ok, so the details.
I have a cz v-22 upper.
I put it on a new frontier poly lower from way back.
I changed to a metal hammer and trigger, but it kept short cycling, where it would pick up a round but not cock the hammer back.
I swapped to a yellow low power hammer spring and it worked fine.

Well then I got stupid.
I put a geissele trigger national match allong with a suppressor on it.
it started to have the not cocking the hammer problem again.
So I put a different none adjustible geissele trigger in and tried it with the yellow hammer spring.
it would shoot maybe 9 out of 10 then I would hear the hammer drop and no bang.
then no bang but a hammer drop every other, then shoot 5 or 6 times and do it again.
So I put some reduced power recoil springs and the full power hammer back in.
now it cycles and cocks the hammer every time, but doesn't go bang every time.
like every 5 rounds it does they no bang for 3 or 4 rounds and then I get another string of it working.

I noticed when I was changing out hammer springs the hammer stuck. I pulled the trigger after pulling the hammer pin and it didn't move.
I noticed when putting in the NM trigger that it had issues with adjusting so I think the lower is a little off on pin holes.

2 things I am thinking of trying, and neither may solve the problem.
I was thinking of getting the hard primer hammer spring with the geissele trigger- I am afraid this will take me back to the short cycling. but figured it might be due to the lower mass in the geissele hammer making it hard to hit.
or swapping the upper to a standard aluminium lower instead of poly in case there is some tolerance issue I have found going to a better trigger. of course it also could make no difference.

Tried with 4 different ammos and mostly was the same except some had feeding issues.
CCI standard
CCI high velocity- feeding issues
Eley bench semi auto
Winchester high velocity - feeding issues.

Any other things I should try?
I don't know if it exists, but is there a hammer gauge? something that can measure force of the impact from a hammer strike to see if I am getting consistent hits?

What does the firing pin strike look like on the rim of the casing? Can you post a picture of the rim strike?

sorry didn't think to do that.
I didn't keep any or pick any up.
I did look at them, and noticed there was barely any mark on it. had to check pretty close to see any kind of mark.
I reloaded them in the mag and they fired till I hit that problem again.

Maybe try a new firing pin? Maybe the tip is broken or too short?

if it never fired maybe, but since it will do strings ok I don't think so.
but I have a spare and will break it down to check. have to punch a pin out to remove it. if I recall correctly. it has been a while since I took it that far apart.
and it could just be gummed up inside the hole for the firing pin. but again, seems like it would be the same no matter what and not change.

Sounds like a thorough cleaning is in order.  Once oil and funpowder residue get to mixing together, it can slow things down quite a bit.  You also alluded to something else with the suspicion of the trigger pin placement.  A quick way to rule that out would be to place it on an aluminum lower.  One with a mil-spec trigger in it preferably.  From there you can experiment with the lighter hammer spring.  Try the new firing pin.  And check to see if there's any interference with the magazine feed lips and the reciprocating bolt.  This could slow the bolt down too.

Look for wear marks on the hammer and on the bottom corner of the V-22 bolt below the firing pin.   Not all hammers play well with all rimfire AR-15 bolts.   With the variation of pressure between rimfire cartridges can have an effect on momentum of the cycling bolt.   Rimfire semi auto AR-15’s are on a fine edge to be reliable.   I would use the provided hammer spring with your match triggers.   Lighter hammer springs can cause the inconsistent ignition your experiencing with rimfire ammunition.    I recommend using the supplied V-22 recoil spring and standard match trigger springs.   I’ll be surprised if the V-22 isn’t reliable with that combo.  I have three friends that own V-22’s and they have many thousands of reliable rounds fired using RRA NM triggers using in spec aluminum lowers.  


As mentioned, inspect and clean the firing pin and use a buffer and spring in the buffer tube.    It is possible your getting excessive bolt movement on the polymer lower.   You might try a pressure pug on the front of the buffer or tape a couple of quarters onto the front of the buffer.   These keep forward pressure on the rimfire bolt and eliminate any excess bolt movement which can zap momentum.   It is possible your getting bolt bounce with the light hammer spring which is contributing the light strikes.   Try making only one change at a time to try and isolate the problem.  Be aware you might have more than one issue contributing to the failure to fire.   Returning the bolt to original recoil spring and original hammer spring in a known good aluminum lower is a good place to start trouble shooting.

OP.....have you read any of the previous threads on this particular firearm.


I used google to search the arfcom forum, click here to read the previous threads discussing your firearm.

 



.

Thanks for the sugguestions
and yes I did quite a bit on making it more reliable.
this is something new after changing the trigger.
the really problem is testing.
the ranges around hear don't like it when you take stuff apart at the firing line, so it is one change go to the range, come back change it again etc..
but I will start by taking it apart further for cleaning and check the firing pin. then shifting the upper to a known good lower first and see if that helps anything before I start with the trigger again.
try to eliminate any other variables.
hmm, actually that gives me an idea, of taking a few lowers with me and trying it that way, in case it is just the lower. if it still fails, then I have to go back to troubleshooting the upper again.

I had a soft back of the firing pin, got peened with the metal hammering it and the pin actually micked out short.

I pulled the firing pin out today and oddly it wouldn't come out without hammering it out.

It looks like there was some build up near the hammer end, not the bullet end of the firing pin hole.
not sure what builds up right there or how anything gets there.

but I guess it could have gone either way, stuck out or just slowed it enough after trying to move after being hit.
not convinced that is the only thing wrong right now, but it is a start.
cleaned it out and the firing pin moves freely now.
will still check a few other things and see if there might be anything else.

Op- I have an ATI m4 style 22 upper, so obviously different. However I have the same lower and experienced the same exact issues. I brought 2 other mil-spec lowers and switched out the upper with them. Worked flawless with the aluminum uppers- once I put the upper on the new frontier lower it was full of issues again. So for now the 22 upper sits on an aluminum standard lower receiver.

The new frontier has been perfect with my 16" pencil barrel A1 upper. It's my woods walk light weight gun that's never had a hiccup- I did replace all the lower parts to metal however.

Try a standard metal receiver and let us know what happens.

I bet I know exactly what is causing your problems with the NFA lower. You need to swap out the standard hammer with the NFA 22/9mm hammer. The standard hammer that comes in the NFA polymer lowers is too thick and won't fit into the 22LR bolts. The 22LR/9mm hammer is thinner so that it will properly fit into the 22LR bolt and fire the round.

Here is the correct hammer that you need.  https://www.newfrontierarmory.com/lw-blow-back-hammer-for-22lr-9mm-uppers

I bought a NFA polymer lower years ago and the hammer was so wide that it would not fit into my CMMG dedicated bolts or my Chiappa bolt (TACSOL copy). So it wouldn't even fire. installing the 22lr/9mm fixed all my issues.