Large Frame AR issue

[Pusher591]

Just built a 6.5 Creedmoor on a SLR set. SLR carrier with a matched bolt/barrel combo from Craddock. 20” barrel with +1 gas system.

I was running a standard AR10 JP SCS but having issue with pierced primers and lots of recoil. I switched it out for a Spikes ST-T3 Buffer and JP enhanced extra power spring. No more pierced primers and ejection pattern is at the 2-3 o’clock. It shot the Hornady factory 143 ELDX at .5 Mo at 100 yards.

The only issue I’m having is when, if bolt is closed and I chamber a round using the charging handle it feeds half way and jams. If the bolt is open and I use bolt release same thing. Other then that I have no feeding issues when shooting and bolt locks back on last round. Any suggestion anyone? @padom

 

[aslrookie]

Bad magazine? Will it chamber a partially loaded magazine?

 

[Pusher591]

Bad magazine? Will it chamber a partially loaded magazine?

Both magazines I have are Magpul Gen 3 Pmags bought at different times and places. They cycle and feed fine firing just the initial charge or release of bolt to charge. Did it with types of ammo as well.

It feels sluggish when I charge it from an empty bolt, just not sure how to fix that

 

[padom]

Pictures of the jam?

Needed the SCS Heavy with spring pack. I run SCS heavy with the heavy spring.

 

[Pusher591]

Pictures of the jam?

Needed the SCS Heavy with spring pack. I run SCS heavy with the heavy spring.

No pics but I’ll get some maybe even a slow mo video

 

[bigjake83]

I would also check your Feed Ramps, as mentioned above pictures would help.

Do you have some friends that may have different Magazines you can test??

Also when it Jams up on you, is the round damaged to a point that you wouldn't feel safe firing it again??

If it's chambering under the normal cycle of operation, next time you go shooting randomly extract a round every now and then checking for case damage. It may be chambering and firing but your ammo could be sustaining damage from the feed ramps or Barrel extension.

 

[hlee]

Are you riding the charging handle closed?

 

[Pusher591]

Are you riding the charging handle closed?

No

 

[ToddM]

How does it feel just cycling the action with the charge handle with an empty mag and no mag? If it's still sluggish you may have something binding. Do you see any evidence inside the upper of galling/grinding, perhaps the charge handle or cam pin? If well lubed it should cycle pretty easy with the charge handle.

Sometimes getting these things to run seems like voodoo, as we see a huge range of recommendations for buffer/etc. setups. I just had a 6.5CM 24" Bartlein +2 gas setup with the standard weight JCS, heavy spring, JP LMOS carrier and HP bolt, and JP adjustable gas block built and it's been running like a champ so far. Ejection is about 3-4 o'clock and clear. Running just enough gas to get reliable last round hold open. Primers look great on factory ammo, if anything it's taking a small amount of denting during ejection.

I was thinking of trying 1 more tungsten weight on the JCS (total of 2) and going to the medium spring as I've read that recommended before (likely old Padom posts) to save the brass a bit and soften the recoil cycle a bit. However, it seems to be running so well now I'm not sure I should mess with it.

 

[bfoosh006]

How do the hand cycled cases look ? ( And bullet while we are at it )

No obvious feeding scratches ?

I am wondering if the cases are dragging on the feed lugs.

 

[Earnhardt]

Pictures of the jam?

Needed the SCS Heavy with spring pack. I run SCS heavy with the heavy spring.

Changed out to all 3 weights in Tungsten?
Or the 2 Tungsten, 1 Steel set-up?
Thanks

 

[Pusher591]

Guys I still haven’t gotten around to “fixing” it but figured out my problem.

I’m running a 7.75” buffer tube and when I swapped over from the JP SCS I didn’t leave the small rubber buffer they supply. It basically doesn’t allow my BCG to lock all the way back that’s why it was creating jam while chambering first round with bolt open.

Putting the spacer back in and do some shooting with a load pack from McCourt soon If work allows

 

[Pusher591]

Ok so I went back and checked, I did not use the longer LMT buffer tube, it’s a standard length buffer tube so no need for the spacer.

I figured out I was sent the wrong spring (Rifle instead of carbine) and it was binding. I swapped in another JP SCS (Heavy this time) and it’s smooth and cycles just fine now.

Will still move to an adjustable gas block to reduce the carbon I’m seeing on some of my brass.