AR Expert Please

[halfmileharry]

I have very minimal gas residue where the gas tube goes in my gas blocks. Nothing else noticeable with over 1k rds in one and approx 400 in the other.
I'm running Colt .750 barrels and BCM low profile gas blocks. No leaks.
Another thought about the buffer spring. Length? Number of coils?
The rifle springs have 41 to 43 coils, and the carbine springs have 37 to 39 coils. The brand-new length of the springs is approximately 12.75″ for the rifle and 10.5″ for the carbine springs

 

[Sniper 79]

I have very minimal gas residue where the gas tube goes in my gas blocks. Nothing else noticeable with over 1k rds in one and approx 400 in the other.
I'm running Colt .750 barrels and BCM low profile gas blocks. No leaks.
Another thought about the buffer spring. Length? Number of coils?
The rifle springs have 41 to 43 coils, and the carbine springs have 37 to 39 coils. The brand-new length of the springs is approximately 12.75″ for the rifle and 10.5″ for the carbine springs

standard weight carbine buffer with carbine spring in carbine tube

 

[halfmileharry]

I'm not one to tell you to start swapping out parts but IF IT WAS MY MONEY... I'd get a new BCM gas block for about $40 and new gas tube. Once I get my gas blocks set properly I'm a fan of setting the blocks in place by dimpling the barrel.
I'm still thinking gas issue. It's minimal 'cause of the 556 running good and 223 being a tad bit light.

 

[natdscott]

You probably think I'm dense. "rifle" to me is 20 inches. Anything less and it is outside original specifications, so some adjustments are often needed.

By cutting off 2" of barrel in front of the port, you reduce the available time for gas to travel down the tube before depressurization. Moving the port BACK to a Mid gas solves this in the 18s.

So what you may have is a situation where the elevated pressure (and maybe slower powder, thus longer pressure curve) of the 5.56 is adequate to run the bolt, but the SAAMI .223 is not. Try to get some "heavy" .223 like Black Hills or Federal 77 grainers.... I bet it runs.

Brass at 5 says short stroke, and I say lack of gas is the reason, so get a lighter carrier or a lighter buffer...or just run 5.56 and heavy .223.

But still...sort out that manifold thing. Wicking Loctite is how...just don't glue the port shut.

 

[halfmileharry]

To me carbine is 16 (aka 14.5) and rifle is 20, mid length is 18.
I just glanced at that picture again and I see one hellova lot of gas residue on the barrel. Looks like it's leaking to me. I could be wrong.
Before I started talking about expensive 223 I'd micrometer the barrel and make sure the gas block is seated properly over the port with both screws being tightened evenly. IF that didn't take care of it I'd be cleaning the face of the port area of the barrel and put on a gas block if needed. That area in your pic just bothers me with all the residue.

 

[55fairlane]

You probably think I'm dense. "rifle" to me is 20 inches. Anything less and it is outside original specifications, so some adjustments are often needed.

By cutting off 2" of barrel in front of the port, you reduce the available time for gas to travel down the tube before depressurization. Moving the port BACK to a Mid gas solves this in the 18s.

So what you may have is a situation where the elevated pressure (and maybe slower powder, thus longer pressure curve) of the 5.56 is adequate to run the bolt, but the SAAMI .223 is not. Try to get some "heavy" .223 like Black Hills or Federal 77 grainers.... I bet it runs.

Brass at 5 says short stroke, and I say lack of gas is the reason, so get a lighter carrier or a lighter buffer...or just run 5.56 and heavy .223.

But still...sort out that manifold thing. Wicking Loctite is how...just don't glue the port shut.

I think Nate hit this right on the head......I will add my 2 cents.....cheap ammo...(wolf gold) , leaky gas block, short stroking because of barrel leanth and gas system port placement..... 16 inch is carbine and 20 inch is rifle, both have / need different spring and buffers, I personally am not a fan of 18 inch AR ...

 

[seedubs1]

My 18” rifle gas ARs are my favorite on a5 or rifle REs. Once turned right, they are butter.

I personally am not a fan of 18 inch AR ...

 

[Sniper 79]

I went out and picked up a few tools myself instead of barrowing again. Upon further breakdown of the gas block it looks as if half the gas tube hole was not aligned with the gas block hole. I tossed it in the trash and placed an order for new. Hurry up and wait I guess. No biggie since it is going to be below zero for awhile. Kids school has already been canceled. Will give it a clean down just because and wait for the parts. Also picked up some different ammo to try. Will see how she does. Glad I was able to narrow down the issue.

 

[Hop]

That looks like a lot of buildup on the barrel. Gas tube / block is most likely your culprit. Report back when you get a new range report please.

 

[Sniper 79]

That looks like a lot of buildup on the barrel. Gas tube / block is most likely your culprit. Report back when you get a new range report please.

Still waiting on parts. Hopefully tomorrow. Stuck home with kids. Been a long three weeks. Everything on lock with this brutal weather.

 

[Sniper 79]

Success!

Replaced gas block and tube and it runs whatever I stuck in it including hand loads and steel case junk. Happy!

It was gas tube to block fit. New Lantac ultra low block and nitro met tube solved it.

Ran about six different 223 loads. All ran good and locked bolt back.

Thanks all for the help!

 

[Fargo]

Success!

Replaced gas block and tube and it runs whatever I stuck in it including hand loads and steel case junk. Happy!

It was gas tube to block fit. New Lantac ultra low block and nitro met tube solved it.

Ran about six different 223 loads. All ran good and locked bolt back.

Thanks all for the help!

Excellent, glad to hear it!

 

[natdscott]

NICE!

 

[halfmileharry]

Success!

Replaced gas block and tube and it runs whatever I stuck in it including hand loads and steel case junk. Happy!

It was gas tube to block fit. New Lantac ultra low block and nitro met tube solved it.

Ran about six different 223 loads. All ran good and locked bolt back.

Thanks all for the help!

Happy for you. I hate a rifle that don't work just right. Glad you got this issue fixed.

 

[BrianT]

I had a problem just like this with a carbine length setup once that I tracked back to an improper flare on the end of the gas tube. I've also seen out of spec extensions cause issues (they were too short, we could get it to cycle but not lock back), and I've had a few that just didn't want to take a seat on the gas rings until they were lubed, cleaned, and fired a few times.