Black powder paper patch bullet alloy?

[littlejack]

I made a mould about three weeks ago, for a bullet to be paper patched and shoot in a 45-70 with black powder. The bullets looks purt near identical to the ones that Hubertus has on his (boolit fairy) thread. I'm having problems with posting my photos.
These bullets are .441 at the top shoulder and .443 at the base. I can adjust the weight by shimming the sliding nose portion of the mould either up or down. I patched with .0025 onion skin to a diameter of .451 to .452. My bore diameter is .451.
At the range a couple of weeks ago, I shot some bullets weighing 475 grains with a 20-1 alloy, and a charge of 70 grains of Goex ctg. I got a group of 3.25" at 100 yards.
QUESTION: Does the bullets need to be cast of pure lead for black powder loads to obturate or is 20-1 soft enough?
The patching that came off at firing, did not look as though it had engraved the rifling and to the groove diameter completely. The rifling marks looked fairly light.
Jack

[montana_charlie]

20-1 is soft enough. Some guys shooting patched-to-groove are using 16-1 because they shoot a bullet which needs a little harder alloy.

How sure are you that your mix is accurate? Do you use 'certified' stuff...or scrap metal?
CM

[littlejack]

Cm:
20-1 is 9.5 pounds of lead and 1 pound of 50/50 solder.
I use 9 pounds of pure lead flashing and 1 pound of 40 tin/60 lead solder.
Jack

[powderburnerr]

actually that light of a bullet would do better softer, it would bump up faster and seal better than a harder one... Whenever I start having problems with a cartrige I always soften up and start again... .dean

[1874Sharps]

I think Powderburnerr is right about his suggestion of softening the alloy. If you go with pure lead it will help the booolit to obturate and fill the grooves of the bore, which does not appear to be happening at present for you. If you use a grease cookie (such as 1/8" of SPG lube between two card wads under the boolit base) it may help to temporarily seal the boolit to the bore/grooves and let the pressure build up a little more and bump up the boolit.

[montana_charlie]

Cm:
20-1 is 9.5 pounds of lead and 1 pound of 50/50 solder.
I use 9 pounds of pure lead flashing and 1 pound of 40 tin/60 lead solder.
Your mixture is so close to 20-1, the difference isn't measureable. And, your metals are probably dependable...even if they are 'scrounged'.

The real value of a lead/tin alloy like 20-1 is the castability. The slight increase in hardness provided by the tin is of no real importance when a charge of BP lights up. When that happens behind any soft alloy bullet, it is going to bump up as far as it can. Your 475 grainer is heavier that some others used in the 45/70, so I am certain it is heavy enough to obturate as it should.

When expressing your concern, you said, "The patching that came off at firing, did not look as though it had engraved the rifling and to the groove diameter completely. The rifling marks looked fairly light."

Did you find both layers of the patch?
The outer layer should have left thin shreds in the grass. Sometimes you have to look hard to find them.
If the paper is pretty thick, or unusually tough, the inner wrap may not get cut by the lands.

I suppose it's also possible that the edges of your lands aren't sharp enough to cut paper.

Anyway, perhaps the pieces you are looking at are only inner wraps...maybe?

CM

[littlejack]

Thanks for the replies fellas. I did use a grease wad behind the bullet. It was sandwiched between two milk carton wads.
CM, The patching material looked to be the outer wrap. Now that you mention it, there was not any of the thin shreads, just pieces tore ragidly by the blast It sounds as though I should either hone out the mould to get a little bigger diameter to start, or patch the bullet with a little thicker paper. The paper was definately not cut by the rifling.
CM, good thought.
When I make the diameter bigger, I will not be able to start the bullet into the bore and/or the rifling. Is this the norm? Do I just patch the bullet to fit the bore and then bump into the rifling?
Jack

[powderburnerr]

charlie, if you shoot a patch that doesnt cut through both layers you will find a 1/2 patch on the ground....
20-1 with a bore sizetapered bullet is a different story.it is not enough resistance to seal properly .....the 16-1 ratio that some use in their rifles are being shot at 1350 with long cases... the 70 doesnt give that power . now a groove dia . bullet may6 be a different story.... Dean

[Lead pot]

Here this will give you an idea what a PP bullet will bump up to using black powder and 1/16 lead tin alloy.
The bullets are .441 diameter unpatched.

http://i22.photobucket.com/albums/b302/940Leadpot/IMG_0223.jpg

Kurt