Interpreting range/load data - too much coffee???

[Cinch]

Having a nice calm day (1C and 6km/hr steady breeze) in Saskatchewan in the 2nd week of December was a nice treat today. After having only marginal success with 75gr Amax (.75MOA average) I decided to work up a load with the 69gr. SMK for an 8 twist .223AI. I had originally planned a ladder test with Varget with 0.2gr increments starting at 24.7gr and finishing at 26.1gr. However, being that it was such a nice day and I was still fire forming brass I decided to shoot 3 shot groups (100m) of each increment instead of the ladder.

Being a hunter first (and having a range in my back yard) I've always quit after finding anything close to a .5MOA load. Based on the following images (in increasing load order) can there really be that much difference in 0.2gr of Varget or did I have one to many coffee's???

 

[agilent_one]

It would be interesting to see if you could replicate this. As long as you're comfortable - I'd jack it up to 26.5 grains and see if it starts to stabilize.

And no, I've never seen 0.2gr make that big a difference before.

 

[Fassteel]

It would be interesting to see if you could replicate this. As long as you're comfortable - I'd jack it up to 26.5 grains and see if it starts to stabilize.

And no, I've never seen 0.2gr make that big a difference before.

.2gr of powder will make a difference in 223.222,204 22 hornet.Not so much in 25-06. Nice shooting P, couldn't ever get the 69gr to work in my CZ 223 Kevlar. FS

 

[tinbird]

your great groups are 25.1,25.5 and 25.9 and are all on the left side of the target, so it's not a case of a difference of .2 that is my question, but rather how you're able to group 'one holers' so to speak with a spread of .8 grain with a cartridge that apparently is sensitive to .2 changes in powder weight?

something isn't quite right and is it possible that the barrel was dirtier on the right side targets as opposed to the left side?

interesting post, never had that happen to me, but then I don't reload a lot compared to some.

my .02 cents (plus GST of course)

TB

 

[r204]

just buy looking at the targets my first impression was that the left side target was first . 3 shots grouped tight then the left target was shot before the barrel cooled down and the group starts to open up. I may be way out to lunch on this one but that is what I gather from looking at the targets.

 

[Andy]

You guys all consider a single three-shot group as sufficient to draw conclusions.

A minimum of three five-shot groups with already fire-formed brass shot on the same day might mean something IMO.

 

[Kelly Timoffee]

I would be inclined to say shooter position on the bench, not much of a difference , maybe not even enough to feel the difference but just enough to put some type of pressure on the rifle when shooting the targets to the right, however this will only work if the target is in the same position for every two load tests.

Also , my 2 pennies.

p.s. did you have Bailey's in the coffee?

 

[caramel]

I do beleive that .02 gr can make a difference in the final stage of load devellopement, many times it is like finding the exact sweet spot of a rifle, with my 6.5 Creedmoor .02 gr meant .4 instead of .6... JP.

 

[just having some fun]

Question

did you let barrel cool after each 3 shot group
did you shoot 6 rounds and then change target ( longer time before 1st target shot


I would do further load testing

24.9 x 5
25.0 x 5
25.1 x 5
25.2 x 5

and do a 5 round group review

Ps I think right target is a shooter position problem

ie rear bag putting pressure on stock etc

not a expert but my 2c

 

[lclund1946]

Interpreting range/load data.

.2gr of powder will make a difference in 223.222,204 22 hornet.Not so much in 25-06. Nice shooting P, couldn't ever get the 69gr to work in my CZ 223 Kevlar. FS

You are right on Fasteel. The smaller the cartridge the more important it is to work up loads in small increments. As well it is important to have the right twist/velocity to get the bullet RPM up to where it will stabilize. Your 1-9" twist barrel is marginal for the 69 grain unless you push it to max pressure/ velocity in the 223.

Here is an example of a .2 grain increase in Varget with a 39 BK in the 204 Ruger. Very similar to the OP,s results. The 28 grain load shoots 1/4" groups in other rifles as well. I got the same response with the 40 V-max and H 4895 in this rifle.

