.30-'06 Spitball???

[Greg Langelius *]

Just spitballing here, I have a screwy question.

I know folks advise against rechambering a .308 barrel to .30-'06 because the shoulder diameter of the .308 falls outside the case wall diameter dimension at the .308's shoulder height above the base.

However, I wonder what would occur if it were to be done anyway, and .30-'06 brass was fireformed to fit the two-step shouldered chamber? Reaming a .30-'06 die with a .308 reamer might complete the process, allowing reloading.

Is there any specific technical argument that invalidates this approach?

If it were to be feasible, this would permits an 'Improved'(?) case capacity for the .30-'06. Obviously, I'd call it the .30-'06 Spitball Improved. (.300 Spitball..., Improved...)

Weird, yes; but could this be feasible?

Another approach might be to create a reamer that continues the sidewall angle to the height of the .30-'06's existing shoulder.

Or...; established an angle at the height of the .308's shoulder that subtended the .308's diameter difference to intersect with the .30-'06's original shoulder.

The advantage (if it's an advantage) would be to allow a .308 barrel to be rechambered, also allowing .30-'06 brass to be fireformed to create the new chambering.

This might also work with the .270 and/or .280.

Honestly, I wouldn't be especially surprised to find out that it's already been tried.
'
Greg

 

[Sheldon N]

I would think the double shouldered case would create problems trying to resize it properly. Not only difficult to get the headspace correct on your sizing die so that it matches the chamber perfectly, also problematic in terms of differential brass hardness if you ever annealed the neck (body would not anneal the same) and differential brass springback due to thicker walls at the body than the shoulder. You'd actually need a smaller reamer to modify the sizing die, if you used the chamber reamer it wouldn't size the case at all after considering springback.

Probably better to either have the gunsmith set the chamber back a bit when reaming to 30-06 to avoid the problem all together, or perhaps going to 30-06 AI would alleviate the issue since it takes out some of the body taper.

 

[domdoc]

Are you getting enough sleep, Greg? Yeah, what Sheldon N says.

 

[gunsnjeeps]

I agree the extra shoulder could cause a problem. I'd go with blowing it out to a straighter wall. No worse of an idea than my .223-06 to use 77-90 grain bullets.

 

[FishDr]

Interesting idea. Prob not gonna work unless set back or remove body taper. How do we contemplate such things …

 

[diverdon]

Completly beyond my ability to knowledgeably comment on, but that has never stoped me before. Why not start with a .30-06 barrel then run in a .308 reemer then you can use the same reemer to touch the chamber and the die.