45Reverse
06-21-2020, 10:23 PM
Looong read, might want to get yourself a cup o coffee.
Some quick background:
Been working on cast loads for 5.56 for several years now, not like most here have been tho. End goal is a Spitzer bullet, plated in thick copper, loaded to FMJ specs, accurate...all that stuff.
Finally got the bullet itself figured out. Took years to get it right. I was doing it in my garage so I give myself a pass for taking so long (first started dabbling with it in 2014).
As I keep testing these I'll post more details on how I did all of this but for now I encountered something that's puzzling me.
Here's the basic bullet and load...
Bullet- Smooth sided (no lube grooves) Spitzer undersized to .210 dia. Cast weight is ~56gr. Finished plated weight is 63 gr. It's plated with between .010-.012 inches of work-hardened copper. If you've done your math right you should realize that's way more than I should be able to get onto this diameter of a bullet...I'll explain how I did it later :)
Alloy- Ridiculously hard. Can't tell you the bnh (gotta be well north of 30) but the mix is WW/lino/pure Pb/tin/copper. Water dropped. Very difficult to scratch or dent. Can survive a 6ft fall onto concrete without a nick on it...
Case- Lake City, trimmed to 1.75", very light chamfer to inside case mouth
Primer- CCI No. 41
Powder- 22.1 gr VV N530 (just above VV factory minimum reload data for 62 gr FMJ with similar profile/weight as my bullet)
COL- 2.25" +/- .005 - Very mild crimp w/ Lee FCD
I expected about 2950 fps. I got between 2990 and 3165 on 10 test shots over a chrony. Gun functioned and fed perfectly, bolt locked open after the last round.
I wasn't testing for accuracy at all this time so I don't have anything to report on that.
Here's what happened
First test shots were this past weekend. Did a fishing trip with my son and took my DPMS 20" flattop (1:9) and 20 rds of the above cast loads with us.
First thing I wanted to test was whether the bullet (and the plating in particular) survived the trip down the barrel doing a bazillion RPMs and 3000+ fps. I was very confident it would but ya never know with stuff like this until you actually do it.
Ballistic gelatin wasn't practical so I did the next best thing I could. I took a 10x12x24 box and filled it heavy paper, note pads,old files, and basically anything else that was sheet paper. All stacked (stuffed) flat. At one end of the box I put two hardcover books, each about 1.5" thick. The full box weighed about 50lbs.
When we got to the river we set box the box in the water and fished for several hours (didn't catch anything). We took the box with us when we left.
Back at camp we set up the box behind a chrony and put 5 test shots into the end without the hardcover books from 10 ft away.
I did a quick inspection of the box- entry holes were clean, no keyholing, no halo from copper or bullet fragments, no exit holes.
The next 5 shots got fired into the end of the box with the hardcover books. Again, clean entry holes, no halo, no keyhole, no exit hole.
I sat down with the box and peeled through the wet pages one by one looking for the bullets. All I found was in the middle of the box after 7-8" of penetration, was a ton of paper and lead "powder" with some copper fleks here and there. That 'pattern' continued toward the other end of the box in a fan shape....Basically, the bullets (all of them) exploded after about 6" of penetration and produced an expanding cone of this debris for another 6 or 8 inches.
After literally sifting through every single sheet of paper (took hours but was aided by cold beer and my son) I recovered 4 bullet fragments totaling no more than 5 gr....everything else was pulverized dust.
Upon very close inspection I noticed something I wasn't expecting...That is the clean bullet holes continued through 6 full inches of paper (no fragmenting, yaw, or anything- just clean paper punches). It was as if the holes had been nicely drilled through the first 6 inches of paper, but after that bullet blows itself into dust. That same pattern occurred in all 10 bullet holes. It didn't matter if the bullets had to go through the wet hardcover books or wet paper sheets.
I half-expected these bullets to explode on contact due to how hard I cast the lead...But if they didn't, then they'd get trapped in the paper and I could fish out fragments to visually check the performance of the copper plating. Except there were no fragments :)
I never would have expected to see such clean penetration for so deep before violently shattering. I did some reading a frangible bullets, did some reading through the forum here in the alloys thread, but I can't determine if I should have expected this or not(???)
I know it's because of the super hard alloy I used, but from what I've read and experimented with on other loads of mine the bullet should have come apart on contact or immediately after impact if it was going to. Have any of you ever seen this kind of terminal performance from a boolit cast from a super hard alloy? Is this normal and I just have terrible google skills? :) Is it possible the copper plate served as some sort of (temporary) stabilizing factor? (Just taking a W.A.G. there)
I don't necessarily care that they blew apart. It's appears to be consistent behavior, so that's a good thing IMHO. I've been working on these as target shooting and plinking rounds, but maybe they'd be good varmint rounds too. I dunno.
I'm 100% certain the copper plating did it's job. The rifle's bore is squeaky clean, as is the gas tube and BCG...I don't have visual proof of that (excpt for the perfect entry holes on the box), but I will get it as soon as I can put a gelatin block together and get out to the woods again...unless of course these things explode after 6" of penetration into that medium too.
