Bullet question

[Mathias]

Hi
I would like to hear your opinion on what bullet that could be sutible for a rifle whit this configuration.
Rate of twist 1:39 (my own meassurement using a ramrod and patch, but i got the same numbers sevrel times so i don't think i'm far off)

Barell length 38.6" (that was easier to meassure :wink: )

Cal .478

This is a old army rifle in wery good condition.
Service load (as far as i have been able to find out) 98.5 gr bp and a compresion bullet 1,158" long nothing about weight

I hawe use a 500 gr bullet whit a hollow base and hawe had a hard time finding a load and consistence. ( i get oval holes if i go under 70gr)
Regards
Mathias

 

[paulvallandigham]

YOu need to size the bullet to within .001" of the bore diameter. The bullet must be cast from soft lead. Keep the powder charge down to 50 grains or so. The "skirts"- that is, the outer edge of the hollow base-- can be very thin, particularly on bullets cast from very old molds.

Too Much powder, or too fast a burning powder will break the skirt off as the bullet is leaving the muzzle, sending the bullet somewhere other than where you want it to go. OR, the bullets can tip, yaw, or begin to tumble, leaving a " keyhole" shape to the hole in your target.

To be able to use heavier powder charges, or faster burning powders, some people will have a machine ship reshape the plug used with the mold to make the hollow base, so that the skirt is thicker, to prevent this problem. This reduces the inside diameter of the hollow base, and increases the weight of the minie ball also.

 

[gmww]

You might want to check out Mountain Molds Cast Bullets.

Mountain Mould Cast bullet online design.

They have an online design program where you pick the size of the bullet and add variables. It gives you the right rate of twist. For kicks I plugged in a weight of 315 grns. and other variables using pure lead and came up with a 1:38" twist. :grin:

A 500 grain bullet according to the program needs a 1:24" twist.

 

[bingo1952]

The reason you are getting oval holes with powder charges below 70 Grains is your bullet is tumbling because of a lack of rotational velocity. 1 turn in 39" is a little too slow for stability with light charges and a bullet of that length. Either use a lighter/shorter bullet or shoot heavier charges so the rotational velocity is higher. Also is this a solid base bullet or a hollow base Minie style bullet?

 

[Mathias]

Hi
Some facts about the bullet i have been using. It is more of a hollowbase then a mine the skirt is .118" thick (3mm) It starts whit thumb preasure downe the barrel
Regards
Mathias

 

[bingo1952]

A skirt of that thickness should not be blowing out even with 100 grain charges. Your light loads may not be providing enough initial pressure to obturate the bullet to the bore and it is simply skiddding across the lands.

 

[longcruise]

At 500 grains, your bullets are too long for your twist rate. Something with a length of about .8" to 1" will probably work better.

I'm sure there are not many molds around for that caliber so it's surely a problem.

Try researching the rifle and the bullets used in it back in the day of the rifle. That should get you going in the right direction.

Mountian molds is a good place to look for a custom mold. They do have a long delivery time though.

 

[paulvallandigham]

Try using a OS card, or OP Wad( thicker) between the powder and the base of the bullet. That will seal all the gas BEHIND the bullet and prevent gas blow by, and gas cutting of the bullet. Sizing the paper patched bullet to bore diameter is essential for best accuracy, AFTER the paper is dried on the bullet.

Also, if you have access to some thick Wool, Felt material, you can use an over sized OP wad cut from wool felt( weatherstipping felt can be used for cutting your own with a punch). In your case, a .50 cal. OP wad in your .45 cal. barrel will work well to protect the base of the bullet. If you lube the felt wad with a good wax/oil lube, it will help soften the BP residue in the barrel, too.

Marmotslayer is right about the length of the bullet for that ROT. The bullet is too heavy, and too long to stabilize. Go for a shorter bullet. Look at Lyman cast bullets for the .45 revolver, in the 240-260 grain ranges. They can be sized down to anything you need to shoot in that gun. Because of the popularity of Cowboy Action Shooting, there are several companies making molds for pistol bullets. There are even some shorter bullets being made for .45 rifles, because of limits imposed on bullet weight to preserve the metal " Bang Plate " targets shot in Cowboy Action Shoots. I shot a 300 grain bullet in my .45-70( .458 diameter) BP cartridge gun. Its only slight longer than 1 inch in length. I certainly would give that bullet a try in your rifles after sizing and PPing it. Its from a Lyman mold, so you can find it in their catalog.

Because the pistol bullets weigh Half what that 500 grain bullet does, the recoil in shooting them will be much less, too.

 

[Dphar]

Hi
I would like to hear your opinion on what bullet that could be sutible for a rifle whit this configuration.
Rate of twist 1:39 (my own meassurement using a ramrod and patch, but i got the same numbers sevrel times so i don't think i'm far off)

Barell length 38.6" (that was easier to meassure :wink: )

Cal .478

This is a old army rifle in wery god condition.
Service load (as far as i have been able to find out) 98.5 gr bp and a compresion bullet 1,158" long nothing about weight

I hawe use a 500 gr bullet whit a hollow base and hawe had a hard time finding a load and consistence. ( i get oval holes if i go under 70gr)
Regards
Mathias

I suspect that you need a bullet very close the the specified length or a little shorter.
A 48" twist would use a bullet about 2 calibers long maximum. So the 1.15 bullet is probably near maximum length in a 39" twist. If the GROOVE is .478. This will be the bullet diameter after firing.
The length of the bullet is the only criteria in stabilization. If you search the internet for "Greenhill formula" you should find a formula determining bullet length for a bore size/twist. But is is generally a little off for small arms so a slightly shorter bullet is recommended. But I suspect the 1.15 is correct. But again design enters in. A bullet with a deep hollow base will stabilize well in a slower twist. A flat base bullet will need a faster twist for the same bullet weight.

Dan

 

[Mathias]

Thanks for all input and tips :grin:
Much appreciated
Mathias

 

[ResearchPress]

What is the rifle you are shooting? You also mention compression bullet rather than the expansive hollow base type bullets. Have you tried sourcing one to original specification?

I am aware Sweden had a carbine with a tige that had 1 in 40 inch twist. This fired a 402 grain solid bullet with a charge of 77 grains.

David

 

[Mathias]

It is a M1860 Wrede and unfortunantly there is not much info about the load it used. What i have been able to find about it so far is through museum and some old books and there they only briefly mension loading prosedure using a compression bullet 29.4mm long and 98.5 gr bp and the vo for that combo was 485 ms (1591 fps) never mentioned the bullet veight . So i have been guessing and not doing too well.

 

[ResearchPress]

I've not been able to find anything about the Wrede. I have a picture (outline drawing) of the bullet used in the carbine above but there's no dimensions.

David