Strange results need interpretation

[pearcetopher]

Hi guys, tried 2 loads this evening and got the opposite of what I expected

First load lee 429-240-R bhn 35 9.7 grains titegroup medium crimp in crimp groove tumble lubed with lee alox smith and wesson 629 6 inch barrel

Results
Medium leading with fairly good accuracy 1450fps

Second load same everything except using 24 grains h110 and bhn 21.
Results
No leading at all, perfectly clean barrel even cleaned off the leading from the previous load, 1750 fps, very good accuracy


How can this be?

Shouldn't the slower bullet lead less with a higher bhn??
Or is this just how h110 works?

[Scharfschuetze]

The slower load is probably operating at lower pressures, thus the boolit is probably not obturating fully in the bore and is thus probably allowing gas to slip past the base and vaporize some of the lead along the boolit and the bore and then leave it as leading. With the very hard boolit in your slower load, the boolit is probably just too hard to obturate and seal the bore.

Higher BHN boolits require higher pressures to slug up or obturate in the bore. The H-110 load has probably reached that threshold for your particular boolit at your reported BHN of 21 and thus the lack of leading.

I would try reversing the BHN hardness of your boolits and shoot the softer boolits with the Tightgroup and the try the harder boolits with your H-110 load, although is sounds like you've already found the perfect match up with H-110 and the BHN 21 boolit. Linotype alloy generally comes out at about the same 21 BHN as your "soft" boolit and that is, for me anyway, on the "hard" end of the scale for my revolver shooting.

[noylj]

What was bullet diameter? How do you get a 35BHN? I have never heard of a lead alloy that hard.
Where was the leading in the barrel? Location leads to cause.
Were any of these starting loads?
TiteGroup burns VERY hot and does not work well with a lot of lead bullets. Any gas blow-by with TiteGroup will be particularly severe.

[BCB]

What was bullet diameter? How do you get a 35BHN? I have never heard of a lead alloy that hard.
Where was the leading in the barrel? Location leads to cause.
Were any of these starting loads?
TiteGroup burns VERY hot and does not work well with a lot of lead bullets. Any gas blow-by with TiteGroup will be particularly severe.

I have achieved BHN of near 30 by heat treating...

SAECO hardness tester has a graph that comes with it to convert SAECO hardness to BHN, and they indicate it can be done (35 BHN) by heat treating as mentioned...

I don't know this for a fact as near 30 was the best I could do and that was on the low side of 30...

BCB

[cbrick]

What do the throats slug? What is the groove diameter?

35 BHN is harder than I have ever been able to achieve with convection oven heat treating. This kinda sounds like incorrectly reading the LEE hardness tester. That would be a mighty hard boolit and there is no need to be shooting diamonds, that hard can cause both leading an inaccuracy.

1750 fps with a 240 gr boolit from a 6 inch barrel? That's well above any testing I've done with the 44 and 10 inch barrels with H-110.

Something isn't right with those numbers but as was already asked, where in the bore is the leading? With the info given in the OP it's pretty tough to give any advice.

Rick

[bhn22]

Big doses of fast burning powders often cause leading for me too. I started reserving fast powders for target loads, where they seem to do their best work.

Of course, YMMV, and one of the next posts will be from someone who shoots Bullseye in their .454 at full power.

[btroj]

How did you measure those velocities? Seem off to me.

Bullet hardness is something that needs to be balanced with pressure and fit.

[44man]

I think the wrong key was hit Rick. And no lead will ever reach 35 BHN so it is confusing.
But some are still going backwards, softer lead can be shot with slower powders, not the other way around.
When will we get rid of slug up to obturate bull? Fit first, with no boolit destruction. I really get sick of the idea you must expand a boolit WHEN IT ALREADY OVER GROOVE SIZE.
Yet so many say hard boolits will lead and you need to "bump up" and soften boolits. So wrong!

[MtGun44]

First concept: Hardness has very little, almost nothing, to do with directly PREVENTING LEADING. Fit,
design, lube and bore condition all have more to do with leading than just hardness.

Frankly, I can't imagine a use for a 35 BHN (real?) cast boolit in a pistol. I never cast beyond about 14 BHN intentionally
and have great results in all the magnums up to full power. I have loaded very soft 8 BHN plain based in
.357 and .44 mag many times with zero leading at the 1400 to 1500 fps (book) range of velocities.

You need to get past the whole old wives tale that "harder prevents leading" -there is only a modest
connection between hardness and leading, it is definitely not the first thing I look at to prevent it.

