Paper patching SWC's

[Marlin Junky]

Can SWC boolits be paper patched so that they'll shoot accurately from a rifle?

MJ

[oso]

Maybe. I've gotten better groups at 100 yds with the Lee C358-158-SWC in 357 Mag through my Marlin '94 with a tracing paper patch over the nose band and no gas check than with a gas check and without the paper.

[axman]

My first patching attempts were .451" 335grn keiths for a nef handi-rifle if 45-70.
They worked pretty good and are a good place to start patching before you get a mould.
:castmine:

[Marlin Junky]

Where should the leading edge of the patch be with respect to the leading edge of the forward driving band? Just behind it? Even with it? Just ahead of it so it laps over the forward driving band? I'm planning to size a 260 grain SWC down to just over bore diameter patch it with two wraps of onion skin lube it and shoot it from a long throated .35 Whelen.

MJ

[Black Jaque Janaviac]

Just ahead of it so it laps over the forward driving band?

I'd start here. The idea is to get paper between the lead and the bore.

[Marlin Junky]

Just ahead of it so it laps over the forward driving band?

I'd start here. The idea is to get paper between the lead and the bore.

Black Jaque,

Thanks for the reply. So in this semi-wadcutter example, I would have no bore ridding surface which I guess sounds fine. So what diameter do I patch the bullet up to? To groove diameter which is about .357" or throat diameter throat diameter which is about .360"?

MJ

[Black Jaque Janaviac]

I would try both.

My guess would be that the throat sized, .360", patch-jobs would work better. I think problems can arise when a bullet is bumped "up" to the throat diameter. I seem to remember some guy found that if his brass length was not sufficient the patch would cut right along the juncture between chamber and throat.

Assuming you're using a reasonably soft alloy swaging the bullet from .360 into the bore will not cause excessive pressure. Also paper jackets are vulnerable to blow-by. Any thing you can do to keep the blow-by in check is a plus.

[Marlin Junky]

Blackjack,

So what paper do I need to create a .360" to .361" patched bullet from a .351" piece of lead? I understand the patch shrinks somewhat when it dries, so 4 layers of .0025" paper probably won't "patch-up" the boolit .010".

MJ

[45 2.1]

Blackjack,

So what paper do I need to create a .360" to .361" patched bullet from a .351" piece of lead? I understand the patch shrinks somewhat when it dries, so 4 layers of .0025" paper probably won't "patch-up" the boolit .010".

MJ

Basic formula = 2 wraps = 4 layers x dry paper thickness -0.0005" will give you patched diameter (or very close).

[Marlin Junky]

The patch shrinkage will depend on length and paper type.

Mathews says he uses two turns of 16 pound to patch-up a bullet .010" and 9 pound to increase by .008". I can only assume he's talking about 25% cotton paper because he mentions preferring it over 100% cotton it earlier in his book.

Tracing vellum doesn't seem to have a distinct grain so I suppose it doesn't work, does it? Tracing vellum isn't all that cheep but it can be found at art supply stores... but it's only .002" thick.

MJ

[Black Jaque Janaviac]

The tracing vellum I use is about 3 mil after shrinkage I get 0.010" added to the diameter (using 2 wraps).


I cannot visually distinguish the grain in my tracing vellum. However it is present and it does make a difference. To find the direction of the grain, I cut two strips from a sheet, I cut each strip 2.5 inches wide. Cut the first strip from the 8.5 inch side first, then the strip from the formerly 11-inch side will also be 8.5 inches long. I suggest marking them because as soon as I get done cutting them and I have two identical looking strips, the phone will ring. By the time I get back to the project I'll forget which strip came from which side.

Anyway, just hold each strip by the end and let them droop down. It will be obvious that one strip is more limp than the other. The limp strip is cut across the grain, and that's the way you want to cut your patches.

I once got the grain mixed up an noticed right away when I patched the boolits. The patches cut with the grain did not stretch and the ends did not meet up after wrapping.

[Black Jaque Janaviac]

Oh, here's a link to the type of vellum I use. I use the 25% rag stuff. I will try a packet of 100% next.

http://www.staedtler-usa.com/vellum_us.Staedtler?ActiveID=24319

[Marlin Junky]

Black Jaque,

Thanks for the reply and the link. I mentioned the paper on the other thread and you can ignore my question there. The tracing vellum we have is only .002" thick so I guess I'll look for the STAEDTLER 16#. I'm wondering if I should try the 100% rag though since I'll be sizing the patched bullet. I still can't imagine the patch loosening up after sizing though.

MJ