Finally got to the range yesterday with my new AR 5.45x39 build. Got set up, first 5 shots go bang. 7th or 8th shot click. Cleared round, click again, cleared round, goes bang than click again. Cleared rounds looked like bad primers or light strikes. Worked action several times, changed to new box of ammo, 4 rounds pop then same thing. Switched rifles to a new Saiga I had converted, and it runs like a champ. By now I'm guessing that the problem is the plastic trigger group that came with the lower when I bought it. I had already changed out the stock hammer spring to a Wolff heavy duty spring because I'd read about regular springs not being able to ignite the primers on surplus rounds. I decided to try the AR one more time, (as many of the old hands around me opined I was just having break in issues), when again I got another FTF, but this time bolt was jammed closed. Range guy came to the rescue with a hammer and rod. Hammered my new Spikes bolt back, and out came the case along with spilling powder, and the bullet remained jammed in the barrel. Tapped out the bullet with the rod, and upon examination case and bullet appeared normal. Ammo is regular 60 grain Wolf. If you look a the attached photo, round on top is one of those that I thought was a bad primer. Now that I look at it closer it appears the bullet is not seated fully in the casing. I'm wondering is this something that happened in the chamber? I didn't headspace the rifle when I built it, as I'd read that on AR's this is not necessary. Could this be the result?

I am not too familiar with the AR platform, but perhaps there is some sort of funny business taking place in the throat area of your chamber. Specifically, the bullet could be engaging the rifling as it is seated in the chamber by the bolt, causing an interference fit between the rifling and the bullet. This would explain why the bullet remained lodged in your barrel upon extraction of the case, and would explain why the round that you thought had a bad primer extracted with an unseated bullet.

Now this doesn't explain the failure-to-fire problem, but that could be caused by excessive head-space. If there was excessive head-space and a particularly tight or shallow throat in your chamber these two factors together could cause this sort of behavior. As the bolt strips a round from the magazine and rams it home, the round's momentum may jam the bullet into the throat and then leave too much room between the bolt face and the primer, causing a light primer strike.

If you have any of the casings from the rounds that did fire, check them for bulging near the case head. This might not be as apparent with steel cases as it would brass though. Are there signs of engagement with the rifling or throat on the bullet?

You need to have this rifle checked out.  The 545 in a at us very finicky and in the 762x39 we break them in with brass first.  But you don't have that luxury.  So we have to make sure everything is on the loose side for the steel case.  Also what kind of lower?  Must be a mil spec hammer trigger and a longer firing pin. I make Those in stainless and titanium to fix that problem

I am not too familiar with the AR platform, but perhaps there is some sort of funny business taking place in the throat area of your chamber. Specifically, the bullet could be engaging the rifling as it is seated in the chamber by the bolt, causing an interference fit between the rifling and the bullet. This would explain why the bullet remained lodged in your barrel upon extraction of the case, and would explain why the round that you thought had a bad primer extracted with an unseated bullet.

Now this doesn't explain the failure-to-fire problem, but that could be caused by excessive head-space. If there was excessive head-space and a particularly tight or shallow throat in your chamber these two factors together could cause this sort of behavior. As the bolt strips a round from the magazine and rams it home, the round's momentum may jam the bullet into the throat and then leave too much room between the bolt face and the primer, causing a light primer strike.

If you have any of the casings from the rounds that did fire, check them for bulging near the case head. This might not be as apparent with steel cases as it would brass though. Are there signs of engagement with the rifling or throat on the bullet?

What you say makes sense. I'm thinking I may have lodged the bullet by smacking the forward advance?

You need to have this rifle checked out.  The 545 in a at us very finicky and in the 762x39 we break them in with brass first.  But you don't have that luxury.  So we have to make sure everything is on the loose side for the steel case.  Also what kind of lower?  Must be a mil spec hammer trigger and a longer firing pin. I make Those in stainless and titanium to fix that problem

Lower is a New Frontier plastic. Pretty sure the hammer in't mil spec because it's plastic. Will definitely be buying a new steel trigger group. Firing pin should be correct (longer) length as I bought it in a complete Spikes 5.45 BCG.

The lower will work with the Longer Stainless Steel Firing Pin.  I doubt the Spikes has a longer firing pin.

But I would recommend switching to a steel hammer and trigger.  I have if you need.

I'm the rep for New Frontier in Hawaii so I have a lot of experience with these lowers.

The lower will work with the Longer Stainless Steel Firing Pin.  I doubt the Spikes has a longer firing pin.

But I would recommend switching to a steel hammer and trigger.  I have if you need.

I'm the rep for New Frontier in Hawaii so I have a lot of experience with these lowers.

Yeah, I know, I bought the lower from you guys. Not that you're wrong, but I don't understand why you think the firing pin is too short, since the bolt assembly was built by Spikes specifically for 5.45, unless you are thinking there's some sort of parts mix up. That aside I noticed the hammer was slightly dimpled where it strikes the firing pin which I'm guessing might explain the short strikes. Wasn't dimpled really bad though. Maybe it's momentarily deforming on impact?

I'm prolly going to stop by the swap meet this time, maybe I'll bring the rifle with me and we can discuss?

yup you can!

Update: Ordered a new / used PSA trigger group I got on ebay for cheap. Took the rifle up to the mountain yesterday, and problem fixed. New trigger is horrible, but now at least I know I can upgrade.

yup you can!

Thanks, and I will definitely make the swap meet this time since I have to return Jon Jon's barrel wrench

Easy to redo the trigger.

Should have brought it to us we would have hooked you up with a good trigger. 

Should have brought it to us we would have hooked you up with a good trigger.

Probably will, jus got the cheap trigger to see if I could make it work before I spend money on a decent trigger.