I haven't scrubbed lead from a bore in many years, and NEVER work to harden boolits. My rifle
shooting with boolits is only at moderate velocities, and I am warned that faster than perhaps
1600-1800 fps will require GCs and maybe harder to hold the rifling, but we are talking pistols here.
I am still learning about rifles, but the pistol, up to the normal magnums, needs no GCs or hardness
beyond air cooled wheel weights for good results and no leading.

I have no experience with the .500 S&W and .454 Casull and those other handguns operating at
true rifle pressures (50-60,000 psi) - they are likely different due to the extreme pressures and
velocities.


Bill

[btroj]

Want to lead a revolver? Shoot undersized and really hard bullets at low velocity and pressure.

[gray wolf]

What do the throats slug? What is the groove diameter?

35 BHN is harder than I have ever been able to achieve with convection oven heat treating. This kinda sounds like incorrectly reading the LEE hardness tester. That would be a mighty hard boolit and there is no need to be shooting diamonds, that hard can cause both leading an inaccuracy.

1750 fps with a 240 gr boolit from a 6 inch barrel? That's well above any testing I've done with the 44 and 10 inch barrels with H-110.

Something isn't right with those numbers but as was already asked, where in the bore is the leading? With the info given in the OP it's pretty tough to give any advice.

Rick

Good post and worth Re-reading.

[C. Latch]

I'm far from being an expert but I don't think your results are strange at all, except for that 1750' figure, and that makes no sense to me at all unless your powder measure or chronograph are badly out of whack.

[243winxb]

1750 fps from 24gr H110 , 6" bbl. Something wrong. Slow powder, less pressure = no leading.

[lwknight]

I second that. 240gr bullet and 24 grains H110
6" barrel 1470 fps max and maybe 1575 with a 7.5" barrel.
One thing for sure: You are not getting 1750 fps from a 6" barrel with H110

[cbrick]

I have no experience with the .500 S&W and .454 Casull and those other handguns operating at
true rifle pressures (50-60,000 psi) - they are likely different due to the extreme pressures and
velocities. Bill

I've done a lot of testing with cast in the 454 & found 30 BHN to be too hard for best accuracy. I wasn't getting any leading but the boolit fit the revolver correctly and the revolver was properly dimensioned. 18 BHN in the 454 with loads comparable to top end 44 mag loads worked best and higher pressure/velocity loads around 20-22 BHN. After that accuracy dropped off. Working with that revolver is when I did all that heat treat testing.

I got pretty much identical results with top end 357 loads in the FA, 18 BHN was as hard as it liked. After than accuracy dropped off.

Rick

[cbrick]

One thing for sure: You are not getting 1750 fps from a 6" barrel with H110

No kiddin, that would be respectable in an 18" closed breech rifle barrel. A 6" revolver???

Rick

[Larry Gibson]

pearcetopher

Both those velocities are 200-300 fps too high. The Tite-Group load should be in the 1200s and the 2400 should be in the 1400s. What distance from the muzzle was the start screen? If closer than 10' (I use 15') the muzzle blast was triggering the start screen. O it is possible the set up of the chronograph wasn't correct.

Larry Gibson

[MtGun44]

cbrick,
Thanks for the insight. I do know what I have done myself, but it is interesting to learn
from others what happens in areas where I have no experience. The high pressure
hand rifles are new ground to me. The closest I have is a 7mm-08 in a Lone Eagle,
but that really IS a 'hand rifle', and I have only shot jbullets in it, so far. And, obviously,
none of the revolver-specific info applies to that.

Interesting to read the comments from the other experts on this thread.

Bill

[LUBEDUDE]

First concept: Hardness has very little, almost nothing, to do with directly PREVENTING LEADING. Fit,
design, lube and bore condition all have more to do with leading than just hardness.

Frankly, I can't imagine a use for a 35 BHN (real?) cast boolit in a pistol. I never cast beyond about 14 BHN intentionally
and have great results in all the magnums up to full power. I have loaded very soft 8 BHN plain based in
.357 and .44 mag many times with zero leading at the 1400 to 1500 fps (book) range of velocities.

You need to get past the whole old wives tale that "harder prevents leading" -there is only a modest
connection between hardness and leading, it is definitely not the first thing I look at to prevent it.




Bill

+ 1 Big Time!

[bhn22]

Wait a minute, how close are your skyscreens to the muzzle? It sounds like there's possibly some muzzleblast involved here.