WC Front Band Diameter And It's Effect On Leading

[jonp]

I've posted a thread on the CastBoolits thread about leading and pressure using a WC in my SW 15-4. Another member has been good enough to PM me with much advice. One of the last things that he asked me about was if I had measured the front, narrow band above the crimp groove.

Measure :shock:? No, it did not occur to me. I measured the boolit and that was it. When I measured it last night it turns out that the main body of the boolit is .358-.359 dropped but the front band is .356. The other member suggested that this may be why the 358-145WC was dropped from production.

Would having a smaller front band than the rest of the boolit contribute to leading? This is the first WC I've tried and I may have picked a bad one. If it does contribute to leading doesn't the mold manu's test the boolits from the molds before releasing them for sale?

[DougGuy]

It was made smaller to fit in cylinder throats. You get to about .3575" and above on that front band and it starts only chambering in cylinders with large enough throats to handle it.

Even then designers were seeing the importance of having the front of the boolit going into the throats.

It's doubtful that this fact alone will contribute to leading. Assuming the cylinder throats aren't downsizing your boolits as they are fired, and the forcing cone is decent and the barrel is not choked, i.e. the revolver is dimensionally correct, leading would be caused by a number of other things but front band diameter is likely not one of the causes.

[GP100man]

I agree with DougGuy, remove the cyl. & slug each throat ,bet a couple or more are downsizing the boolit.

If ya need that fixed DougGuy is THE MAN to do it as he recently finished some throats & cones for me.

If ya think the size is the problem load em backwards.

& by the way DougGuy I`ve shot 2 of em kinda hurriedly at my steel plates & accuracy was better(all hits from 25-50 yds) & that little bit of annoying leading at the cone is gone!!

Gonna get em on paper 1 day when time permits.

[Mal Paso]

The narrow front band could be part of a set of conditions allowing high speed gas past the boolit vaporizing some of it.
I had 2 429421 molds like that, one of which I fixed. I'm sure the taper was intentional to make sure the boolit chambered. I think bullet performance was secondary.
I changed too many things to say that was the cause of my leading but I know of 2 cases where a larger boolit solved the problem with no other changes.
I like a wide full size front drive band that is just in the chamber throat where that is possible. In my 629 the throats are too far forward for that. It had .4285 throats that would have caused chambering complaints had the chambers been SAAMI Specification length.

They all seem to fudge a little and I think performance takes a hit.

[texassako]

I can't grasp how a small front band can cause leading when the gas is at the rear. Wouldn't the gas need to get past all the other bands first cutting lead on the way? My main WC, a 35891 with a small .354" first band, doesn't lead. I would go with DougGuy's suggestions before blaming the mold.

[Char-Gar]

I've posted a thread on the CastBoolits thread about leading and pressure using a WC in my SW 15-4. Another member has been good enough to PM me with much advice. One of the last things that he asked me about was if I had measured the front, narrow band above the crimp groove.

Measure :shock:? No, it did not occur to me. I measured the boolit and that was it. When I measured it last night it turns out that the main body of the boolit is .358-.359 dropped but the front band is .356. The other member suggested that this may be why the 358-145WC was dropped from production.

Would having a smaller front band than the rest of the boolit contribute to leading? This is the first WC I've tried and I may have picked a bad one. If it does contribute to leading doesn't the mold manu's test the boolits from the molds before releasing them for sale?

Doug Guy is 100% correct about the reason for the smaller front band. I am also confident that it has nothing to do with any leading you are experiencing. Leading doesn't come from the front of the bullet. Leading occurs because of one or a combination of;

1. Bullet body to small
2. Alloy to hard for the pressure
3. Alloy to soft for the pressure
4. Bad bullet lube
5. Rough forcing cone
6. Tiny micro-burrs in the barrel. (i.e. a rough barrel).

I have a Smith and Wesson K-38 (Model 17) that was made toward the end of production. It would lead no matter what I tried to correct it. I thought about trading if off, but it was one of the most accurate handguns I have ever fired when it wasn't full of lead.

The last thing I tried was polishing the inside of the barrel and that ended the leading. I am so glad I held on to the handgun until I broke the code.

