Correct firing pin length

[yat3b35]

What is the max and min. firing pin length from the bolt face to the tip of the pin on a Remington 700 ? I had my bolt face opened up from .223 to .308 and have been piercing primers. I think maybe the pin may be to long.

Thanks in advance , John

 

[blawton]

The proper protrusion should be .0625" anywhere in between .06 and .07 usually works just fine. So if you bolt face was .135" deep then you should get right around .07 from outer face to pin.

 

[yat3b35]

Thank you sir , I'm well in that John

 

[blawton]

Have you checked the clearance that the firing pin has? The hole may need bushed and re drilled. That will case blanking fast if there is to much room and allows the pressure a place to go. Good luck!

Also you can buy spring kits from brownells and try lighter springs untill you get FTF's and go back up one or 2 weights. But thats not likely the problem.

 

[Laurie]

John,

you don't say what cartridge you're using. If it's one of the .308W (0.374" dia) case-head designs such as the BRs or 6.5X47 Lapau that use a Small Rifle size primer, you get primer cratering at quite modest pressures.

This is partly about firing pin fit in the bolt-face as others have suggested, but also firing pin tip diameter. I have this problem with two rifles - one a Remy 700 where I did the same as you having what was originally a .223 rebuilt with the bigger bolt face and a Sako extractor to become 6mmBR, the other an FN SPR (Winchester 70WSM receiver but with a .308W controlled feed bolt) rebarrelled to 6.5X47L. The Remy I can live with, the FN / Winchester is REALLY bad and I'm losing 200 fps or more due to primer blanking at what should be mild loads. (Primers pierce while still rounded - no flattening at all.)

Answers?

1. Use the toughest / thickest primers going, ie SRMs. CCI-450 and CCI-BR4 are the best. Maybe PMC / Wolf Russian made SRM (still to try them in my rifle). Rem 71/2BR and Fed 205M are better than standard primers but crater quicker than the CCIs.

2. Run at lower loads than you'll see quoted in the 6BR section in the main website and eslewhere.

3. Get a stiffer bolt mainspring from Brownells - a technically inelegant solution, but it will help a bit as it helps the firing pin resist being pushed back by the primer as it extrudes into the bolt face.

4. Get the bolt bushed and the firing pin turned down. Greg Tannell does this at a very reasonable price with a few days turnaround. He's perfected an efficient way of achiveing this job and has the jigs all set up to do it quickly.

http://www.gretanrifles.com/prices.asp

$64 i/c shipping - I wish we could get this done as easily / cheaply on this isde of the Atlantic.

The bushing / turn-down method is the complete and best answer.

Laurie,
York, England

 

[blawton]

Good suggestion. A .069" firing pin will help out with whats going on here as well.

 

[yat3b35]

I had all these problems while using CCI450 Mag primers in a 6BR. The reciever was being used first as a 223 ,then a 6ppc. Neither of those blew any primers. The ppc was running at uper pressure window and not a single blown primer , even using Fed. br primers.
I just got my bolt back from Gre-Tan . He bushed the firing pin hole and turned the pin to fit a .062' and if the weather holds , I'm going to the range today and see what happens.
The reason for my question is the fact the pin looks like it is a bit longer that before , but after measuring ,it falls into speck. I just didn't want to fire it without knowing the correct length. Greg at Gre-Tan is quite hard to get on the phone or I would have called him with my question. Thank you both for your replies , I'll post the results when I retun from the range , it's supposed to hit 40 de. here today. HEAT WAVE John

 

[yat3b35]

Just returned home from the range. A balmy 38 deg. Virgen Lapua brass , 30.5 gr. Varget , Berger 105 vld .010 jam. no primer flow at all,beautiful fireing pin strike,no blown primers. Most likely have to back off a half grain of powder or so for warmer days .