changing bolt head ??

[cooperman223]

Hi lads, just a quick question about bolt heads,

i know that savage bolt heads are interchangable but how close are they machined ?

if i were to change a bolt head then how will this affect my head space ? ???

thanks
john.

[groupshooter22]

There not that close. Whenever you change a bolt head you ALWAYS have to reset headspace.

[cooperman223]

Thanks for the reply, the reason i am asking is that i am just building a new 6x47 lapua rifle (small primer, small flash hole)

i have used a savage single shot target action RB/LP and a 1-8 twist true-flight barrel,

my barrel is being run in with a light load to start with but i am getting craterd primers, (cci450m)

at first i thought its excessive pressure but i now think it is primer flow as the primers are not flat,

could it be that the hole where the firing pin exits the bolt face is too large allowing a small gap for the primer to flow back into ??

i have also tried cci400 and fedGM, the fed primer craters the least
thanks.

[BillPa]

could it be that the hole where the firing pin exits the bolt face is too large allowing a small gap for the primer to flow back into ??



First, if you look closely at the firing pin tip you'll see it ground to a taper from the body of the pin to the tip. On a primer, which actually stops the pin forward travel regardless static protrusion setting, the bottom of the taper allows a gap between the pin and pin hole in the bolt face with the typical impact depth on a primer in the .020" range, the taper is generally longer than the typical primer impact depth allowing the primer cup material to flow into the gap. Re-contouring the tip to a .020" radius will help keep the full diameter of the pin in the hole reducing or totally eliminating cratering unless it being caused by other factors, too hot loading and etc.

Second, typically the bolt faces are "dished" to some extent from the polishing process, the larger sizes being the worst and if you look very closely may see may be a slight chamfer on the edge of the pin hole allowing or adding to the gap between the pin and pin hole A light facing cut across the bolt face eliminates both the dish and chamfer issues.

The combination of re-contouring the pin tip and squaring the bolt face should eliminate the cratering.

Bill

[cooperman223]

Thanks Bill, that is a very informative reply,

just the answer i was looking for, that confirms my thoughts,

skimming the bolt face is not an option as the barrel has been fitted/headspaced by a gunsmith

without the nut, i know it is a mild load that i have been firing, so its not a pressure issue,

i think i might have to just live with it,

will it cause any problems ??

http://i170.photobucket.com/albums/u256/stirkhouse/P1011851.jpg

http://i170.photobucket.com/albums/u256/stirkhouse/P1011860.jpg

thanks again,

[BillPa]

Thanks Bill, that is a very informative reply,

just the answer i was looking for, that confirms my thoughts,

skimming the bolt face is not an option as the barrel has been fitted/headspaced by a gunsmith

without the nut, i know it is a mild load that i have been firing, so its not a pressure issue,

i think i might have to just live with it,

will it cause any problems ??




Well, this is my opinion and my opinion only. Cratering is a visual annoyance more than anything else. Blanking or perforating is a problem! Looking at your picture its more than I care to see and would fix it. You might want to re-contour the pin tip. That may or may not reduce it somewhat. Adjust the pin protrusion to .030-.035 then see what happens.

The sure cure is bushing the pin hole and re-contouring the tip with affecting you barrel setup. I'm sure Fred can do it, but Greg Tannel (Gre-Tan) may have a quicker turn around time. I haven't had him do any Savages, but I assume he has or will. Give him a call. (http://www.gretanrifles.com/)

Bill

[Don - LongRangeSupply]

you can have the firing pin hole bushed without changing the headspace.

That should get rid of the problem.

[cooperman223]

Thanks lads, i will have to see how i get on with it for the time being,

Bill, thank you for the link and advice but i am in the UK so i will have to sort things over here,

i have made a phone call to a chap who could drill out the bolt face and fit a bush to the correct size,

without affecting my head space and re-profile the pin while he has the rifle.
thanks again
john

[Joe O]

I'm having a primer flow problem.The hole in the bolt is a snug fit with a #48 drill shank .0728,and I believe is ok.I would reconture the fireing pin,and I will,before I would have the bolt face bushed.Can't post pic

[BillPa]

Take a look at this thread. I posted some pictures showing the difference between the pin tips, one factory and one re-contoured. Its not a big deal to correct, about 30 seconds with a belt sander, a file. or even sandpaper then readjust the protrusion if necessary to ..030"-.035".

http://savageshooters.com/SavageForum/index.php/topic,27382.0.html

Bill

[Three44s]

There are two different firing pin diameters with Savage rifles.

You may want to check that your firing pin may be the newer smaller diameter and see if your bolt head that you changed to is not the larger hole size.

Otherwise, it may well be cheaper to just buy a new head from Midway ..... twenty bucks or so.

Three 44s

[BillPa]

There are two different firing pin diameters with Savage rifles.



The difference in diameters ( .145 and .095) is only the portion forward the adjustment nut to the step as shown here.
http://i50.tinypic.com/2l456a.jpg
,
The section forward the step are the same diameter on both size pins.

Bill