Smallest size for "the O-Ring Trick"?

A local guy who inherited a Lee Enfield was put in touch with me.  He's done some reading to help himself get up  to speed on the rifle.  He's bought some commercial ammunition and intends to fire it with an O-ring above the rim to help with brass longevity.

From what he told me, his rifle has a tight enough chamber that whatever O-rings he bought are too thick in cross-section so that he can't turn the bolt down to complete chambering the rounds with whatever size of O-ring he's attempting to use.

I haven't seen either the rifle or the O-rings he's trying to use nor the ammunition.

Anybody who uses O-rings with a relatively tight chamber have a size they use that is small enough that their rifle chambers the rounds once the O-ring is in place?  We do have numerous open stock hardware stores around here that carry lots of O-rings.

You just resize the neck and bump back the shoulder if they get hard to close the bolt on. 

If you barely pass the "Field" gauge, then maybe it will help keep it centred on first firing. But even then I don't think it's worth the effort. Better to correct the headspace!

Technically that's not "Headspace"!

Anything further from the back end of the rim to 0.074" in front of it is "a Generous Chamber"

Oh yes, absolutely.

I actually have 3 setup tool heads for the Dillon RL 550b!

One for each rifle.

Shamu wrote: I actually have 3 setup tool heads for the Dillon RL 550b!

I have had my XL 650 practically since they were first announced while I was an obsessive PPC competitor.  But I have always had a mental block about reloading centerfire rifle in it, other than the high volume 5.56mm loadings.  All the fullbore 5.56 stuff gets processed through the Co-Ax, one at a time.  I did go the extra mile of buying an aftermarket tool head that is set up with set screws to precisely hold the head in place. (I never bothered doing a before and after test to see if it actually improved the grouping ability of the load I was using).

I just can't shake the belief that if I want precision results out of a rifle with reloads, it has to be a precision, one step at a time, handloading process.  I am pretty sure I am wrong about that, but it is a mental block.  Could save myself a lot of time if I was turning out my 22-250 loads for sod poodle trips on the Dillon, rather than one at a time on the Co-Ax. 

Two hundred shots a day over a few days amounts to a lot of ammunition and a lot of time standing in front of a reloading press.  And a Lee Enfield isn't in the same ball park as a quarter MOA custom barrelled varmint rifle.