AR Pistols

[GJM]

The only reference I see to that is a quote from Shockwave that someone said that in a phone conversation, which I don’t find authoritative.

The only actual reference I find is:

“It’s important to clarify here that it’s the permanent end of the pistol, so an extended brace would need to be permanently attached in an extended position to count toward the length.”

I take this to mean that the measurement is to the end of the buffer tube.

Thoughts?

I have seen reference to it several times, including in some new product announcement at SHOT. Figure it is better to be safe than sorry. You could use something like the SB M4 model and fix it shorter than 13.5.

[MolonLabe416]

I have seen reference to it several times, including in some new product announcement at SHOT. Figure it is better to be safe than sorry. You could use something like the SB M4 model and fix it shorter than 13.5.

Good point. I think I’ll order one. Thanks.

[Jay585]

Hello. Quick question. What problems do you see in a rifle that’s overgassed?


Sent from my iPhone using Tapatalk

I'm still learning about this, but it seems that an overgassed set up leads to shorter parts life. Cracked bolts apparently.

From the same thread, made by me on another forum

f not and it’s 5.56 there are guns out there that run well at 10.5”. They are however a more self destructive system than even an 11.5” barrel that is just 1” longer. The longer barrel you can stand, the better off you are in the long run durability wise. Longer barrel life less cracked bolts etc. The short sweet spot for me is the 11.5 to 12.5 range.

[GJM]

Isn’t the sweet spot 14.5 inches for 5.56 and 8-9 for .300 BLK?

[Jay585]

Isn’t the sweet spot 14.5 inches for 5.56 and 8-9 for .300 BLK?

If you're addressing me: I don't know. Just posting what some other fella said on some other forum. I'm not sure about the etiquette of linking to another forum, which is why I didn't.

[Weaponeer]

I'm still learning about this, but it seems that an overgassed set up leads to shorter parts life. Cracked bolts apparently.

From the same thread, made by me on another forum

Thanks for the reply.


Sent from my iPhone using Tapatalk

[Poconnor]

IIRC the sweet spot for short AR-15 barrels depended on the ammo used, the port size and the buffer weight. They can be tuned to work. But it’s been a long time since I went to Colt’s armorer school. I thought the 14.5 barrel length was from a marine recon test with issued 62 grain ammo. I have a friend with an SBR and he reported reduced serving life.

[Coyote41]

Isn’t the sweet spot 14.5 inches for 5.56 and 8-9 for .300 BLK?

AAC claims 9” for full powder burn of .300 blk. The funny thing about it is the lack of standardization in well...everything (i.e. there is no mil-spec port size or M193/M80 from which to say “this works”), so depending on ammunition and manufacturer, this may or may not hold true. Also, consider suppressed vs unsuppressed and subs vs supers. .300 blk becomes unpredictable very fast. BCM gives a “this works for our guns” on their website, which can be considered a starting point when using their uppers. As such, that’s who I recommend for .300 blk.

[Casual Friday]

I have a couple of 11.5" setups. This one is a 6933 upper paired with a Colt lower I purchased from Brownell's. In comparison to some PSA and other lower tier uppers, it doesn't feel like you're shooting an 11.5" gun. With Colt and BCM, they seem to always have the gas ports "right" and run well and shoot flatter than most others with just and H buffer. I've ran a bunch cheap ammo like Wolf Gold (brass case) and PMC Bronze, as well as hotter 5.56 stuff and it just flat out works.
Attachment 35020

[Shawn Dodson]

I built an 11.5" 5.56 pistol with a Law Tactical folding adapter. The Law Tactical bolt carrier extension weighs the same as the steel weights in a standard carbine buffer. Because of that I removed all the weights from the buffer and I use a Sprinco blue spring. My pistol has virtually zero muzzle jump. Brass ejects to 4 o'clock.