debugging misfires

[SolisDelendaEst]

I have a pretty new PSA Sabre that runs everything I have put through it perfectly, except Hornady Critical Defense .223 73 grain. With that round in particular, I get misfires about 10% of the time. I want to believe that it's just hard primers in that round in particular, but I want to make sure that there's no issue with the rifle. So I'm interested in ya'lls thoughts.

I've tried to measure firing pin protrusion with calipers, and it *seems* in spec, but I'm not confident in my ability to measure it accurately. I have a proper tool to do this on the way.

I've checked, and the hammer spring is not installed backwards.

Below are some pics of spent casings from my last range trip. Do these look like deep enough primer indents to you?

I shot one box each of 4 different types of ammo: 1) Hornady Critical Defense .223 73 grain, 2) Hornady Frontier 5.56 55 grain (m193 clone), 3) PMC X-Tac 5.56 55 grain (m193 clone), 4) AAC OTM 5.56 77 grain. I had 2 misfires with the Critical Defense, and everything else shot flawlessly.

The first attached picture has the 2 misfires from the Critical Defense. The second picture has one random spent casing each from each of the 4 types of ammunition, in the following order: 1) Critical Defense, 2) Frontier, 3) PMC, 4) AAC

To my eyes, the misfired Critical Defense rounds have pretty light primer indents, the successfully fired Critical Defense & Frontier both have somewhat light primer indents, and the PMC & AAC look better. But maybe they're still not deep enough? What do you think?

First image, misfires: https://imgur.com/bNBfL0B
Second image, spent casings: https://imgur.com/yPwxmuW

I've shot a wide range of other brands and loadings without any issues - including some others from Hornday, but I don't have any of the spent casings or pics of them to compare.

[battlemidget]

I think you're right. Is it time to sell the Hornady or the Sabre?
What kind of Sabre you get?

[bellavite1]

If everything else is firing ok, I would chalk it up to the ammo.
You could get some extra power hammer springs and see if that fixes it.
It will increase the pull weight, but that is not supposed to be a long range precision rifle, I assume...

[SolisDelendaEst]

Yeah, not a long range rifle.

This is the complete upper I got: https://palmettostatearmory.com/psa-sabre-forged-13-7-fn-chf-cl-mid-length-5-56-with-13-qd-rail-and-jmac-gfhc-e-pin-and-weld.html. And this is the lower: https://palmettostatearmory.com/psa-sabre-15-forged-lower-with-sabre-stock-and-grip-black.html.

[Linkless]

The spent cases look like they were pretty light hits as well. Does the Sabre use standard ar components? I'd try a different BCG first and see what it looks like then start digging. Maybe try a different trigger group/lower as well?

[Erni]

I was going to ask about fp protrusion but you measured that. Compare it to another bolt and firing pin.
Either something is binding or pin is short, or your hammer springs.

[SolisDelendaEst]

Sabres do use standard AR components. I don't have another lower or BCG to try or compare to, but it's a good idea.

I'm not certain fp protusion is good yet. Trying to measure that with calipers felt like I needed more hands to make sure everything was in place, and I got a wide range of of numbers when I repeated the process. Most were in spec, but I still don't really trust it. But I should have this tool in a couple days, so I'll get a proper measurement: https://www.creedmoorsports.com/product/creedmoor-sports-firing-pin-protrusion-gauge/creedmoor_sports_brand

[beast556]

It could be the angle of the picture but all the casings in bolth pictures look light to me.

Let me know if you wanna hit the range, I'm a menber at NCRG club . I'll bring a few bcg's ond lowers we can try in your rifle.

[battlemidget]

That's a nice build you got there! Aside from the light primer strikes, what's your review of the sabre? Hows the recoil? How's that trigger? Would you buy it again?

[SolisDelendaEst]

It could be the angle of the picture but all the casings in bolth pictures look light to me.

Let me know if you wanna hit the range, I'm a menber at NCRG club . I'll bring a few bcg's ond lowers we can try in your rifle.

Yeah man, I'd love to find a time to do that, thanks.


That's a nice build you got there! Aside from the light primer strikes, what's your review of the sabre? Hows the recoil? How's that trigger? Would you buy it again?

This is the only AR I've owned, or had any serious time with, so I don't have much to compare to. But so far so good. The trigger does feel pretty nice, and the recoil doesn't seem bad to me. As long as I don't put Critical Defense through it, everything seems great.

[SolisDelendaEst]

Firing pin protrusion is 0.034 inches, so that does not appear to be the issue.

[SolisDelendaEst]

Finally determined the issue. PSA Sabre lowers come with a Hiperfire trigger with reduced power springs, which is known to cause misfires with duty ammo that has hard primers like... Critical Defense. So fundamentally: user error, everything was working as expected. But I replaced the trigger so I won't have that problem anymore.