AR build, light primer strike

[pronstar]

Took my freshly built PSA 300BLK AR pistola to the range last night. Rounds were loaded in a standard AR PMAG.

Two FTF, with light primer strikes.
The second one jammed in the chamber, putting it completely out of action. I cleared the jam when I got home.

It’s my first build, admittedly my buddy who’s done it before helped tremendously.

Hoping you guys might have some insight into where I can start with this.


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[Darqhelmet]

Check the spring legs on your hammer.

 

[Sam7sf]

What ammo/primers were used? Light strikes can be from a weak spring but you could have a firing pin out of spec.

 

[grasshopperglock]

Where the FTF rounds loaded first in the mag? How many rounds before it did the FTF?

Do any of the other spent casings have gouges, dents, or deep scratches? If so, where? Neck, shoulder, or the body?

Did you try a different mag?


On the light strike. Manually push the firing pin fully forward. Is the pin protruding out the firing pin hole enough? Is the movement free and smooth? No gritty feeling or hanging up on a burr?

Shine a flashlight down the bolt firing pin bore. Inspect for anything not smooth.

Double check the firing pin spring. Compare the height to a 5.56 spring. Check the hammer for freedom of movement. Take a rag and use it to cushion the hammer on the removed lower receiver. Keep it from banging again the receiver.

Test the movement of the hammer.


Another area is to check the recoil spring.

Barrel ramp and chamber...

...


Keep in mind your build us brand new. It'll take a little bit of break in to smooth out.

 

[deemus]

Check the spring legs on your hammer.

View attachment 150140

View attachment 150141

Beat me to it.

 

[EZ-E]

I recently built a AR 9mm pistol & used the JP Enhanced Ignition Reliability spring kit with the red hammer spring. It would not strike the primer hard enough & had to go back to the stock hammer spring. Once i changed to the stock hammer spring no issues.

 

[pronstar]

What ammo/primers were used? Light strikes can be from a weak spring but you could have a firing pin out of spec.

S&B factory new loads.
200gr subsonics


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[pronstar]

Where the FTF rounds loaded first in the mag? How many rounds before it did the FTF?

Do any of the other spent casings have gouges, dents, or deep scratches? If so, where? Neck, shoulder, or the body?

Did you try a different mag?


On the light strike. Manually push the firing pin fully forward. Is the pin protruding out the firing pin hole enough? Is the movement free and smooth? No gritty feeling or hanging up on a burr?

Shine a flashlight down the bolt firing pin bore. Inspect for anything not smooth.

Double check the firing pin spring. Compare the height to a 5.56 spring. Check the hammer for freedom of movement. Take a rag and use it to cushion the hammer on the removed lower receiver. Keep it from banging again the receiver.

Test the movement of the hammer.


Another area is to check the recoil spring.

Barrel ramp and chamber...

...


Keep in mind your build us brand new. It'll take a little bit of break in to smooth out.

Zero rounds downrange, gun has yet to fire a single round.


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[EZ-E]

What trigger & springs are you using?

 

[grasshopperglock]

Zero rounds downrange, gun has yet to fire a single round.


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Did you notice any set back on the bullets? Did the tiny shoulder have a dent?

 

[grasshopperglock]

Without seeing it. I'd suspect the rounds getting damaged after being stripped out the mag and up the ramp. The round won't seat correctly. Holding the bolt slightly open. Causing the hammer to short hit the firing pin.

Or the chamber has an issue with the rounds used.

Or the Overall cartridge length is long.

 

[pronstar]

I’ll check the rounds but I think they looked intact.

What trigger & springs are you using?

PSA lower build kit.


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[deemus]

I’ll check the rounds but I think they looked intact.




PSA lower build kit.


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My money is on backward trigger springs, since you are not using the light springs.

Also, be sure you lube the trigger parts while you have it apart, including the pins.

 

[Charlie]

Sorry to hear about your problem. Looks like you've got some good recommendations here.

 

[EZ-E]

My money is on backward trigger springs, since you are not using the light springs.

Also, be sure you lube the trigger parts while you have it apart, including the pins.

This^^^^

If you have a bench grinder with buffing wheel its also a good time to polish the trigger & pins.

 

[Charlie]

This^^^^

If you have a bench grinder with buffing wheel its also a good time to polish the trigger & pins.

^^^
This also!

 

[deemus]

This^^^^

If you have a bench grinder with buffing wheel its also a good time to polish the trigger & pins.

Yep.

Here are some easy videos. FYI, I use 1500 grit sandpaper to do mine.

https://www.youtube.com/results?search_query=ar+trigger+job'

 

[Dad_Roman]

All that stuff there ^^^^^^^^^

Who's BCG? I get the "BearCreek" ones from Primary and I have to admit they had an "OOPS" run a while back and turned out a batch of bad ones. Primary made em good, no questions asked. I use the plural because I had two people follow me in the store on a Sat morning with the same issue.

BUT, it would fire, just every other round

 

[Sam7sf]

S&B factory new loads.
200gr subsonics


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They aren’t known for hard primers. So it’s down to the hammer spring or the fillet on the firing pin that effects protrusion

 

[pronstar]

How did you guys know the trigger is crappy? LOL

It’s like half the mating surfaces are made from chalkboard, the other half fingernails...


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