SBR OAL-8.5" with longer stock to get 29" or 10.5"and stand stock?

thai · Mar 25, 2016

I was wondering what is the consensus of going with an 8.5" SBR with longer buffer tube, thicker butt pad, and large stock to comply with the 29" rule , OR-
Keep the standard configure stock and stay with a 10.5" barrel.

Personally I would prefer the benefit of the 10.5". With the modification to get an 8.5" to comply, I don't see any benifit, and you have additional weight and bulk to detract from looks and is cumbersome.

erwos · Mar 25, 2016

Your instincts are correct. I own both an 11.5" AR-15 SBR (standard stock) and a pre-ban 8.25" AR-15 SBR (with NEA CCS stock). 8.25" guns are toys in general, and the only reason to have one is to minimize OAL... which you can't do anymore anyways.

Squaregrouper · Mar 25, 2016

From my research, going under 10" in 5.56 kills the velocity to the level of "why even bother". On the other hand, a 7.5" .300BO would be a fun toy.

outrider58 · Mar 25, 2016

thai said:
I was wondering what is the consensus of going with an 8.5" SBR with longer buffer tube, thicker butt pad, and large stock to comply with the 29" rule , OR-
Keep the standard configure stock and stay with a 10.5" barrel.

Personally I would prefer the benefit of the 10.5". With the modification to get an 8.5" to comply, I don't see any benifit, and you have additional weight and bulk to detract from looks and is cumbersome.

You can go shorter than 10.5" by going with a particular Vltor stock(not sure of model) and pinning and welding your muzzle device. 10.5" is considered minimal standard for 5.56 ballistic efficiency though.

erwos · Mar 25, 2016

outrider58 said:
You can go shorter than 10.5" by going with a particular Vltor stock(not sure of model) and pinning and welding your muzzle device. 10.5" is considered minimal standard for 5.56 ballistic efficiency though.

10.5" is not acceptable, IMHO, in terms of ballistic efficiency. It's simply the shortest length where you are not inviting problems with your gas system (and can run carbine length).

outrider58 · Mar 25, 2016

erwos said:
10.5" is not acceptable, IMHO, in terms of ballistic efficiency. It's simply the shortest length where you are not inviting problems with your gas system (and can run carbine length).

I did say minimal not optimal.

erwos · Mar 25, 2016

outrider58 said:
I did say minimal not optimal.

I understand, but I think it's on the edge of minimal. I've spent a lot of time lately screwing around with ballistics calculators for my 10" Sig 556, and the velocity loss starts having serious consequences for 5.56x45 trajectory even without considering lower-velocity terminal effects. If it makes you feel better, I have relatively similar feelings about my 11.5" Colt Commando clone.

IMHO, the M4 got this one right (probably by accident).

fred333 · Mar 25, 2016

erwos said:
IMHO, the M4 got this one right (probably by accident).

outrider58 · Mar 25, 2016

erwos said:
I understand, but I think it's on the edge of minimal. I've spent a lot of time lately screwing around with ballistics calculators for my 10" Sig 556, and the velocity loss starts having serious consequences for 5.56x45 trajectory even without considering lower-velocity terminal effects. If it makes you feel better, I have relatively similar feelings about my 11.5" Colt Commando clone.

IMHO, the M4 got this one right (probably by accident).

I'll not argue with ya there. It becomes pretty evident by the size of the fireball when shooting them.

MacGuns · Mar 25, 2016

I recently submitted my Form 1 for a 10.5 barrel on a 5.56 platform knowing I would probably end up with something longer. I figured I may as well submit for the minimum and could easily go longer.

While doing my research I found this article that had some interesting data:
http://www.sadefensejournal.com/wp/?p=1093

This was an interesting quote (my bold emphasis):

The maximum velocity for the M855 projectile occurred in a 20-inch barrel. This is anticipated since the cartridge was designed specifically for this barrel length. Velocity drops rapidly as the barrel length decreases, especially below 10 inches where the velocity drops below 2,500 fps. M855 bullets traveling below 2,500 fps when impacting a target will not produce a lethal wound channel.

The article also mentions suppressor life problems on shorter barrels.

One of the authors has measured port pressures in the entrance chamber of one of his company’s 5.56mm suppressors with both a 14.5 inch and 10.5 inch barreled HK416, and there was a 50% increase in suppressor chamber pressure of the 10.5 inch barreled weapon as compared to the longer 14.5 inch version. This correlates well with the difference in bore pressure at the instant of bullet uncorking.

In my research I have seen several other mentions of suppressor life being diminished on shorter length barrels <= 10.5".

