Home Forums Hunting & Shooting Gunsmithing Firing pin not hitting center of primer ??

I have hundreds of spent brass from a 722 Rem that I am considering using as the basis for a custom rifle. In examining the brass, I noticed that the firing pin is not hitting in the center of the primer. Is this something that should be addressed when the action is being "trued" etc? How can you center the firing pin without using a larger diameter pin? Im mostly asking because I have lots of interest but zero experience with the precision machining aspect of gunsmithing.

A reply to a question on off center firing pin strikes on BR.Com. Jackie Schmidt is a good BR shooter from Houston and with his brothers own a huge machine shop that does primarily tug boat type repair work. He does know machining and competition gunsmithing.


jackie schmidt





"I don't tighten up the entire bolt, I just bush the section that engages the rear, which keeps the trigger cocking piece from lifting the bolt too much.

When I first did my old 721 project, I noticed that the firing pin strike was still a tad off center, despite my best truing efforts. I then bushed the rear section to where it only had about .001 clearance, and now the firing pin indention is dead center. It was cocking the bolt that much".

It is a standard problem on a factory Remington and other bolt guns that the rear of the bolt moves upward when the bolt is cocked. It can cause 2 problems-It takes the upper bolt lug away from the receiver and has the firing pin traveling at an angle not perpendicular to the base of the case.
Does all this make a lot of difference? I really don't know. I have wanted to take a factory rifle and make one step at a time and shoot it to see to my satisfaction what each step will do.
Butch

If you examine the primer dents in many firearms you'll find a lot of 'em slightly off-center.. Rifles, shotguns, handguns - it's common for all..

Another thing to consider is if you place an undersized cartridge in an oversized chamber, the cartridge will want to lay on the bottom of the chamber causing an off center hit. Of course if you flip the gun upside down then you have the opposite problem.

Another thing to consider is how the rifle is to be used.

"I then bushed the rear section to where it only had about .001 clearance..."

That's not much clearance for field use with dust and dirt flying around.

While on the subject of firing pins, I have a Rem 700 338Rum with a pin bore in the bolt face that looks as if it were touched with a cutter off center at the factory. Pin bore is .080, pin is .075, and the errant cut is .020+- deep, close as I can measure. Gave me some pressure indicators that didn't show on the other test rifle same load and day. I figured it out OK, but now I'm wondering if I should weld and re-cut, or bush it, or just leave it be?

Any experience with similar findings on Rem bolts?

The loads levels are starting and very slow powders, that's what got my attention with the radical primer indications. Both rifles were chambered with the same reamer and neck sized cases inter-change perfectly.
Rem brass and Over-size primer pockets kinda POd me, Pin gauge says .2125 new from the factory. Other brass is at .2105 to .2110, and stays close to that after use.

Reference the bushing of the bolt play, does Jackie bush the bolt or the rear bridge?

Jackie sleeves the rear of the bolt. Instead of sleeving, I install two inserts at the rear of the bolt body to produce "bumps" which eliminate clearance when the bolt is locked up. I prefer this as the bumps have no effect of fore and aft travel of the bolt; only coming into play when the bolt is turned down. I dovetail the inserts into the bolt body.
Your bolt face can be bushed to correct the firing pin hole. If bushing the bolt face, one can reduce the firing pin diameter to 1/16. The smaller diameter pin eliminates primer blanking but the larger diameter pin is more tolerant of an off-center strike. Blanking is more of a problem with small rifle primers. GD

I see this a lot. Customers mistaking firing pin hole irregularities for cratering. A "shallow", cratered pin strike might concern me a little but for me, a sticky bolt gets my attention every time. As far as what to do, I would say, that as long as you know what it is, I wouldn't worry too much about it. You can correct the problem when you rebarrel.

I used a 7mag as a donor on mine, the problem child was a factory RUM to start with. No centering problems, just the cratering indicator. I considered the .062 pin and bushing,but believe I'll let it be. Lotta work considering the crappy brass life in this caliber. owner doesn't think its a big deal now that he's aware of the cause. Would rather put the $ into a brake.

Thanks

Malm, I agree. I doubt either rifle will see a new tube any time soon, and IF I do It will be a Lapua. Damned RemRum brass any how..

When you employee bushings for any reason when dealing with a bolt, are these bushings "welded" in place or "threaded" in place? I watched a video where silver solder was used. Is silver solder strong enough to use on bolt faces?

Sometime if you have a oversize chamber and the spring loaded plunger in the Rem bolt will push the case to one side in the chamber and make the firing pin strike look off center. You can sometime go to a lighter spring and correct this. I believe if the barrel isn't indicated properly and the chamber cut sightly off center it cause this also. You would be surprised how many rifle have this and still group well. Most of the time you are just worrying for nothing.

I was thinking of just snapping it with a quick spot of filler and re-cutting the face and hole. Not enough heat to worry the lugs.
When I bush 45 slides, they are threaded in. For a bolt gun I think the bushing would have to be larger than the primer size and have a countersunk feature to keep the stress on the threads to a minimum. I've yet to do a bolt, so its just a theory on my part, but I think thats what I would do. Irritates me to have to do this to a factory screw up in the first place.

Silver solder gets the bolt head way too hot for my liking. I prefer a pressed fit using a good retaining compound like LocTite 609. Once it has cured it is there to stay.

I make bolt face bushings with a flange (looks like a top hat) and the bushing is pressed in and retained with LocTite. The bushing is drilled from the front after installation. The bushing has to be long enough to support and guide the front of the firing pin. After installation, the bushing is invisible.
I have one on a Model 70 which has been in place for 15 years. Threading a bushing is a good system when it is possible to thread the bolt. This is not always possible (sometimes they are just too hard) and a press fit works as well. GD