Can anyone give me a estimate of what the velocity would be for a 75 grain Amax in a 22-250 with 32.4 grains of H414. The rifle is a 26 inch 1 in 9 twist barrel. I am shooting this with good results out to 600 meters, at 800 and 900 meters the grouping goes all out of shape and I am wondering if it is caused by instability problems from the velocity dropping too low. I know I could load it much hotter but this load groups less than .250 at 100 meters for 5 shots.
Velocity estimate
- Thread starter moeben
- Start date
You could play with a ballistics program until you find the velocity that matches your drop chart. Use .435 for a BC.
You really should get a chronograph, velocity spread can really beat you up at longer distances.
You really should get a chronograph, velocity spread can really beat you up at longer distances.
rnbra-shooter
CGN Ultra frequent flyer
- Location
- New Brunswick
Hi Moe, do you have recorded your elevation settings for 100m, 600m and 900m? That's another piece of the puzzle that can help.
Hodgdon's online data for _70_ grain bullets indicates 31.0 H414 giving 2860fps 42,000CUP, and the max load of 34.0 H414 giving 3117fps 49,400 CUP. Barrel length isn't quoted, but it's probably close enough to 26" as to not make much of a difference there.
My SWAG would be that your load of 32.4 H414 is probably giving you 2900-2950 fps. Are you using H414, or are you using an H414 lookalike? (e.g. I have some WC852, which is "similar to" H414).
A Hornady 75 Amax is 1.110" long. The Miller stability formula indicates a stability factor of 0.99 at 2900fps in standard conditions (59F sea level) - this is *right* on the ragged edge. It would not be surprising to find that your ammo can't hit the target at 100 these days, now that the air is 5c or 10C colder (and therefore denser) than the last time you fired your rifle at Batouche.
It is probably worth your while to load your ammo hotter for a number of reasons. Firstly, it is often the case that velocities become more *uniform* as the load gets hotter. This does not matter a 100, nor does it matter at 600m, but it matters quite a lot at 800m and 900m (the slower shots end up landing quite a bit lower on target than the faster shots) - this is the most likely cause of your big groups at 800m and 900m. Secondly, a faster m.v. will make the bullet slightly more stable, and since you are so close to the ragged edge it's probably worthwhile to do this. Third, the 75 Amax has just a bit more drag than a .308 Sierra 155, so it'll tend to slow down quicker. The 75 Amax at 2900fps is about subsonic at 900m - this can make shooting difficult because if the target markers don't hear your shots arriving, your target service can get dreadfully slow. If you could your m.v. up to 3050fps, you'd be more comfortably supersonic at 900m (and your wind drift at 900m would be nearly 10% less, which doesn't hurt!!).
At your earliest convenience try to buy or borrow a chrono; it'll really help you develop better long-range ammo.
Hodgdon's online data for _70_ grain bullets indicates 31.0 H414 giving 2860fps 42,000CUP, and the max load of 34.0 H414 giving 3117fps 49,400 CUP. Barrel length isn't quoted, but it's probably close enough to 26" as to not make much of a difference there.
My SWAG would be that your load of 32.4 H414 is probably giving you 2900-2950 fps. Are you using H414, or are you using an H414 lookalike? (e.g. I have some WC852, which is "similar to" H414).
A Hornady 75 Amax is 1.110" long. The Miller stability formula indicates a stability factor of 0.99 at 2900fps in standard conditions (59F sea level) - this is *right* on the ragged edge. It would not be surprising to find that your ammo can't hit the target at 100 these days, now that the air is 5c or 10C colder (and therefore denser) than the last time you fired your rifle at Batouche.
It is probably worth your while to load your ammo hotter for a number of reasons. Firstly, it is often the case that velocities become more *uniform* as the load gets hotter. This does not matter a 100, nor does it matter at 600m, but it matters quite a lot at 800m and 900m (the slower shots end up landing quite a bit lower on target than the faster shots) - this is the most likely cause of your big groups at 800m and 900m. Secondly, a faster m.v. will make the bullet slightly more stable, and since you are so close to the ragged edge it's probably worthwhile to do this. Third, the 75 Amax has just a bit more drag than a .308 Sierra 155, so it'll tend to slow down quicker. The 75 Amax at 2900fps is about subsonic at 900m - this can make shooting difficult because if the target markers don't hear your shots arriving, your target service can get dreadfully slow. If you could your m.v. up to 3050fps, you'd be more comfortably supersonic at 900m (and your wind drift at 900m would be nearly 10% less, which doesn't hurt!!).
At your earliest convenience try to buy or borrow a chrono; it'll really help you develop better long-range ammo.
This information, written by rnbra-shooter, one of the very most knowledgeable shooters on these threads, should have a permanent place on here.
Then, the vast numbers of shooters on here, who think accuracy for their rifle is around the starting load in reloading, could read it, and and see what velocity they should be loading.
