vertical stringing by cast batch

[charger 1]

I got a batch of bullets here (458's) that I cast the identical way I've cast other batches. The same alloy,temp,you name it. They measure identically the same by micrometer with tenth graduations. They weigh the same as other batches...Now I know hardness testers vary,but all testers can be depended upon to do comparitive readings. Their the same hardness....Everytime I load em up their 2 inches lower at 60 yds than other batches..Put a bullet from another bath back in,back up to zero.These beggers are consistant left to right and group consistantly,just consistantly lower. Now by guess is their not bumping to make the same chamber pressure,but why if they measure same hardness and size..I'm trying to remember back to my tool making apprentice days when I was told that hatdness and ductility were not the same. and that is true,but with everything being the same should those to things not be in this case...I know I'm going to turf them,I'd just like to know what to watch for next time

[Bass Ackward]

Charger,

Of all the things that you mention, something .... has to be different because you are generating different barrel time which indicates a different pressure. Were your bullets water dropped? Did you size them after water dropping? How old are they? I have some 280 LBT's that were molded in 1991. They measure 20 BHN today. But only the nose. Where they were sized the thumnail says they are straight WW or softer. (My tester can't measure on a radius.)

[charger 1]

All my bullets were cast aprox 2 weeks ago. All water dropped. All sized after 4 days sit time. My sizing is only .0005" touch anyway. All lubed same. All GC'ed same,all brass same,all,all,all...You get the point..Oh, All 17.5 brinell...The only thing I can guess is that something got into that batch of wheel weights to start with that didnt effect hardness,but did effect ductility. That was the only batch that I experimented with a little parafin wax along with my normal flux method

[chunkum]

charger,
For what it's worth, in my experience the BRN of different batches of WW has varied from 10.0 to as much as 15. I'd think it possible that there is enough variation in their composition to account for this. If that is the situation, then perhaps such a variation in composition could alter the ductility without a discernable difference in BRN?

Bass Ackward,
To test the hardness of the internal material of those bullets, could you not file the nose of it down flat some and recheck the reading on that surface?

Best Regards,
chunkum

[Bass Ackward]

To test the hardness of the internal material of those bullets, could you not file the nose of it down flat some and recheck the reading on that surface?

Best Regards,
chunkum


Chunkum,

If you check the flat on the nose or the base, then it is 20 BHN. These were as hard as 28 BHN and then stabilized at 20. But where they were sized, they softened. If you file off the soft portion, they would be 20 BHN under neath. How deep? That is what I can't tell ya.

Many people don't realize that an alloyed bullet is hard because of chemical composition. If it is 22 BHN today, it will be 22 BHN 100 years from now. But a heat treated bullet is hard because of the cristiline structure induced by the rapid temperature change. Disturb the structure, and hardness goes back to the same as its chemical structure before the heat treatment.


Charger,

All I can tell you is that I flux with different stuff all the time based on what is handy and my bullets go to the same location. In fact, I can pretty much go up in size .002 in 45 caliber and they will still go to the same location indicating very little change in pressure. Ductility would seem to be a factor if you are needing to obturate and fill a space. If you are shooting a rifle and the barrel sizes the bullet down at all, then obturation or bumping isn't part of the picture.

So it depends on how you are shooting them I guess. At 17 BHN you bullet should be fine to 28,000 to 34,000 psi in 45 caliber. I use 14 BHN to that range and they could be loaded and fired again except for the rifling. They will start to compress the grease grooves at @ 45,000 psi. So if you aren't going above that pressure level, then hardness and ductility shouldn't be a factor.

While it seems frustrating that you have .... covered the bases and obviously understand the process, there is something that you are missing that is causing your pain. Maybe the easiest thing is just to remelt them. If it saves your sanity, then why not?

[BABore]

I've ran into a similar situation with my MM462-420 gr GC bullet. I don't WD them, but do OHT them. I size them in their soft state then HT them. My lube-sizer die is the same diameter as my homemade sizing die that I use first. Yeah, I need to open it up a tad, lazyness. Anyway, if I wait more than a day to lube the bullets I can feel the difference in the die. I found that it did effect my groups and POI.

I'm thinking that you may want to size your WD bullets immediately after casting. I know you waited for four days on each batch, but there may be just enough difference in alloy, between batches, that the hardness is not the same at sizing time.

[charger 1]

Well its like this..I'VE HAD IT There were 4 batches in total. The goofy batch being the lowest number...This morning I grabed a bullet from each batch,loaded and fired all 4 at 75 yds. Ya thats 3 in that hole and I'll bet you can spot goofy hiding down there.Well its sheer luck that my kid needs slingshot ammo now isnt it...PLUK EM
http://i7.photobucket.com/albums/y259/Chargerdive/HPIM0736.jpg

[felix]

Every post in this thread seems to be right on the money. The final grouping of a boolit lot is entirely guesswork given a "standard" load, and must be optimized according to the boolit lot on hand. Size and shoot on the same day seems to cure some of these ills, most especially if the sizing die does a lot of work. The very best boolits, only warrented for BR guns, are heat treated, sized, but not lubed or checked, and then re-heat treated, and finally checked and lubed. It is hard to size the boolits straight when they are soft, especially when applying a check too, and most especially with a Gator check which grips like KingKong. No, I don't do this anymore, and is only recommended for boolits that must be sized to fit the gun. Best to not size at all if that can be done for the gun on hand. ... felix

[felix]

Charger, you got me! Slingshot ammo? Seems like it. ... felix

[Char-Gar]

Yep.. it is starting to make sense. If the goofy bullets were the softest, they sluged up the most, gave the most resistance to the gas, raised the pressure a mite, have faster speed, therefore, less barrel time and hit lower on the target do to leaving lower in the recoil arch. See how simple it all it! :-)

BTW...Welcome to the board..but we are bound to get mixed up on this board. ChargEr and ChargAr.

[BABore]

Maybe. Maybe not.

While working up loads for my 420 gr out of a 450 Marlin GG I got the following velocities with identical powder charge weights

50/50 alloy WW-Pb OHT 22 Bhn: 1,763 fps, ES: 17 fps (5 shot avg)

OHTWW alloy 28 Bhn: 1,853 fps, ES: 7 fps (5 shot avg)

[Char-Gar]

Oh well... What was that now? Oh yes!!... It is the exception that proves the rule! That is my story and I am sticking to it...Right!!!!