Faster powders and barrel leading

[wobbly34b]

Are faster burning powders like Bulls-eye more conducive to barrel leading than say something like HS-6?

Bob

 

[Chuck 100 yd]

Actually I find the reverse to be true. Faster powders seem to cause the bullet to obturate better,or at least faster, sealing up the bore preventing blow by.
Assuming loads are kept to reasonable levels of course. Extremes will often cause leading no matter what you do.

 

[Clovishound]

Well, one of the things I did to reduce leading in 9mm was to switch to Universal from Titegroup. It helped IMO.

 

[Rick Courtright]

Hi,

There are many factors involved with barrel leading, including bullet size, alloy hardness, powder "speed" (as related to chamber pressure) AND barrel condition.

There's an old rule of thumb to figure if you're generating ENOUGH pressure to obturate lead bullets well enough: multiply your lead alloy's hardness (BHN or Brinnell Hardness Number) by 1422 (often rounded to 1400 for convenience/ease of memory.) The resulting pressure is a rough minimum required to bump up the bullets adequately.

For example, we have a .38 Spl bullet with a BHN of 10, which multiplied by 1422 gives us 14220. So we'd want a load that generates at least 14,000 psi of pressure for that bullet to behave well. That same size and weight bullet, only cast with a different alloy at a BHN of 18, times 1422, gives us a min number of 25,596. So in a .357 Mag loaded to at least 25,500 psi, it should work ok, but likely wouldn't do so well loaded at .38 Spl pressures.

'Tis just a rule of thumb, but helpful for "eyeballing" numbers in your reloading recipes...

Rick C

 

[mikld]

I asked a similar question over at Castboolits.com; "Fast or slow powder best for cast?", and had about 15 or so follow up posts/answers. There was no evidence that a fast powder is any better than a slower powder for handguns shooting lead bullets. Good bullet fit using either a slow (like W296) or a fast powder (W321) is the key...

 

[Chuck 100 yd]

In the question of fast or slow powders, a look at data suggested by majors like Lyman,Speer etc. will show what powders are suitable for cast bullet loads.
They have tested all of them and just don't include powders in their data base that do not work well. Lyman notes what powders work best.

 

[jsh]

As mentioned size is king.
I find a lot alloys are actually to hard. I won't mention names, but some of the top bulk go to bullets I have had a lot of issues with in the past.
I think some store bought bullets are so hard that they skid on the rifling rather than grabbing. The same thing can be said when to soft. There are store bought out there that have found that happy medium.
Slow vs fast powders.
I shoot the majority of everything I shoot with cast any more. I have some of balls that there is very little info for cast. I study a fair bit, then go with a jacketed start load.
There is a pile of rifle data out there using 2400. I got in a bind and had a lot of ball powder but not enough 2400 on hand to make me happy, so the 2400 was saved back for handgun use.
I have a lot of H335. Went with a start load of that in a 30-30 rifle. Accuracy and speed were over the top of any other load I had used in this rifle.
Fast forward a few years. I did the same thing with several other calibers of rifles with exceptional results.
I use a lot of slow burning pistol powders in my revolvers. I like a pretty full case, so that a double charge is not going to happen. I won't go into details but some of my better cast loads are right there with jacketed loads.
IMHO leading occurs because of one of these things, size, alloy or lube. There are bore issues of course to throw in there. But if your really serious about shooting cast, you would find a bore issue before you started.
I expect no less from a CB than I would from a jacketed bullet, out to 200ish.