Recommended distance between bolt lug face and breech face? (Making barrel swap video and want to verify my numbers)

[TonyBen]

So I'm finally getting around to making a barrel swap video and I recently disassembled my Savage 12FV (308 Win) that I got last year on Black Friday. It headspaced at 1.631" (I have a 10-piece headspace gauge set). With a 1.631" gauge, and taking protrusion measurements off the gauge and depth measurements off the factory bolt, I got a factory gap of around 0.015" from bolt lug face to breech face.

I swapped in a Criterion featherweight barrel and using a GO gauge (1.630") the gap with the factory bolt head increased to 0.025".

PTG sent me a bolt when they sent me the action wrench to demo and it has a deeper bolt face of 0.130". My protrusion with the Criterion barrel is 0.131". With a PTG bolt, that gap is now 0.001". That's sort of okay for me since I'll be chambering it to 1.632" anyways, as I don't like using SAAMI minimum, and the gap will be 0.003".

What's the recommended max/min bolt lug face to breech face distance? I was going to recommend 0.005" to 0.010" for a general purpose rifle.

Tony.

[Robinhood]

Your numbers are right on. The PTG bolt head is too deep. I just measured 3 PTG BH's and 5 Savage BH's for you.

The PTG's BH's measured: SPC -.115", 308-.116", WSM .115".

The Savage BH's Measured: . 223 -.114", .115, 308-.111", .115", .115"

Most smiths shoot for .125"-130" protrusion.

[mnbogboy2]

Total agreement with Robin hood here. I try for .125-.130 when cutting a chamber. I've found several missed dimensions on a PTG bolt head including the counter bore at .130. For my hunting rifles I don't want a pine needle to cost me a big buck. Using Savage bolt heads and shooting for .010 clearance allows more case head encapsulated by barrel steel, without the super tight conditions that may fail/jam in the field.
If I remember right when I screwed a different tube on that PTG headed action I could not headspace it like I wanted and had to remove some material on the breech face.
My answer .008-.015 with Savage bolt heads. .124 -.130 go gauge protrusion.
IMHO

[Robinhood]

The other issue I have to fix is the depth of the ejector hole going to the .140" ball It needs to be drilled deeper about a 1/16th".

[sharpshooter]

The other issue I have to fix is the depth of the ejector hole going to the .140" ball It needs to be drilled deeper about a 1/16th".


??? could you explain that?

[TonyBen]

Thanks for the info! What about protrusion for magnums?

Tony.

[Robinhood]

??? could you explain that?

You got me. I went to edit it and I had timed out. I meant the extractor hole. With every PT&G bolt I have added the .140" ball to the detent spring hole was not deep enough. The correct drill bit for the spring diameter and a slight deepening of the hole, the ball can be depressed enough to allow the extractor to slide over. I don't know if it is all of them or just a some of them.

[TonyBen]

I did some digging and it looks like 0.125" is the target for both standard and belted magnum-type case-head protrusion. I'll include this in my video.

Thanks again for all the help.

Tony.