Sizing for a fatter boolit

[Big Dipper]

I think this will work but I have never tried it. I am casting for a 375 H&H Winchester model 70. I am using COW plus 2% tin in two 375449 molds. They are dropping boolits 269 grains with gas check and .376in dia. my bore is .376. I am using a LAM with a .375 die and the boolits size to .376. I am loading them with 30 grains of 4759 going 1830fps. Accuracy is so so, 5 shot groups -3 inches usually 3 shots together about 1 inch and 2 fliers. I would like to try a fatter boolit. I have two sizing dies at .375 I want to ream one of them to .378 and size my boolits larger. Will this work? I think the LAM should force the boolit into the .378 die and I'll have fat boolits and I be happy. Or do I need to start with a bigger mold and size down to .378? I have no experience here and no one to ask

[Tatume]

It sounds like you're asking if the lubri-sizer will bump up your bullets to a larger diameter. It won't.
You must start with bullets equal to or greater than the final size in order to size to the desired dimension.

[Big Dipper]

Thank you Tatume. That is exactly what I was trying to ask. I feel I have gone as far as I can with what I have. Is it time to get bigger custom molds and dies or are there other options, different components, different alloy. My results so far are not bad but I am not satisfied. Maybe I will change the Leupold 1.5 X 5 to a higher power target scope maybe part of it is my shooting or poor eyesight.

[DougGuy]

Afaik, different alloys drop different sizes from the same mold. And yes you do need to start larger to size down. Have you done a pound cast to determine throat diameter in your barrel? This would be the limiting factor in what you can size to. But it sounds like a .377" or .378" could improve groups. Sounds like.. There are other considerations that have a bigger effect on groups. Are you using fire formed brass? This usually makes a huge improvement, are you seating out to .020" or .030" shy of the rifling?

[Echo]

Or maybe lap out one mold cavity to throw .377 boolits. See stickies on lapping cavities. And try them unsized, loobed with Recluse loob. If they chamber, shoot 'em...

[Yodogsandman]

At one time, I had the Lee mold and I think it cast at .378" with COWW.

Another quick option would be to powder coat your boolits to increase the boolits size and then resize to the diameter you want.

[Tatume]

The Leupold 1.5-5x scope is an excellent instrument, and is the only variable power scope I will buy these days. It offers enough magnification to shoot sub MOA groups at 100 yards. If it was mine I wouldn't even think about removing that scope.

Try the mold that Yodogsandman suggests. It can be had for $22. It will cast a few grains lighter than 269 perhaps (maybe not), but when you go on your elephant and buffalo hunt you can buy some store bought bullets :-). For everything else the Lee bullet is more than sufficient.

DougGuy is right also. If you add some antimony to your alloy it will enlarge bullets. The effect is small, and may or may not be enough.

https://www.midwayusa.com/product/476137/lee-2-cavity-bullet-mold-379-250-rf-375-winchester-38-55-wcf-379-diameter-250-grain-flat-nose

[JSnover]

I'd try Echo and DougGuy's advice first.
Lapping is easy, adding Antimoney is even easier and you're only looking for a .002" increase.
Best thing about either method is if you like your mold, you can keep your mold. Even after lapping it is still useable for 'smaller' .375 H&H barrels with your current .376" die.

[Tatume]

Before lapping the mold you might try "beagling" it. Instructions can be found in the stickies, it's easy to do, and it is a revocable decision (no permanent modification). You can easily get 0.002-0.003", and any out-of-roundness will be corrected in the sizing process.

[Tatume]

Try the mold that Yodogsandman suggests. It can be had for $22. It will cast a few grains lighter than 269 perhaps (maybe not), but when you go on your elephant and buffalo hunt you can buy some store bought bullets :-). For everything else the Lee bullet is more than sufficient.

BTW, the Lee mold is plain based and good for practice loads in the vicinity of 1400 fps.

[runfiverun]

my 375449 makes 379 boolits without any trouble.
and I don't use straight ww alloy.

yeah,, that helps you zero amount.
but.
your gonna learn a valuable skill when you own/buy newer lyman molds.
it's called lapping.
you can open the mold about .002 fairly easily, then open the sizing mold to correspond and your in business.
be mindful of the gas check shank.

[44man]

I found most fliers are from brass so you might give it a test. Watch every hit with a spotting scope and pull out any case that shows a flier. Put them in the plinking pile.
Good suggestions if you want a larger boolit and is always worth a try.