Firing Pins, Clearance, & Small Rifle Primer

[Phil3]

A well known custom gun builder told me in no uncertain terms that if I attempted to build a 6.5 x 47 on a Howa action, I would have cratered and pierced primer problems. From what I understood, this is due to the Howa having a large diameter firing pin, a loose pin clearance, impacting a small rifle primer (SRP). If that is true, then I would expect a factory 223 or 5.56 (SRP) with a fat firing pin and loose pin/hole clearance to have cratered and/or pierced primers, but from what I see, they don't. How can that be? Maybe because a 6.5 x 47 is higher pressure than the 223?

I have an AR-15 chambered in 223, and it has never cratered or pierced or primer. The pin impacts on the primer tend to wander a bit over the primer, and are not always dead center, so thinking the pin/hole clearance is not tight. Primers used are Remington 7-1/2s.

Thanks for any clarifications.

Phil

 

[Coyotefurharvester]

What was the context of the conversation, up selling some gunsmithing work?

 

[boltfluter]

A well known custom gun builder told me in no uncertain terms that if I attempted to build a 6.5 x 47 on a Howa action, I would have cratered and pierced primer problems. From what I understood, this is due to the Howa having a large diameter firing pin, a loose pin clearance, impacting a small rifle primer (SRP). If that is true, then I would expect a factory 223 or 5.56 (SRP) with a fat firing pin and loose pin/hole clearance to have cratered and/or pierced primers, but from what I see, they don't. How can that be? Maybe because a 6.5 x 47 is higher pressure than the 223?

I have an AR-15 chambered in 223, and it has never cratered or pierced or primer. The pin impacts on the primer tend to wander a bit over the primer, and are not always dead center, so thinking the pin/hole clearance is not tight. Primers used are Remington 7-1/2s.

Thanks for any clarifications.

Phil

Someone needs to tell my Remington bolts, with loosy goosey firing pin fit, that I should be piercing primers in my 6 Dashers. But they don't. Maybe time to find a new Smith. To date, I have not been asked to bush a Howa bolt firing hole. Just sayin. Lol
Paul

 

[swd]

You won’t know until you try it and the fix is easy enough to have Boltfluter above or a few other gunsmith’s bush it if it does need it.

 

[spudgun]

It is well known that a larger dia hole can cause the firing pin to wiggle and cause craters in the primer. I had a Savage 12, 6.5 CM that was cratering the primers.

I had 2 solutions send the bolt off the get it bushed or go to a harder primer.

Went to CCI #41 (military secs).
The problem was greatly reduced.

Now my Savage Axis is doing the same thing.

 

[hoz53]

Someone needs to tell my Remington bolts, with loosy goosey firing pin fit, that I should be piercing primers in my 6 Dashers. But they don't. Maybe time to find a new Smith. To date, I have not been asked to bush a Howa bolt firing hole. Just sayin. Lol
Paul

hi paul—. i have pierced one in the gun im talking about in other post. that must bee one out of about 500. the bolt is a ptg. dont know if the hole will eventually erode and erode the FP or what. i do know ive had a number of 6brs with factory pin and none of them ever pierced. also above gun is shooting so good i hate to take it out of svc 4 even a day.

 

[gunsandgunsmithing]

IME, Howas use a lot of fp spring pressure but they do have a bit of clearance. I believe both matter to cratering but it's not just one or the other. I'd say spring pressure is a bigger factor and pin diameter, than clearance. Not 100% but just to make my point is all...imagine the brass in the primer being a liquid for a minute. The pin strikes it, drives the case barely(hopefully) forward and then the case rebounds against the bolt face/fp driving the fp rearward with some force and inertia. So, if the firing pin bounces out of the hole, or nearly so, you have a stretched, thinned and weakened area of brass around the pin that is free to flow, to some degree. The bigger tip displaces and stretches a larger area of the brass, right? Comes a point where it can intrude into an area of clearance around the pin. Remember, it's thin, weakened and somewhat fluid at this point. Bottom line, a larger pin is the culprit, most likely but it all combines to create the issue of craters. Pressure matters a good bit but should not be considered an indicator of too much pressure. Just trying to draw a mental image of what's going on here. A smaller pin tip displaces and weakens less area/material. A weak spring can back completely out of the hole. That's an almost certainly cratered primer or even blanked. Notice I didn't say "pierced"? The pin won't pierce a primer unless the primer is far weakened beyond the other conditions and is just unlikely to be a first sign.

