Gunsmithing Off-Center Primer Strikes???

S

scotharr

Gunny Sergeant
Full Member
Minuteman
Jan 8, 2005
1,772
28
Scottsdale, AZ
#1
Hi All,

Got my new custom rifle back a few weeks ago and wanted to pose this question to those "in-the-know." The rifle is custom with a top-o-the-line action, Krieger barrel, etc. One of the best gunsmiths in the country put it together. It is in a switch barrel configuration: 243WIN & 308WIN.

Primer strikes are consistently and visibly off-center with both barrels: 243 & 308. I measured several primers and estimate they are about .02 off-center on average. Ignition has been reliable thus far. I highly doubt there is a gunsmithing problem: he is highly regarded and I doubt he would have screwed up two different barrels.

I have sent the rifles back to the action maker for inspection(a second rifle but at the same time also has this problem to a lesser extent).

So, here are my questions:

1. How much might this affect accuracy?
2. What are the possible causes of this problem?
3. Should I be concerned? I spent a lot of money to have this rifle built with top-notch components. It seems like I should expect the primer strikes to be centered.

Thanks,
Scooter

PS. please don't ask me which action I have...don't want the discussion to go there.
 
#4
Re: Off-Center Primer Strikes???

This is a new rifle, so the problem has occurred with both new brass and reloads. The primer is the same amount off center with either barrel. Did not note orientation while extracting.
 
#6
Re: Off-Center Primer Strikes???

It sounds unusual with the use of top-notch-components but it is likely that something is not as concentric as it should be to be .020 off. All my customs have very centered pin strikes.

Concentricity on a rifle starts with the bolt bore of the action. Could be that the firing pin hole is off-center with the bolt or the receiver threads are not concentric with the center-line of the action.

Could be that the barrel threads are not concentric with the chamber and are in effect, holding the cartridge off-center with the bolt face and firing pin when the barrel was attached. Maybe you have some brass with off-center primer pockets.

Does it matter? I guess not if it shoots well, but I would not like it if it were mine. Should you expect more from a high dollar build? I would, .020 is a long way off unless there is something that else going on here.

Ever read 300snipers posts on how he trues and chambers. Most good machinist can work at much tighter tolerances than what you are reporting.
 
#7
Re: Off-Center Primer Strikes???

If it's a custom action, seems unlikely that they would have threaded the action off-center. So, my guess would be they drilled the FP hole off and it needs to be bushed.
 
#8
Re: Off-Center Primer Strikes???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Scooter-PIE</div><div class="ubbcode-body">Hi All,

Got my new custom rifle back a few weeks ago and wanted to pose this question to those "in-the-know." The rifle is custom with a top-o-the-line action, Krieger barrel, etc. One of the best gunsmiths in the country put it together. It is in a switch barrel configuration: 243WIN & 308WIN.

Primer strikes are consistently and visibly off-center with both barrels: 243 & 308. I measured several primers and estimate they are about .02 off-center on average. Ignition has been reliable thus far. I highly doubt there is a gunsmithing problem: he is highly regarded and I doubt he would have screwed up two different barrels.

I have sent the rifles back to the action maker for inspection(a second rifle but at the same time also has this problem to a lesser extent).

So, here are my questions:

1. How much might this affect accuracy?
2. What are the possible causes of this problem?
3. Should I be concerned? I spent a lot of money to have this rifle built with top-notch components. It seems like I should expect the primer strikes to be centered.

Thanks,
Scooter

PS. please don't ask me which action I have...don't want the discussion to go there. </div></div>

So, here are my questions:

1. How much might this affect accuracy? <span style="color: #FF0000">If this is a field or tactical rifle you are going to be hard pressed to see it.</span>

2. What are the possible causes of this problem? <span style="color: #CC0000">Could be several including your brass. Put brass in a lathe and true the outside diameter and watch what the primer pocket does. It's not always the rifle. You could have a firing pin hole exactly in the center of the bolt and still have off center pin strikes. There could be stacked tolerances that are affecting it as well.</span>

3. Should I be concerned? I spent a lot of money to have this rifle built with top-notch components. It seems like I should expect the primer strikes to be centered. <span style="color: #CC0000">Maybe but if it shoots well for you then you are worrying about nothing, and if it's your brass there isn't going to be anything you can do to the rifle.</span>
 
#9
Re: Off-Center Primer Strikes???

Your problem is an off center firing pin hole in the face of the bolt. It is unacceptable in any action, especially a custom action, and needs to be corrected. It will affect velocity spreads. In mass produced actions, it's a problem; in custom actions, this is inexcusable, especially with the CNC equipment available today. Perhaps yours is just a one off glitch, which happens to everyone, but I would not accept it. I would ask for a new bolt properly headspaced to your rifle.
 
#10
Re: Off-Center Primer Strikes???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1ZNUF</div><div class="ubbcode-body">Your problem is an off center firing pin hole in the face of the bolt. It is unacceptable in any action, especially a custom action, and needs to be corrected. It will affect velocity spreads. In mass produced actions, it's a problem; in custom actions, this is inexcusable, especially with the CNC equipment available today. Perhaps yours is just a one off glitch, which happens to everyone, but I would not accept it. I would ask for a new bolt properly headspaced to your rifle. </div></div>

Bold statement without seeing the bolt.
 
#11
Re: Off-Center Primer Strikes???

