Can anyone help?

I have had a number of single shot rifles in 45-70 45-90 45-120, and enjoy shooting black powder in them. This has always given me good accuracy from 100-1000 metres (target) shooting, however. I have been really struggling with my latest acquisition, an Uberti 38-55 falling block. 1-18 twist with a 26 inch barrel. I have used a 255g bullet for shot range with nitro with no problem - AA 5744 and IMR 4198, so thought I would start long range with BP. For this I bought Lyman 330g BP bullet. Now I know that it will tumble with nitro but out of ten shots with BP, seven will hit the target at 100m side-ways. Any help would be greatly appreciated. Thanks Ed.

Since you have experience with BP cartridge, some of this may be "old hat".

Are the bullets casting properly? No voids, consistent weight? Alloy too hard for BP use? How about mechanical issues in the the chamber, throat and/or bore? Have you slugged the bore to check for tight spots and also get the groove diameter (bullets should be groove diameter plus 0.002"-0.003") Something that bit me in the butt a long time ago was the seating die pin pushing the bullets into the case at an angle - caused keyholes at 25 yds, fixed the pin and problem solved. Are you getting enough velocity to put enough RPM's on the 330gr bullet?

Thanks for your reply, I think you may have a point with the bullet hardness. I cast this at 1-20 not pure lead so will try a softer mix. The size drops out at 377 with a bore of 375. Though the 255g work well at 1-20 maybe the larger bullet just has not the time to setup in the bore properly before it starts to move. Thanks Ed.

Are the bullets casting properly? No voids, consistent weight? Alloy too hard for BP use? How about mechanical issues in the the chamber, throat and/or bore? Have you slugged the bore to check for tight spots and also get the groove diameter (bullets should be groove diameter plus 0.002"-0.003") Something that bit me in the butt a long time ago was the seating die pin pushing the bullets into the case at an angle - caused keyholes at 25 yds, fixed the pin and problem solved. Are you getting enough velocity to put enough RPM's on the 330gr bullet?[/QUOTE]

Just a few thoughts; and forgive me if these seem to simplistic.

1. Just becasue they say it is a 1:18 doesn't mean it really is....mistakes have been made before, and I'd certainly measure that twist rate to be sure.

2. If your 38-55 is a .375" bore, that would be very rare, even in new production guns. It may well be...but I'd measure it to be sure.

3. Had one 38-55 that would never shoot worth sour-snail-snot (but not to the extent of tumbing) uless it had either a fiber wad or a lube-cookie under the bullet.

4. Same rifle as #3, even with a .3785" bore, refused to shoot well until bullets were .380".

(For #3 and #4, i never did find a sadisfactory reason...it just "was"...so rather than spend my days wondering and experimenting to find out, i just fed it what it wanted.)

Thanks, interesting what you say about the bore, will double check. Ed.
1. Just becasue they say it is a 1:18 doesn't mean it really is....mistakes have been made before, and I'd certainly measure that twist rate to be sure.

2. If your 38-55 is a .375" bore, that would be very rare, even in new production guns. It may well be...but I'd measure it to be sure.

3. Had one 38-55 that would never shoot worth sour-snail-snot (but not to the extent of tumbing) uless it had either a fiber wad or a lube-cookie under the bullet.

4. Same rifle as #3, even with a .3785" bore, refused to shoot well until bullets were .380".

(For #3 and #4, i never did find a sadisfactory reason...it just "was"...so rather than spend my days wondering and experimenting to find out, i just fed it what it wanted.)[/QUOTE]

Drop down to 3f.

Can anyone help?

I have had a number of single shot rifles in 45-70 45-90 45-120, and enjoy shooting black powder in them. This has always given me good accuracy from 100-1000 metres (target) shooting, however. I have been really struggling with my latest acquisition, an Uberti 38-55 falling block. 1-18 twist with a 26 inch barrel. I have used a 255g bullet for shot range with nitro with no problem - AA 5744 and IMR 4198, so thought I would start long range with BP. For this I bought Lyman 330g BP bullet. Now I know that it will tumble with nitro but out of ten shots with BP, seven will hit the target at 100m side-ways. Any help would be greatly appreciated. Thanks Ed.
I currently shoot a uberti 38/55 had no luck with it untill i leadlapped the bore (had a tight spot). i put a stopper at the muzzle for a tapered bore. found it shoots best with a paperpatched lyman 255g sized to 380 over 40g 3f &4g of whatever is loaded in 30/06 mg rounds with a lube cookie between. it sounds like you need to increase your velocity with the 330g proj. bore seat the proj. and load up your case. i,ve had (measured) 65g of 2f chinese cracker powder using a swizzlestick with just enough room for the lube cookie. and thats in a standard win.38/55 case. hang in there and best of luck.

Can anyone help?

I have had a number of single shot rifles in 45-70 45-90 45-120, and enjoy shooting black powder in them. This has always given me good accuracy from 100-1000 metres (target) shooting, however. I have been really struggling with my latest acquisition, an Uberti 38-55 falling block. 1-18 twist with a 26 inch barrel. I have used a 255g bullet for shot range with nitro with no problem - AA 5744 and IMR 4198, so thought I would start long range with BP. For this I bought Lyman 330g BP bullet. Now I know that it will tumble with nitro but out of ten shots with BP, seven will hit the target at 100m side-ways. Any help would be greatly appreciated. Thanks Ed.

A 1 in 18 inch twist should stabilize a bullet of approx. 1 !/16 to 1 1/8 inches long depending on velocity according to the Greenhill Formula for rifle twist. My 260 grain cast lead bullets are approx. 1 1/16" so a 330 grain bullet must be quite a bit longer and may not stabilize in a 1/18 twist. Try the numbers yourself and see what you come up with.

Link to calculator: http://kwk.us/twist.html


The classic Greenhill equation is

T' = 150 / L'

where the twist and the bullet length are in calibers. Removing bullet diameter from twist and length gives the equation often found:

T = 150 * D^2 / L

The Greenhill equation includes no term for muzzle velocity, and several sources suggest replacing the 150 with 180 for muzzle velocities over 2800 fps. Increasing muzzle velocity increases bullet spin, and spin provides the stability. An article in the 11/2001 Single Shot Exchange cites an article by Les Bowman in the 1962 Gun Digest offering an equation which includes muzzle velocity (in fps):

T = 3.5 * V^0.5 * D^2 / L

At 2800 fps, this equation is equivalent to using 185 in the Greenhill equation, and at 1840 fps, this equation is the same as Greenhill's.

I agree with SS1884, sounds like you are not getting your bullets stabilized. A lot of shooters using 38 and 40 caliber rifles are using 1-12" or 1-14" twist barrels for longer, heavier bullets. Emery