Remington 300gr.(45-70) bullet

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Re: Remington 300gr.(45-70) bullet

Postby Epaphroditus » Wed Jan 29, 2014 3:16 pm

Curious as to how one would go about estimating the BC and SD values for reswaged 45-70 bullets?
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Re: Remington 300gr.(45-70) bullet

Postby pitted bore » Thu Jan 30, 2014 7:29 am

Epaphroditus wrote:Curious as to how one would go about estimating the BC and SD values for reswaged 45-70 bullets?
Epaphroditus-

The standard formula for finding ballistic sectional density is SD=(W/7000)/(D*D), where W=bullet weight in grains and D=bullet diameter in inches. For a 300-grain bullet with a diameter of 0.458", SD=0.2043. If squeezed to a diameter of 0.452", SD=0.2098

A very rough estimate of the new BC would be the BC of the original unsqueezed bullet times the ratio (squeezed SD/unsqueezed SD). In this case, the ratio is about 1.027.

I cannot find a published BC of the 300-grain .458" Remington jacketed hollow point bullet. The very similar Hornady bullet has a BC of 0.197. If that bullet were squeezed to 0.452", then (0.197*1.027) would produce a BC=0.202. That's pretty close to the BC of 0.200 given by Hornady for the 300-grain XTP/Mag 0.452" bullet.

Feel free to point out errors and misconceptions in the above.

--Bob
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Re: Remington 300gr.(45-70) bullet

Postby Exits45 » Sat Mar 15, 2014 8:46 am

Update on this report. Sorry to take so long but I had order a Pac Chronograph and they never sent the unit. I emailed them a couple on times with no
reply and emailed with cancelation, and still no reply. Anyway I ordered a Chrony F-1 ( thanks sheepdog) :P . I went to the range and shot a couple
of the loads and got a speed for the 34.0 gr charge @ 1999 fps and then for 35.5 gr. charge @ 2035 fps. I need to go back out and do more serious report.
I was pressed for time. Had to go fishing with my brother.
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Re: Remington 300gr.(45-70) bullet

Postby wildcatter » Sat Mar 15, 2014 6:07 pm

pitted bore wrote:
Epaphroditus wrote:Curious as to how one would go about estimating the BC and SD values for reswaged 45-70 bullets?
Epaphroditus-

The standard formula for finding ballistic sectional density is SD=(W/7000)/(D*D), where W=bullet weight in grains and D=bullet diameter in inches. For a 300-grain bullet with a diameter of 0.458", SD=0.2043. If squeezed to a diameter of 0.452", SD=0.2098

A very rough estimate of the new BC would be the BC of the original unsqueezed bullet times the ratio (squeezed SD/unsqueezed SD). In this case, the ratio is about 1.027.

I cannot find a published BC of the 300-grain .458" Remington jacketed hollow point bullet. The very similar Hornady bullet has a BC of 0.197. If that bullet were squeezed to 0.452", then (0.197*1.027) would produce a BC=0.202. That's pretty close to the BC of 0.200 given by Hornady for the 300-grain XTP/Mag 0.452" bullet.

Feel free to point out errors and misconceptions in the above.

--Bob



Interesting question.

I just did some computing.

Using the Doc's numbers (and they will be real close). A BC of .204 a speed of 2000fps on said .458. With a 150yd zero, at 300yds and a 10mph full value wind. That bullet drops -32.78" and Wind drift is 27.7". Compared to the resized .458 to .452" (same values). The .452 drops -32.16 and drifts 22.7 all @ 300yds.

So using these values, the shrunken .458 to .452, the .458 loses by .62" or the distance of half way down the bridge of my nose, starting from point of aim between my eyes.

The drift, again at 300yds, for the .458 is 27.7" vs the resized .452 equaling 26.8" for a difference of .900". The .452 wins again. This with a point of aim smack between my eyes in a 10mph full value wing. That bullet, under these circumstances, drills out the center of my down wind eyeball.

I was graphic on purpose to demonstrate that worrying about the little bit of difference in BC between the normal vs the resized bullet has little effect on bullet strike. With the "FEROCIOUS RESIDUAL POWER", that we have, your going to Bang Flop most animals anywhere. But of course, if benchrest competition is your game then there is something to consider in the differences. I'd suggest you use the Doc's advice and use the BC of the 300gr of the XTP Mag.

If you sight-in at 150yds (I personally use 200yds). Put the crosshairs on the back bone of a moose (standing broadside @ 300yds), with the vertical on the shoulder. You Will see, a bang flop (try that with your 300 mag)!

FYI.. The .458 at 300yds has 877 ft/lb energy, whereas the .452 has 898 ft/lb. Both have a TKO of 22.5!!

..t
Safety First..t
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