I have an AR10 built with a high end barrel I won't name right now, but it has had failure to feed, cycle etc. issues since it was installed. Headspace is ok. After trying everything in my tool box, I sent it to a gunsmith. He says that the "factory" ammo I sent him to test was too long for a gas gun. I checked and its has the standard COAL of 2.180". In my mind that's a problem with the chamber. Please correct me if you have other thoughts. PS. I really don't want to handload shorter COALS for an AR.
6.5CM AR10 Issue
- Thread starter Larry DESANTIS
- Start date
TxBowHunter409
Gold $$ Contributor
All good questions
I assume by 2.180 OAL you mean 2.810 OAL? Generally a AR10 in 6.5 CM would have a standard SAAMI chamber, which can accommodate 140 gr class bullets at an OAL of 2.810.
The chamber, freebore, and resultant headspace may be a completely separate issue from whether or not a semi auto runs reliably.
The chamber, freebore, and resultant headspace may be a completely separate issue from whether or not a semi auto runs reliably.
Coyotefurharvester
Silver $$ Contributor
Does it matter which side of the mag the round is coming off from? Asking because you stated headspace was ok, and using factory ammo.
A friend gave me a bunch of 308s he had and wanted to shoot out of his Winchester 88. He and I both had no idea why they would not feed. I asked if he had any that would feed and he handed me a box of Winchester factory loads. After measuring I found that Winchester loaded anything that would be a good load to shoot in a lever action shorter than was standard. When I bumped the handloads back to the size of the factory ammo they chambered just fine. While you may want to not load shorter COAL, you may have to,to get it to function.
Steve Donlon
Gold $$ Contributor
Also what bullet? Could be your set up with the springs and timing. Could be the shape of the bullet, if it's to pointed, it could be to long to feed right. Need to try different ammo and bullet weights and profiles.
Built several. 6.5 CM is not plug and play as in an Ar10 platform. PP 308 is (mostly). You need a high pressure bolt ( the one with the small firing pin hole ) for magnum small rifle primers. A standard spring and buffer weight will not work successfully a lot of the time. And yes, an adjustable gas block. Ask me how I know.
Coyotefurharvester
Silver $$ Contributor
Tubbs flat wire spring, on the heavy side buffer, adjustable gb.
10XSHOOTER
Gold $$ Contributor
What is the failure to feed? Could be a magazine problem.
Can you single feed and have the gun fire?
Does it eject?
Are you using small rifle primers or large as you should be?
No adj gas blocks. you need all the gas to get that heavier bolt to move!
Can you single feed and have the gun fire?
Does it eject?
Are you using small rifle primers or large as you should be?
No adj gas blocks. you need all the gas to get that heavier bolt to move!
wrong wrong wrong
You got that right. 65 CM are not plug and play,
I built a 6.5 Creedmoor on an Aero Precision upper with a Proof barrel, and I also had all kinds of issues with it ejecting and not feeding right. It really upset me because I had built a 308 the year before and it operated flawlessly and shot solid .5 groups. I contacted Proof and they had me send my upper to them. I believed what they actually did was extended the opening on the ejection port or something like that. When I got it back it ran like a sewing machine and was a solid .5 and under gun for 5 shot groups...
A coworker built one about 6 years ago. Had so many issues with it. It would shoot and thats about it. Feeding issues and ejection issues. He put it away a d did not look back. Damaged countless pieces of brass. I told him there is a reason when looking at factory rifles in 308, then 6.5cm the price jumps up. He is that guy that thinks its just easy like a 223, can buy ebay parts and it works. I just scratch my head.
Ditto to Raptor. All AERO on more than one 308. Disaster struck with the 6.5 CM.
I am in the process of putting together a Aero 6.5. There is no way it could go worse that the Seekins 6 arc I put together. (Knock on wood). Eventually it boiled down to two main problems. 1) the machining on the upper where the gas key rides was too loose and the bolt had issues going into full battery. Even broke a bolt or two. 2) the gas port in the barrel had to be opened up to get reliable operation when she was dirty. After addressing those issues it is all good.
Why to people post this stuff with only vague information and expect to receive back a reasonable diagnosis.
You believe it is the chamber "In my mind that's a problem with the chamber" why do you think that ?
What parts are in this rifle? Who built it? What is happening exactly?
My leg hurts what is wrong doctor? Sure OK.
I have built many and fixed many misbuilt 6.5cm AR's..
What barrel, custom built barrel like a Bartlein, Krieger, etc? Or just a name brand off the shelf?
What factory ammo.. as you get up into the 140gr ammo, ESPECIALLY 140 Bergers, you need a proper feed code in the tenon to assist the longer pointy bullets up out of the feed ramp and into the chamber otherwise they stab into the back of the barrel tenon and dont feed. Ive seen this many times with "high end" 6.5cm barrels. Also a lot of high end 6.5cm factory ammo is too hot for 6.5cm gassers..
130 hybrids are best suited for 6.5cm gassers
6.5cm large frame gasser are not like building an AR15.. you can throw one together, but getting it to run reliably and properly is completely different.
