far as the reliability; while it should technically be true that the longer barrels are more reliable than a 10" gun with good components I've had great luck with 10" guns and never seen or known of anyone with reliability issues with good 10" setups.
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I general rule of thumb with almost every load in an AR is going to be 50fps/inch lost in shorter barrels. I've found this to be true for my 18, 16, 12.5, and 10.5.
Only the slowest powders don't seem to follow this trend for me for some reason.
Example- H380 with 45 grain Sinterfire frangible projos. Average fps loss/inch is closer to 20.
Link Posted: 8/5/2017 11:42:16 PM EST
Do you shoot with a support arms extended? 12" barrel allows 11" rail which gives you more rail-estate. Also doesn't crowd you light, laser, BUIS etc.

Longer dwell time increases reliability, even if only slightly.
Link Posted: 8/7/2017 2:22:58 PM EST
The manufacturer is probably the biggest determinant when it comes to the reliability of your rifle. I have owned all 3 of these lengths and there is little difference. I use a 10.5" LMT right now.
Link Posted: 8/7/2017 3:00:11 PM EST
I have a Colt and a Bushmaster with 10.5" barrels.  Adco did both and I assume they adjusted the gas port.  Both guns were 16" and have no mods after the chop.  Both run fine with or without the suppressor.  I don't know why some folks have so many problems getting them running.  I guess some times it is better for me to be lucky than good. 
Link Posted: 8/16/2017 11:36:59 PM EST
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Originally Posted By SilenceThis:
I general rule of thumb with almost every load in an AR is going to be 50fps/inch lost in shorter barrels. I've found this to be true for my 18, 16, 12.5, and 10.5.
Only the slowest powders don't seem to follow this trend for me for some reason.
Example- H380 with 45 grain Sinterfire frangible projos. Average fps loss/inch is closer to 20.
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Originally Posted By SilenceThis:
Originally Posted By FiveToOne:
A bit of velocity. A user did a great comparison over on the ar15 ammo sub-board recently. 12.5" in many loads chrono'd much more like a 14.5" and 11.5" in a lot of loads had minimal difference from a 10.5"; that was my take away at least.

As far as the reliability; while it should technically be true that the longer barrels are more reliable than a 10" gun with good components I've had great luck with 10" guns and never seen or known of anyone with reliability issues with good 10" setups.
I general rule of thumb with almost every load in an AR is going to be 50fps/inch lost in shorter barrels. I've found this to be true for my 18, 16, 12.5, and 10.5.
Only the slowest powders don't seem to follow this trend for me for some reason.
Example- H380 with 45 grain Sinterfire frangible projos. Average fps loss/inch is closer to 20.
Here's the thread: http://www.ar15.com/forums/t_3_16/714088_Suppressed-5-56-SBR-Velocity-Tests--41-Factory-Loads-from-10-5--11-5--12-5-and-14-5-ALL-DONE-.html

I've heard the 50fps rule forever but that didn't hold true in my testing.
Link Posted: 8/23/2017 2:29:18 AM EST
Velocity will be sort of all over the place based on the material, finish/lining, and rifling type of your barrel, plus individual variation from barrel to barrel. I have a 12.5 that shoots faster than most 14.5's
Link Posted: 8/23/2017 4:16:50 AM EST
Major differences are velocity and length. The 10.5" is the shortest and would be the easiest to move around indoors. The 12.5" gives you the most velocity, but ya know it's a tad bit longer. I love the 11.5" barrel the best, decent velocity and still very short. I think you'll be happy any way you go though, it's not that huge of a difference, ha 
Link Posted: 8/23/2017 9:58:59 AM EST
The velocity difference is insignificant (if it even exists) for the above reasons. Dwell time can be a factor, but only really matters if you get failures. There will be greater wear on your extractor parts, but it takes most shooters years to wear that stuff out anyway, so I wouldn't worry about it.

The length difference of 10.3" vs 11.5" is most noticeable when adding a sound suppressor. If you won't be using one, I recommend an 11.5" barrel.
Link Posted: 8/23/2017 12:00:05 PM EST
FWIW my Ballistic Advantage 10.5 with M16 BCG and H2 buffer has been flawless suppressed and unsuppressed using everything from Wolf to M855 NATO.
Link Posted: 8/23/2017 12:06:13 PM EST
Like any AR barrel, longer is better in every way except handling.
Link Posted: 8/24/2017 11:32:04 AM EST
[Last Edit: 8/24/2017 11:43:36 AM EST by JoshNC]
I have Colt 11.5 inch, Noveske N4 10.5 inch, and LMT 10.5 inch guns. All have been 100% reliable when fired semiauto, fullauto, suppressed, unsuppressed....so long as they are appropriately lubed.

I personally prefer 10.5s for their shorter OAL.

