Faster powders with cast vs jacketed

[Charlie98]

In the bit of cast bullet rifle cartridge handloading I've done I've noticed that, typically, you will see faster powders favored for cast bullets over slower powders, and vice versa for jacketed bullets. I understand most cast bullets are loaded to lower velocities than jacketed, but that's not always the case. Is there a generic reason for this?

 

[Hondo 60]

A slower burning powder will usually give a faster velocity.
I know, it seems backward.

Cast bullets usually don't do so well with higher velocity - they will generally leave leading.

But having said all that, notice I said "usually & generally".
It's not always the case.
When the bullet to barrel "fit" is right, you get some pretty impressive velocities.

This is where you'll hear - slug your barrel.
This'll tell you exactly what diameter bullet will work best.

Excellent question! Please stay safe.

 

[Charlie98]

My main point of reference is with both the .348WCF and the .308. I drive 200grn cast gas checked bullets just as fast as factory (~2200fps) in the .348, and I have driven 170grn gas checked bullets about as fast in my Savage 99 in .308. Granted, the .308 isn't pushing factory velocity, but you get the idea.

Loading cast bullets almost exclusively in my lever-actions and single-shot, I've completely abandoned slower powders... the slowest powder I use is IMR3031 in the .348, and it's likely I could drop it in favor of IMR4198 if I didn't need it for other cartridges.

 

[243winxb]

The 30 WCF (30-30 Win. ) works well with IMR 4895. Lead GC or Jacketed. At a working pressure of 42,000 PSI, this is not cast bullet friendly, even with a GC.

The reason it works is, lead needs less powder to get near the same velocity, as jacketed. . Less powder= less pressure = less heat produced in a shorter time span.

Temparature of burning powders 3400 to 4700 F degrees.

On primer firing, about 1/3 of the powder is burnt. The rest is pushed against the bullets base, as it continues burning. . The powder in direct contact with the bullets base is last to burn. Less heat transfer.

Plain base cast bullet bases may have imprints of some powder kernels on the base, when recovered.

 

[forrest r]

Actually it's the other way around, you want slower burning powders for cast bullets in rifles. The slower powders have more of a push/softer short start pressure then faster burning powders. With cast bullets that's where the games won or lost.

The front/nose of the bullet enters the rifling and starts to twist. The back of the bullet is still leaving the case and the pressure of the load is bumping the back of the bullet up in diameter to the size of the ball throat. The back of bullet seals the ball throat grabbing the sides of the bbl while the front is still twisting in the lands. Rotational torque is exerted on the bullet from this and bad things can and will happen.

I've done a lot shooting/testing with cast bullets in several different 308w bbl's/rifles. bl-c2, varget, 4064, 4895, 4320,4350,rl16, rl19, 380, leverevolution, 414, tac all work well in the 308w.

My go-to powder in the 308w is h335 for a general all around plinking powder.

Get a # of rl19 and cast up some 180gr or heavier bullets for the 308w and work loads up. You'll get impressive velocities/accuracy with that slow burning powder and heavy bullets in the 308w.

 

[Charlie98]

Actually it's the other way around, you want slower burning powders for cast bullets in rifles. The slower powders have more of a push/softer short start pressure then faster burning powders. With cast bullets that's where the games won or lost.

That statement is the complete antithesis of what I have learned about loading cast in rifle cartrdges... straightwall or bottleneck... and differs from my limited amount of testing. Further, faster powders obturate the base of the bullet better than a slow powder, important for bullets without gas checks. Granted, I'm looking at cast bullets for long distance steel shooting, where velocity is not as paramount, not hunting... where velocity is a major part of the equation. I'm not doubting the results you got with your testing, mind you, it's just contrary to what I have read and learned in the past few years, hence the reason for the OP.

In .308WIN, specifically... for me... the slowest powder I use is IMR4064, and that in a 24" Savage shooting SMK's, not cast. It's IMR4198 or IMR3031 for everything else .309", jacketed or cast.

I have used slower powders in the .45-70... IMR's 3031, 4895, 4064... and they about beat me to death. Yes, the velocities were up there, for sure, but they had to send a search party out for my retinas. If I was hunting... sure. Same-same with the .348WCF, I initially started with H4831, the powder I used with jacketed bullets. The results were not good.