I use custom built barrels using JP QPQ honed and polished barrel extensions i give to my smith to use when cutting me a Bartlein, Krieger, Rock Creek 6.5cm and always go with +2 Gas on 20-22" barrels.
I use JP or RCA High Pressure bolts that have small firing pins and give them to my smith to headspace to my barrels.
I use either SLA AGB or RCA BCG with AGK along with JP SCS Heavy with their spring pack.
I tuned the AGB or AGK, depending which one i used to lock back on last round then open another 1/4 turn. I then put 50rd through it, 5rd at a time, making sure it locks back eveey time. Sometimes you need to open up another 1/4 turn during this 50rd test.
I then tune the JP SCS swapping steel and tungsten weights and springs until I have my lock time adjusted properly so the brass is not being ripped out of the chamber before pressure has subsided and brass has shrunk back down. Sometimes gas has to be adjusted again during the SCS tuning.
I think this is the most crucial part of properly tuning a 6.5cm large frame gasser thst 90% of people don't do.
Guys not using honed/polished barrel extensions and non-tuned gas and buffer setups have obvious signs of this.
Big gouges and deep scratches down the bullet during loading into chamber.. deep scratches and gouges down neck and shoulder upon ejection. Raised burs and smears on case heads.
Why is this? Because your improperly polished and honed barrel extension is gouging bullets as they go uo feed ramp and into chamber. Because the sharp, pointy backside of lugs are cutting into your cases upon ejection..this is evident by the 2 lines down the neck and big deep gouge in shoulder..
And the raised burs and smear and ripped rims from your bolt moving too early and ripping the case out of the chamber before pressure has subsided.
The tuning noted above keeps that bolt closed until pressure has subsided.
My brass that comes out of my 6.5cm looks like it was fired out of a bolt gun. No scratches or gouges, case heads have no marks.. and recoil impulse is light.
Hopefully some of this helps you with your issues without. You havent provided much info to narrow it down.
What barrel, custom built barrel like a Bartlein, Krieger, etc? Or just a name brand off the shelf?
What factory ammo.. as you get up into the 140gr ammo, ESPECIALLY 140 Bergers, you need a proper feed code in the tenon to assist the longer pointy bullets up out of the feed ramp and into the chamber otherwise they stab into the back of the barrel tenon and dont feed. Ive seen this many times with "high end" 6.5cm barrels. Also a lot of high end 6.5cm factory ammo is too hot for 6.5cm gassers..
130 hybrids are best suited for 6.5cm gassers
6.5cm large frame gasser are not like building an AR15.. you can throw one together, but getting it to run reliably and properly is completely different.
I use custom built barrels using JP QPQ honed and polished barrel extensions i give to my smith to use when cutting me a Bartlein, Krieger, Rock Creek 6.5cm and always go with +2 Gas on 20-22" barrels.
I use JP or RCA High Pressure bolts that have small firing pins and give them to my smith to headspace to my barrels.
I use either SLA AGB or RCA BCG with AGK along with JP SCS Heavy with their spring pack.
I tuned the AGB or AGK, depending which one i used to lock back on last round then open another 1/4 turn. I then put 50rd through it, 5rd at a time, making sure it locks back eveey time. Sometimes you need to open up another 1/4 turn during this 50rd test.
I then tune the JP SCS swapping steel and tungsten weights and springs until I have my lock time adjusted properly so the brass is not being ripped out of the chamber before pressure has subsided and brass has shrunk back down. Sometimes gas has to be adjusted again during the SCS tuning.
I think this is the most crucial part of properly tuning a 6.5cm large frame gasser thst 90% of people don't do.
Guys not using honed/polished barrel extensions and non-tuned gas and buffer setups have obvious signs of this.
Big gouges and deep scratches down the bullet during loading into chamber.. deep scratches and gouges down neck and shoulder upon ejection. Raised burs and smears on case heads.
Why is this? Because your improperly polished and honed barrel extension is gouging bullets as they go uo feed ramp and into chamber. Because the sharp, pointy backside of lugs are cutting into your cases upon ejection..this is evident by the 2 lines down the neck and big deep gouge in shoulder..
And the raised burs and smear and ripped rims from your bolt moving too early and ripping the case out of the chamber before pressure has subsided.
The tuning noted above keeps that bolt closed until pressure has subsided.
My brass that comes out of my 6.5cm looks like it was fired out of a bolt gun. No scratches or gouges, case heads have no marks.. and recoil impulse is light.
Hopefully some of this helps you with your issues without. You havent provided much info to narrow it down.
Last edited:
Here some pictures of a "High End" 6.5cm gasser barrel having feeding issues that I diagnosed and had the makers fix.
The black barrel in the below pictures is one of my custom 6.5cm gasser Bartleins with JP QPQ honed extension showing the difference and fix for this issue to the maker...
The black barrel in the below pictures is one of my custom 6.5cm gasser Bartleins with JP QPQ honed extension showing the difference and fix for this issue to the maker...
AS I said earlier, and you explained it much better. 6.5 CM is not just plug and play
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