Ok, I'll switch to the coatings forum to talk about that plating work.
Some quick background:
Been working on cast loads for 5.56 for several years now, not like most here have been tho. End goal is a Spitzer bullet, plated in thick copper, loaded to FMJ specs, accurate...all that stuff.
Finally got the bullet itself figured out. Took years to get it right. I was doing it in my garage so I give myself a pass for taking so long (first started dabbling with it in 2014).
As I keep testing these I'll post more details on how I did all of this but for now I encountered something that's puzzling me.
Here's the basic bullet and load...
Bullet- Smooth sided (no lube grooves) Spitzer undersized to .210 dia. Cast weight is ~56gr. Finished plated weight is 63 gr. It's plated with between .010-.012 inches of work-hardened copper. If you've done your math right you should realize that's way more than I should be able to get onto this diameter of a bullet...I'll explain how I did it later :)
Alloy- Ridiculously hard. Can't tell you the bnh (gotta be well north of 30) but the mix is WW/lino/pure Pb/tin/copper. Water dropped. Very difficult to scratch or dent. Can survive a 6ft fall onto concrete without a nick on it...
Case- Lake City, trimmed to 1.75", very light chamfer to inside case mouth
Primer- CCI No. 41
Powder- 22.1 gr VV N530 (just above VV factory minimum reload data for 62 gr FMJ with similar profile/weight as my bullet)
COL- 2.25" +/- .005 - Very mild crimp w/ Lee FCD
I expected about 2950 fps. I got between 2990 and 3165 on 10 test shots over a chrony. Gun functioned and fed perfectly, bolt locked open after the last round.
I wasn't testing for accuracy at all this time so I don't have anything to report on that.
Here's what happened
First test shots were this past weekend. Did a fishing trip with my son and took my DPMS 20" flattop (1:9) and 20 rds of the above cast loads with us.
First thing I wanted to test was whether the bullet (and the plating in particular) survived the trip down the barrel doing a bazillion RPMs and 3000+ fps. I was very confident it would but ya never know with stuff like this until you actually do it.
Ballistic gelatin wasn't practical so I did the next best thing I could. I took a 10x12x24 box and filled it heavy paper, note pads,old files, and basically anything else that was sheet paper. All stacked (stuffed) flat. At one end of the box I put two hardcover books, each about 1.5" thick. The full box weighed about 50lbs.
When we got to the river we set box the box in the water and fished for several hours (didn't catch anything). We took the box with us when we left.
Back at camp we set up the box behind a chrony and put 5 test shots into the end without the hardcover books from 10 ft away.
I did a quick inspection of the box- entry holes were clean, no keyholing, no halo from copper or bullet fragments, no exit holes.
The next 5 shots got fired into the end of the box with the hardcover books. Again, clean entry holes, no halo, no keyhole, no exit hole.
I sat down with the box and peeled through the wet pages one by one looking for the bullets. All I found was in the middle of the box after 7-8" of penetration, was a ton of paper and lead "powder" with some copper fleks here and there. That 'pattern' continued toward the other end of the box in a fan shape....Basically, the bullets (all of them) exploded after about 6" of penetration and produced an expanding cone of this debris for another 6 or 8 inches.
After literally sifting through every single sheet of paper (took hours but was aided by cold beer and my son) I recovered 4 bullet fragments totaling no more than 5 gr....everything else was pulverized dust.
Upon very close inspection I noticed something I wasn't expecting...That is the clean bullet holes continued through 6 full inches of paper (no fragmenting, yaw, or anything- just clean paper punches). It was as if the holes had been nicely drilled through the first 6 inches of paper, but after that bullet blows itself into dust. That same pattern occurred in all 10 bullet holes. It didn't matter if the bullets had to go through the wet hardcover books or wet paper sheets.
I half-expected these bullets to explode on contact due to how hard I cast the lead...But if they didn't, then they'd get trapped in the paper and I could fish out fragments to visually check the performance of the copper plating. Except there were no fragments :)
I never would have expected to see such clean penetration for so deep before violently shattering. I did some reading a frangible bullets, did some reading through the forum here in the alloys thread, but I can't determine if I should have expected this or not(???)
I know it's because of the super hard alloy I used, but from what I've read and experimented with on other loads of mine the bullet should have come apart on contact or immediately after impact if it was going to. Have any of you ever seen this kind of terminal performance from a boolit cast from a super hard alloy? Is this normal and I just have terrible google skills? :) Is it possible the copper plate served as some sort of (temporary) stabilizing factor? (Just taking a W.A.G. there)
I don't necessarily care that they blew apart. It's appears to be consistent behavior, so that's a good thing IMHO. I've been working on these as target shooting and plinking rounds, but maybe they'd be good varmint rounds too. I dunno.
I'm 100% certain the copper plating did it's job. The rifle's bore is squeaky clean, as is the gas tube and BCG...I don't have visual proof of that (excpt for the perfect entry holes on the box), but I will get it as soon as I can put a gelatin block together and get out to the woods again...unless of course these things explode after 6" of penetration into that medium too.
Ok, I'll switch to the coatings forum to talk about that plating work.