working up an accurate load ?

[rebs]

When you guys work up a load, do you use the smallest tightest group for your best load or do you take the average size of say 4 groups eliminating the smallest and largest group ?
Say you shoot 4 groups with 4 different powder amounts, everything else being the same and 1 = 1/4th", 1 = 1/2", 1 = 3/8th", and the last is 3/4th". Which load would you use for your best load ? If you use the 3/8th" load can you shoot 3/8th regularly all the time ? Or would you use the 1/2" load figuring you can shoot a 1/2" group all the time ?

[4runnerman]

I use Dan Newberry's approach. After i find the best group of 5 different loads i start messing with the COl. After that you can tweak it a little more by messing with the powder charge in 1/10 gn increaments. Remember-What shoots good at 100 yards is not always a good load. You need to test at 200 yards min-300 would be best.

[old roper]

I look at repeatable groups so I won't base anything on just one groups at one yardage one day at the range. I may take test loads 200/300yd for week of shooting or longer.

[Bart B.]

When I measure something, if I don't get the same reading each time, then the tool I measured with is broken or I am.

So, the best way to measure the accuracy of a given load in a given rifle shot by a given person is to shoot enough shots per test group with that load that they're all the same size. If you shoot several groups with the same load that ain't all the same size, only the largest one is best to represent what your and that rifle and that ammo will do all the time. Smaller ones represent what happens when the variables start cancelling each other out.

'Course, if you want to feel good about what you, your rifle and your ammo do once in a great while, stick with the smallest group(s) you shoot.

So, Rebs, I'd shoot 20 shots of each load.

[rebs]

I generally load 10 rounds of each load and shoot two five round groups.I guess I should be loading 20 rounds of each load and then shoot 4 five round groups, right ? Then take the most consistent of the 4 groups as my best load ? Right ?

[Misssissippi Dave]

Are you loading rifle or pistol ammo? I would have a devil of a time trying to see how the groups I might shoot are at 300 yards with a 4" pistol. I'm just not that good of a shot.

[Bart B.]

Rebs, shoot all of the same load in one group. That'll show what it does. It'll have a composite of five 4-shot groups, four 5-shot groups, two 10 shot groups, six 3-shot groups one 15-shot and one 5-shot or any other combination you care to use. They don't matter. It's where all 20 shots go and all of them will tell you where about 80% of all your fired shots with that load will go. Shoot 100 shots per group and you'll know where abouit 95% percent of all the shots go. Military arsenals shoot 200 or more shots per test group; they want near 100% assurance of where all the shots will go.

5-shot groups only show what about half the fired bullets will do.

[Rimfire5]

Even a blind pig finds an acorn eventually and even a marginal load occasionally produces a good group, probably because the shooter and all the other variables happen to align. A single serendipitous event doesn't prove the pig can see or that a load is a good load.

As you know, lots of things can mess up a group:
a) neck sizing variations might not result in a repeatable neck pressure and cause a velocity difference
b) powder drops might not be exact so velocity can be different round to round.
Velocity will vary anyway as part of the normal process and the point of impact will change. But if the variation is cause by the loading process, then the process is not testing the same load in every cartridge, even though that was the intent.
c) seating depth might not be the same from cartridge to cartridge and might cause some change in the point of impact.
d) the shooter might not get behind the rifle the same way for every shot and actually not be aiming at the exact same aim point.
e) the barrel might get hot during the process of shooting the group and cause a change in the point of impact for one or more rounds.
f) the shooter can jerk the trigger or manhandle the stock, changing the point of impact for one or more rounds.
g) wind gusts can cause drift and open up a group
AND there are lots of other possible causes of variation in the process of shooting groups.

In any statistical process control effort, the first thing that is done is to identify any measurements that have known causes for variation and eliminate them from the analysis. They represent causes of variation that are not elemental to the process and don't represent what can be controlled.
If you know you messed up one of the shots in a group, or something went awry, it is best call it and don't count the group.
Including a group that has a known error only messes up your ability to make any conclusion about the load.

I measure at least 4 groups when I am investigating loads and take an average.
The ones that look very promising, I duplicate and shoot at least 10 groups.
There is always some range of group sizes. The loads that groups sizes that are similar are very promising. Those are the ones that I will examine in more detail. The others I record but don't necessarily do much with them.

When I shoot more groups, I look at the median and standard deviation of the groups for each load.
The loads with the best averages and medians and with low standard deviations will produce the best groups over the long term.
For the really good loads, I gather data on at least 20 groups so there is statistical significance. I then calculate the range that 90% of the groups will fall into so I know what the load will proably produce based upon those two measurements. My 10 best loads fpr a rifle may have upwards of 30 groups and if those loads retain a small standard deviation over a large sample, I can be confident that those loads will produce similar results time and again.

Some people seem to believe that a very small, single group indicates a great load.
All one group indicates is that everything went just right for that instance, or more likely, enough compensating things went wrong in just the right combination that the bullets happened to hit in the same spot.
If the next set of groups doesn't come close to matching that great group, then either the shooter can't repeat the techhnique, there is some anomaly like the wind that is causing deviations, or the load is not repeatable.

[jwrowland77]

I shoot all my test loads from a rest where my gun has been strapped down. That way I am taken out of the equation. With me taken out of the equation (except for the trigger pull), I can see what a particular load will do in my rifle. Once I find a load that I knows does good in my rifle, then I start shooting it holding it myself. Then if something is off, then I know it's me, not my rifle or the load I am shooting.

That's just what I do. I like to take as many things out of the equation that could possibly mess up the shot.

