Bad day at the range: part 1

[va_connoisseur]

Went to the range to test/chronological some new rounds and test my new magnetospeed. It was not a good day for either:

I have been having issues with my trigger and light primer strikes, so I decided to try a new trigger. Switched out the rise armament for a POF trigger. Still having the same issues with light primer strikes only on Factory ammunition. My reloads fire fine, but I cannot get any Factory Hornady ammo either the black or the 123 SST to fire.

I am using a monster Bolt from the group by and a standard hardened arms bolt carrier group. The firing pin is the standard firing pin that came with the bolt carrier group. I am at my wit's end. Any suggestion at this point would be helpful.

The setup is the monster 12.7 inch barrel compatible gas block and gas tube. Everything else is pretty much standard. Meaning mil-spec. Where should I measure to determine if the boat face or the firing pin is the issue.?

[Arkhangel5]

The fact that you said light primer strikes, says to me trigger, trigger springs put in correctly? I would start there.

SY

[va_connoisseur]

Replaced the Rise Armament one piece trigger with a Patriot Ordnance Factory one piece trigger. No trigger springs to deal with and they function properly in the other gun

[Arkhangel5]

Ok, maybe try a trigger with a heavier hammer? Just to rule out that it is not the trigger.

SY

[maxxmojo]

You can measure the length of the firing pin itself or if you have the capability measure the firing pin protrusion from the bolt face. Or swap in another firing pin and try it out.

[VASCAR2]

http://www.65grendel.com/forum/showthread.php?17715-Firing-pin-measurment/page2

[va_connoisseur]

VASCAR2, I decided to measure the firing pins and found that the one that was making light primer strikes measures 3.248. My “functional” AR has a firing pin that measures at 3.271. Did a little digging online and found the measurement should be 3.270 +/- 0.009.

So I’m swapping pins and heading to the range tomorrow. I’ll report back.

[Sticks]

Sounds like you have or had a proprietary Grendel bolt that is the incorrect length. I can't remember who, but there is a MFG that put one out that is a Mk136, but standard AR15 bolt length, they just put in a shorter firing pin.

[va_connoisseur]

I am using the Monster bolt from the group buy. I am heading to the range with a proper length firing pin and I’ll report back on the results.

[VASCAR2]

The measurement you found for firing pins sounds very plausable, fits with the firing pin protrusion .028”-.036”, or .008”. I guess that explains the various lengths I got on my firing pins. I have a schematic that shows overall length of 3.277” and another with 3.278” with no tolerance specified. Personally I’m not sure of the exact specification other than the minimum and maximum firing pin protrusion which is most important.


I have a feeling you found the problem.

[va_connoisseur]

Put the new firing pin in and went 40 for 40 at the range. Problem solved.

Thanks for all the input. I'm going to pick up a couple of backup firing pins