Need Help understanding shot groups

[disdp1]

Well using my DPMS LR-308, had a horrific deer season missing multiple deer running shots, which I normally make w/ my Weatherby. I went to the range today to see whether I had bumped the scope. I shot several groups that are so odd, I thought I'd post here with the following information for analysis. My loads are 90% of the time sub MOA at 500 yards. Today I had a 5mph 3/4 value wind that was pushing my rounds 7"s. The first group of 5 rounds were an adjustment off a previous group. I made an adjustment of .4mil to center for the wind. 3 rounds were centered around .75" Left of Center and and .75 low. The gap was 1.3/8"s, and the other 2 rounds of the group were near center for height but 8.5"s right. I had the correct elevation of 2.1 mils but the two fliers in the almost exact position is questionable. Could the wind totally died down for those two shots? Yea but... The next 5 shot group I moved the target out to 570yards. This group was just a spray of 5 rounds all around the bullseye w/ a max gap of 14"s. The conditional variables did not change that much over the 70 yards. I'm just perplexed that the grouping was so odd from 500 to 570. For the most part my LR-308 is sub-moa but today just raises questions.

I welcome logical insight into my range event today. My loads are 41.5grns of IMR4895 shooting Hornady SST 180gr .308.

Thanks for the input.

 

[ghorsley]

Re: Need Help understanding shot groups

David,

There are experts on this forum that can specifically answer your question. However, if it were me (and I am no expert) I would go bottoms up. Get a good zero at 100 where you can see your shots which I doubt you can at 500 plus. Put the info into a ballistics app like JBM. Move to 200 and 300 making adjustments along the way. You can see your holes at 300 so you could use that as your new zero. Dial in your come ups for 570 and you should be in the meat.

Gil Horsley

 

[derrekmorehead]

Re: Need Help understanding shot groups

I can second MRH's advise.. Go back to 100, Bag it and concentrate to eliminate as many variables (technique)as possible. If you can produce acceptable groups at that distance then it was more than likely something to do with the wind. If not it could be something mechanical. The wind may have been possibly swirling out at the longer distance. Remember...some days you're the fly swatter and some days...the fly. keep your head up.

 

[disdp1]

Re: Need Help understanding shot groups

Sorry guys, not the respones was looking for. I've shot over 700 rounds greater than 400 yards with just under MOA at ranges out to 600 yards.

Anyways, talked to numerous accomplished shooters on my side and the common agreement was the wind died for the 2 shots that seemed to be flyers. The drift for those 2 shots was a little more than I had dialed into my Vortex for wind correction. Would have been cool to have all 5 rounds together and the first sub 5 round 1/4 MOA at 500 yards, but I'll have to load up and punch some more holes. To reduce issues, I have Lapua brass on the way.

I've been reminded that the 6" groups I continually shoot at 600 are killers but I have this continual drive to reduce that spread.

Regards,

David