[ltc444]

I have enjoyed this post and wish to thank everyone for their contributions.

Given all of the variables I am still amazed that I can hit the paper with my reloads.

[rebs]

This is a very informative thread and I appreciate all your efforts. I feel I have learned quite a bit from all of you.
Thank you

[4runnerman]

Rebs. All info aside-Google Dan Newbarrys long range load devolpment and put it to use. You will not be dissapointed. Also do your testing at 200 yards or more.
I have seen to many people talk 3/4 groups at 100 yards. This means nothing,any good laod will shoot that. I have seen loads do that size group and then they go to 300 yards and the groups open up to 3 or 4 inches. Change only one aspect of your load at a time. 20 shot groups are IMHO a waste of ammo. Find a good 5 shot group first and then see if it repeats itself over and over. As others have posted one good day at the range does not mean next one will be. And Again--Read Dan Newberrys load page and follow it.

Also-What range are we talking about shooting?.300 or less?400 to 600? Over 600?.

[rebs]

I do not hunt any longer since my lower back injury so I just target shoot and reload my own rounds. A couple walks to the 200 yd targets leaves my back very sore so I shoot more at 100 yds.

[hounddawg]

Just something to keep in mind. It is a heck of a lot easier to shoot a tight group at 100 than gets at 200 and harder still at 600 and 800 and 1000. I do my load workups at 100 for long range and I have yet to find a group that shoots good at 100 has not shoot well at 800. Now if that load were to go subsonic at 800 or 1000 it would be a different story. Also keep in mind I have only developed loads and for 3 calibers at 600 plus ranges so I am still in the learning phases

can't really figure out why a load that shoots 1.5 MOA at 100 would be a .5 MOA load at 800. Maybe someone has a theory on how that could happen

[Bart B.]

4runnerman, a 20-shot group is nothing more than four 5-shot ones fired one after the other. A 30-shot group's 50% more 5-shot groups fired one after the other.

If one shoots five 5-shot groups aiming at the same point a few inches away from group center with a separate paper in the same place over the target for each group, you'll have two things. One is a 25-shot composite of all shots fired. The other is five separate 5-shot groups.

Compare the size of the 25-shot one to each of the 5-shot ones. More often than not, the 25-shot composite group is larger than any single 5-shot one. Take your favorite .22 rimfire to a 100 yard range and shoot ten 5-shot groups, each on separate paper atop a backer that shows the composite. An inexpensive and excellent way to understand all of this.

This relates to a phone conversation I had in the early 1970's with a Lake City Army Ammo Plant's ballistic engineer regarding some issues with one lot of M118 7.62 NATO match ammo. He mentioned an incident with a new hire that was learning the ropes how their ammo was tested for accuracy. They had just shot a 200+ shot group with a lot or M118 match ammo at 600 yards from their machine rested test barrel. Looking at that near 10-inch diameter group, he commented: "Look at all those half inch or so 5-shot groups on that target!!" To which the newly hired engineer responded: "Yup, there's a couple dozen or more of them. Too bad they ain't all at the same place." He told me he did this to asses the new hire's knowledge of what constitutes accuracy and was pleased that kid knew all the right stuff. They had fired over forty 5-shot groups at that target. They were not all the same size. One of them may well have been 1/2 inch and another almost 10 inches. But that ammo would shoot about no worse than 1/2 MOA at 100 yards.

[old roper]

Rebs, all my load development is for hunting/varmint rifles and I do have some varmint rifles that I also shoot 100yds just targets.

If I only shot 100yds I develop load at that yardage and I'd take the smallest group if it's repeatable and be done with it.

I don't think I'd be shooting 20 shot group either with one load or even 10 and I'm not saying it's bad.

It might have been helpful had you explain about shooting 100yd only.

[cw308]

Rebs, When you find a load that works well for you, fine tune it. With the same powder charge,do slight changes in OAL. see what works best, than try full size, neck size & partial neck size. This is for bolt guns only, fire formed cases the same make. can also try different primers.Good case prep is a must. Hope I helped, Be Safe Chris

[Bart B.]

This thread has a close relative at:

http://thefiringline.com/forums/showthread.php?t=507765

[4runnerman]

Bart- I do not argue with your approach. More power to ya. When i work up loads for my rifles my steps are much different and a lot less costly
I load ( same primer,powder,col) 5 rounds of each with 3/10 gn powder difference. Fire round robin style. Pull out 2 tightest groups, Reload 5 more of each same everything as first round. Pick out best of the 2.
Now i jump to 10 rounds of this load (x3) changing powder by 1/10 gn. Shoot again, Pick out best group again.4TH round 10 rounds of that load , only thiing i change is COL. I have never had a issue with it not working for me. I guess in the long run i probebly shoot as many rounds as your method. I just don't see any reason on the first 2 times out to load 20 rounds. I do 5 different loads to start each time. That would be 100 rounds to test. If i have 1 or 2 loads that do not work, That is 20 rounds i need to either shoot or tear down for nothing.
If a load is going to be something to work with ,it will shine in 5 rounds.

[hooligan1]

When Im trying to use a certain bullet in my rifle, i start by lookin in the manual and pick the most suitable powder. I always star with the lowest powder load and in .3 grn increments I work until my groups get tight and then loosin up. I usually pick the tigjtest grouping nearest my zero, and develope the best coal for my rifle bullet combination.

[tobnpr]

OCW or Ladder, if you have the range. Opinions on both sides of that fence...

http://www.6mmbr.com/laddertest.html