38-55 patched bullet diameter

Greetings,
I have 38-55 with .365 bore and .375 groove diameter. I have .365 bullets patched with .15 paper. Total bullet diameter with the patch is .380. Will this be to tight for this bore? Thanks for help.

Regards,
JeffL

With that deep of grooves you may have a dickens of a time getting that rifle to shoot patched. With the finished diameter you have getting them to chamber without chewing up a bunch of the case capacity is likely to be a problem.
I would suggest a bullet no more than .360 diameter.

If those .380 diameter bullets fit your fire formed cases you need some thicker brass! With lead bullets no matter what diameter bullet you put in the chamber it will be case inside diameter when the light comes on. You can minimize that some with really hard alloy, maybe, but with any commonly used alloy and black powder your bullets will bump up to fill all available space when the powder is detonated.

As Don said, with a groove diameter or slightly over groove diameter bullet (+.001 to .002") you'll have to seat most of the bullet shank in the case and give up a good amount of powder capacity. How much will depend on the length, weight and/or design of the bullet. With a cartridge like the .38-55 you are a bit limited already.

If you want to shoot groove diameter PP a better situation would be cases that were .376-.377 ID after fire forming and bullets that are a slip fit into those cases. If your rifle has some freebore that would allow for seating the groove diameter bullets out more and allow for more powder.

I'm not sure but you seem to be saying that the paper you are using when wrapped around the bullets twice adds .015", .365+.015=.380? That would mean you are using paper that is nearly .004" thick. That's pretty thick for paper patching, .0012 to .0022 being more commonly used.

With thicker walled cases and paper closer to .0025 to .003" thick you might have a better chance of success. That thickness of paper would get you to a .375 to .377 patched bullet diameter. Then if that was a slip fit in your fire formed cases you'd only have to deal with the limited powder space under the bullets.

There are a number of diameters to get all lined up to have the best situation using paper patch bullets, but the bullet fit to the brass and chamber of your rifle is key to accuracy. That starts with a full understanding of how paper patch bullets work best and a chamber cast of your rifle and then having a bullet and paper that give the best fit possible to YOUR rifle.

The boolits from the Accurate mould I bought I size to 0.358” and patch with two wraps of 0.0015” tracing paper for use in my .38-55 with the 0.375” groove diameter. They push through the bore easily with the paper marked ( but not compressed or torn) by the rifling lands.

I wrote the experiments up in this section somewhere; shouldn’t be too hard to find.

Bent Rod - do you mean 0.358" that's very small.

Ascast,

What we have here is the difference between bore diameter and groove diameter paper patch bullets. Both can work very well, but again diameter sizes are very important to understand.

A bore diameter PPB is patched to sit up in the bore on top of the lands and are usually seated fairly shallowly in the case. Most of my bore diameter PPB are only .090 or less in the case, the rest of the shank of the bullet is sitting snugly in the bore of the rifle. This offers perfect alignment of the bullet with the bore and grooves. When the powder is sparked the force of the explosion bumps the bullet up before it even starts to move much at all so that it fills the grooves.

A groove diameter PPB is patched to or slightly over the diameter of the grooves and can not be pushed up into the bore. It must therefore be seated in the case far enough to allow the cartridge to chamber.

A 3rd type of PPB is the 2-diameter and it has both a groove diameter base band and a bore diameter forward section that are both wrapped in paper. This type offers both a good fit in unsized cases and a long patched section that is snug in the bore for good alignment.

This is mostly in regards to target shooting. Hunting loads using paper patch bullets are a totally different animal and have different requirements to allow for follow up shots without having to clean the barrel between shots as is required with the first 3 types above.

Bent is talking about bore diameter PPB in his post.

I ordered my mould to cast at 0.364” diameter. I could use the slugs as-cast with two wraps of tracing paper in my antique rifles with ~0.380” groove diameters, or with one wrap of paper (the Chase patch method) in the reline job with the 0.375” groove diameter. In order to use it with two wraps in the latter, I size it down to 0.358” in a homemade push-through die.

As DT (as well as other sources, like Elmer Keith) mentioned, paper-patched boolits of the sporting type are an upsettage proposition. Over half of the black powder combustion products are solids; less than half are gases. At the instant of firing, you have an aerosol of tiny solid particles traveling at the velocity of the expanding gas. This hits the base of the boolit like a hammer, and slugs or rivets it up to groove diameter before it has a chance to move. What we see as billowing clouds of white smoke ahead of the muzzle or gritty fouling in the bore is a very violent process in the chamber and barrel. But very useful, in this case.

If the boolit temper isn’t right, it can fail to fully do this, or will do it a few milliseconds late, or will mash the boolit nose to one side or the other, causing the results on targets that discouraged the BPCR shooting authorities of 25 years ago to give up on them as hopeless, and stick to grease groove boolits for their recommendations.

A lot of those barriers have fallen now, as the technology has been rediscovered and applied. If you’re going to get into this paper patch stuff, background research is definitely needed, unless you have a magazine full of powder and primers to expend doing it all yourself. The back pages of this forum, the appropriate threads on the Shiloh forum, and the threads on the Historic Shooting Forum are primary reference sources for the aspiring paper patcher. Fire up your printer and start copying those discussions, using the results to set up your own experiments. Soon, you’ll be telling us how it’s done. :mrgreen:

Thanks everyone for your assistance.

Best Regards,
JeffL