AR Builds!

A bucket for anything that does not fit the above forum categories, both longgun and handgun.

Re: AR Builds!

Postby Archer » 18 Nov 2022 21:58

I've looked this up a time or two before but it's been a few years...

PSA is using midlength gas but putting the A frame at the rifle position. They claim timing is the reason for this (not enough dwell time) but other sources claim the tendency to use an oversized (or maybe over-oversized or OVERsized) gas port by some builders is the problem in producing a good build.
https://palmettostatearmory.com/psa-16- ... 49779.html

(added by edit)
PSA also makes a carbine length upper, (but they apparently offer about 3 to 1 mid length to carbine models at least for the uppers)
https://palmettostatearmory.com/psa-16- ... or-ch.html

Windham Weaponry (the old Bushmaster folks who started up after the non-compete with Remington/Cerebus expired.) is using a M4 profile but doesn't mention the gas length. They also marry their Dissipator upper with a carbine lower.
https://www.windhamweaponry.com/firearm ... ipator-m4/

I've seen mention of Del Ton using a rifle length gas system but I know the last ones Midway sold were listed as carbine gas systems.

LWRC makes a sightless mid length gas with a free float mid length handguard and a 16" barrel on a carbine lower that they call 'dissipator' by those specs I've probably built several on both carbine and rifle lowers but most of mine have at least had back up sights and some of them have had rifle length free float rails...

Then there's this: https://www.pewpewtactical.com/what-is- ... issipator/ but I've found the historical narratives to be somewhat less than reliable at times.
Archer
2000 Shots
2000 Shots
 
Posts: 3902
Joined: 04 Feb 2014
Has thanked: 134 times
Been thanked: 599 times
My Rossi Choice: M92
Location: SoCal Loco

Re: AR Builds!

Postby GasGuzzler » 19 Nov 2022 06:45

I've only built one 20". It had rifle gas if I remember.

Almost all the 16" units I have built have used mid-length gas systems.
__________________________________________________________________________________________
I've always been crazy but it's kept me from going insane.
User avatar
GasGuzzler
Moderator
Moderator
 
Posts: 2636
Joined: 02 Nov 2015
Has thanked: 293 times
Been thanked: 421 times
My Rossi Choice: M92
Location: Cooke County, TX

Re: AR Builds!

Postby Archer » 19 Nov 2022 23:26

I'm not sure I can count all the ARs I've put together since I did some of that at the shop as well as helping out with friends on top of my personal builds for my own personal use.

Carbine gas length was more or less designed around a 14.5" barrel for the M4 the military adopted.
The initial rifle designs were 20" barrels, it can be expected that rifle length gas systems are matched to that length.
Mid-length gas systems are lengthened from the carbine system to match the 16" minimum civilian length barrels.

That covers most of the standard length systems but there's more...

Some folks feel the need to make the AR even shorter and turn it into a pistol. In spite of loosing half of their velocity in most AR calibers they make a pistol length gas tube for barrels under 10".

Apparently they've made an intermediate length gas tube. I assume that's for 18" barrels since it is longer than mid length but shorter than rifle length. Every 18 inch barrel I've ever since is ported for a mid or rifle length system. I think I've built three or four 18" ARs.

I've seen + 1 and maybe +2 length gas tubes for custom builds with barrels over 20" long but they tend to be few and far between. The couple 24" builds I've put together used rifle length gas systems.
Archer
2000 Shots
2000 Shots
 
Posts: 3902
Joined: 04 Feb 2014
Has thanked: 134 times
Been thanked: 599 times
My Rossi Choice: M92
Location: SoCal Loco

Re: AR Builds!

Postby GasGuzzler » 20 Nov 2022 06:41

I built one 18". It had a mid-length gas system.
__________________________________________________________________________________________
I've always been crazy but it's kept me from going insane.
User avatar
GasGuzzler
Moderator
Moderator
 
Posts: 2636
Joined: 02 Nov 2015
Has thanked: 293 times
Been thanked: 421 times
My Rossi Choice: M92
Location: Cooke County, TX

Re: AR Builds!

