Carbine VS Rifle Buffer

[daddoz777]

Did you use a pin gauge?

Used a combination of drill bits and a digital caliper. No where near .096". A .078" bit will not fit in the hole.

 

[Cerberus Group]

Used a combination of drill bits and a digital caliper. No where near .096". A .078" bit will not fit in the hole.

If you drill it out, don't use a regular drill bit...as it'll push debris into the barrel. People think they can shoot it out, but what is still attached to the barrel is harder than copper and lead and will obviously cause accuracy issues.

I'll probably get this wrong, so hopefully a machinist type will come along and correct if needed...but use a bottom type machine bit, as they pull everything up and out of the hole...leaves everything clean.

 

[powermad]

There is a tool that deburrs the gas port on the inside leaving a nice chamfered hole.
Molon posted pics of it on M4C in a barrel thread.
I noticed from the pics that Triarc does this on the outside, most likely on the inside too.

My SR762 is a piston drive and came with a carbine buffer and spring that ran on setting 1.
I went with a fixed stock with rifle buffer and spring.
Runs on setting 2 now using 7.62 NATO and shoots much smoother.

 

[CamoDeafie]

Agreed that Aero's telling you something they were told to tell.

FWIW.... the Navy SEALS got a Recon Rifle in 16" with carbine gas and fixed A1/A2 rifle buffer. There's also the Canadian C7A2 20" rifles that have the Carbine stocks...

More specifically to your AR10 question....

SR25 Enhanced Combat Rifle, 20" 7.62x51 with carbine stocks.

 

[DirectDrive]

I just measured my gas port at about .062". According to what I'm seeing on a cursory Google search it should be about .096" for an 18" .308 rifle length barrel. WHOA am I missing something here???

That seems small.
If everything else checks out...
- gas block properly aligned over gas port
- AGB functioning properly and set to wide open
- correct buffer length (BCG will manually lock back)
Then I would start opening up the gas port a little at a time.
My Internet Guess is that you'll end up at about .085

ETA
Agree that Aero is totary fawked up with their boiler plate response.

 

[ar addict]

The biggest problem with using a drill bit to open up gas port.
Is bit catching and pulling through and hitting other side of barrel.
That issue can be stopped with brass rod or wood dowel inserted.

Reamers can be used but the process is slow and need many expensive
reamers.
Drill or taper reamers don't work well on blind holes. Tip will hit other
side of barrel before hole is proper size.

End mills produce the best finished hole, no burr inside. But they don't
like to start milling on a rounded surface. So a bit is needed for starter
hole.

I use a small mill, pin gages, and number bits.
Pin gage is used to true barrel in vice.
To get .096 the last two bits used would be #42 .0935 #41 .096.
A difference of .0025 so the burr on any side of gas port would be
.00125.
A human hair is .003 to .004 thick.

 

[Hueco]

I had the same question as I just built an AR15 rifle with carbine buffer. Lots of people run rifle length gas systems in the AR15 with a carbine length buffer without issue. I dont know about AR10s builds.
My guess is with an adjustable gas block and maybe the right buffer weigh it should be fine?

I ran an A5 with my rifle length and it was such a pleasant shooter. Loud AF with the little bastard muzzle break but a light recoil impulse. Should give it a try!

Sig 716 308 run a standard AR-15 type buffer system.

Me thinks the Aero person was reading from a script.

Yea…Aero support is useless.

 

[daddoz777]

I learned two things: (1) I should be able to use either style of buffer system and (2) my gas port is too small.

It seems that due to the lack of .308 AR standardization, manufacturers make their ports small with the unspoken undersanding they will be enlarged as needed by the builder/gunsmith.

Almost no manufacterers list their port sizes on factory barrels but many web-wide posters cite short-stroking issues, claiming ports somewhere between .062" and .075" from the factory.

I'm seeing pretty consistent information indicating the correct port size for my barrel (18" .308 with a .75" journal and rifle length gas system) to be between .089" and .096".

I think I will probably have my local smithy ream it to .089" and see where that takes me.

 

[Certaindeaf]

Stoner wasn't a stoner so you could probably pick up an original carbine and a measuring stick and Bob's your uncle.

 

[DirectDrive]

I learned two things: (1) I should be able to use either style of buffer system and (2) my gas port is too small.

