8mm pp in .338 questions

[wmitty]

Would the 8 mm Maximum boolet at .325" as cast diameter be a total failure in a .338 Win. barrel (.3305" lands / .3382" grooves) if paper patched to groove diameter plus .001" ? This is Oldfeller's design for worn throated Mausers and it weighs in at 244 grains unchecked. Figured I'd ask before proceeding with rebarreling a .375 to .338 to use as a cast boolet rifle.

[bcp477]

"Total failure" is a relative term - depends on how you define it. There is no absolute reason why what you propose wouldn't work, especially if several factors are favorable.

First, what is the rate of rifling of the .338 you intend to use ? I should think that you'd need around a 1 in 10 twist to stabilize such a bullet. I'm not familiar with the .338...perhaps a twist rate that tight is standard, I don't know.

Another factor would be the throat characteristics of the .338 rifle - and whether the patched bullet will fit well. About 0.001" over groove dia. is generally the correct dimension - provided the throat isn't too oversize.

As you probably know already, you'll have to choose your patch paper, in part, for thickness - so the final patched diameter will be right. Two wraps is typical - so that the layers on the bullet will be even all round. 0.3382 + 0.001 = 0.3392". 0.3392" - 0.325" = 0.0142. 0.0142 / 4 = 0.00355". That is the paper thickness you'll likely need. The paper I use, for instance, is just about 0.0026 thick - so you'll need paper a good deal thicker than that. So, you've got to find the right paper.

Of course, the third factor is the load itself.

On all of these issues, I think you'll need to find out by experimentation. In fact, I know it. My feeling is that the bullet, at 0.325", will be just a bit small. Something like 0.328" would be better - but I could be wrong. As well, there might well be no such bullet diameter as that. In any case, some experimentation will be necessary to really determine if it will work.

[pdawg_shooter]

What is the bore diameter? I have had my best luck sizing the cast bullet to .001/.0015 over bore diameter before patching.

[wmitty]

Bore is .3305" as near as I can measure so I am a minimum of .0055" undersize. I don't know if the mould can be beagled that much; haven't had a chance to try it.

I do appreciate the help!

[Nrut]

Your best bet is to get a cheap .338 LEE mold and a .332" push thru sizer from Buckshot..
Then wrap your bullet with a paper thickness that will give you a patched dia. that will fit snugly in your throat or your fired unsized brass...

You should use a expander that is enough smaller than your patched bullet so once seated the bullet can't move..
You don't want your expander so small that sizes down the bullet under the patch..
Paper will compress at least up to .005" before it sizes down the bullet it covers..
It doesn't take much paper compression to keep the bullet in a case neck..

Set your seating die to only take out enough case mouth flare to chamber your round..
Start with "starting to med." jacketed loads using the slowest powder listed and work up...
If you start out with low vel. loads you may need to go to a tougher paper when you go to high vel. loads..

That's the basics..

[geargnasher]

I agree with Nrut. The boolit you have might go through the gun just fine if patched to a bit larger than groove, but I doubt it will group if you have the same experiences that I have with smokeless-powder loads and boolits that are smaller than bore diameter.

Gear

[303Guy]

Wouldn't the 375 be a highly suitable paper patch candidate? If you go ahead with it, what would you be doing with the old barrel?

[wmitty]

Actually I have two .375's, one Win 70 and one Rem 700. The m 70 is a proven performer with ggcbs and I plan to try the pp boolets in it and the m 700 also, which has the wierd tapered throat which I'm concerned is going to cause problems (throat tapers from .390" at case mount to .377" groove dia. over a distance of .200" or so. If I do change the barrel out for the .338, I'll have the .375 set back and rechambered to clean up the throat.

[Nobade]

Actually I have two .375's, one Win 70 and one Rem 700. The m 70 is a proven performer with ggcbs and I plan to try the pp boolets in it and the m 700 also, which has the wierd tapered throat which I'm concerned is going to cause problems (throat tapers from .390" at case mount to .377" groove dia. over a distance of .200" or so. If I do change the barrel out for the .338, I'll have the .375 set back and rechambered to clean up the throat.

That weird tapered throat works awesome with PP boolits! Just measure some fired cases to find out what size will be a nice snug slip fit, and that is your size. That way you don't need any reloading dies at all - just decap, recap and you are good to go. And that tapered throat allows you to seat your boolit so it engraves nicely when the bolt is closed. Then figure out what kind of powder is safe with a compressed load (I use a lot of IMR7383 and Win 760 in my 375), drop that back 1CC or so to make room for filler, add powder and filler on top, hand seat boolit, and go shoot.

Most 375 reamers have about the same neck diameter, .404" or so. That allows a .378" boolit to be seated. I either size mine to .372" and patch with onionskin to .378" or use .366" 9.3mm boolits, patch with notebook paper or the green bar paper and size to .378" and load. Both work fine and give quite good accuracy, like 5 shots you can cover with a quarter at 100 yards - and 250 grains at 2600 fps is nothing to sneeze at power wise.

[nanuk]

Nobade: what is the bore diameter on your .375's?

[Nobade]

nobade: What is the bore diameter on your .375's?

.366".

[wmitty]

Nobade, thanks for the heads up on the throat on the .375 barrel! I will certainly give the Remington barrel a chance with the pp boolets. I shot the Winchester today ( broken extractor and all) and was surprised at the accuracy I was able to obtain with my first attempt at paper patching.