Postby Arroyoshark » 20 Nov 2022 15:24

Archer wrote:I'm not sure I can count all the ARs I've put together since I did some of that at the shop as well as helping out with friends on top of my personal builds for my own personal use.

Carbine gas length was more or less designed around a 14.5" barrel for the M4 the military adopted.
The initial rifle designs were 20" barrels, it can be expected that rifle length gas systems are matched to that length.
Mid-length gas systems are lengthened from the carbine system to match the 16" minimum civilian length barrels.

That covers most of the standard length systems but there's more...

Some folks feel the need to make the AR even shorter and turn it into a pistol. In spite of loosing half of their velocity in most AR calibers they make a pistol length gas tube for barrels under 10".

Apparently they've made an intermediate length gas tube. I assume that's for 18" barrels since it is longer than mid length but shorter than rifle length. Every 18 inch barrel I've ever since is ported for a mid or rifle length system. I think I've built three or four 18" ARs.

I've seen + 1 and maybe +2 length gas tubes for custom builds with barrels over 20" long but they tend to be few and far between. The couple 24" builds I've put together used rifle length gas systems.


Archer, methinks some of your ballistic understandings are un poco loco ...
When sitting down to clean a gun, the first step is to load another gun - Elmer Keith
User avatar
Arroyoshark
250 Shots
250 Shots
 
Posts: 283
Joined: 03 Sep 2012
Has thanked: 16 times
Been thanked: 82 times
My Rossi Choice: M92
Location: fin del sendero, New Mexico

Re: AR Builds!

Postby Archer » 21 Nov 2022 00:32

Arroyoshark wrote:
Archer, methinks some of your ballistic understandings are un poco loco ...


Could be. I guess you could call the gas system part of the internal ballistics.

Rainier sells ALL the gas tube lengths I mentioned before including the 'rifle + 1', 'rifle +2' and a 'pistol -1' that I didn't know about.
https://www.rainierarms.com/gas-tube-stainless-steel/
Archer
2000 Shots
2000 Shots
 
Posts: 3902
Joined: 04 Feb 2014
Has thanked: 134 times
Been thanked: 599 times
My Rossi Choice: M92
Location: SoCal Loco

Re: AR Builds!

Postby Arroyoshark » 21 Nov 2022 15:54

RE: 'Some folks feel the need to make the AR even shorter and turn it into a pistol. In spite of loosing half of their velocity in most AR calibers they make a pistol length gas tube for barrels under 10"."
When sitting down to clean a gun, the first step is to load another gun - Elmer Keith
User avatar
Arroyoshark
250 Shots
250 Shots
 
Posts: 283
Joined: 03 Sep 2012
Has thanked: 16 times
Been thanked: 82 times
My Rossi Choice: M92
Location: fin del sendero, New Mexico

Re: AR Builds!

Postby Archer » 21 Nov 2022 22:40

Arroyoshark wrote:RE: 'Some folks feel the need to make the AR even shorter and turn it into a pistol. In spite of loosing half of their velocity in most AR calibers they make a pistol length gas tube for barrels under 10"."


Ok, maybe a small exaggeration... and possibly thinking more in terms of energy than velocity

What I was thinking of WRT .308 Win energy:
SBRs in 7.62x51 vs. 7.62x39...
https://www.youtube.com/watch?v=U2dtJsXLIOI

Still going from a 20" or 16" to a 10.5" in 5.56... 390 to 580 FPS delta depending on ammo
https://www.youtube.com/watch?v=sNZv5Z1LpqI
Archer
2000 Shots
2000 Shots
 
Posts: 3902
Joined: 04 Feb 2014
Has thanked: 134 times
Been thanked: 599 times
My Rossi Choice: M92
Location: SoCal Loco

Previous

Return to All Other Firearms

Who is online

Users browsing this forum: No registered users and 2 guests

cron