I'm hoping to get my old Adams Arms 5.45 upper running again but running into reliability issues.


To preface, I've been running 7.62x39 and 7.62x25 ARs for years. They've always been 100% with 3.5lb and 4.5lb POF triggers.


My 5.45 upper ignites maybe 50%. It has an enhanced firing pin that has about .003" more protrusion than the AK74 I measured. Diameter is smaller. I've tried all my POF trigger weights as well as milspec FCGs and extra power hammer springs. Best reliability is with the 4.5lb POF.

Ideas?

Are you absolutely sure the bolt is fully locking up?   What do the primers in the rounds that don't fire look like?  What ammo are you using?

Is yours the gas piston variety?  Does the bolt lock back on an empty magazine?  On the bolt face and not the bolt carrier?   If yes on piston and no on locking back or locking on the bolt carrier instead of the bolt, open up the gas to give the bolt more travel.

Does it always fire on the first round out of the mag and then not on following rounds?  If so, you might have too much drag from the magazine and slowing down the BCG, causing it to not fully lock up.  Make sure the bottom of the feed lips are not dragging excessively on the case, slowing down the BCG upon chambering.  Also make sure the top of the feed lips are not rubbing on the bottom of the bolt carrier, slowing it down.

Pretty sure it is locking up. When it runs, it runs awesome.

Primers look like they've been hit with a punch and a sledge hammer. Huge deep dimple in the primer. The AKs dont make anything that looks as mean.

Im running RAS 5.45. Laqure stuff I run in my AKSU. AKSU runs 100% with that as does my full size AK74.

Yes, piston. Holdra Arm (Adams Arms). I cant remember making it through a mag so I cannot tell you if it locks back. Ejection is strong when it does pop a primer. I usually run suppressed. Didnt notice any changes in ejection between full open and suppressed setting as if it were over or under gassed. Gas off is difficult to extract the spent casing. Not unexpected.

It seems completely random on when it doesnt fire. Might work the first couple rounds, most of a mag, not at all. Its never just the first round that has a problem.

The bottom of the bolt doesnt even have marks from dragging across the rounds in the magazine. None of the mags have any marks on the feed lips. Mags are ASC. Same lower I run 7.62x39 upper on with ASC mags. Rifle buffer.

Have you fired this lot of ammo in other uppers with success? I would be certain to rule out ammo first.

So are you saying that even when it doesn't fire, that the primers were hit hard?  If that is the case sounds like bad ammo.....but sounds like you are running 7n6?  That is about all I shoot with no issues.
I've been running full auto 5.45 since the 7N6 stuff came in cheap.

I've run lots of ammo through the AKs in that caliber. Ammo is fine.

Not 7N6. I only run non corrosive. All new manufacture. Usually RAS branded as it's the cheapest laqure I can find usually.

Yes, the primers are hit hard.

Ammo is fine. Been running cases of the stuff in the AKs for years. Cheap laqure rocks for the AKSU.

I can take one hit by the AR and it will go off 100% of the time in the AK.

Then it doesn't sound like it is getting hit hard enough.  
I'm presuming you are not running full auto otherwise, I'd suspect bolt bounce and suggest a heavier buffer.
You probably want to measure your firing pin protrusion.  I know you stated you have an enhanced FP but you may have a situation where you may need to remove some material off the tail of the bolt for the FP to protrude more.  I've seen some posts recommending like .038" but I know I've gone typically around .040"

Until the Tenko adapter is released I wont be running FA with my AR uppers. Missed out on a PAWS M16 by about 3 hours on my last NFA purchase but scored the Mac!


As said in my OP the firing pin protrusion is a few thousandths more than that of a Bulgarian (not Arsenal, real bulgy stuff) AK74. Wayyyy more than the standard AR protrusion. If I remember right its closer to 0.090". I was thinking of removing another 0.005" off the FP. Id rather modify the FP first to gain another couple thou. Im wondering of the FP diameter is not helping me here. The AKs always ignite these primers but the FPs are much larger OD.

Seems like the "enhanced" pins tend to sit around 0.080" on the long side usually from my reading.


Believe me, its getting hit hard. Unfortunately the weather is garbage, very soggy, so I likely wont be getting a sample for you today.

Have you tried cleaning the firing pin channel.  I have one and can only go aroung 300 rounds before I have to clean the bolt.  Have same symptoms as you describe.

The upper has so few rounds in it the gas block barely has any evidence it's been shot. I might have 30 rounds down it. It was unfired when I got it.  

Checked the FP channel. Had a little dirt but nothing I would expect to cause issues. Cleaned it out with a pipe cleaner. I'll have to function check it when it stops raining.

Got a chance to test fire it today. Ran 30 rounds with RAW laqure ammo. it ran 29/30. I did NOT restrike the round that did not ignite.

Its never run this good before!

I had a tiny bit of junk in the firing pin channel. Barely any but maybe that made the difference?

Spent casing on the left, fail to fire on the right





Its hitting it pretty good, IMHO. Would have easily set off any primer Id be able to get my hands on to load.

Beauty shot!



Beat up old Spikes lower. POF 4.5lb trigger. Romeo 5.

My experience with two separate 7.62x39 builds and a 5.45x39 build, all with enhanced firing pins, is that the 7.62x39s ran fine with std. 4-5 lb hammer springs but my 5.45x39 ONLY ran 100% with a Wolff xtra power hammer spring, regardless of commercial or 7n6.
Don’t know why. Even filed the shoulder of the firing pin to get more protrusion than the enhanced pin, no improvement.
A single stage trigger with a Wolff xtra power spring is a heavy pull, like 10 lb pull. So I tried it in a 2 stage RRA and it was great, only slightly heavier than the stock 4 lb spring. And never had a light strike.

Was going to say try extra power spring also.

When I switched to Geissele triggers my 5.45 ignition problems disappeared.

We played around with a bunch back in the day before S&W came out with the 15r.  It sounds like you have done everything we did, but when you say 4.5 hammer spring I'm thinking we used the yellow ones, don't remember the weight on them.

Let’s just say everything you have mentioned is exactly right.   Ammo is ruled out.  Only thing left is fire pin, so larger diameter, longer nose or more spring pressure.   It’s risky and I doubt that is your problem but could be. Could be crud not letting it travel all the way.

The JP springs, yellow is light for sure, I had a bunch of them, and red was either standard or heavy, I cannot remember which on that one.
For what it’s worth, on my 5.45, an old, now DCed ARP barrel with their 5.45 super bolt, also now DCed in that size, I use a regular firing pin with 2H buffer, standard buffer spring, and Wolff extra power hammer spring.  H insisted I use the Wolff extra power hammer spring.  IIRC their bolt in that caliber was made for more firing pin protrusion so you could use a standard firing pin.  It’s never missed a beat with that 7n6 or 76n (or whatever the hell that crap is) or Hornady black box and 50 round red box ammo.