My current plan is 12.5, but as stated above the 14.5 is becoming more attractive and may win out as I continue to research while I wait for my stamps.

outrider58 · Mar 25, 2016

MacMoov said:
I recently submitted my Form 1 for a 10.5 barrel on a 5.56 platform knowing I would probably end up with something longer. I figured I may as well submit for the minimum and could easily go longer.

While doing my research I found this article that had some interesting data:
http://www.sadefensejournal.com/wp/?p=1093

This was an interesting quote (my bold emphasis):

The article also mentions suppressor life problems on shorter barrels.

In my research I have seen several other mentions of suppressor life being dimensioned on shorter length barrels <= 10.5".

My current plan is 12.5, but as stated above the 14.5 is becoming more attractive and may win out as I continue to research while I wait for my stamps.

Just picked up my Phantom 762 can(YHM) and they state minimum barrel length for warranty coverage is 10.5''.

erwos · Mar 25, 2016

You can get around the "terminal effect" issues through selection of other ammunition that performs more adequately at a lower velocity. The rest of it, though... there's really nothing wrong with 16" barrels, and I say this as a guy who owns a whole bunch of SBRs.

Biggfoot44 · Mar 25, 2016

I get it, sometimes you want to do somthing because it's cool, or just because you want to. I have suitable platforms, where someday I'll run a 7.5in *just because-* .

But to be even vaguely practical, under current Md oal requirements, nothing to be gaimed to go shorter than 10.5in.

And if someone chimes in with the various reasons why 11.5 or 12.5 have advantages, I wouldn't argue with them.

If you think 14.5in is the bee's knees, good for you, but at that point may as well weld a flashhider (oppsn muzzle break) and avoid the paperwork, expense, and transport restrictions.

outrider58 · Mar 25, 2016

Biggfoot44 said:
I get it, sometimes you want to do somthing because it's cool, or just because you want to. I have suitable platforms, where someday I'll run a 7.5in *just because-* .

But to be even vaguely practical, under current Md oal requirements, nothing to be gaimed to go shorter than 10.5in.

And if someone chimes in with the various reasons why 11.5 or 12.5 have advantages, I wouldn't argue with them.

If you think 14.5in is the bee's knees, good for you, but at that point may as well weld a flashhider (oppsn muzzle break) and avoid the paperwork, expense, and transport restrictions.

Done this too.

quattroginger · Mar 25, 2016

I'm doing 10.5 now. If I don't like it.......ill just build another for the collection

Sent from my iPhone using Tapatalk

Pinecone · Mar 26, 2016

Already beat to death:

http://www.mdshooters.com/showthread.php?t=185187

outrider58 · Mar 26, 2016

Pinecone said:
Already beat to death:

http://www.mdshooters.com/showthread.php?t=185187

^^^That's funny. Read third post down...^^^

Hawkeye · Mar 26, 2016

I am presently in the middle of building an 8.5" .300BLK. For .300BLK it does make sense, because that's about the length that the round was originally designed for. It's tricky to get 29", but it can be done.

I pulled my muzzle device yesterday and took a ton of measurements, but I didn't finish up. Unfortunately my notes are sitting on my PC at home, and I am traveling to visit family for Easter. I'll post specifics when I get home on Monday.

outrider58 said:
You can go shorter than 10.5" by going with a particular Vltor stock(not sure of model) and pinning and welding your muzzle device. 10.5" is considered minimal standard for 5.56 ballistic efficiency though.

Yup. If you use a VLTOR eMod stock AND an A5 buffer tube, you can get there with a pinned muzzle device. Otherwise you'll be just a tiny bit short.

An ACS-L with the extended .70" buttpad should do it without a pinned device.

Pinecone said:
Already beat to death:

http://www.mdshooters.com/showthread.php?t=185187

Yeah.... I'll update that thread when I get home and look at my specific measurements.

Pinecone · Mar 27, 2016

outrider58 said:
^^^That's funny. Read third post down...^^^

First one I ran across.

Hawkeye · Mar 29, 2016

Pinecone said:
Already beat to death:

http://www.mdshooters.com/showthread.php?t=185187

That thread is updated with some precise measurements.

SBR OAL-8.5" with longer stock to get 29" or 10.5"and stand stock?

The #1 community for Gun Owners of the Northeast

Member Benefits:

Active Member

The Hebrew Hammer

Kragaphile

Eats Bacon Raw

The Hebrew Hammer

Eats Bacon Raw

The Hebrew Hammer

Banned

Eats Bacon Raw

Ultimate Member

Eats Bacon Raw

The Hebrew Hammer

Ultimate Member

Eats Bacon Raw

Active Member

Ultimate Member

Eats Bacon Raw

The Leatherstocking

Ultimate Member

The Leatherstocking

Users who are viewing this thread

Log in

Forum statistics