Reduced velocity for decreasing wind drift

[flatsguide]

RFD, 100 yds with 200 yds occasionally. Occasionally means I don’t test at 200 but when I do it also is under 1 MOA. The MOA groups are at a bench with a forward bench rest and rabbit ear sand bag at the rear. I have not tested my groups from prone X sticks but manage to clean most of the sillhoette targets( we won’t talk about the chickens though). The load is Starline brass annealed stretched and trimmed to .005” shorter than chamber length, 81.5 guns Swiss 1 1/2 compressed.030” wad is .063 LDPE and one freezer paper wad under bullet, bullet is 530gn elliptical .444 dia. Patched to .4495. Seated .125”. CCI BR2 primers. Rifle is Miroko knock off of an 1885 Winchester, it is theBPCR model. MVA 8x scope. Shaver-trigger job at a heavy to me 4 lb.
Richard I can’t upload any of my other target photos for some reason

[flatsguide]

For some reason I cannot load any photos. If someone watching can post them for me that would be great. I can send them to you via email then you could post them.
Just PM your email to me. Thanks a Richard.

[Chill Wills]

For some reason I cannot load any photos. If someone watching can post them for me that would be great. I can send them to you via email then you could post them.
Just PM your email to me. Thanks a Richard.

I see one picture in post 41. were there any more? If not, you are doing it right.
Nice wallet group. I've never shot a group that small ...but, I test 5 to 10 shots at a time.

[Chill Wills]

I just reread your group details and match performance. I would say you have it going for you. You are there. Cleaning all the lay-downs is saying something.

[flatsguide]

Hopefully the pics show up...

[flatsguide]

Reading SPG’s “BP Cartridge Reloading Primer” p.112, states that with a 10 mph crosswind, a somewhat elliptical.45/500gn bullet with a MV of 1100 FPS has a 6.33” wind drift at 200yds whereas the same bullet starting out at 1200 FPS has a wind drift at 200yds of 7.34”. Is it worth the effort, probably. If the bullet does not have to go through that transition one may gain even more accuracy in no wind conditions.

[Chill Wills]

I think you are in a sweet spot now with velocity in the mid 1200's .
However, ...I'll be reading your report to see what you come up with.
On a different note.... Too bad it is so far from one BPCR silhouette match location to another. It would be fun to shoot shoulder to shoulder with everyone I would like to. See how it goes for them.

[fiberoptik]

Nope. 750.


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[flatsguide]

Chill, that would be nice. Unfortunately my short flirtation with Silhouette shooting is about over, I’m almost 83 and my bad back makes it agonizingly painful getting down and up from the prone position and sitting looses to much long range hits. A local club that I’m going to join has BPCR 200yd shoots off a bench twice a month so I’m looking forward to continuing to shoot there.
Fiberoptik, I would probably get below subsonic with that heavy a bullet but I doubt that the rate of twist, 1:18, in my barrel especially at that low a velocity would stabilize that long of a bullet. Good thought though.
Cheers Richard

[Chill Wills]

Nope. 750.


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45-70-750 black powder Blackout fun stuff to muse about

[flatsguide]

When Fiberoptik mentioned the 750 gn bullet I did a google search for it and found nothing so I thought he mistyped and meant a 570gn bullet. Can one of you guys steer me to the “blackout” loads for .45-70.
Thanks Richard

[Don McDowell]

Chill didn't you guys over there on the west slope get Bernie to build you some 700's grain mold blocks?

[fiberoptik]

I read an article in a gun magazine where the guy had a .45-70/.45-90/.45-120. He was talking about using the biggest, longest, heaviest bullet he had, which was made for the.45-120. He said if he couldn’t go over the sound barrier, he was going to make sure he launched the heaviest bullet he could, to carry velocity as best with the highest B.C. to carry it through. I’m certain he said it was a 750 grain cast boolit. Wish I could remember where I read it.
That boolit looked like a cigar! Maybe paper patched?
Looking at moulds, maybe I do have it wrong.......

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[flatsguide]

Lol, I bet it looked like a cigar. I have searched high and low for that bullet. I guess it was a custom mold.
Cheers Richard

[Idaho Sharpshooter]

750gr...? Maybe Accurate Moulds or NOE?

Rich

[MichaelR]

I hate to rain on somebody’s parade, but a .45 bullet going 1100 FPS is not going to be subsonic. It’s not the speed over the ground that counts, it’s the speed of the air over the bullet. The air has to travel a lot farther around a .45 bullet than a .22 bullet.

[flatsguide]

And that’s why it’s called the transonic range.

[Chill Wills]

I hate to rain on somebody’s parade, but a .45 bullet going 1100 FPS is not going to be subsonic. It’s not the speed over the ground that counts, it’s the speed of the air over the bullet. The air has to travel a lot farther around a .45 bullet than a .22 bullet.

100% correct. The displaced air accelerates as it is compressed going around the bullet. Then add the additional drag as turbulence filling the cavitation behind the bullet. Much drag in the transonic zone. Marginally stable bullets can get lost en route to the target.

However, starting it slower = less time in the critical center of the zone. That may or may not be beneficial to the end goal. Details mater.

"The air has to travel a lot farther around a .45 bullet than a .22 bullet."
I think that would depend competently on there individual sectional density. Hmmmmm....

[flatsguide]

I’m not sure Michael is correct. A bullet at a standard day at SL is just below the speed of sound at 1100fps. by definition it is air speed and if there is a no wind condition it is ground speed too and is not related to the Mach shock waves on the bullet, which are supersonic. To Michaels second point, unless I am mistaken, it is more a function of the thickness to length ratio or fineness ratio if you will. Say a .45 caliber bullet with a length of 1.750 inches and a PP diameter of .444”, .444/1.750 =.253 or thickness ratio of 25%. For a .22 LR bullet with a bullet length of .480 and a diameter of .222, .222/.480 =.46 or 46% . This shows that a .22LR bullet has almost twice the thickness ratio of a 45 cal BPCR bullet. What I take away from this is the air has to accelerate quicker over the .22LR bullet, but not necessarily further, to create the Mach shock wave on the bullet. It is the thickness ratio that determines the airspeed/FPS that the onset of the shock wave start on the bullet. I believe that is called the Critical Mach number. One only needs to look at airfoils thick curved ones to operate well in the subsonic ( we don’t want any shock waves on these airfoils) and supersonic airfoils that have very fine thickness ratios and non or almost no curvature. Interestingly, I don’t know of any aircraft that are designed to operate in the transonic zone. They are either operating about 15% below the speed of sound or well above it.
Bullets that are decelerating and are just above the speed of sound experience a rapid rise then rapid drop in pressure I think this may rapidly change the center of pressure location on the bullet and that is the cause of the transonic stability problems.
I’m not a ballistics expert, just an old not too bold pilot with just enough knowledge of aerodynamics to get in trouble. Would it not be fun to shrink down, strap a saddle on a bullet and ride it out a thousand yards or so...

[Mr_Sheesh]

Only if you like the dizzy part of being spun up to many, many RPMs, oh and the G forces from firing LOL