vertical dispersion question

[boltman223]

I don't have a lot of experience shooting/testing at 600 yards so I am asking for your alls help. Today I shot at 600 yds to try out a new load(I have already done100 yard development) since we do twenty shot strings at our matches I did a twenty shot group to see how it would do.

The vertical of group measured 5.5". There was a lot of mirage and I'm not sure how much of an effect this has on group size. Watching the target bounce around I would think or could considerable? Is 5.5" a good number with a lot of mirage?

Just to give you an idea of the rifle. It is a trued Remington XR 100 with a bartlein barrel. The majority of my groups at 100 yds are in the .3 range. no I can not do it every time. I have shot this load once at 300. I did a 10 shot group and it measured 1.1 vertical and 1.6 horizontal with a very slight breeze.

What are your thoughts on the vertical dispersion. Please teach me. Thanks

 

[Terry]

Did you do a ladder test?

 

[boltman223]

No I haven't. I haven't had a chance to use a chrony yet either, which would be valuable info probably haha. Are ladder test suppose to be done at 200 yds?

 

[Steve Blair]

No I haven't. I haven't had a chance to use a chrony yet either, which would be valuable info probably haha. Are ladder test suppose to be done at 200 yds?

[br]
600 yards would be much better.

 

[Lapua40X]

You're shooting under 1MOA 20 round groups at 600 yards in heavy mirage and you're unhappy?
OK - I would be unhappy too. But I'm a little crazy.
My suggestion would be don't lose sleep over it. You're pretty darn good fella. I'd be happy to shoot alongside you any time.

 

[boltman223]

Thanks lapua40x. If you are ever passing through Minnesota ill gladly go shooting.

I'm not unhappy with the results at all. More just wondering if I should be unhappy lol. I have little experience to base a judgement off of. Of course I'm am going to try to improve on this.

A ladder test is in the near future and so is trying to shoot in More ideal conditions. Also, once I get my chrony up and running again I will be chronographing this load.

 

[ShootDots]

Boltman, it has been my UNfortunate experience that if there is little to no wind and heavy mirage, you will get vertical stringing, drifting HIGHER than the actual target. Try and get a really calm day that is overcast and I would bet a tidy sum your vertical would be close to half that!

 

[Immike]

When I am serious about load testing, I am at the range at the crack of dawn. I have a series of prepared test ready and targets in order. I will be finished before the mirage or winds become factors. The dog days of summer are perfect for this.

 

[effendude]

Boltman,
Do you have a mirage shield or band on the barrel? Without those, your barrel can cause most of the mirage you see, especially during a 20 shot string.

One MOA of vertical is a good start, but you should be able to tighten that up. Ladders sometimes work at 300 yards, sometimes they don't as the groups are too small. I had Lisa shoot 5 shot groups of different powder charges at 600 yards earlier this year to determine which had the smallest vertical. It worked real well.
Good Luck,
Scott

 

[22BRGUY]

I think you are doing very very well already also. For me it is always trying to improve a little at a time. In your case, I would suggest trying small incremental powder charge changes, maybe 2/10s gr and 4/10s gr more powder and 2/10s and 4/10 less powder from where you are and see if there is improvement in vertical one way or another from there. Then do small changes in your seating depths about 5 and 10 thou one direction and then the other and see if the horizontal spread improves by something there. Also some experiment changes with different primers and primer seating force (I found I wasn't seating primers firmly enough at one point) can make some improvements sometimes also.
Best Wishes

 

[boltman223]

Thanks for all the input everyone. I am loading up some rounds tonight with different powder charges. Hopefully Tomorrow I will be able to get out and try them at 600.

 

[boltman223]

So I made it out this evening to try a ladder test at 600 yds. It was a good night for shooting as there was no mirage. I did four 3 shot groups, I shot one cartridge from each of the the four different powder weights(24.5, 24.7, 24.9, 25.1).

In my original post the group I mentioned was shot with 24.9 grains, this load just happened too show the biggest vertical spread in my ladder test.25.1 being the best. If you are wondering the groups went as follows, 24.5: 2.5"; 24.7: 3-1/16; 24.9: 4-5/8 and 25.1 was 2-3/8. The 25.1gr load also showed the smallest ES also.

Now for the kicker, and this kinda frustrates me. I did a second ladder test this evening also. On this test the 24.7 and the 25.1gr loads switched for having the smallest groups.

The sun was getting very close to the horizon during my second ladder test and my velocities were kinda eratic it seemed,my 24.5 gr load had one of the shots with velocity the same as the 24.9gr load. All the velocities were getting a little faster too. I had a 20 minute cool down time in between my ladder test and the temp we about 75.

I wanted to at least post my results and maybe I will get some feedback too.

And also wanted to say thank you for everyone's input.

 

[22BRGUY]

Of the 24.7 and the 25.1 second round groups, which had the smallest vertical?

In my experience with ladder tests, I ONLY pay attention to the vertical spreads and totally ignore the horizontal spread. After I'm satisfied that I have found the best charge with the consistently least vertical, then I go back to seating depth changes to find the place of least horizontal...JMHO

 

[boltman223]

Sorry, those numbers were the vertical measurements. The smallest one on the second ladder was the 24.7.

 

[22BRGUY]

Is 25.1 max safely? Also, how long are you waiting between shots?

 

[boltman223]

I wait about a minute between shots and I don't put a loaded round in the chamber until I'm ready to shoot . I have not had any pressure signs and the book says 25.3 is the max. I think I am going to try 25.1 and see how it goes.

 

[22BRGUY]

I don't know what weight barrel you have but sometimes the vertical can increase from barrel heat if the rounds are shot too close together, especially in warm weather, in a string has been my experience. When trying to do a ladder test test I usually wait about 4 minutes between shots to make sure that barrel heat is not affecting the group. Some may disagree and I respect that, its just happened to me often enough that I eliminate it from the equation. Best Wishes again.

Also on going with the 25.1 charge. a suggestion might be to shoot 3 each of 24.6, 24.7, and 24.8 and then 3 each of 25.0, 25.1, and 25.2. This should tell where the best harmonics are of either the 24.7 or 25.1 charge weights.

 

[boltman223]

Thanks BR. I think I agree with waiting longer too. And I'm going to try the three different weights like you have mentioned.

Then there is seating depths, wow this turns into a lot of testing! What a bummer I'm gonna have to shoot more ;D. Thanks for the suggestions I think they are going to help.

As far as this weekend at elk river I'm going to go with 25.1gr and we'll see how it does. Oh yea, and the barrel measures .905 at 28".

 

[Steve Blair]

I don't know what weight barrel you have but sometimes the vertical can increase from barrel heat if the rounds are shot too close together, especially in warm weather, in a string has been my experience. When trying to do a ladder test test I usually wait about 4 minutes between shots to make sure that barrel heat is not affecting the group. Some may disagree and I respect that, its just happened to me often enough that I eliminate it from the equation. Best Wishes again

[br]
If you shoot competitively, the shots. ranging from ten to about twenty-five, discipline dependent, must be fired in a fairly short time span. It is a lot better to know whether they are going to string vertically in those conditions before a match. If you are hunting or just shooting a few rounds at longer ranges, it's probably not important. Since I compete in F-Class, I do all load testing at typical match cadence. My rifles generally hold 20-shot 4-8" vertical spreads at 1000 yards, in real world conditions.

 

[boltman223]

Gator good point. Would shooting the rifle as you mentioned show how the rifle reacts to the heat more so than the loads? Of course I think it is important to test and know how your rifle does shoots as well as the loads.