Side note, the Gemtech suppressed bolt carrier is OUTSTANDING in a 10.5. A friend has one in his 10.5" LMT MRP upper. It makes for a very nice shooting suppressed 10.5 with zero gas blowback to the shooter. Here are some videos (a friend's channel, not mine) of my Colt M16 lower, h3 buffer wearing a friend's LMT MRP 10.5 upper, Gemtech SBC, SiCo Saker 762 with Dead Air Key-Mo mount.

https://m.youtube.com/watch?v=d5eI8TswUFg

https://m.youtube.com/watch?v=1SdWE5y-F3w

https://m.youtube.com/watch?v=1RqJ5_qiokg

Oh and a 10.5 vs 11.5 discussion wouldn't be complete without linking this:

Paul Buffione on 10.5 vs. 11.5
Link Posted: 8/24/2017 11:37:10 AM EST
I like the idea of getting an 11.5in barrel and then pin and welding one of the new Trek II silencers to it, that way you're only paying for a single stamp. I wonder how well the can would hold up without any sort of sacrificial baffle.
Link Posted: 8/24/2017 11:44:13 AM EST
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Originally Posted By joe_sun:
I like the idea of getting an 11.5in barrel and then pin and welding one of the new Trek II silencers to it, that way you're only paying for a single stamp. I wonder how well the can would hold up without any sort of sacrificial baffle.
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Cut a barrel down. Even then you'll be overgassed. An 11.5 will commonly have a .076" port but you only need something like .055" with a can.
Link Posted: 8/24/2017 12:01:37 PM EST
[Last Edit: 8/24/2017 12:02:03 PM EST by KitBuilder]
The latest DD MK18 barrels are .070" but they will swap out if you have an older one.
I read an article about drilling & tapping a set screw into the gas block to change orifice size, but haven't done it. Adjustable GBs aren't terribly expensive though. 
Link Posted: 8/25/2017 9:05:34 AM EST
[Last Edit: 8/25/2017 9:06:24 AM EST by Phildo]
I remember reading a barrel length test on here. From 10.3 to 11.5 you gain something like 150 fps more. That's pretty huge considering the barrel is only 1.2 inches longer.
Link Posted: 8/25/2017 9:50:50 AM EST
That can happen, but it's uncommon. That's essentially the greatest difference achievable, and a difference of 150 fps is relatively insignificant.

There are just too many variables to set a number that high as the average difference. Most of the time the difference will be less. 
Link Posted: 8/25/2017 10:13:19 AM EST
I went 11.5" because it's a good compromise between reliability and handling. No ragrets. 
Link Posted: 8/27/2017 7:06:50 PM EST
[Last Edit: 8/27/2017 7:08:19 PM EST by IHTFP08]
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Originally Posted By boltcatch:
Velocity will be sort of all over the place based on the material, finish/lining, and rifling type of your barrel, plus individual variation from barrel to barrel. I have a 12.5 that shoots faster than most 14.5's
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@boltcatch.

Lol what? Please post proof of your 12.5" velocities faster than a 14.5 using the same ammo. You can't change physics.
Link Posted: 8/27/2017 9:00:36 PM EST
[Last Edit: 8/27/2017 9:02:15 PM EST by boltcatch]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By IHTFP08:


@boltcatch.

Lol what? Please post proof of your 12.5" velocities faster than a 14.5 using the same ammo. You can't change physics.
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It's well known that certain materials - usually stainless - will shoot faster than a regular chrome lined barrel; throw in polygonal rifling, then look at a short barrel that is on the faster end vs. a longer barrel that is no the slower end, and there you go. It's not an apples-to-apples comparison other than using the same ammo in the same ambient temps and conditions.

I have a chrono and a bunch of barrels and have been handloading for years - and last time I checked, I'm capable of reading an LCD display.
Link Posted: 8/28/2017 6:59:52 PM EST
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Originally Posted By boltcatch:



It's well known that certain materials - usually stainless - will shoot faster than a regular chrome lined barrel; throw in polygonal rifling, then look at a short barrel that is on the faster end vs. a longer barrel that is no the slower end, and there you go. It's not an apples-to-apples comparison other than using the same ammo in the same ambient temps and conditions.

I have a chrono and a bunch of barrels and have been handloading for years - and last time I checked, I'm capable of reading an LCD display.
View Quote
Please post at least one anecdotal piece of evidence of a 12.5" barrel with higher velocities than a 14.5" barrel using the same ammo under similar conditions. Otherwise it seems like you were implying you can achieve 14.5" velocities out of a 12.5" barrel. Also link to the magic barrel so we can all upgrade our sbrs. Thanks.
Link Posted: 8/28/2017 7:04:42 PM EST
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Originally Posted By IHTFP08:


Please post at least one anecdotal piece of evidence of a 12.5" barrel with higher velocities than a 14.5" barrel using the same ammo under similar conditions. Otherwise it seems like you were implying you can achieve 14.5" velocities out of a 12.5" barrel. Also link to the magic barrel so we can all upgrade our sbrs. Thanks.
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I know of s number of Noveske 12.5s that are faster than issue M4 barrels.
Link Posted: 8/29/2017 6:50:33 AM EST
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Originally Posted By Combat_Jack:


I know of s number of Noveske 12.5s that are faster than issue M4 barrels.
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I've seen a few references to fast noveske barrels but haven't found any direct comparisons or data. Any links to chrono data?
Link Posted: 8/29/2017 9:14:40 AM EST
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Originally Posted By IHTFP08:


I've seen a few references to fast noveske barrels but haven't found any direct comparisons or data. Any links to chrono data?
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Google what Wes Grant said about it on arf back in the day.
Link Posted: 8/29/2017 8:01:46 PM EST
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Originally Posted By JBecker_72:
No ragrets. 
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Hahahahaha. Well played. Great movie; a total sleeper.
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