Light primer strikes

[Tcrocker]

I have an AR15 that shoots brass rounds fine but when I shoot steel I get light primer strikes any ideals how to fix. Been told I should get a Palmetto State nitride bolt group. I just don't want to spend the money if I don't need to. The AR is a Anderson Arms upper and lower 5.56 223

[bj139]

Do you have a mil spec hammer spring?
A light hammer spring could cause this.

[grayfox]

Measure the length of the bolt, and the length of the firing pin, with a caliper. Lengths here should not be a problem but just to eliminate them from a cause...
How many rounds downrange (looking for the amount of breakin)?
What bolt/bcg do you currently have, is the bc phosphated or what.
yes, maybe the trigger group/hammer spring.
maybe smoothness/cleanliness of the bolt, inside and out. Do you remove the extractor when cleaning to get at the insides of the bolt...
Do you have another bcg to try, I'm guessing by your comments - not. Having a few key spare parts is a really good idea btw... 1 is none, 2 is one.

These are some ideas that occur to me.

[Crusty]

I had a Maxim bolt that gave me light strikes. I bought an enhanced 7.62x39 firing pin and that solved the problem. It extends proud of the bolt face by .042" and it leaves a nice dimple.

My Alexander bolt works fine straight out of the box with the standard pin.

[VASCAR2]

There is a spec for the proper firing pin protrusion min. 028 to maximum .036 from the breach face. Brownell’s actually sells a gauge to quickly check to see if the bolt/FP are within spec.

https://www.brownells.com/gunsmith-tools...26477.aspx


This issue has come up before where tolerance stacking causes light strikes. Some times the bolt overall length is greater than 2.81 and the firing pin is on the short side of spec. You could also have the hammer spring installed improperly or have less than milspec hammer spring. Some aftermarket FCG produce insufficient hammer blow on hard military primers. This ia fairly common problem on 7.62X39 but I’ve never experienced an issue with my 6.5 Grendel AR-15’s and Wolf steel cased ammo.

The only other issue with failure to fire is where some manufactures have used 2.80 length bolts and shorter firing pins. If you replace the bolt with a 6.5 Grendel bolt like AA or the GB Monster 2.810 bolt and use a short firing pin you can get light strikes.

A milspec firing pin should measure 3.279 + or - a thousandth or two.

[1Shot]

Sounds to me like you either have a too light of force hammer spring or a too light hammer. The too light springs decreases the force needed to apply the force of the hammer to the firing pin to set the HARD primer of the Wolf ammo off. Or your hammer is too light, this happens with bobbed hammers and some lighter drop in trigger hammers to apply enough force to set off the HARD primers of the Wolf ammo.

[Greyling]

I was under the impression that bobbed hamers hit harder because they were moving faster. That the reason JP could get away with lighter springs was the bobbed hammer. You know, force equaling mass times velocity squared.

[NugginFutz]

I was under the impression that bobbed hamers hit harder because they were moving faster. That the reason JP could get away with lighter springs was the bobbed hammer. You know, force equaling mass times velocity squared.

You can't swing a rolled up piece of paper fast enough to drive a nail...

(Just sayin')

[Kswhitetails]

You can't swing a rolled up piece of paper fast enough to drive a nail...

(Just sayin')

That sounds like real world experience...?

[bj139]

You can't swing a rolled up piece of paper fast enough to drive a nail...

(Just sayin')

I brought this up on a thread last year and was told by the more experienced members of this group that bobbed hammers work just as well if not better than full tailed hammers. I just accepted that and moved on. Was I right?

[Randy99CL]

I've always preferred light hammers for fast lock time.

But setting off a C/F primer requires force and inertia. Especially the thick cup primers we use.
It's possible that a light hammer might not have enough mass/momentum to force the firing pin deep enough to hit the compound. Might be bouncing off the firing pin.

[1Shot]

The Wolf ammo has HARD primers and it takes a good lick to set them off. That is the reason that many have to go to stronger hammer springs in 7.62x39 and I have seen notifications in the past from companies that state that the use of Wolf or any steel case ammo may not fire in their rifles.

I have a friend that has been a gunsmith for 40+ years that I went to for advice when I was having some fail to fire problems with an older Ruger 77 bolt rifle. The first thing he told me was change the spring in the bolt. These older Ruger rifles he said had springs that would weaken over time and cause fail to fire problems even though it would leave a pretty good dent in the primer. He just happened to have a spring in stock because he was seeing this problem a lot. I got the spring and installed it and never had another fail to fire. So even with a heavy hammer you can get it going too slow and it will not fire and you can get a light hammer going fast but if it does not have enough weight to provide a hard enough blow it will not fire.

"You can't swing a rolled up piece of paper fast enough to drive a nail..."

I love this, simple but true.

[LR1955]

Guys:

I moved this from the Technical Training forum because it deals more with troubleshooting a mechanical problem than a training issue. Also I bet more people who have experienced this thing will see it.

LR55

[Lastrites]

As mentioned by Grayfox and Vascar2, break out the calibers and start measuring your fp and bolt.

[mateba]

I had similar results with my hammer spring up side down.