Any one with quickload able to get an estimation on pressure for me?

[Deja vu]

45-70 Govt

Starline Brass.

Winchester Large Magnum Rifle Primers

Woodleigh 550 grain Weldcore RN SN bullet. (1.42inches long)

22.1 Grains of 2400 pistol powder

2.584 inches OAL


So far no tumbling and accurate enough at 100 yards. What do I want it for? Suppressed American Bison Hunt

[Unclenick]

Do you have a measured velocity and barrel length? Often with straight wall cases, QuickLOAD has to be tweaked by a virtual change in case capacity of several percent to get a velocity match before the pressure number is good.

[Deja vu]

1070 FPS

18.5 inch barrel.

Measured at 15 feet from the chronograph.

It is a copper jacketed 550 grain bullet so pressure should be higher than with Cast lead.

[Unclenick]

QuickLOAD didn't like the data. It wanted to give me about 1285 fps and 35,600 psi. I had to change the case volume way too much to get down to your velocity, so I switched to a more simple means of estimating using QuickLOAD's muzzle pressure number as real and got an expected peak pressure of about 22,000 psi.

The discrepancy may be due to the roughly 62% case fill you have. If the powder is forward in the case (up against the bullet) do you get a significantly different velocity than with the powder over the primer? I'm not sure how much position sensitivity to expect from 2400 with such a heavy bullets. I'd have thought, not much. Another sign of an ignition issue would be a lot of unburned powder. If you put a white piece of paper on the ground a few feet out in front of the firing point, does it collect a lot of unburned flakes? If so incomplete combustion could be the issue.

If you can do it, take a .22 rimfire rifle and fire some match ammo over the chronograph to verify its accuracy. That usually comes within 50 fps of what is published on the box when fired from a rifle. That's because of the huge expansion ratio and the fact the bullet stops accelerating somewhere between 16 and 19 inches down the tube, then doesn't lose velocity very quickly with additional bore. That makes the exact barrel length non-critical.

If you have the chronograph over light colored soil, I would lay some black plastic or flat black cardboard on the ground in front of the instrument to prevent light glinting off the bullet, which can cause early triggering of the front screen. I might even go for a supplementary diffuser if the sunlight is direct.

This is all a matter making sure of the readings. I would also move the chronograph back to 20 feet. I don't think you should see muzzle blast effects at 15 feet with this charge weight, but if a lot of flakes are blowing out ahead of the bullet, then that's another possible source of early triggering of the front screen. Just don't shoot the machine.

[Deja vu]

the 22lr test came out pretty close.

The 45-70 bullet is subsonic because I shoot it through a suppressor and can not hear a sonic crack so it is certainly not going faster than the speed of sound.

As far as case volume goes the bullet takes up alot of the volume.

I got this data from the #2 hornady manual. The load was the minimum load for the 500 grain bullet with the 2400 powder.

The manual says that a 500 Grain Hornady round nose over 22.1 grains of 2400 should be doing 1100 FPS.

[Deja vu]

I tested it again at about 30 yards. (after seeing where I would hit with some practice shots. Its still showing about 1055-1075

Any way either data you gave me is still under pressure. Thanks for the info.

p.s. shot a piece of paper at about 1 yard to see how much powder I am wasting. I did not see much powder burn but there was a lot of carbon.