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View Full Version : .429 VS. .430 Cast Bullet



GREYGHOST
04-26-2011, 03:55 PM
I experienced an interesting observation today at the range. While shooting the same gun with the same bullet, powder charge, primer, brass, etc., the .429 sized cast bullet shot consistently 35-45 fps faster than the .430 bullet over the chronograph. I would have thought it to be the reverse, ie., larger bullet diameter, higher pressure etc. Any comments?:confused:

44MAG#1
04-26-2011, 04:01 PM
Yes I have a comment. That velocity difference is insignificant. Powder will vary that much from lot to lot within the same powder number. So your velocity difference with 2 different bullet diameters is close enough. I chronoed a 300 WSM once with the same identical load within 20 minutes of the other and the velocity average was 25 fps apart on those. Same ammo from the same box. So I ignore stuff like that. Statiscally you are withing reasonable differences. So to me there is no differnce.

GREYGHOST
04-26-2011, 04:51 PM
Yes I have a comment. That velocity difference is insignificant. Powder will vary that much from lot to lot within the same powder number. So your velocity difference with 2 different bullet diameters is close enough. I chronoed a 300 WSM once with the same identical load within 20 minutes of the other and the velocity average was 25 fps apart on those. Same ammo from the same box. So I ignore stuff like that. Statiscally you are withing reasonable differences. So to me there is no differnce.

In understand what you are saying. I know there will be no difference in bullet impact, accuracy, etc. But, when firing 25 rounds of each bullet diameter with no other changes just caught my attention that there would be a consistent difference in velocity between the two different diameter bullets.

Regards,

Char-Gar
04-26-2011, 05:13 PM
Repeat that one a week for the next two month and average the results with both bullet diameters. I am willing to bet a modest sum, the difference you noted will go away or flip flop.

Echo
04-26-2011, 05:25 PM
There is a statistical procedure you can use to determine if there is any significant difference between the two samples. It's called a t-test, and requires that you have the MV's of each round fired.
On the other hand, if you replicate the experiment, and get the same results, it looks more and more as thought the first findings repeat, and that would be surprising.

Omnivore
04-26-2011, 05:28 PM
There is a saying out there someplace; "If you chrono your (gun/load) once, you'll know it's velocity. If you do it a second time, you'll never know again."

Something like that.

The issue could just as well be in your sample size. If you average ten shots, and then average another ten shots, you'll probably get a different average every time.

I notice that even after identifying everything about the gun and the load, the Speer manual will list velocity to the nearest 1 fps, whereas the Sierra manual rounds to the nearest 50 or even the nearest 100 fps. The Sierra method probably makes more sense, given all the variables a reloader and shooter will be facing.

What's the very best attainable Standard Deviation any competition reloader can achieve? What's the very best Extreme Spread? What does it take to get to that level of consistency? I don't know, but a friend who studies this sort of thing and has written an exterior ballistics program (see Modern Ballistics) says an SD of 5 fps is attainable. Even then, with two consecutive 10 shot averages, you'll see some variation.

GREYGHOST
04-26-2011, 05:35 PM
Thanks for the comments, just thought it interesting.

Larry Gibson
04-26-2011, 05:41 PM
Based on 40+ years of chronographing a lot of loads, many with cast bullets in revolvers, that If everything else was the same with those loads including powder and primer lot #s, The bullets were cast at the same time and lubed with the same lube with the only difference being .001 in sizing and they were loaded at the same time with no adjustments to the loading equipment then I would have to say that with a 25 shot string of each that 35-45 fps is significant. A 25 sample of each is statistically valid. However, as suggested a carefully controlled repeat of the test would be necessary for any sort of validation.

Larry Gibson

GREYGHOST
04-26-2011, 05:58 PM
Based on 40+ years of chronographing a lot of loads, many with cast bullets in revolvers, that If everything else was the same with those loads including powder and primer lot #s, The bullets were cast at the same time and lubed with the same lube with the only difference being .001 in sizing and they were loaded at the same time with no adjustments to the loading equipment then I would have to say that with a 25 shot string of each that 35-45 fps is significant. A 25 sample of each is statistically valid. However, as suggested a carefully controlled repeat of the test would be necessary for any sort of validation.

Larry Gibson

Everything you state above is accurate, however, I did not start out to conduct an experiment and have no desire to repeat it to make a validation. It just happened, as I was trying to make everything as close to the same as possible to see which bullet diameter my particular handgun preferred, all things being almost equal (don't want to get into the powder scale variations, etc.) I haven't been chronographing for nearly as long as you have, but I have been handloading for 42+ years. Again, I thank you for your comments. :)

runfiverun
04-26-2011, 06:35 PM
okay.
so why would the smaller boolit do that?
neck tension releasing sooner?
boolit not jamming in the throat?
friction in the bbl?

GREYGHOST
04-26-2011, 06:58 PM
okay.
so why would the smaller boolit do that?
neck tension releasing sooner?
boolit not jamming in the throat?
friction in the bbl?

Don't know. Actually, I was satisfied with Post # 6 & 7. Have a great day!

mooman76
04-26-2011, 07:28 PM
Just a educated guess but maybe it was following the rifling(smaller bullet) and was slipping just enough to cur down on rpms a hair adding to the speed yet not slipping enought to cut down on accuracy. Sort of like a skater that is twirling and put their arms out and slow down, yet they bring their arms in and speed up.
I don't remember where I read years ago but someone was experimenting with BP patched RBs. He found that the unpatched RBs, even though they lost some of their sealing pressure from lack of gas seal from the patch, were chronographed at a faster speed than the patched ball..

Bret4207
04-27-2011, 06:28 AM
I'm not going to dispute or endorse any ideas in this thread, but it would be interesting to know which shot the tighter group and what the pressure curves looked like. I know .001 can make a big diff in accuracy.

cajun shooter
04-27-2011, 09:28 AM
This is just a guess as I have not tested this difference myself. I do shoot 44-40 BP loads with .429 bullets down .427 bores. What about the .430 bullets laying down just enough fouling such as lead, powder, residue to slow that bullet down by the 25 FPS. That would not show up to the naked eye nor a scope. Your barrel could have one spot that is different in such a small way to cause this. To dis prove this theory, your entire barrel would have to be checked with the proper gauges. Take the same ammo and test it from another rifle and see what the results are. If the same then this idea is put to rest.

Doc Highwall
04-27-2011, 02:41 PM
Knowing that the velocities were close to one another and they might or might not be statistically valid I would see which one was the most accurate at a longer distances and go with that diameter and then play/tweak with the powder charge then chronograph the load.
Distance can be a cheap friend when trying loads. I had two loads that I could not tell the difference at 100yards but I could at 200 yards. Now I am testing at 300 yards which is the limit at my club.

GREYGHOST
04-27-2011, 03:58 PM
Great suggestion!! Thanks!:)