------------------------------------------------------------------
"It is probably worth your while to load your ammo hotter for a number of reasons. Firstly, it is often the case that velocities become more *uniform* as the load gets hotter. This does not matter a 100, nor does it matter at 600m, but it matters quite a lot at 800m and 900m (the slower shots end up landing quite a bit lower on target than the faster shots) - this is the most likely cause of your big groups at 800m and 900m. Secondly, a faster m.v. will make the bullet slightly more stable, and since you are so close to the ragged edge it's probably worthwhile to do this. Third, the 75 Amax has just a bit more drag than a .308 Sierra 155, so it'll tend to slow down quicker. The 75 Amax at 2900fps is about subsonic at 900m - this can make shooting difficult because if the target markers don't hear your shots arriving, your target service can get dreadfully slow. If you could your m.v. up to 3050fps, you'd be more comfortably supersonic at 900m (and your wind drift at 900m would be nearly 10% less, which doesn't hurt!!)".
Then, the vast numbers of shooters on here, who think accuracy for their rifle is around the starting load in reloading, could read it, and and see what velocity they should be loading.
------------------------------------------------------------------
"It is probably worth your while to load your ammo hotter for a number of reasons. Firstly, it is often the case that velocities become more *uniform* as the load gets hotter. This does not matter a 100, nor does it matter at 600m, but it matters quite a lot at 800m and 900m (the slower shots end up landing quite a bit lower on target than the faster shots) - this is the most likely cause of your big groups at 800m and 900m. Secondly, a faster m.v. will make the bullet slightly more stable, and since you are so close to the ragged edge it's probably worthwhile to do this. Third, the 75 Amax has just a bit more drag than a .308 Sierra 155, so it'll tend to slow down quicker. The 75 Amax at 2900fps is about subsonic at 900m - this can make shooting difficult because if the target markers don't hear your shots arriving, your target service can get dreadfully slow. If you could your m.v. up to 3050fps, you'd be more comfortably supersonic at 900m (and your wind drift at 900m would be nearly 10% less, which doesn't hurt!!)".
- Location
- Somewhere on the Hudson Bay Coast
I agree that a 1:7 twist would be a better choice for this bullet, but if it works, it works. If you pay attention to your drop at long range, that should give you a pretty good idea of what your velocity is if you enter the local conditions into a ballistics program and compare the drop you observe with the program's prediction . . . or you could get a chronograph.
Ran your load through Quickload and came up with this:
Cartridge : .22-250 Rem. (SAAMI)
Bullet : .224, 75, Hornady A-MAX 22792
Cartridge O.A.L. L6: 2.350 inch or 59.69 mm
Barrel Length : 26.0 inch or 660.4 mm
Powder : Hodgdon H414
Charge : 32.4 grains or 2.10 grams
Velocity : 3101 fps
This load shows a Load Density of 87.9 Percent. I believe, typically, that using a powder that will give you close to 100 fill capacity should work better.
EDIT TO ADD: Changing the C.O.A.L. changes things up quite a bit in the program, the above listed OAL would be the SAAMI spec length and this is assuming the bullet would be jumped and not jammed.
Varget or H4895 would get you around the 97% Fill rate with the same 32.4g load and bump your velocities to the 3260ish mark. YMMV of course but these numbers should be close.
33.4g of Varget shows slight overpressure and 99.7% Load Density with a Velocity of 3345fps
Cartridge : .22-250 Rem. (SAAMI)
Bullet : .224, 75, Hornady A-MAX 22792
Cartridge O.A.L. L6: 2.350 inch or 59.69 mm
Barrel Length : 26.0 inch or 660.4 mm
Powder : Hodgdon H414
Charge : 32.4 grains or 2.10 grams
Velocity : 3101 fps
This load shows a Load Density of 87.9 Percent. I believe, typically, that using a powder that will give you close to 100 fill capacity should work better.
EDIT TO ADD: Changing the C.O.A.L. changes things up quite a bit in the program, the above listed OAL would be the SAAMI spec length and this is assuming the bullet would be jumped and not jammed.
Varget or H4895 would get you around the 97% Fill rate with the same 32.4g load and bump your velocities to the 3260ish mark. YMMV of course but these numbers should be close.
33.4g of Varget shows slight overpressure and 99.7% Load Density with a Velocity of 3345fps
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Hehehe....Yep
I would work up. Quickload is pretty accurate (has been for me so far) but to err on the safe side would be the way to start. Every action/barrel combo will react differently to different loads.
Start at 31 and go up in .5grn increments watching for flattened primers, sticky bolt, etc...
Once you work up, let me know how close my predictions were.
Start at 31 and go up in .5grn increments watching for flattened primers, sticky bolt, etc...
Once you work up, let me know how close my predictions were.
