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.
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.
The Dunning-Kruger effect is alive and well.
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
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".
The Dunning-Kruger effect is alive and well.
Originally Posted by Robinhood
??? could you explain that?
"As long as there's lead in the air....there's still hope.."
Thanks for the info! What about protrusion for magnums?
Tony.
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.
The Dunning-Kruger effect is alive and well.
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.
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