Making oversize bullets from a standard mold Updated

without permanently modifying it.

Why?  Because there are a lot of older rifles out there- milsurp in particular- that have other-than-nominal bores.  A friend, for instance, has a WWI-era Enfield that has a .314 bore; the nominal was supposed to be .311", but a lot were made at this size(no, I'm not going into that bit of history).  The bore is in fine condition, but it won't shoot standard .311 bullets worth a damn, so he needs some larger.

Yes, there are people making molds that throw larger-diameter bullets(spendy), or you can order a custom(spendier); if you can find something a bit bigger than you need you can often size it down, but between .311-312 the next step is up around .318 if you can find it; that's a LOT to size a bullet down.  What to do...

Then I ran across this article on the subject, with a simple solution: use aluminum tape on one of the mold blocks

to move them slightly apart, thus getting a slightly larger-diameter bullet.  So, I gave it a try.  It worked, but on my Lee mold it didn't increase the diameter enough.  So I tried putting three more strips on the other block, and that did.

Downsides: this gives the bullet a slightly elliptical shape.  And it makes it easy for some lead to get between the blocks, thus making wings on the bullet

Not on all of them by any stretch, but some.  Most thin enough that they're easy to break or shave off.  Screwed around with this and got a dozen good ones*, opened up some gas checks as in the article, and used a .314 sizer die to size and seat(have access to this, not anything larger in this class).

Yes, the shape caused them to be sized more on two sides.

Right now they're loaded over a standard practice-load charge of 16.0 grains of 2400 powder, waiting for a chance to test-fire them.   If they work decently(sure can't work worse than the .311), I'll cast more.


Update:  It works!
The weather is turning to crap, and I needed some groceries, so extended the trip to include the range so I could try these out.  This rifle, with .311 bullets, didn't shoot groups: it shot patterns of oblong holes.  Now

Four rounds just trying on another target, then this is two 3-shot groups, 30 yards from a so-so rest.  Top group holding on the center, bottom three holding on the '5'.

I'm going to call this a success.





*Didn't want to cast a bunch until I find out if they work