Trouble with load development

[N2TRKYS]

There's 60-70% variability in 3 shot groups, with the same load you could get from .3" groups to 1.7" groups. If that's good enough for you, great. But people wanting to learn need to know that 3 shots absolutely will not give you any valid indication of what the load is capable of producing consistently.

It absolutely will give you valid data. A 3 shot group that’s 2 inches won’t get tighter with more shots. You may think that it will, but it’ll still be at best a 2” group. But, you keep wasting components on it though.

 

[N2TRKYS]

To confirm accuracy is bad, yes. To confirm it’s good, no.

That’s not been my experience, but ok. Lol

 

[mtnbound]

There's 60-70% variability in 3 shot groups, with the same load you could get from .3" groups to 1.7" groups. If that's good enough for you, great. But people wanting to learn need to know that 3 shots absolutely will not give you any valid indication of what the load is capable of producing consistently.

Can you provide more detail on the 60%- 70% variability in 3-shot groups?

I have always shot larger round-count groups, but only after I have found a load that shows it can be accurate and does not show signs of pressure. These test loads are always 3 round groups. Then, I load up, usually 10-20, for additional proofing.

 

[Jake H]

At the moment im just trying to get good three shot groups. when I start getting somewhere ill start doing some 10 shot groups. if im getting 2" three shot groups, it's only going to get bigger. I figured if im wanting to shoot under an inch, why shoot 10 shots when im already consistently over that with 3 shots.

 

[wind gypsy]

Can you provide more detail on the 60%- 70% variability in 3-shot groups?

I have always shot larger round-count groups, but only after I have found a load that shows it can be accurate and does not show signs of pressure. These test loads are always 3 round groups. Then, I load up, usually 10-20, for additional proofing.

Assume he's referring to this from Hornady: https://rokslide.com/forums/threads/your-groups-are-too-small.290821/

Basically their data suggested that from the average 3 shot group size of a given rifle/ammo combo, one could expect that combo to shoot a smallest group about 60% smaller and a largest group about 60% larger if a sufficient number of groups are shot. So basically if you've got something that averages around an inch, expect that combo to shoot 0.4" and 1.6" groups as well. If you're using these 3 shot groups to develop loads, which one is the truth, the 0.4" one or the 1.6" one?

 

[Koda_]

At the moment im just trying to get good three shot groups

Yes. Ignore the rabbit hole distractions.
There are 3 parts to load development: combustion, harmonics, ballistics. Thats it. Your in the combustion phase, no need to discuss other things right now. Find your Optimal Charge Weight (combustion), is what your after here, with your components. You should be able to get a group size no bigger than 1.5moa, from there you can move to harmonics (seating depth adjusting). If you cant get at least 1.5moa, change a component ( start with powder). IMO start OCW testing .020" off the lands. Measure your coal from the bullets ogive for best consistency. Consiste is key to get those OCW group sizes to stabilise and give usable info.

Note: I would not worry about replicating your factory ammo coal, those are not using your components, totally different round.

Look up OCW testing for some good reading. I like the Ultimatereloader.com website.

 

[wind gypsy]

At the moment im just trying to get good three shot groups. when I start getting somewhere ill start doing some 10 shot groups. if im getting 2" three shot groups, it's only going to get bigger. I figured if im wanting to shoot under an inch, why shoot 10 shots when im already consistently over that with 3 shots.

Focus on good practices, don't oversize the piss out of your brass if you can avoid it, get a decent chamfer/debur.

I'm generally a proponent of change bullet and powder combos until something shoots without fuss. I'd hate to know the # of rounds ive wasted thinking i could take a mediocre combo and get it to shoot good with the right charge and seating depth..

First things first though, i do wonder if your process is just resulting in poor ammo.

 

[Harvey_NW]

Can you provide more detail on the 60%- 70% variability in 3-shot groups?

@wind gypsy nailed it. Litz/AB also has some publications on the statistics.

At the moment im just trying to get good three shot groups. when I start getting somewhere ill start doing some 10 shot groups. if im getting 2" three shot groups, it's only going to get bigger. I figured if im wanting to shoot under an inch, why shoot 10 shots when im already consistently over that with 3 shots.

I feel like it's implied that if your 3 shot groups aren't acceptable you should stop there, but apparently not. But to proof a load, you definitely need more. And if that 3 shot group is unacceptable, it's very likely that no amount of tweaking it with seating depth or powder charge will make it shoot acceptable consistently. Dropping powder charge can reduce the amount of dispersion if you're okay with the velocity loss. But it takes a pretty significant drop of like a full grain or more, not .2. The most effective change is going to be swapping bullet or powder.

Yes. Ignore the rabbit hole distractions.

Look up OCW testing for some good reading. I like the Ultimatereloader.com website.

