PSA AR-9 Buffer & Spring Questions

[Captains1911]

I just purchased this PSA Glock lower (http://palmettostatearmory.com/psa-9...lower-blk.html)
and this upper (http://palmettostatearmory.com/psa-1...516447421.html)

This is my first AR-9 and I have a few questions regarding the buffer and spring. The lower came with a 5.5 oz. buffer of the same length as a carbine, H, etc buffer. I’ve read that without a longer buffer or a spacer/cushion at the rear of the receiver extension, there is a risk of breaking the bolt catch from the bolt slamming into it. However, since this particular lower does not have a last round bolt hold open feature, am I correct in assuming that there is little risk in breaking the bolt catch? Is there any other benefit to a spacer or cushion, like reducing excessive wear on the lower?

My other question relates to the spring. I read somewhere that the PSA AR-9 lowers come with an AR-10 spring. How can I tell an AR-10 spring apart from a standard AR-15 car spring? I have a spare Wolff extra power car spring laying around, how does it compare in terms of strength to an AR-10 spring, and is there any benefit to using it instead?

Thanks for the help.

[uffdaphil]

With the stock PSA buffer/spring combo I was getting burst fire and violent cycling. A heavy Q buffer/Wolff XP spring solved both problems.

http://heavybuffers.com/9q.html

[Captains1911]

With the stock PSA buffer/spring combo I was getting burst fire and violent cycling. A heavy Q buffer/Wolff XP spring solved both problems.

http://heavybuffers.com/9q.html

What is the likelihood of a heavier 8.0oz. buffer causing reliability issues? I'm just wondering if I should go ahead and order one without first trying the 5.5 oz. buffer.

[uffdaphil]

Mine is just one example, but from what I’ve read it sounds like it would be more, not less, reliable.

FWIW I have the PSA BCG and lower on an 8” pistol.

[Captains1911]

Mine is just one example, but from what I’ve read it sounds like it would be more, not less, reliable.

FWIW I have the PSA BCG and lower on an 8” pistol.

Mine is a 16" barrel, so wouldn't that make the blow back pressure even greater?

[uffdaphil]

Mine was also gtg with supressor which increased pressure. I think you would be fine.

[Captains1911]

Mine is just one example, but from what I’ve read it sounds like it would be more, not less, reliable.

FWIW I have the PSA BCG and lower on an 8” pistol.

Unrelated question...I just noticed that there is a fairly sharp edge on the bottom of my PSA bolt where it contacts the hammer (unlike standard AR bolt carriers that are rounded at this location), and it’s wearing two small nicks in the face of the hammer. Is yours this way, and is it anything to be concerned about?

[uffdaphil]

Yes, my PSA hybrid is also not rounded like a 5.56 carrier. It does cause some marks on the hammer, but not enough that I am concerned. My XP spring slowing down the bolt may result in less violent contact. Or not. I’m no expert.

[RWA007]

Well, because of this thread (not totally, but mostly), I went ahead and bought another 9mm pistol upper, this time with a 7.5" barrel. My first 9mm upper for this PSA stripped new lower was a really cheap 10.5" 9mm pistol upper. It didn't work very well at all. I then sold that non reliable upper and bought the 16" factory Kaw Valley Precision upper and it has had zero issues in over 600 rounds, 100%. But I've always wanted to go back to the original pistol configuration that I built it for first.

This new 7.5" pistol upper has not been 100% as the 16" upper, but is WAY better than my original pistol upper that I started with. I put about 100 rounds thru it with more than a few failures to feed on the first round, but mostly reliable once cycling normally. I think it did have one stovepipe in the middle of a mag. In looking up the symptom, some suggest a lighter buffer spring so I tried a regular carbine spring (instead of the AR10 spring) with no other changes (other than cleaning it again), and this time I had zero failures in 50 rounds...and then I ran out of ammo. So it's not conclusive yet, but the lighter spring might have helped with the failure to feed issue I was having with it.
As far as cycling goes...I can't tell a difference in recoil, noise, or anything, other than it feeds every time now...at least 50 out of 50 shots.

FYI...I paid $600+ for the Kaw Valley complete upper...and it has been 100%. I only paid $240 for this complete upper and I can already see that in some cases you get what you pay for. (twice now...you would think I would learn my lesson here). Before I take it out again, I am going to polish up the feed ramp (chamfer/angle/whatever) to the barrel and polish the part of the bolt that grabs the next round. I'll leave the carbine spring in it. If I can go 200 rounds clean, with no issues at all...I'll deem it a success. Here is a pic with the 7.5" barrel. I'd love for this to be dependable enough for a home defense type gun, but unless it's 100% it's just a range toy at this point...

Edit: I forgot to add, I am using 124gr FMJ from Aguila. This was the ammo that worked the BEST in my FIRST 9mm pistol upper, and is what has run 100% in my 16" upper. I haven't tried any other ammo in this pistol upper yet.

[RWA007]

Update: I went ahead and built a 7.5" 9mm Pistol and kind of went with the same components that I used in my rifle. I used a 7.5 ounce Kaw Valley buffer in this one also, but just used the standard spring and it seems to work fine. Curiously...I purchased two identical complete uppers and my cousin was going to build one. I got them both home and went and tested them both out on the same lower. One ran like a sewing machine the other one failed miserably. I think I tried about 50 rounds and I'd be surprised if 5 of those loaded/fired/ejected without issue. It ended up being a faulty bolt although I could not see the difference. One worked the other didn't. Since the supplier didn't have any other bolts he refunded me for the faulty upper and I called my cousin and told him he was out of luck!
Anyway, these 9mm AR's are fun.