Need advanced advice/help: AR Pistol reloading issue

[skiutah02]

Thanks for all of the input. I solved the issue.

I could close the BCG on a empty sized case (with the upper separated) with just moderate thumb pressure.

When @Nedd Ludd suggested decomposing factory brass a remaking it with all of my components, 1 of the 3 did not fire. That was a surprise. Note: When I said ftf it was meant to mean failure-to-fire.

Although I have long been thinking that there was something that was not allowing the firing pin to hit the primer hard enough and things like improper headspace, improper sizing, too thick a primer cup, improper primer depth, short firing pin, not enough lube in BCG/fp, firing pin tip erosion, too little firing pin protrusion, too large a base on brass, etc, etc were my focus. Turns out that the hammer spring was too light. I got out my Midway "AR Ooops kit" and traded out the hammer spring and voila! I noticed right away that it took more effort to manually close the hammer when I tested the trigger function. Now functions perfectly. Shot 20 rounds of pre-hit rounds that ftf including 3 steel cases, and 60 reloads of 77, 75, 55, 50 and 40gr, reloads of 1x fired brass in the barrel, and 100% fired and cycled perfectly.

As to why the lower worked in my rifle AR, my best hypothesis is that since many 1000s of rounds had been through it, it was worn enough to allow a harder hit when the brand-new, tighter clearance pistol was just too tight to get a good whack.

Thanks for the help, Drew

 

[Twdmar]

You're not the first person to have this happen. Weak hammer spring, improper placement of the hammer spring legs etc is usually the reason for ignition problems with the ar15.

 

[Metal God]

Haha , hammer spring ! I thought about it but figured that was to easy lol . It’s another one of those analysis paralysis things . Overthinking the problem , of course that should have been the first things checked haha . Oh well

 

[Uncle Ed]

Shot 5 round of factory ammo. No issues. Tried some reloaded ammo (for my AR rifle). About 75% ftf. Tried 10 more factory rounds of federal 55 gr ammo. Worked perfectly. Changed course and reloaded some range brass to meet the specs of the unfired factory ammo. Also issues. Reloaded the factory brass fired in that chamber. Still about 75% ftf. About 25% of the 75% ftf would fire if I manually loaded into chamber and closed bolt from locked open position.
Thanks,

This problem is still strange, factory ammunition fired OK but your reloads did not.

There is more here than just a hammer spring problem.

 

[Metal God]

Maybe CCI #41 in the reloads and not in the factory loads cus if he’s using #400 or other standard primers in the reloads . It does seem strange .

Hmm anyone notice I’m pretty much just blowing the way the wind blows now lol

 

[skiutah02]

Yes #41s primarily, but a few 450s were in the mix.

 

[Uncle Ed]

Are you sure you didn't have a "whoops".

 

[skiutah02]

Are you sure you didn't have a "whoops".

When I looked at it initially, I was expecting that, yes, I had it backwards, but sadly, it was installed correctly. Not the first thing I though of, but it did come up as a likely problem and I had confirmed it was installed correctly well before trying the zillions of other things I mentioned. Apparently this is a common mistake, but not for me this time. It just appears that my spring kit had a lemon spring.

 

[skiutah02]

Haha , hammer spring ! I thought about it but figured that was to easy lol . It’s another one of those analysis paralysis things . Overthinking the problem , of course that should have been the first things checked haha . Oh well

It wasn't the first thing I had checked, but before posting, I had read that putting it backwards is a common mistake, but it was installed properly (at least after I put in anti-walk pins) and moved on to other things mentioned in the OP. Looks like a bum spring ended up in my parts kit. Lesson learned and did learn alot about the function of these rifles troubleshooting it so often.