[HIKayaker]

I've been doing a little reading on ballistics recently.

One of the things I've learned is that bullets traveling at or near the speed of sound are affected by forces that make them much less accurate than the same bullets flying faster or slower than the speed of sound.

This is why 22 LR match ammo (standard velocity) is kept below 1100 fps (usually around 1070 fps) and long range shooters like Palma and CMP select their loads to stay supersonic at 1000 yards.

Does anyone have experience with this phenomenon with our Marlin 444s, 44 mags, and 45-70s? This would be in the reduced velocity ranges of 1100-1300 fps.

Should I expect to see larger groups at 100 yards with ammo in the 1100-1300 fps range than for ammo shooting faster or slower? If so, how much difference? As much as 1"? More?

For perspective, again using 22 LR, my standard velocity/match ammo I can expect less than 0.5" groups at 50 yards. With the best HV 22 LR ammo I've tried, I get about 1.5" groups. Significantly larger.

FWIW, the most accurate HV 22 ammo I've found is PMC HV (no longer made) and CCI HV Match. I've not found anything HV 22 ammo that comes close. Rifles: Marlin 39a, Ruger 77/22 stainless, CZ 253 (heavy barrel varmint),

 

[rx7dryver]

It is the transition that matters. I would expect the same thing to happen to centerfire loads it is just that it is not that common to experience in a rifle as most are either well above or slightly below the threshold but yes a mild 4570 load with a heavy bullet may experience this within normal ranges to target.

 

[bryan alder]

Shorter bullets will travel through the transonic barrier better than longer because they are inherently more stable

 

[AdirondackAl]

That's a rabbit hole that will only lead to more rabbit holes. I have resigned myself to the fact that there are way too many variables to come up with one comprehensive solution. Besides velocity & bullet weight - temperature, humidity, air pressure, elevation, and wind will all have some kind of effect on the results; add on the differences of different ammo in different firearms & the human behind the bullet launcher and the equation today may not be the same equation tomorrow.

Hypothetical question: Would a larger group be the result of that reduced load transitioning to sub-sonic, or the result of a heavy bullet travelling too slow for the twist-rate to be properly stabilized? Or a little bit of both? Without access to a million-dollar ballistics lab, we're never sure. I have two of the guns mentioned, and I don't use them for benchrest matches. We generally hunt with them, because they don't 'pinpoint' accuracy - 2 or 3 inches off our aiming point will still put meat in the freezer. Heck, 4 or 5 inches off would do it....

Work up your loads and make note of the good ones, learn your rifles at various ranges, and practice reading the wind a lot - you'll become a legend at the shooting range. I would tend to think rifle loads reduced that low wouldn't be used much past 50 yards or so anyway; not really far enough for "the science" to have a big effect on group size. Just some thoughts on some of my experiences. And yes, your mileage will definitely vary.

 

[buckeyeshooter]

I've been doing a little reading on ballistics recently.

One of the things I've learned is that bullets traveling at or near the speed of sound are affected by forces that make them much less accurate than the same bullets flying faster or slower than the speed of sound.

This is why 22 LR match ammo (standard velocity) is kept below 1100 fps (usually around 1070 fps) and long range shooters like Palma and CMP select their loads to stay supersonic at 1000 yards.

Does anyone have experience with this phenomenon with our Marlin 444s, 44 mags, and 45-70s? This would be in the reduced velocity ranges of 1100-1300 fps.

Should I expect to see larger groups at 100 yards with ammo in the 1100-1300 fps range than for ammo shooting faster or slower? If so, how much difference? As much as 1"? More?

For perspective, again using 22 LR, my standard velocity/match ammo I can expect less than 0.5" groups at 50 yards. With the best HV 22 LR ammo I've tried, I get about 1.5" groups. Significantly larger.

FWIW, the most accurate HV 22 ammo I've found is PMC HV (no longer made) and CCI HV Match. I've not found anything HV 22 ammo that comes close. Rifles: Marlin 39a, Ruger 77/22 stainless, CZ 253 (heavy barrel varmint),

Want to do testing on your idea, but some green box remington 405. Velocity on the box is less than 1200 fps. I have no idea about 22's, I generally shoot them at 50 feet max.

 

[graymustang]

Civil War Sharps rifles approximately a .54 caliber, 480 gr bullet at 1200 fps were known to shoot 2 inch groups at 200 yards open sights (MOA accuracy), the buffalo cartridges all very similar and accurate at long range as well. Bullet design must have a lot to do with the issue of remaining accurate before/while and after transiting the speed of sound.

Utilizing pure lead bullets, the rounds were deadly, the crucial factor for the marksman was very accurate range estimation and wind drift calculations.

Have a Spencer and a Sharps 1859, both with pristine bores, and very accurate developed BP loads. Accuracy is similar at 50 yards, as the range extends, the Sharps is progressively more accurate, like higher velocity modern rounds it is an effect related to bullet shape and rifling twist rate.