Hey All,
To start, let me cover some of the basic info about my rifle.
- The Lower is the PSA Gen3 PA10 .308 Lower, SKU: 5165790563 (Ordered 10/11/20)
- The Upper is the PSA Gen3 PA10 .308 Mid-length 18” Stainless Upper, SKU: 5165491811 (Ordered 10/27/2020)
Diving further into the area of concern…
- Buffer: 2.5" long, I think the standard 3.8 oz?
- Buffer Spring: 28/29 coils ~ 11.5 inches
- Buffer Tube: Internal depth is about 7 1/16th
- Buffer Tube to lower tower face: about 7 1/8” initially
From what I gather this is the DPMS set up (vs normal buffer weight [3.5"], longer [7 5/8"] Tube).
The issue I’m noticing is glace marks on the buffer tube/lower at the 1, 4, 7, and 11 o’clock positions.
This is my first AR 10 platform, and I haven’t seen this before but 20 min on various forums suggests this is carrier over travel. The wear marks on the BCG and visual position of the buffer tube within the lower compliments that theory.
Information on those same threads suggests that the DPMS buffer tube setup relies on an exact 7” internal buffer tube depth to prevent BCG overtravel. If the buffer tube isn’t screwed into the lower all of the way, a pseudo depth increase is generated – which is what I observed in my assembly. When measuring the depth of the buffer tube I had almost 7 1/8” to the front face of the lower buffer tube tower. I also noticed the buffer tube was almost not capturing the buffer retainer pin.
The “quick fix” is to drop two quarters (~1/16” each) into the buffer tube and then reassemble. Doing so would bring the measured depth to right at 7”. In my case I elected to screw the buffer in another turn. I had to clearance the 6 o’clock area of the front lip of the buffer tube to make clearance for the retaining pin.
Doing so brought the buffer tube right to the front face of the lower buffer tube tower and the internal depth measurement to 7 1/16”. I still needed a quarter to get me to the 7” measurement.
My question to those still reading, should I seek another buffer tube that is closer to spec? Or should I convert over to the longer (7 5/8”) tube so I can use normal 3.5” buffers?
Thank you in advance for reading through my post and I look forward to hearing your opinions. I can share other photos but this forum won’t let me post multiple at first.
Lastly, some of the symptoms I had prior to investigating were: BCG catching while hand cycling and occasional sharp recoil pulse with weird ejection pattern.
-sh_meats
4 Likes
PSA uses an intermediate tube…a little longer than a carbine, shorter than a rifle tube. I would put a heavier buffer in it rather than quarters.
1 Like
Can you post a pic of the carrier? I haven’t got any brilliant ideas, but I am very curious to see the carrier where it is striking. I have a PA65 myself.
1 Like
Yep, here is what I have for pictures of the BCG. I can take more later if need be.
1 Like
I have a KAK LR-308 Carbine Heavy Buffer on order.
Trust me, not excited to put quarters in my rifle to get it to not impale itself.
Please correct me if I’m wrong but PSA uses two different buffer system combinations with their lowers.
- An intermediate length buffer tube with normal carbine buffers (~3.25")
- A carbine length buffer tube with a shorter buffer (2.5")
I believe either path functions when properly installed and parts are to spec.
3 Likes
Yes. But lots of factors in play, including ammo. I use an adjustable gas block and a suppressor to tame my ar10.
1 Like
They have had 2 AR10 buffer setups. Like you said one uses a standard ar15 tube with a buffer shorter than a standard ar15 carbine buffer. The other is a longer tube that uses a standard ar15 carbine sized buffer. It sounds like you may have the longer tube but the shorter buffer which is causing the overtravel.
1 Like
Thanks for the comment! Here’s a measurement of the buffer tube on the lower in question.
I measure the same 7.25” on two of my AR-15s.
@sh_meats, was this resolved? I’m having similar issues with my .308, gen 3. What did you do?
Apologies for the delayed response.
They had me send the whole rifle in for repair. This was the response I got from the customer rep once they took a look at it. ,“ …Replaced the BCG. There is no “milspec” standard on the AR10 platform. A lot of the AR10 parts are AR15 parts. The retention pin on the lower is fine also. Test fired rifle in its entirety and it fired with no malfunctions. BCG is cycling through a metal receiver and has a lot of power with a .308. The BCG is going to have wear marks on it sooner than later.”
Take from that what you will.
The rifle ran okay afterwards and after ~200 rds the wear on the bcg/buffer tube tower isn’t back or getting worse.
I still think the bcg was over-traveling because the rubber pad on the buffer wasn’t bottoming out before the bcg was hitting the buffer tower. Two quarters seemed to take up that difference before I sent it in.
1 Like
PSA has used 2 carbine lengths… one is the usual DPMS Pattern, using a AR15 carbine buffer tube, and a 2.5" buffer.
The other “intermediate” sized carbine tube ( a Vltor A5 tube / Armalite Carbine buffer tube ) uses a standard 3.25" AR15 carbine buffer>
The 2 systems do not interchange parts.
I use the Tubbs 308 Flatwire recoil spring in all my recoil setups, it works with the DPMS pattern , Vltor / Armalite pattern and the rifle length setups.
As for the OP’s issues, it looks like a tolerance issue… clearly the bcg is over-traveling some how.
Honestly the add a quarter at the bottom of the buffer tube subject does work, but if you don’t want to do that I get it.
I would buy a 5.4oz KAK 2.5" buffer and a Tubbs 308 Flatwire recoil spring.
If those don’t help… try a different AR15 carbine buffer tube .
I am curious, does your PA10 have an adj. GB ?
https://www.ar15.com/forums/industry/PSA-when-did-you-guys-switch-the-buffer-system-length-on-the-PA10-/301-286585/
