Light and slow

[GoBig]

One of the things I enjoy doing seeing how slow and quiet I can launch a bullet for a rifle. I was wondering how low a charge of bullseye I could use in a 7.62x54r with a 77 grain cast bullet. I've found mention of using a 125 grain bullet with 5 grains bullseye for 900-1000 fps. I've also found someone mention a 90 grain bullet with 3.2 grains bullseye for 907 fps. I've tried primer only like I did with a round ball in a 45 auto, but the larger case size didn't even push the bullet out of the case. I'm looking to hit the 600-700 range with this 77 grain bullet. So long as I make sure the bullet leaves the bore before I fire a second round, would charge weights of one or two grains be dangerous, beyond the risk of erratic ignition or sticking a bullet?

[Walter Laich]

Not a direct answer but I regularly send 125 gr .38 Sp lead bullets down the barrel at 1.8 gr of Red Dot/Bullseye. I call these my "better half" loads.
pretty much zero recoil even in a S&W J frame

as always YMMV

[NavyVet1959]

If you have a chrono, just start at the 3.2 gr Bullseye level and work your way down. Keep a rod handy to hammer out stuck bullets, just in case.

Of course, you could use a binary search for your target velocity if you don't mind hammering out the stuck bullets and you can reload the ammo at your shooting bench.

Try 3.2 gr. It will probably be too fast.
Try 1.6 gr. If too slow, go to (3.2+1.6)/2 = 2.4 gr. If 1.6 is too fast, go to half that 0.8 gr.
Just keep splitting the difference in the ranges and you'll narrow it down pretty quickly.

For example:
3.2 gr too fast, 1.6 gr too slow, try 2.4 gr.
2.4 gr too fast, so try (1.6+2.4)/2 = 2.0 gr.
2.0 gr too fast, so try (1.6+2.0)/2 = 1.8 gr.
1.8 gr too fast, so try (1.6+1.8)/2 = 1.7 gr
1.7 gr too fast, so try (1.6+1.7)/2 = 1.65 gr.

How accurate is your powder scale and how repeatable is your powder measure? I suspect most of us would stop at 1/10th of a grain.

Even if you were testing a cartridge that could hold 100 gr of powder, you could narrow it down to within 0.01 gr within 14 loads.

[GoBig]

If you have a chrono, just start at the 3.2 gr Bullseye level and work your way down. Keep a rod handy to hammer out stuck bullets, just in case.

Of course, you could use a binary search for your target velocity if you don't mind hammering out the stuck bullets and you can reload the ammo at your shooting bench.

Try 3.2 gr. It will probably be too fast.
Try 1.6 gr. If too slow, go to (3.2+1.6)/2 = 2.4 gr. If 1.6 is too fast, go to half that 0.8 gr.
Just keep splitting the difference in the ranges and you'll narrow it down pretty quickly.

For example:
3.2 gr too fast, 1.6 gr too slow, try 2.4 gr.
2.4 gr too fast, so try (1.6+2.4)/2 = 2.0 gr.
2.0 gr too fast, so try (1.6+2.0)/2 = 1.8 gr.
1.8 gr too fast, so try (1.6+1.8)/2 = 1.7 gr
1.7 gr too fast, so try (1.6+1.7)/2 = 1.65 gr.

How accurate is your powder scale and how repeatable is your powder measure? I suspect most of us would stop at 1/10th of a grain.

Even if you were testing a cartridge that could hold 100 gr of powder, you could narrow it down to within 0.01 gr within 14 loads.

This seems like a great method to hone in on a target velocity, thank you very much.

As a small test before I load enough for a chrono test, I loaded 1 grain of bullseye and fired it into a pile of old towels. Penetrated 16 layers and dented the plywood backer. Will load and chrono 1.0 grains, 0.8 grains and 1.2 grains.

[NavyVet1959]

This seems like a great method to hone in on a target velocity, thank you very much.

As a small test before I load enough for a chrono test, I loaded 1 grain of bullseye and fired it into a pile of old towels. Penetrated 16 layers and dented the plywood backer. Will load and chrono 1.0 grains, 0.8 grains and 1.2 grains.

If you are starting at 1.0 gr, you probably won't have that many tests to do. You'll need to weigh every charge for the tests and then figure that when you start using your powder measure, it might vary +/- 0.1 gr anyway. You might even need to make yourself a custom sized dipper out of an old .22LR shell, filed down to just the right size for the powder and charge in question.

[GoBig]

As you might imagine, I'm not after pinpoint precision 100 yard accuracy so as long as it exits the bore every time I'm not concerned about a .1 grain variance. Great idea making a dipper from a .22LR. I doubt my uniflow will go that low reliably and it's very tedious weighing out a grain of powder for each cartridge. One grain could hardly be called a dusting.

[NavyVet1959]

As you might imagine, I'm not after pinpoint precision 100 yard accuracy so as long as it exits the bore every time I'm not concerned about a .1 grain variance. Great idea making a dipper from a .22LR. I doubt my uniflow will go that low reliably and it's very tedious weighing out a grain of powder for each cartridge. One grain could hardly be called a dusting.

At this level, the cost of the lead will significantly outweigh the cost of the powder, so other than possible noise issues, there's not much to be gained by going really slow.

Of course, you might just find a sweet spot where the accuracy greatly improves.

[GoBig]

My lead is free in exchange for the effort of cleaning the range trap. My biggest cost is now the primer. It's mostly an exercise of how low and quiet can I go and a close range varmint/prairie chicken load if it works well enough. 7000 rounds to the pound ain't too shabby either. Because I can is also a factor, as it is in most of my endeavours.

I appreciate you sharing your knowledge and experience.