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Posted: 12/22/2020 5:43:09 PM EDT
I'm sure this has been discussed or answered somewhere else before but I was not able to find anything through searching. Is there a significant drop in performance or reliability between a 13.7" or 13.9" AR pattern rifle and a 14.5" ? I know that 13.7" is the new hotness, but since the military seems to stick to 14.5" my guess is that it is more battle proven. All things being equal (gas system length, manufacturer, quality) is there a significant difference between the options?
Link Posted: 12/22/2020 6:08:11 PM EDT
16”. Pin and weld and never swap handguard or gas block?
Link Posted: 12/22/2020 6:45:24 PM EDT
I’m not sure I understand why the 13.7 would be that awesome.

A 14.5 with the right muzzle device comes to 16 and the one I have will properly mount a bayonet. There is no shortage of 14.5” barrel selection.

ETA: the 14.5 has a touch more dwell time and the gas port sizes are likely better established.
Link Posted: 12/22/2020 9:34:20 PM EDT
As mentioned already, dwell time is different.  Barrel length in front of the port and the size of the port dictates dwell time and the amount of gases to operate the gun.  It was previously argued by 11.5" is better than 10.5".  11.5" was more reliable in cycling the BCG because of the increase in dwell time.  It made it less sensitive to a variety of ammunition.  10.5" overcame that issue by having a large .093" gas port size which is huge compared to other's ~.060"-.080".  The over gassing can be felt by increase in recoil of the BCG getting hit harder, brass will be deflected forward, and more blow back gas.

But being 13.7/9", it's going to be somewhere between 10.5" to 16".  I haven't heard of many running the 13" variants, but many have ran the 12.5" with no issues.  Reliability should be fine since 11.5-12.5 runs fine.  I have ran an LMT, and 2 different Noveske 10.5" barrels with no issues running gas port sizes between .089" and .093" with PMC, WWB, federal xm193 and m855.

Since your goal is to pin an weld, I'd honestly do the 14.5/14.7".  It will give you maximum barrel length for maximum velocity while keeping it short as possible.  Plenty of muzzle devices that will get you to 16" when pinned.  Your muzzle device would have to be at least 2.1-2.3" longer than the muzzle to meet the minimum requirement going with a 13.7/9" bbl.  I'd rather have the longer barrel instead of a bigger muzzle device.  

Is really the extra length of a muzzle device really going to hinder your goals with a standard 16" barrel because you are going to at the very least have a 16" total length bbl/muzzle device?  I change configurations ever so often, so I like the ability to swap things out.  I would at the minimum get a .750" diameter muzzle device to have it welded on so I can still remove and install gas blocks and barrel nuts.
Link Posted: 12/22/2020 10:15:48 PM EDT
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Quoted:
I’m not sure I understand why the 13.7 would be that awesome.
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Quoted:
I’m not sure I understand why the 13.7 would be that awesome.


I’m guessing the OP is wanting to use a longer than normal MD and keep it right at 16”, 13.7” is your only option if you’ve got a near 3” MD.

Quoted:
16”. Pin and weld and never swap handguard or gas block?


If you’re trying to clone or want a certain look and not go the NFA route, than a p&w is it. Sure, it makes it a little more difficult to swap parts around, but p&w MD’s can be removed. If all else fails, sell it and start fresh. Or just keep it and start fresh.
Link Posted: 12/22/2020 11:37:26 PM EDT
Not much of a difference tbh. But if you want to run a surefire warcomp or a solgw nox comp or a be Meyers and still be under 16, a p&w is the way to go.

If you don’t care about having a comp/flash hider combo like those 3, then 14.5 will suit you and, like has been mentioned, it’s easier to change the gas block/muzzle device if that’s your thing.

I built my 13.7 p&w and have no intention of changing anything about it. It’s a solgw barrel with an A5 buffer/BCM intermediate tube and their nox mount, so I know it’s properly gassed and will be forgiving for a can if I ever decide to run one.

But, honestly, if I run a can, I’ll go the 11.5 sbr route.
Link Posted: 12/22/2020 11:47:26 PM EDT
Not sure what the deal is with 13.7” barrels right now. It’s not short enough to really be all that different than a 16” if you’re SBR’ing the rifle, and it’s going to end up being 16.1” anyway if you’re planning on P/W, not to mention you’ll have way less options for a muzzle device.

11.5” and 12.5” carbine systems have plenty of dwell time for proper function. I wouldn’t see why 13.7” would be an issue.
Link Posted: 12/23/2020 11:46:40 AM EDT
Quoted:
I'm sure this has been discussed or answered somewhere else before but I was not able to find anything through searching. Is there a significant drop in performance or reliability between a 13.7" or 13.9" AR pattern rifle and a 14.5" ? I know that 13.7" is the new hotness, but since the military seems to stick to 14.5" my guess is that it is more battle proven. All things being equal (gas system length, manufacturer, quality) is there a significant difference between the options?
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Short answer....the cunt hairs difference between a 14.5 and 13.7 is a non-issue.  Personally, if I'm going to get a barrel sub 16" it's going to be a 10.5, 11.5, or 12.5".  I'm not dicking with 14.5" anymore, it's 16"+ for rifles.
Link Posted: 1/19/2021 6:19:54 PM EDT
Update - Centurion Arms made my decision for me. I'd been hoping to snag a 14.5" midweight on their next barrel re-stock and had been neurotically checking their website every couple hours since Corrie said they were dropping last week. I got lucky and checked at the right time, those were out of stock but they had a 13.7" lightweight profile which was the first time I even saw them advertise those/that length. Picked up a SOLGW NOX since there's not many other options at that length.
Link Posted: 1/19/2021 7:33:34 PM EDT
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Quoted:
Update - Centurion Arms made my decision for me. I'd been hoping to snag a 14.5" midweight on their next barrel re-stock and had been neurotically checking their website every couple hours since Corrie said they were dropping last week. I got lucky and checked at the right time, those were out of stock but they had a 13.7" lightweight profile which was the first time I even saw them advertise those/that length. Picked up a SOLGW NOX since there's not many other options at that length.
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You’ll love the 13.7 and the nox. I’ve heard over and over that the nox over drives the muzzle downward but that hasn’t been my experience.

My solgw 13.7 has an A5 buffer system and the muzzle  just stays in the same spot when I fire it
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