[/IMG]

My 20 EXTREME runs 6-8 grains less powder than the 204 Ruger so I work up loads in 0.1 grain increments. Here are the results of a ladder test that I did, in my wildcat, with the 32 V-Max and H 4198. I did 5 shot groups but 3 shot groups yeild the same results. While the 20.6 grain load did the best group the 20.3 grain load had the best ES and SD. Subsequent tests proved that the flier, in the 20.3 grain load, was not due to the load as it shoots well in all rifles that it is tested in.

[/IMG]

Another consideration, especially with small capacity cartridges, is that different brand cases have different case capacity which can drastically alter the load. In my 20 EXTREME there is a 0.8 grain increase in capacity with the 222 rem brass compared to the 222 Win brass. Going from new brass to FL or Neck Sized brass can also yeild a significant increase in case capacity that has to be considered. I have overcome that problem in my EXTREME design in that I form new brass, and size fired brass the same, with my dies so fireforming is eliminated. Temperature extremes can also cause groups to open up from 1/2" to 3/4" with the same load.

You are on the right track, with your 223 AI, Cinch. Looks like you and your rifle are capable of 1/4 " groups so 3 shot ladder tests are just fine. I suggest that you fireform your brass with the 25.1 grain Varget load and the 69 SMK. I believe that you are running nearly a 100% case fill at that point. Start there, with your fireformed cases, and work up in .2 gain increments untill you find a sweet spot which should come somewhere between 25.5 grains and 100% case fill.

 

[Cinch]

You guys all consider a single three-shot group as sufficient to draw conclusions.

A minimum of three five-shot groups with already fire-formed brass shot on the same day might mean something IMO.

...You are on the right track, with your 223 AI, Cinch. Looks like you and your rifle are capable of 1/4 " groups so 3 shot ladder tests are just fine. I suggest that you fireform your brass with the 25.1 grain Varget load and the 69 SMK. I believe that you are running nearly a 100% case fill at that point. Start there, with your fireformed cases, and work up in .2 gain increments untill you find a sweet spot which should come somewhere between 25.5 grains and 100% case fill.

Thanks Andy and Iclund, good advice on how to proceed.

I guess my suspicions were correct, the differences can not simply be attributed to differences in charge weight. As a point of reference, I shot all 8 groups consecutively from lowest charge weight to highest over a 20 minute period (the barrel never even got warm to the touch) with only a couple brief coffee breaks (no Baileys but that's a great idea I'm going to pour one now). Too damn bad I want to see what this rifle is capable of as it would make a hell of a good coyote gun as is, when you consider that over laying all 8 groups (24 shots) would go into little more then 1MOA.

 

[cptchaos]

Try this on for size- takes a bit of organization

Shoot 1st bullet from first test group of cartridges at 1st target;
1st bullet from second test group at 2nd target and repeat through your ladder.

This, I am told, is how some factory ammo testing is done.

Apparently this smooths out the shooter induced variances between your first and last load test groups. ie. all the third shots come out of an equally dirty barrel and you are equally fatigued or shook up.

 

[rnbra-shooter]

Here's an experiment you can do in your head. Thinking through the implications of it will make you a better reloader.

Let's say you have 15 rounds loaded identically. With these 15 rounds, fire five three-shot groups, as carefully as you can.

Now measure the groups. You wouldn't expect all groups to be identically sized, rather it's pretty likely that each group will have a different size.

One of these five groups will be the smallest and one of them will be the biggest.

Depending on how God threw the dice while you were firing your 15 rounds, you might be even be able to see a pattern to the sizes of your groups:
- perhaps the groups started large, and mostly got smaller as you went
- perhaps the other way around?
- perhaps the first and last groups were larger but the middle groups were smaller?

Now what if I were to come along and have a look at your groups, and start telling you thing like:
- choose this load (points to smallest group), not this load (points to largest group)
- look here's the sweet spot (points to two or three small adjacent groups)

 

[lclund1946]

Here's an experiment you can do in your head. Thinking through the implications of it will make you a better reloader.

Let's say you have 15 rounds loaded identically. With these 15 rounds, fire five three-shot groups, as carefully as you can.

Now measure the groups. You wouldn't expect all groups to be identically sized, rather it's pretty likely that each group will have a different size.

One of these five groups will be the smallest and one of them will be the biggest.