Hope this helps in a small way. There's a fair amount of confusion about the real cause of craters and blanked primers. Just hope this draws enough mental image of the main factors to let people know what to look for first.

 

[Alex Wheeler]

Weird primer strikes

6 Dasher. New Alpha brass, CCI400 primers. (can't find any 450's) 31.3 Varget, Berger 105 Hybrids. 2nd time this has happened. Today, the first 3 rounds had a heavy primer strike, but all normal after that. No pressure signs & load is accurate at 300yds ( less than 1/2 moa) The case on the...

forum.accurateshooter.com

 

[D-4297]

I would like to confirm what @guns&gunsmithing said by my own experience . I built a custom Mosin-Nagant with the original 1943 Action , and a 30" Kreiger 1-10 , 5r . Rifle shot very good , and I was a happy camper , till I started getting cratered and blown out primers .
Sent the Bolt to Grimstod , whom I had met on a Mosin site some years ago , and not only did he put a new Bushing in the Bolt , He turned down , and reshaped the tip of the F/P . Excellent work by Grim , and haven't had a single primer issue since , and that was about 4,000 rounds back .
The key is reducing the diameter of the F/P so there isn't as much material being moved in the primer .
Lest I forget ; and for those who don't know , A Mosin take Large Primer Brass , and that would amplify the issue .

 

[Phil3]

What was the context of the conversation, up selling some gunsmithing work?

Was corresponding with a custom gunsmith firm about a Howa action working with a 6.5 x 47 and building a rifle. In the e-mail thread, I asked the following (among other things).

"{...Does the Howa need to have the firing pin bushed? If so, what is the cost for that..."?

The part of the reply that pertained to the question above was as follows.

"...Yes it will if you plan on using small rifle primer brass. They have the .075" firing pin not the .062" so you will pierce primers if you reload using small rifle primer brass. We do not offer a guided firing pin service, and we do not know anyone that does...".

Given this response, it seemed like building a 6.5 x 47 on a Howa action was a non-starter, but I was not 100% convinced, hence my question here. I still wonder why I seldom hear of cratered or pierced primers on 223 or 5.56 brass, which uses small rifle primers. Maybe it does happen and I just don't hear about it. It just seems weird to me cratered and pierced small rifle primers can be a problem on .0.473" bolt faces (i.e. 6.5 x 47), but seemingly not a problem on 0.384: bolt faces (i.e. 223/5.56). I must be missing something here...

 

[Eric Leonard]

I put a 6.5x47 barrel on a Rem 700 and the first shot pierced the primer and turned a Jewell trigger inside out. That was when you could send the trigger in and have it fixed for 60$$, now days you would be bad news.

Greg Tannel fixed the bolt and Jewell fixed the trigger and all was well

 

[KMart]

Was corresponding with a custom gunsmith firm about a Howa action working with a 6.5 x 47 and building a rifle. In the e-mail thread, I asked the following (among other things).

"{...Does the Howa need to have the firing pin bushed? If so, what is the cost for that..."?

The part of the reply that pertained to the question above was as follows.

"...Yes it will if you plan on using small rifle primer brass. They have the .075" firing pin not the .062" so you will pierce primers if you reload using small rifle primer brass. We do not offer a guided firing pin service, and we do not know anyone that does...".

Given this response, it seemed like building a 6.5 x 47 on a Howa action was a non-starter, but I was not 100% convinced, hence my question here. I still wonder why I seldom hear of cratered or pierced primers on 223 or 5.56 brass, which uses small rifle primers. Maybe it does happen and I just don't hear about it. It just seems weird to me cratered and pierced small rifle primers can be a problem on .0.473" bolt faces (i.e. 6.5 x 47), but seemingly not a problem on 0.384: bolt faces (i.e. 223/5.56). I must be missing something here...

If you think that you would be ok on the primer cratering with a LARGE primer, 6.5x47L brass can easily be made out of 6XC LRP brass. I made 50 of them just for a test and they work fine. A little extra work but they work fine. Neck up, set shoulder back, trim length and fireform. May take neck turning depending on which brass you use,