Need help with my AR lower build

[Hokie_PhD]

folks as documented in my other thread I recently completed my first AR lower build.

All seemed fine as it went together without a hitch. It seems to function fine. But when I put my PSA upper on it, it jambs and has failure to fires.

The build is an Anderson stripped lower, a PSA LPK with the ALG trigger and Magpul grip. The stock is an Ace Skeleton with their spring and rifle length tube and buffer.

Mags go in and drop fine, and it seems to fire fine. And yes I made sure not to let it hit with the rest of the lower when testing.

Anyway, I swapped the PSA lower back and had no problems so I know it's not the ammo or mags. So is there something I might of done wrong worth the build? Is the rifle length buffer and issue with the carbine upper? I was told no. Or is this a break in issue or something else?

 

[GunnyUSMC]

First off. Is the firing pin leaving light strikes on the primer? If it is you have one or two problems.
First problem is that you may have the hammer spring installed wrong. If installed backward it will work but not have enough power.
Second, some fire control groups come with two hammer springs, light and standard. You may have a light spring and you will get light strikes on hard primers.

 

[Hokie_PhD]

Thanks Gunny
I thought the spring might have got turned around.
I just wanted to check before I take it apart.

The ALG only came with one spring and I don't recall reading about a light spring.
I'm using CCI primers on my reloads and I also tried some factory ammo.

Any ideas on the ammo jamming up after a round fired?

 

[GunnyUSMC]

Be sure that your springs look like this.



When reloading for a simi auto you need to full length resize your cases.
Some barrels have tight chambers.
Are you just having trouble with your reloads?

 

[Hokie_PhD]

Gunny
Thank you SO MUCH
AGAIN!!!!

It looks like the hammer spring was in wrong.
Your pics were so helpful.

My reloads have been great on the PSA upper and lower combo. They shoot great if I say so myself.
In fact I hate to say it but once I swapped the lowers not a single issue.

 

[MistWolf]

Why your rifle is malfunctioning cannot be determined until you explain what the malfunction is.

If it's a double feed, where two live rounds are getting jammed in the action, the magazine is bad and should be beaten with a hammer or shot several times and replaced with a new magazine.

If an empty and a live round is jamming the action, the extractor spring is weak and needs to be replaced, preferably with a Colt extractor spring with black insert (no O ring).

If the empty is pulled out of the chamber, but is not being ejected and a fresh round not stripped from the magazine, the rifle is short stroking.

If the rifle is ejecting and a fresh round is not being stripped from the magazine, the rifle is short stroking.

To test for short stroking-
-Field strip, clean, lube and reassemble the AR. Perform function check
-Choose an empty magazine that is known to work. Insert empty mag in the mag well and pull the charging handle all the way to the rear. The carrier should lock back. If not, check the bolt catch for proper function and use another magazine
-Place a single round in the tested magazine, load and fire the weapon. If functioning properly, the carrier will lock back. Perform this test three times

If the carrier doesn't lock back, the bolt catch and mag are good, the rifle is short stroking. The problem is either a blocked or leaky gas system, or weak ammo

 

[Hokie_PhD]

Thanks

Could the striker spring being in wrong affect the feeding? I fixed that after seeing Gunnys post. But haven't been to the range since fixing it.

If not it Sounds like short stroking from what you describe but the mags are fine when I change lowers.

So could the rifle length buffer and spring be an issue with the carbine upper?

The ammo is fine as it worked in the same upper swapped to the PSA lower ditto for the mags.

 

[Walkalong]

It looks like the hammer spring was in wrong.

Been there done that, doesn't work well.

 

[GunnyUSMC]

Try a carbine buffer.

 

[JeeperCreeper]

I love PSA, but their triggers leave much to be desired. On my third build (so I kinda knew what I was doing), I used a PSA LPK for my Spikes lower. I had failure to fire on every other round. I would pull the tirgger, it would go bang, cycle, then on the next pull the trigger was dead. I'd rack/charge it, get another shot, then dead trigger. It was very upsetting as I spent quite alot on this build compared to my super budget builds that ran better.

