6.5 Creedmoor build not running until I cut buffer spring?

[giannid]

So I recently just finished up a 6.5 creedmoor build using all aero components except a 16 inch faxon barrel and superlative adjustable gas block. When I put the aero enhanced 308 carbine buffer tube kit, I noticed the spring was very tight. I dimpled the barrel with a jig to make sure I had proper alignment of the gas block.

Today I went out and shot some test rounds to check function of the rifle prior to load development. With the gas block wide open, the gun would barely eject a round and would not load a second round or stovepipe one in the chamber. Shot a few rounds with a can and it ran fine. After checking and double checking everything, I figured I'd try cutting the spring to see if I could get it to run. Started cutting one coil at a time until I got it to function without the can and end up taking 4 turns out of the spring to get it to run dependable.

Not a big fan of having a cut spring in the gun. I did get it to run reliably but I'm wondering if I should be looking at something else. I haven't built many AR10's and most of my experience building is with the standard AR15's. Comparing the ar10 spring to an ar15 spring, I notice they are very different. I installed a regular ar15 spring in the gun and it seems to close up the bolt fine but I did not try running rounds through it.

Where should I go with this? I'm wondering if I should buy one of the fancy spring kits or just run the cut spring, or something else. One though I had was the gas port isn't big enough but rather not mess with opening it up. This is going to be primarily a thermal hunting rig and I want this gun to run like a sewing machine.

 

[KimberGuy]

Get an A5 tube, regular H2 or H3 buffer, and then choose the appropriate recoil spring. I like the Tubbs flatwire spring or SR25 carbine spring.

I am not a fan of standard carbine tubes and short buffers.

 

[Jigstick]

Why a carbine length tube and spring on a large frame gasser?

 

[giannid]

Why a carbine length tube and spring on a large frame gasser?

M5 .308 Enhanced Carbine Buffer Kit

Shop M5 .308 Enhanced Carbine Buffer Kit and more at AeroPrecisionUSA.com!

www.aeroprecisionusa.com

This is the kit I purchased for this gun. Figured I'd use it as it's all aero components and figured it would work well with it.

You guys think this could be causing my problem? I figured it was the way to go as I wanted an adjustable stock.

 

[Jigstick]

Could be a multitude of things. You running handloads or factory ammo? Is the ammo underpowered? Sounds like you got enough gas with your can on. It can be a bitch to tune the large frame guns. Ammo, gas port placement and size, BCG weight, buffer length and strength all have to work together.

 

[hlee]

All of the above, and gas guns sometimes just need to wear in for a bit, before you really get a good running gun.

 

[giannid]

I'm running hand loads which are 42 grains of H4350 under a 120 grain sierra bullet. This is a moderate load and on the higher end of the reloading data.

I haven't played around with the large frames AR's before, but both my prior builds ran fine which were 6mm creedmoor builds. Both those used a rifle buffer tube. I'm relatively certain the gun will run as it's running suppressed and with the spring cut. Didn't want to cut the spring but figured it was a cheap fix to see if I could get it to run. I'm just not a fan of modifying stuff and rather it run right without a cut spring.

 

[hlee]

Maynr the gun just needs to wear in all of the mating surfaces.

Maybe the gas port is small.

Maybe it is partially obstructed. Do you have a bore scope? The best use for one that I have found is checking the alignment of a gas block.

If it is running and not damaging anything- like the receiver extension tower, run it for a while. See how it goes.

 

[richiecotite]

a5/armalite buffer tube or a rifle length buffer would likely help. Dont like the idea of cutting coils on the standard buffer spring, but if it works it works.

 

[Kocher]

Hello. I would verify that the spring is correct (rifle sping in a carbine tube ect. Also, the Tubs flat wire spring in my testing would work in the Carbine tube, not the rifle length.
Also+ double check your loads , but the spring does sound like it is a bit too heavy.
I had a AR15 build chambered in a 17Remington. Had to cut coils from spring to get it to function. was using IMR 4198

Switched the powder to Tac, H223, and Varget and ran reg spring, buffer ect.w/o issue The powder was not producting enough gas to operate properly.​

This may or may not help.. It could be many things.... but start simple 1st... hope you figure it out.