New 260 AI build

[Shortround]

First "build" in 40 years so it's kinda like starting over again.

Savage 111 left hand .338 Win Mag donor action.
PTG bolt head w/.473" face
Criterion Savage bull barrel (1"muzzle) 28", PTG reamer.

Lapua .260 brass measures 1.767" average base to neck/shoulder junction.

Lapua .260 brass after "slight crush fit" measures 1.7625" - 1.7630" at neck/shoulder junction after setting headspace and torquing barrel nut to 50 ft lbs.

Does this sound about right?

Dimensional data could be off slightly, but the same tools were used on all measurements so I think the data should be good as far as differences are concerned.

All input is appreciated.


Shortround out

 

[Jay Christopherson]

What did you use to set the headspace?

 

[Shortround]

Used a standard GO gauge as a NO GO. Then turned the barrel in 3/8" in rotation. Hope that makes sense. Rotating the barrel .067" = .001" headspace adjustment.

Loaded one round to fire form. Measured. Adjusted to match chamber dimensions, fired another round.

I measured from the base to the neck/shoulder junction. PTG prints show 1.768" and I'm at 1.765" now. New Lapua brass is running 1.776", which is still a tad long. Will readjust a hair and shoot another round. Want .004" crush on the 260 case.

With the camming action on a bolt gun, you can very easily have too much crush on the brass.

Hope it didn't confuse you.


Shortround out

 

[JBeagle]

Not sure why you want to crush fit. Headspace on the go gauge tight and call it good. This way you have a solid reference point should you ever need to remove the barrel.

Is there a reason for the crush fit?

 

[Jay Christopherson]

Used a standard GO gauge as a NO GO. Then turned the barrel in 3/8" in rotation. Hope that makes sense. Rotating the barrel .067" = .001" headspace adjustment.

Loaded one round to fire form. Measured. Adjusted to match chamber dimensions, fired another round.

I measured from the base to the neck/shoulder junction. PTG prints show 1.768" and I'm at 1.765" now. New Lapua brass is running 1.776", which is still a tad long. Will readjust a hair and shoot another round. Want .004" crush on the 260 case.

With the camming action on a bolt gun, you can very easily have too much crush on the brass.

Hope it didn't confuse you.


Shortround out

Thanks, I think I can follow...

IMO, your headspacing methodology is a pretty shady. Your 'Go' gauge is a minimum length measurement for your chamber. You shouldn't be turning in past that. Below that and you start running into the issues you are experiencing.

I would also be very curious to know why you are working to a crush fit with your brass...

 

[Erik Cortina]

The difference between go and no go is .005", stay in between the two and you'll be fine. There is no need to modify it in any way.

 

[Shortround]

Had a temporary head up the hiney syndrome. Backed off, had a cold brewski, and chilled out for a bit.

Discovered I was about 10 thou off. Went back and looked at a couple of articles I had and did a Homer Simpson dope slap. Readjusted and loaded up a round, popped it off. All looks good. Works like it's supposed to.

Sometimes if you read too much into something simple, you get screwy results. I'm glad I'm anal enough to back off, pull up resources or call someone that is more knowledgeable, and re attack the issue, whatever it is.

Thanks for the info. It's greatly appreciated.

Shortround out