It seems that due to the lack of .308 AR standardization, manufacturers make their ports small with the unspoken undersanding they will be enlarged as needed by the builder/gunsmith.

Almost no manufacterers list their port sizes on factory barrels but many web-wide posters cite short-stroking issues, claiming ports somewhere between .062" and .075" from the factory.

I'm seeing pretty consistent information indicating the correct port size for my barrel (18" .308 with a .75" journal and rifle length gas system) to be between .089" and .096".

I think I will probably have my local smithy ream it to .089" and see where that takes me.

Make sure he's not a hack that is going to use a handyman drill bit that leaves a nice burr inside your barrel.
It happens.

 

[Diamondback]

Agreed that Aero's telling you something they were told to tell.

FWIW.... the Navy SEALS got a Recon Rifle in 16" with carbine gas and fixed A1/A2 rifle buffer. There's also the Canadian C7A2 20" rifles that have the Carbine stocks...

Usually Rifle gas plus CAR tube/spring means heavy buffer--H3 for semi only or H6 for full-auto IIRC. (H6 is what's in the "official" USGI M16 telestock conversion kit; same weight as an H3 or rifle buffer but biasing springs (IIRC) inside to dampen and tune harmonics.) C7A2 runs a heavier buffer too IIRC, per the CF gunplumbers who've helped me setup my gal's iron to CF spec.

 

[DirectDrive]

H6 ? !!!

 

[Diamondback]

H6 ? !!!

Don't ask me why they called it that.

H6 Buffer Upgrade Kit from Damage Industries

Previously, if you wanted to use a collapsible carbine stock on your 20″ AR-15 with rifle length gas system you didn’t have many choices. You could do what I did for years and use an H3…

jerkingthetrigger.com

H6 Buffer.

I've never seen the correct weight for the H6 CAR buffer posted anywhere, so for reference here is the correct weight: 5.15 oz, the same as a rifle buffer.

www.m4carbine.net

 

[daddoz777]

I just measured my gas port at about .062". According to what I'm seeing on a cursory Google search it should be about .096" for an 18" .308 rifle length barrel. WHOA am I missing something here???

I just wanted to post an update. I had the gas port reamed from .062" to .098" and like magic it runs like a top. Problem solved! Now I just need to upgrade to that Geissele trigger so I can hit something....

 

[Koda]

Carbine vs. rifle buffer assembly. Everybody says they know what they're talking about but I believe few people really do. The question is whether the buffer assembly type has a correlation to the gas length, specifically on an AR10/.308.

So it sounds like the buffer assembly type doesnt have anything to do with the rifles gas length, even in 308/AR10 builds?

 

[DirectDrive]

So it sounds like the buffer assembly type doesnt have anything to do with the rifles gas length, even in 308/AR10 builds?

It's more about the "balance" of several elements.
Gas port size
Dwell time (barrel length forward of gas port)
Buffer weight
Recoil spring power
Ammo (pressure)

 

[Koda]

It's more about the "balance" of several elements.
Gas port size
Dwell time (barrel length forward of gas port)
Buffer weight
Recoil spring power
Ammo (pressure)

so then no...

That makes sense, and that it would apply to both platforms regardless of caliber.

 

[CamoDeafie]

It's more about the "balance" of several elements.
Gas port size
Dwell time (barrel length forward of gas port)
Buffer weight
Recoil spring power
Ammo (pressure)

FWIW, it seems to be confirmed that gas port size is more important than buffer system setups, and more important than gas length system although these two are very much linked to each other.

 

[Certaindeaf]

As Brandon would say, that is a bunch of malarkey, it all boils down to the size of the gas port. Something to keep in mind about adjustable gas blocks, they will only decrease your available gas they are incapable of increasing it.

Yo obviously are unfamiliar with the concept of 11.




Lool

 

[daddoz777]

As Brandon would say, that is a bunch of malarkey, it all boils down to the size of the gas port. Something to keep in mind about adjustable gas blocks, they will only decrease your available gas they are incapable of increasing it.

Yeah, totally. I started out at 3 turns from fully closed and it would eject but not lock back. Same with 4. At 5 turns it was ejecting, locking back and throwing the brass at about 4:00. Perfect. As near as I can tell, 5 1/2 turns on my AGB is fully open, so I don't really need one.