OCW literally IS the rabbit hole distraction. It's a complete fallacy, and produces different results every time you test it. It's all just random distribution and small sample noise, the load either shoots or it doesn't. The easiest way to prove it to yourself is the next time you do an OCW test, take the worst result and the best result and load 10 of each and compare them. Be sure to report back with the results, if you do.

 

[Koda_]

OCW literally IS the rabbit hole distraction. It's a complete fallacy, and produces different results every time you test it.

People have been using the OCW method for decades befor that recent article came out about large sample sizes. That article is interesting but not conclusive end all to load development. The OP needs answers to his task at hand at his experience level and done correctly an OCW test will show the best charge weight for those components.

 

[mtnbound]

Assume he's referring to this from Hornady: https://rokslide.com/forums/threads/your-groups-are-too-small.290821/

Basically their data suggested that from the average 3 shot group size of a given rifle/ammo combo, one could expect that combo to shoot a smallest group about 60% smaller and a largest group about 60% larger if a sufficient number of groups are shot. So basically if you've got something that averages around an inch, expect that combo to shoot 0.4" and 1.6" groups as well. If you're using these 3 shot groups to develop loads, which one is the truth, the 0.4" one or the 1.6" one?

Thanks for the link. That is good information; just about everything they talk about was taught to me by my dad long ago. Based on the video, I will continue to do 3 round load development. Their average group size difference for a system that shoots good was for 3rds about .5moa, for 5 rds was .6moa, and 10rds was .8moa, so we are talking on average a .3 moa at 100 yards between 3rd and 10rd groups. For a system that doesn’t shoot as well, it was about 1.5moa for 3rds, 2moa for 5rds, and 2.5moa for 10rd groups, for an average of 1moa. Multiple variables could contribute to making a less accurate system, so I am not sure how to interpret that data. With a good shooting system, it's a .3moa difference; seeing how I am a part of that system, I am still the most significant problem, not my 3-round load development group. Once again, thanks for the link.

 

[wind gypsy]

Thanks for the link. That is good information; just about everything they talk about was taught to me by my dad long ago. Based on the video, I will continue to do 3 round load development. Their average group size difference for a system that shoots good was for 3rds about .5moa, for 5 rds was .6moa, and 10rds was .8moa, so we are talking on average a .3 moa at 100 yards between 3rd and 10rd groups. For a system that doesn’t shoot as well, it was about 1.5moa for 3rds, 2moa for 5rds, and 2.5moa for 10rd groups, for an average of 1moa. Multiple variables could contribute to making a less accurate system, so I am not sure how to interpret that data. With a good shooting system, it's a .3moa difference; seeing how I am a part of that system, I am still the most significant problem, not my 3-round load development group. Once again, thanks for the link.

The point is that a load that averages 0.5” 3 shot group would be expected to shoot groups roughly 0.2”-0.8”. Dudes do their load dev thinking the powder charge or seating depth for the 0.3” group is better than the 0.6” group when in reality the difference is typically just random dispersion rather than the factors people think they are testing.

The argument isn’t that doing 3 shot load dev can’t result in a good load but rather if the results are actually optimized or materially better than someone just picking a safe charge below pressure and loading to a nominal jump would have come up with.

 

[Vern400]

A bullet my rifle likes, and one it does not like.
Same case, primer, powder, charge and cbto. And bullet weight. Shot this last week. 2 sets of groups resulted in the same group sizes and the same love hate relationship! I even fired a 6th round into the right hand group because I didn't think the result was real. I either missed the paper or the bullet went through a pre-existing hole. You can decide.

I did not develop either load. But I know which one I'll be tuning now.

Try a Sierra 2125 on 45 or 46 gr Varget. F210 at mag length. That load works well in a lot of lightweight rifles. I've got one rifle that likes 165s better and another that likes 150s better.

Don't fight the rifle. Being able to hit the eyeball far outweighs getting 50 fps more or using a specific bullet most of the time.

 

[TaperPin]

I like to eliminate groups/loads that aren’t shooting well - if you want a 1 moa load (or whatever size), stop shooting as soon as the group grows above that and try another combination. Two shots at 1.25” - stop. If two 3 shot MOA groups stacked on top of each other aren’t 1 MOA - stop and try something else. More shots will never make your gun shoot better - this is good to tattoo on the inner forearm.

If your bullets and powder aren’t grouping small enough to meet your max group size - stop. Usually at this point guys either adjust what they will accept or get a new barrel - either one is ok.

 

[TaperPin]

Outside of competition it must be human nature to focus on finding a load that is “best” rather than “good enough”.

If I’m after 1 MOA and the very first 3 shot group is under that, and the second and third 3 shot group stacked on top of it are under MOA I’m done - that’s good enough. A different powder or bullet may shoot slightly better, but it doesn’t matter to a binary good enough/not good enough mentality.

My friend will shoot 300 more rounds to find the best load for his rifles, but he enjoys that process.

I’m human to and do have a couple of barrels that are just to play with getting groups as small as possible, but those aren’t hunting guns.