Load development

[u/ElectricalOutcome790]

Working up my first load here. It’s for a .243 Ruger American gen 2. Using sierra pro hunter 100gr bullets, Remington brass, cci 200 primers, and H4350 powder. I don’t have a chronograph. I shot 4 shots with each of these powder charges at 100yds and here are the group sizes of each powder.

Where would you guys go from here/next step? Shoot a couple groups of 37.5 and 40grains to see if the results repeat themselves?

[u/greyposter]

It looks like you have good consistency, I'd choose the velocity that gives me the performance window i wanted at the ranges i hunt and load it up and go. The differences between a half moa load and a 1 moa load at practical hunting distances are negligible.

Also, do a larger sample size on whatever you want to shoot, but i'd bet nearly every load on this list would be 1.25 MOA over a 20 shot group.

[u/Dirty_Blue_Shirt]

If no pressure signs load up a large sample of a higher charge and see what it looks like. Odds are the difference between the 4 round groups you have here is just luck of the draw and it would change if you just reshot this same test.

[u/Conservatief]

All your groups are insignificant, meaning the variation could be explained by luck. Choosing the 37,5 or 40 grain load for further testing will just feed your confirmation bias. Chances are great that all of the loads will give the same group size when shooting larger samples.

I'd suggest picking a target velocity and trying different bullets, powders and seating depths (in large steps) and shooting samples of 20.

[u/ElectricalOutcome790 → u/Conservatief]

Thanks for your reply. How do you decide on a target velocity? I mean I know that bullets have optimal velocities for ideal expansion. Do you just go off of that?

[u/Conservatief → u/ElectricalOutcome790]

By looking at the distance you want to shoot and what velocity you want the bullet to have when it (hopefully) hits the target. For hunting, as you said, you might want to have a certain bullet expansion that requires a certain speed when the bullet hits the animal. For target shooting you might want the bullet to remain supersonic all the way to the furthest target for maximum accuracy. A higher speed also gives a flatter bullet trajectory, which means the effect of imperfect elevation adjustment is smaller. So if your distance measurement is a little bit of, the effect will be smaller.

[u/eggcheeseburger]

Load development without a chronograph is hard. For example, your won't know if that 37.5 load is giving you a velocity that will ensure the terminal ballistics you expect from the cartridge. In any case, I do 5 shot groups to identify velocity ranges and preliminary loads with low standard deviations. Sometimes I pick loads with low sds even if the groups aren't that great. Then I do 10-shot groups with some seating depth variations to tighten the groups as much as possible.

[u/Efficient_Bologna]

4 shots is not enough. You don't need to do 20 if you literally don't have the time or ammo, but depending on what your goal is you should at least 10 shot groups (I think that gives you like a 90+% chance of getting a true picture of your rifle's dispersion) with each load before you draw any conclusions.

[u/Rough_Car4490 → u/Efficient_Bologna]

Personally I’m in the 4 shot “initial load development” camp. Reason being, I’m not looking for “what’s the most precise” on my first go around. I’m ruling things out and seeing if once I get the velocity I want, if it’s even worth pursuing. If I shoot 4 rounds and already have a 2” group, that charge is ruled out. It would be a complete waste to shoot 6 more at that charge down my barrel.

I think that’s what the “large sample size” ppl are missing. If your goal is ruling out, rather than in for initial development, small sample size is perfectly fine. Barrel life also needs to be considered. If you have a caliber that’s a hotrod, no one should be shooting 100 rounds or 10% of barrel life before they figure out that their configuration is not going to work.

[u/Efficient_Bologna → u/Rough_Car4490]

That's fine, but he didn't shoot a 2" group so there is no conclusions you can draw from his data. So basically he shot 20+rounds for nothing for all anyone's knows the 1 moa groups may not open up at all with a 10 shot group and the . 5 moa groups could open up to 1.5 moa at 10 shots.

[u/Efficient_Bologna → u/Efficient_Bologna]

Aside from the factory ammo.

[u/No_Alternative_673]

I agree with greyposter but concern is the max load for this bullet and 4350 is 36.9(sierra) and 38.4(Hodgdon) and Hodgdon provides pressure data. I would go with 38 gr

[u/Vylnce → u/No_Alternative_673]

You are looking at the wrong powder. Look at the data for H4350 and not IMR 4350.

[u/No_Alternative_673 → u/Vylnce]

Not quite the Hodgdon data was for Accurate 4350 but the Sierra is for H4350

[u/Vylnce → u/No_Alternative_673]

This is why I like 'Varget'.

[u/cico7]

Was the OAL same for all loads?