I was researching and researching with no good answers that were cheap, then decided to just dry fire the gun in my apartment when I watched TV. By the time I went to the range the next time, it ran fine. The trigger pull sucked (I'd guess well on the upper end of "milspec" and may be 10 pounds or more). So it works, but I'll swap it out eventually. But it works.

My guess, PSA has rough QC when it comes to where they get their triggers or when they make them themselves. I worked it out to force it to file whatever crappy tolerances were there. Dunno if that helps, but it's what happened to me.

 

[Hokie_PhD]

Gunny, the upper is going to have a rifle length gas system. I'm just using this upper to test that the lower was put together right. And that's to you, I found that I made a mistake with that spring.

JeeperCreeper, it's a PSA parts kit, but the upgraded one with the ALG trigger. Compared to my PSA complete lower the ALG is a rob better. Down the road I may get a much better trigger but for a value (not the cheapest but rather the best parts for the price parts I could find) build the ALG seemed like the way to go.

 

[redneck2]

So it works, but I'll swap it out eventually. But it works.

PSA has their enhanced FCG (fire control group) trigger. IIRC, it's normally $39.95 and goes on sale every few months for $29.95. I got one for my latest build. I haven't used it yet, but my friend that's a pretty hard core gun guy says they're pretty good, and the price is great.

It's a version of a standard trigger with the contact surfaces polished and some kind of slick hardening

 

[GunnyUSMC]

Gunny, the upper is going to have a rifle length gas system. I'm just using this upper to test that the lower was put together right. And that's to you, I found that I made a mistake with that spring.

Hokie
Don't feel bad, it happens more often then most will admit. Before I started building ARs, I had already taken the fire control group out of a few M16s. You would not believe the things Marines do to get their rifles ready for inspections.

I love PSA, but their triggers leave much to be desired. On my third build (so I kinda knew what I was doing), I used a PSA LPK for my Spikes lower. I had failure to fire on every other round. I would pull the tirgger, it would go bang, cycle, then on the next pull the trigger was dead. I'd rack/charge it, get another shot, then dead trigger. It was very upsetting as I spent quite alot on this build compared to my super budget builds that ran better.

I was researching and researching with no good answers that were cheap, then decided to just dry fire the gun in my apartment when I watched TV. By the time I went to the range the next time, it ran fine. The trigger pull sucked (I'd guess well on the upper end of "milspec" and may be 10 pounds or more). So it works, but I'll swap it out eventually. But it works.

My guess, PSA has rough QC when it comes to where they get their triggers or when they make them themselves. I worked it out to force it to file whatever crappy tolerances were there. Dunno if that helps, but it's what happened to me.

The trouble you had with your fire control group was the trigger reset. This is common with a lot of standard parts kits. You know the old saying, "You get what you pay for." Now when I say a lot, it's not like one in every five. When you buy one of the better triggers your not only paying for the sear points to be polished, but all contact points.
You problem was most likely the trigger. There was most likely some small burs on the ends where the pin goes through. The top of each end is cut down to allow the hammer spring contact the notch in the trigger spring.
If you use a small fine file and clean up both sides, which only takes a few minutes, everything will be ok.

 

[Hokie_PhD]

Gunny,
I don't feel bad. Just a little annoyed as I checked it several times. I guess what I looked at wasn't as clear as your pics.

I'm looking forward to hitting the range again.

I guess the next step is to see what happens. If I continue to get jambs I'll swap the buffers for the test. I'm hoping I don't have to do that and hoping that if I do that'll fix everything as I'd like to move on to the upper build.

 

[GunnyUSMC]

Sometimes parts can be out of spec. Check the ring where the buffer tube screws into the lower. See if there are any marks where something is hitting or rubbing.
On one of my builds, l could not pull the charging handle to the rear when the upper and lower were together. A quick check and I found that the receiver back plate was thicker on the top and it was stopping the charging handle. This was a nice single point back plate. I re shaped and coated the back plate and everything was fine.