Extra compression = extra boom?

[Pdragon22]

The wife and I shot a BPCR gong match this weekend and she had one round hit her pretty hard.
I was on the scope and it did impact quite a bit higher than the rest in the string. The only difference
I can come up with is there might have been a .060 wad instead of the .030 used in all of the other rounds.
45-70, 535 gr postell 20-1 63 gr. Olde Eynsford 2f.
Thanks Mark

 

[arcticap]

Who loaded the rounds?

 

[Pdragon22]

I did. Cannot come up with any place else I could have screwed up.

 

[arcticap]

Could a casting void inside the bullet cause that?
Or perhaps a bullet fractured when it was fired?
Maybe a combination of both.

 

[Pdragon22]

It happened on a 1000 yard target and clearly impacted about 2 feet higher than the rest of the shots. If their had been a void or fracture wouldn’t it fly off to
Aunt Nancy’s?

 

[arcticap]

I was only considering a reduction in the bullet weight and how that might affect trajectory.
A bullet can fracture in a lot of different ways.
If the bottom broke off cleanly then maybe it would only make the top of the main remaining bullet slightly shorter.
Or perhaps the wobble is what made it shoot high?

And another idea would be what if one of the fractured pieces caused some kind of a mini-collision in the bore, or some kind of minor/temporary barrel obstruction or disruption.
It could have been such a minor obstruction that maybe it could have been like 2 moving objects slightly bumping into each other inside the bore.
Not really an obstruction, but still some kind of disturbance that slightly interfered with the normal exit of gases.

I guess that speculation is the devil's playground, like trying to discover quirks and quarks in the universe.

Fraankly, I didn't think that the possible .03 difference in wad thickness would make much of a difference in powder compression and trajectory either.
At least your theory could be tested by test firing the same suspected error in loading the 2 wads.
Why not try that to see if you can eliminate that possible cause?
Intentionally load the 2 different size wads in 2 new rounds to see if you can duplicate the anomaly and then report back to us.
If the wads were the cause then it should be repeatable, right?

 

[Pdragon22]

Thanks, we will load up some rounds to test the wad theory. Appreciate the speculation, the learning is what brought me into this game in the first place.

 

[DocRock]

Compression itself should not increase pressure to the degree it sounds like your wife experienced. Increased recoil and velocity, both of which I take it you are inferring from what your wife felt and from the bullet hitting higher than other cartridges, are the result of higher pressures.

It's not like you could have double charged the case, so that's out. I shoot the same Postell bullet, but with Olde Eynsford 1.5Fg and 73 grs under considerable compression - much more than the 1/8" that is common, but for whatever reason, it works really well for me. We can't compare how my round "feels" compared to yours, but I can tell you that in developing that load, I didn't feel like it was really markedly harder recoiling than a 67grs load that I started with. So, you think a double wad ? Easy enough to do, but hard to see how that would substantially increase resistance and spike pressure.

Couldn't have been a different primer? Couldn't have been 3F instead of 2F?

If none of the above, lower bullet weight somehow, as suggested above, would seem the logical conclusion.

 

[damoc]

Just an idea If it was noticeably harder recoil its probably not just lighter bullet causing higher hit on target. I have had a void/no compression in a load create a faster yet less reliable round and probably unsafe as well.

 

[DocRock]

Just an idea If it was noticeably harder recoil its probably not just lighter bullet causing higher hit on target. I have had a void/no compression in a load create a faster yet less reliable round and probably unsafe as well.

Interesting point. Are you thinking no wad, meaning loose powder and maybe an air gap under the bullet?

That has merit. It might create a significant pressure spike that would explain the “symptoms”. The Postell seats pretty deep, so an air gap would be well contained in the brass. .030” might be enough to make something happen. Breech seared bullets over black powder as used in Schuetzen would generally have less of a gap, and the gap closer to the case mouth.

Good thinking.

 

[Pdragon22]

Thanks everyone for your insight. I realize trying to identify the cause of a one off event is near impossible. I use an electronic powder dispenser and a compression die. Bullets are seated into the lands. In going through my bullets I found variations in nose diameter of about 1/2 a thou.
In developing a load for my trapdoor I tested from 58 gr to 68 gr. 66 gr shot great everything ok. At 68 gr noticeable increase in recoil and terrible accuracy.
Went to 65 gr and won some matches.

 

[damoc]

Doc rock yes or whatever could allow the powder to flash over in the cartridge in stead of burn uniformly.