Thanks for the feedback. The rifle has been sent back to the action maker for inspection. Time will tell. In my simple way of looking at it: if all my ARs can strike the primer dead center, I would expect my $4000 bolt action to be able to do it. :)
 
#13
Re: Off-Center Primer Strikes???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1ZNUF</div><div class="ubbcode-body">Your problem is an off center firing pin hole in the face of the bolt. It is unacceptable in any action, especially a custom action, and needs to be corrected. It will affect velocity spreads. In mass produced actions, it's a problem; in custom actions, this is inexcusable, especially with the CNC equipment available today. Perhaps yours is just a one off glitch, which happens to everyone, but I would not accept it. I would ask for a new bolt properly headspaced to your rifle. </div></div>

Bold statement without seeing the bolt. </div></div>

Randy;

Hmm. You may be right, your credentials speak for themselves. In truth, any statement we make without seeing the rig could be considered "bold". My chief concern is this man's rifle problem, so you are likely to know something I/we don't. I went through possible causes I've seen, and the <span style="font-style: italic">most likely </span>cause I could come up with is the firing pin hole. When the cartridge is in battery, the head of the case is centered by the bolt rim. I did <span style="font-style: italic">assume</span> that the bolt face and lugs were reasonably true to the chamber; if the weren't true to the point that the firing pin strike was off center, the round should bind on chambering and the head of the brass would be bent, so I discarded that theory. The only other thing I came up with is brass with off center priming pockets; I've personally never seen it, but from what I'm reading and what you posted, I guess that's possible as well. Like I said before, I have seen a few bolts with off center firing pin holes, especially in certain factory actions and the occasional custom action. This is a problem as the off-axis (to the chamber/bore) firing pin strikes the firing pin at an angle, pushing the loaded round against the wall of the chamber instead of forward to the headspace point, and will result in loss of accuracy and reduction in the quality of fired brass, which will take a memory set at the postition it was fired; if the brass is not indexed back in the chamber the same way, the reloaded round will not shoot to the same point of impact.

So yeah, you're right, a bold but well considered statement intended to help a brutha out, not to show my very limited store of knowledge; what else do you think it might be besides off center firing pin hole or off center primer pockets? I'll be the first to admit I may be missing something, and this man has a gun that needs to be fixed, so I'm all ears. To quote from one of my favorite movies, <span style="font-style: italic">Kung Fu Hustle</span>, "Master, teach me"
laugh.gif
. That's why I'm here on the Hide; to learn what I can and help where I can.

Respect,

Wes

 
#14
Re: Off-Center Primer Strikes???

Wes no worries,

You are correct in that it could very well be a firing pin hole not in the center but without seeing it that's why I didn't commit to saying that was the case, there are other factors to consider. But .02.

That in itself could just simply be stacked tolerances as well, both with the action and or the machine work. There are so many things that for me to say its just one thing would be a stretch.

The OP asks specific questions and I gave honest answers without implying that it had to be a one and only problem.

Just for shits and giggles I put five never fired pieces of brass in my lathe to check them as an example. Out of the five not one had a perfectly centered primer pocket compared to the outside diameter. They were .01 to .04, well within the OP's measurements.

Now take a little here and a little there and the OP could have exactly what he has with the firing pin hole exactly in the center of the bolt.

I will be interested in seeing what the action manufacture says.


 
#15
Re: Off-Center Primer Strikes???

It is Lapua brass and pretty much all the fired cases have the problem..which lead me away from the brass as a problem. But I dunno and will let you know what I learn from the manufacturer and my gunsmith after they are done looking at it.
 
#16
Re: Off-Center Primer Strikes???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body">Just for shits and giggles I put five never fired pieces of brass in my lathe to check them as an example. Out of the five not one had a perfectly centered primer pocket compared to the outside diameter. They were .01 to .04, well within the OP's measurements.
</div></div>

.040" off center? What brand of brass was that?
 
#17
Re: Off-Center Primer Strikes???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 918v</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body">Just for shits and giggles I put five never fired pieces of brass in my lathe to check them as an example. Out of the five not one had a perfectly centered primer pocket compared to the outside diameter. They were .01 to .04, well within the OP's measurements.
</div></div>

.040" off center? What brand of brass was that? </div></div>

LOL. Remington. But you would cut the measurements in half based on the centerline of the brass, so .040 would actually be .020 off the center line.

I found some new Lapua and it was also off, less but still off. .010 to .0235

I didn't have any unfired Winchester to check but I know from doing it in the past it's off as well.

I also checked the brass by zeroing off the rim instead of the body before checking the pocket. It made no difference. No two surfaces were equal, they were all different from each other.

 
#22
Re: Off-Center Primer Strikes???

I have had a recent bolt problem from a high dollar custom action maker also.
surgeonboltface008.jpg

As far as I am concerned there is no excuse for these kind of things when you spend this much money. Quality is one of the things you are paying for yet apparently there is no quality check. We ordered three actions and only one of them had no problems. The other two,well one you can see in the pic and the other had machine swirlys on the outside of the whole action(to deep to aluminum oxide blast off). I didnt get any pics of that one cause it was sent right back and they fixed of course,but it should have never came out of their shop like that.
 
#23
Re: Off-Center Primer Strikes???

Agreed, having a CNC machine does not guarantee quality. I have heard of only two companies that are beyond reproach(at least for now :)): BAT & Stiller. Might be others, but those are the two that keep getting mentioned for top machining tolerances AND good quality control.
 
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