[jonp]

Doug Guy is 100% correct about the reason for the smaller front band. I am also confident that it has nothing to do with any leading you are experiencing. Leading doesn't come from the front of the bullet. Leading occurs because of one or a combination of;

1. Bullet body to small
2. Alloy to hard for the pressure
3. Alloy to soft for the pressure
4. Bad bullet lube
5. Rough forcing cone
6. Tiny micro-burrs in the barrel. (i.e. a rough barrel).

I have a Smith and Wesson K-38 (Model 17) that was made toward the end of production. It would lead no matter what I tried to correct it. I thought about trading if off, but it was one of the most accurate handguns I have ever fired when it wasn't full of lead.

The last thing I tried was polishing the inside of the barrel and that ended the leading. I am so glad I held on to the handgun until I broke the code.

I also don't think the front band is the reason for the leading but this is the first WC mold I've tried and the first where the front band is smaller than the body. I am probably being over cautious with this SW 15-4 but it is so nice I don't want to muck it up. Dougguy's post answers the question pretty darn good and makes sense.

I'm trying #2 in both directions first. Soften the alloy with the same charge and load the 10.5bhn I have cast with a higher pressure. I'm pretty sure after reading all of the suggestions that one of those two and probably both will work. The incorrect pressure for the loading that I was using that caused the leading I've found in 3 places now. I think its a case of everyone copying everyone else. The good members on this board saw the problem right off.

[Char-Gar]

Jonp....The notion of a smaller front band to enter the throat is as old as wadcutters themselves, with some designs going back to way before WWII. I currently have several K Miester HBWC made the same way. They perform very well, but sadly Miester no longer makes them. The body is .358 and the front part is .355. These bullets shoot very well and the HB skirts are thick enough so I can use full charge (3.5/BE) loads without the risk of them blowing off. Being swaged, they are pretty soft. I will include a pic of this bullet just for fun.

Back in the mid-60's I got the bright idea of casting some wadcutters for the 38 Special from linotype. The result was the worst leaded barrel and throats I have ever seen. That hard stuff is also difficult to remove. That is the day I learned that harder is not always better.

[DougGuy]

I can only tell you to try what works for me in my .44 magnum, that would be 50/50+2% alloy, soft enough I can scratch it with a thumbnail and lube with FELIX lube. The stuff just WORKS.

Although my C430-310-RF is a gas check boolit, the bore remains what they call a "black bore" between shots as lube and powder residue are what's left in the bore and this tends to "season" the bore for following shots. I got a lube star at the muzzle. Pushing this 310gr boolit over 17.0gr H2400 for 1190 - 1200f/s it is not loaded to the max, and groups well. This is my deer load. I never clean this bore. There is nothing to clean out of it that I would not want already in there for the next shot.

3 things will jive when you hit on them in combination, this is rifling and twist rate, alloy hardness (or not hardness), and velocity. Ruger and S&W rifling is VERY different, and too soft an alloy may skid and open up gas vents in the corners with the S&W rifling, where the same alloy may work like magic in the Ruger barrel. You just have to see what that barrel likes and doesn't like.

Another thing I use with PB boolits, is dental wax. I get .060" thick sheets of dental wax from fleabay, and once the flared case is charged with powder, I lay a piece of this over the case mouth and press a flat object down on it to cookie cutter it into the case mouth, then seat the boolit over it normally. It's a wax gas check, they work, and they season the bore rather nicely between shots. Something to try, and cheap enough that if you don't like it, you won't waste much money because you can convert them to lube if need be.

[jonp]

I tried the same boolit today with increase from 2.4 to 2.9gr Promo to increase the pressure as several have pointed out was probably the trouble. Accuracy was superb and in 25 rds the leading was less and in a much narrower band near the front. Again, soaked avfew minutes with kroil then a scrub and it came right out.

My barrel seems to be .357 and throats all .358 if I measured correctly

BTW: almost all of the leading is from 1000-1400 with most at noon

[Char-Gar]

Leading at the front of the barrel means your lube has rolled snake eyes when the bullets got that far.

[jonp]

Leading at the front of the barrel means your lube has rolled snake eyes when the bullets got that far.

Not the front. I worded it wrong. At the start of the rifling in the barrel. The rest of the barrel was clean, no ribbons, smears or anything

[popper]

Same as autoloaders with no throat. Bump up the charge and nose slump solves (partially) the problem. Leading at noon indicates an alignment problem.