flynth
06-04-2021, 02:20 PM
Hi,
I'm starting this thread because I'm trying to figure out something peculiar that happened while I'm trying to develop a load for my 45-2.4 1874 Pedersoli Sharps rifle. This is not specific to the rifle or the fact I use black powder with it. It has to do with cast boolits in general so I'm posting in this forum hoping someone who saw something similar might answer even if they use smokeless powder, different guns etc.
Basically, I cast a bunch of boolits using Lyman 457122 HP mold a year ago using pretty hard (for me) antimony containing alloy that measures at bhn 15~16 with my Lee hardness tester (indentation size 45-50 thou). I sized it in a Lee 458 die and I left those boolits on a shelf for a year. (the die sizes to 458.2~3).
Now a year later I cast some more boolits using that mold using few different alloys including the same alloy as before (ingots I cast from what was left in the pot back then). I loaded some ammo including some with the old bullets.
During shooting I discovered old boolits group great, new not so much. I initially thought this is just a matter of different alloy casting slightly under size. That's when for the second shooting session I cast using exact same alloy. I sized cast boolits using the same sizing die and I even made two more batches one sized with a die 1 thou bigger and one usized(in hope it would be bigger) . Unfortunately the boolits measured 458.3~6 as cast so running them through a 459 die didn't do much.
When I shot all those loads (loaded exactly the same) old boolits consistently performed much better. I include a photo of a 100m target. The distance between circles is slightly under an inch. The group on the top is 10 boolits as alike as the old ones as I can make. The group in the middle are 5 old boolits (rear sight was adjusted to separate groups) - there is one flier because of a flinch. This was shot using a cheap plastic bench rest, allowing the rifle to recoil freely.
Old boolits weighted the same as new ones (21.8g 336.4grain). I measured them with an electronic micrometer at 458.5~6. The precision of the micrometer is approximately 2/10 000ths inch.
So it seems the old boolits grew in storage few 1/10 000th of an inch over a year in storage and it was enough to cause such a difference in group size.
Unfortunately I can't make any more precise measurements of old boolits because I shot all I had :-(
I shot my best group ever with this rifle using those old boolits with n two consecutive shooting sessions. One could be coincidence, but not two. As you can imagine I'm trying to replicate this without having to leave boolits in a drawer for a year... Did anyone see anything like this? I vaguely remember reading somewhere antimony containing alloys can grow as they age, but I can't find that text now. Any information about this phenomenon would be great.
https://i.ibb.co/8xCnfQg/20210604-181735.jpg (https://ibb.co/LgFDcsd)
I'm starting this thread because I'm trying to figure out something peculiar that happened while I'm trying to develop a load for my 45-2.4 1874 Pedersoli Sharps rifle. This is not specific to the rifle or the fact I use black powder with it. It has to do with cast boolits in general so I'm posting in this forum hoping someone who saw something similar might answer even if they use smokeless powder, different guns etc.
Basically, I cast a bunch of boolits using Lyman 457122 HP mold a year ago using pretty hard (for me) antimony containing alloy that measures at bhn 15~16 with my Lee hardness tester (indentation size 45-50 thou). I sized it in a Lee 458 die and I left those boolits on a shelf for a year. (the die sizes to 458.2~3).
Now a year later I cast some more boolits using that mold using few different alloys including the same alloy as before (ingots I cast from what was left in the pot back then). I loaded some ammo including some with the old bullets.
During shooting I discovered old boolits group great, new not so much. I initially thought this is just a matter of different alloy casting slightly under size. That's when for the second shooting session I cast using exact same alloy. I sized cast boolits using the same sizing die and I even made two more batches one sized with a die 1 thou bigger and one usized(in hope it would be bigger) . Unfortunately the boolits measured 458.3~6 as cast so running them through a 459 die didn't do much.
When I shot all those loads (loaded exactly the same) old boolits consistently performed much better. I include a photo of a 100m target. The distance between circles is slightly under an inch. The group on the top is 10 boolits as alike as the old ones as I can make. The group in the middle are 5 old boolits (rear sight was adjusted to separate groups) - there is one flier because of a flinch. This was shot using a cheap plastic bench rest, allowing the rifle to recoil freely.
Old boolits weighted the same as new ones (21.8g 336.4grain). I measured them with an electronic micrometer at 458.5~6. The precision of the micrometer is approximately 2/10 000ths inch.
So it seems the old boolits grew in storage few 1/10 000th of an inch over a year in storage and it was enough to cause such a difference in group size.
Unfortunately I can't make any more precise measurements of old boolits because I shot all I had :-(
I shot my best group ever with this rifle using those old boolits with n two consecutive shooting sessions. One could be coincidence, but not two. As you can imagine I'm trying to replicate this without having to leave boolits in a drawer for a year... Did anyone see anything like this? I vaguely remember reading somewhere antimony containing alloys can grow as they age, but I can't find that text now. Any information about this phenomenon would be great.
https://i.ibb.co/8xCnfQg/20210604-181735.jpg (https://ibb.co/LgFDcsd)