Anyone have a hint why I get so poor accuracy with the bullet above in my Remington ABG in 458 WinMag?? I load it with NORMA 200 powder to 2450fps. I only see about 8-10MOA at 100 yards.

With Hornady 500Gr RN i can easily get 1,5-2 MOA so the rifle is quite accurate.

Too high velocity pherhaps?? (Tried to load it down to 1850fps but with poor result as well).
It seems like the HORNADY gas check don't have a tight press fit.

Any good ideas or should I trash the mould?

Arvid, a few thoughts on what can cause poor accuracy with cast bullets.

First, did you clean all jacketed fouling from the bore first? Cast bullets generally prefer to be shot from a bore that is free from jacketed bullet fouling.

What is the dia of the bullets after you sized them? Cast bullets should ideall be sized to fit your rifles throat, and generally .001-.002" over bore dia, so .459-.460" in dia.

How hard were the bullets, ie what alloy did you cast them from? For high velocity rifle use, which is over 2000 fps for cast bullets, the bullet needs to be hard, or it will get torn up by the force of the rifling.

What type of lube did you use? Not all bullet lubes are equal, and some simply won't put up with high velocities.

What is your rifles barrel twist? Cast bullets are friendlier to slower twists, and if your 458 is a custom with a fast twist, you'll have to keep your velocities down.

Lastly, 2540 fps is very fast for a cast bullet, cast bullets can be accurately driven that fast if everything is perfect, ie bullet hardness, lube, sizing and proper barrel twist. That said, I try and keep my velocities in the 2000 fps range, 2200 max, as it is much easier to make a cast bullet shoot when driven at those speeds.

What Paul H said, plus some 458 throats are very long. You can get away with a long jump to the rifling at low velocities, but as velocities and pressures go up, it becomes more important for the nose of the bullet to touch the rifling and more important for the base of the bullet to form a snug gas seal.

I get great accuracy with a RCBS 500gr GC bullet (actually casts at 525grs). I have driven this bullet to 1900fps with great accuracy, but prefer to shoot it at 1500fps. At the lower velocity, I get 1.5" groups at 100yds.

But the 500gr bullets are long enough to reach across the looong thoat. They have lots of bearing surface to deal with the steep rifling (1:14 in most .458's . . . . 1:20 in most 45-70's). They hold lots of lube.

AND my 500gr bullet casts at .459 or .460, which is important since the throat is not only long, but also wide.

I have tried several 300, 350, 375, and 405 grain profiles.

I can't get the 300gr Lyman to shoot at all. The 350gr Lyman will do well IF I shoot it at .464 diameter. This is a pain, since the dies don't work well for this diameter, and the shell barely chambers.

The 375gr GC will shoot very well if I keep velocity below 1700fps. The same for the 405gr GC.

There are 4-5 factors that work against cast bullets in a .458WM. The 500+ grain bullets solve some of these. The lighter bullets make things harder.

Hello again
Nice to see some serious reply from you guys.

Here is some more info about my stuff.
The sizer is .458 dia, the alloy is primarily wheel weights but I add some tin to increase the hardness. (This alloy I use in 45ACP and 357 Mag handgun loads with very good accuracy result) They are quite hard but I don't have any "Brinell hardness" data. The weight of the complete bullet is 326 grain including the gas check and the JAVELINA grease.
The twist I haven't been able to find yet, the rifle is a Remington "African Big Game", from the custom shop. (I beleive it is 1:14 but am not sure)

Maybe we can iron this out together!

Regards/Arvid

Arvid,

Thanks for the info. I would suggest running your pot and mold hot, and dropping the bullets into a 5 gallor er ah 20 liter bucket of cold water to quench them. That will nearly double the hardness of an air cooled bullet, and should be good to upwards of 2400 fps.

Sounds like your barrel twist shouldn't be a problem. I would consider a .459" sizer.

I shoot a 500 gr Lyman cast from ww's and waterquenched from my 458 Lott, and they produce accuracy on par with jacketed bullets. I haven't tried lighter bullets, but don't see why they wouldn't work as well, so long as you keep the speed down. The real key is finding a suitable powder to get accuracy with the lighter bullets at ~2000-2200 fps.

I'd also check your barrel for leading, I'd imagine you might find a fair bit from pushing those bullets over 2500 fps!

If possible, seat the bullet out until the nose engraves the rifling lightly.

0.458" is pretty small for a cast bullet. Chances are rifle throat is way oversize and the bullet is wobbling around and getting gas cut in the throat. Try shooting a few without any sizing at all.

Javelina NRA type lube is a better than average lube and fine for modest velocities, but I have had better luck with Rooster HVR at high velocities.

I suspect you would find it easier to get good accuracy with a long heavy bullet, maybe 500 - 600 grains, maybe sized 0.460" - 0.462".

A 1:14 twist is about right for a 700 grain bullet. The fast twist is not helping matters, but I think the main problem is the fit in the throat.

Hello again boys
Your idea of getting a little more open sizer i will try. 459 or 460 or even as you propose unsized cast bullets.
I actually quench the bullets in a bucket of cold water, that as an old habit and I can tell you they are hard.
Yesterday I made some where I reduced the load down to 2200fps nominally according to QUICKLOAD. We see what happen.

Any comments about my observation that I have a feeling for that the gas check have a little poor fit (not as hard press fit as my 357Mag gas checks) on the bullet. My theory is that if the gas check have too loose fit it could possibly separate from the bullet after leaving the barrel as the combustion pressure is dropping and not pushing the gas check on to the tail of the bullet so to speak. When it separates from the bullet it might cause a instability to the flight path?

Regards/Arvid

quote:

Originally posted by Arvid:
My theory is that if the gas check have too loose fit it could possibly separate from the bullet after leaving the barrel

If the gas check is coming off in flight then you should find at least a few of them on the ground 20 - 50 meters in front of the firing line. Also, if the gas checks are coming off in flight, they will occasionally hit the chronograph. If you want to be sure, try setting a large paper or cardboard target at about 10 meters. If the check is staying on, there should be only one hole for each shot. If the check is coming off, it should hit the target and create an "extra" hole.

The Hornady 45 check is really a 0.452" pistol check that is too small to crimp on tightly in a 0.458"+ die, however, it usually works satisfactorily despite the poor crimp. Even if the check is loose, the shank may obturate and make the fit tighter. Also, the check will be crimped on tighter when it is engraved by the rifling.

When a cast bullet fails, it is usually because of a poor gas seal or because the bullet tilts to one side in the barrel and becomes unbalanced.

Please let us know what happens.

The gas check wouldn't be my guess, but it wouldn't hurt to look at it. I have a .358" 200 gr gc bullet that has a very loose gas check fit, but it has produced steller accuracy in 357 mag, 357 max, 357 Herret pistols, and 35 whelen AI and 350 Rigby rifles.

My primary thought is you were simply pushing the bullets too fast. The secondary thought is that your rifle has a generous throat and hence will be finicky with cast bullets, especially the smaller ones.

I would doubt the GC being your problem also.

My most accurate loads with the 500gr RCBS bullet do not have a tight GC. I crimp the GC's in a .459 sizer, and you can still turn the GC by hand after sizing.

But, they seat fine in the case and shoot into 1.5" @ 100yds.

Hej Again
Your ideas sound logic, I will se if can rig up a sheet 30-40feet away and look for "extra holes" from the gc. I will try my new loads att 2200fps.
I keep you updatet about my findings.
Regards/Arvid