Yes, I know that it's a stupid combo.

But here's my problem. I have a 338 Federal that is a re-bore. It fouls horribly! A bore scope indicates it's pretty rough with tool marks. I've tried Osso and JB's to maybe smooth it up but it still has a long ways to go.

So I got some 'Tubbs' bullets and want to run 10 of those thru it to see if that helps. And they turned out to be 300 grain. Hence, I'm looking for a powder load that will fit, get them down the tube, and not tear up the primer pockets.

If got several powders on hand that might work; Trail Boss, 1680, Re7, TAC, H335, CFE 223, 3031.

Suggestions?

Your probly going to have to use them single shot and you don't want to seat them too deep to fit the magazine I suspect..Have no experiance with the 338 Fed..

Did some guess-and-by-golly 8th grade math and went with a 20% lower load of H335 than the 225 grain starter load. And dropped it one more grain to be 'more safer'. This was 30 grains H335

Yes indeed, the 300 grain bullet took up a lot of space in the ~little case.

First shot was taken with a lot of safety including a 10' lanyard on the trigger. No problem. Fired the next 9 shots at the 300 yard gong and with lots of kentucky windage/elevation I managed to hit it a couple times.

Now we will see if these Tubbs 'Final Finish' barrel lapping bullets smooth this rebore barrel up.

I guess it gives lots of bearing surface for the compound to work, with that long a bullet.
Keep us informed, I hope it helps.

Not the same cartridge obviously; I use 11 grains of trail boss with a 245 grain lead bullet in a 308 win. Trail Boss is pretty forgiving, a little more is better than too little and make sure the bullet clears the bore before the next shot.

Or you can just fire about 200 or so rounds at p dogs or rocks, that polishes a bore as a rule, unless its really rough in which I would have it rebored by someone other than the last guy to a 9,3 or 375 for a couple of hundred bucks. I use Hill country reboring and refleing..Polishing, lapping or shooting is a process of wear as you wear the barrel out..