Depending on how God threw the dice while you were firing your 15 rounds, you might be even be able to see a pattern to the sizes of your groups:
- perhaps the groups started large, and mostly got smaller as you went
- perhaps the other way around?
- perhaps the first and last groups were larger but the middle groups were smaller?

Now what if I were to come along and have a look at your groups, and start telling you thing like:
- choose this load (points to smallest group), not this load (points to largest group)
- look here's the sweet spot (points to two or three small adjacent groups)

It escapes me how this advise would do much to make one a better reloader.

Continue to work up loads as you are doing and as suggested. Once you have found a good load, or two, then load up a few and test them again at 100 yards and then again at 300 yards or further to see how they perform. Here is an example where I found a couple of potential loads with Remington Brass and the 40 V-Max, in my 20 EXTREME, and compared it for point of impact with a 39 Sierra BK load that shot good at both 100 and 300 yards.

[/IMG]

Here are the 100 and 300 yard targets where I tested the two best 40 V-Max loads and retested some loads with the 39 BK. The target in the top right corner was 3 shots with the best 40 V-max load just worked up in Rem Brass, 3 shots with the good 39 BK in Rem Brass, and three shots with each of these bullets in Winchester brass.

[/IMG]

This method of working up loads has proven very successful for me. All of these groups were shot in my varmint rifle from the bi-pod. As well I have about 40 other loads that have shot under 1/2 inch, many of them that would fit in the 12 shot group above, from that CZ 527 Varmint/Kevlar rifle.

As I said before, Cinch, is on the right track.

 

[rnbra-shooter]

It escapes me how this advise would do much to make one a better reloader.

To avoid chasing false leads.

To make better ammo you need to try one or more different things, then see which is better and do that, or see which is worse and avoid doing that. In order to "choose the better" or "avoid the worse", you need to know what you know. You also need to know what the data is *NOT* telling you, otherwise you will spend time and effort following false leads.

My little thought experiment was meant to provoke some thought from the simple observation that different groups have different sizes even when they are the same load.

As I said before, Cinch, is on the right track.

Agreed. He has shown us 8 three-shot groups, the largest of which is 0.7", the smallest is 0.06", and the average group size is .35". I would have to say that he is shooting well, and his rifle is shooting well.

Just to provoke some discussion along the lines of what I was getting at, how can we tell by looking at those groups whether or not the powder charge weight is having *ANY* effect on his group size at all? Is it possible that he would have gotten similar groups just by shooting the same load eight times?

 

[lclund1946]

To avoid chasing false leads.

To make better ammo you need to try one or more different things, then see which is better and do that, or see which is worse and avoid doing that. In order to "choose the better" or "avoid the worse", you need to know what you know. You also need to know what the data is *NOT* telling you, otherwise you will spend time and effort following false leads.

My little thought experiment was meant to provoke some thought from the simple observation that different groups have different sizes even when they are the same load.



Agreed. He has shown us 8 three-shot groups, the largest of which is 0.7", the smallest is 0.06", and the average group size is .35". I would have to say that he is shooting well, and his rifle is shooting well.

Just to provoke some discussion along the lines of what I was getting at, how can we tell by looking at those groups whether or not the powder charge weight is having *ANY* effect on his group size at all? Is it possible that he would have gotten similar groups just by shooting the same load eight times?

I have shot hundreds of 3 -5 shot ladder tests, with small caliber/cartridges, in .1 -.2 increments with the same results as Cinch got. This, and the fact that his shooting appears to be right on, make me confident that the powder charge is having an effect on his groups. Shooting over a Chronograph helps as it kind of tells you if you are heading in the right or wrong direction from load to load. Here is another example:

[/IMG]

Cinch would be better off retesting the 25.1 grain load at 100 yards and further to see if it is consistent. Experience tells me that this load is nearly 100% fill and likely already compressed, depending on bullet seating, and that it will have more than enough pressure to fireform his loads. Experience also tells me that his fireformed 223 AI cases will hold about 1 -1.2 grains more Varget than his new cases. This means that somewhere between 25.1 and 26.5 grains, working up in .2 grain increments that he should find a sweet spot before having pressure problems. Once he has found that sweet spot he can check to see if the ES is acceptable and fine tune by going up or down 0.1 grains and/or adjusting seating depth .