284 shooting 2 different groups

[sharpshooter_308]

Just finished a Savage target build. 284 win, Broughton barrel, .313 neck, Tracker Stock, Sightron SIII. The barrel was done my Mr. Whidden and still has the nut. Shooting Berger 180 VLD's on top of H4831 short cut. Lapua brass necked up With a 53.5 gr charge I had 3 shots group in about .25" at 200 yards and about an inch to the 5 o'clock position from that was my other 2 shots in about .2". Any ideas on where I should go from there? I think I'm going to go down 2 or 3 tenths on the powder and do the same but higher. I had always heard that if it shot "2" groups like that, the load was a little off. Don't know how true that is.

 

[Bulseyetom]

Vertical grouping, assuming the wind was not coming straight at you or behind you, can sometimes be caused by the load. Try increasing and decreasing in 0.1 grain increments to see if that helps. There is a good article on this site someplace by Speedy Gonzales talking about how to cure vertical groups. Good luck. Tom

 

[sharpshooter_308]

Thanks for the info. I'll try to find it. That's the only load that did it. The other loads looke like "normal" groups just not as tight, so I don't think it's equipment problems. Could always be operator error. Hard to shoot well when its 106 with high humidity. Gotta love north Louisiana.

 

[Heavies]

Articleis here.
http://www.accurateshooter.com/shooting-skills/cures-for-vertical-stringing/

Also, you may be slightly out on powder charge. Maybe on one of the normal groups is where you want to be. Mess with seating depths to pull them in closer.

 

[limbic]

I couldn't tell from reading your first post but I once had a gun that shot two groups. It would alternate POI. Shots 1,3,5 ect were in one group and shots 2,4,6ect were in another group. The groups were 1-2" apart. I had the rifle bedded and that took care of it. Probably not your problem but I thought I would add that.

 

[holstil]

From what I've been reading on here lately, you should explore futher on your seating depth.

Check out http://www.youtube.com/view_play_list?p=7D85822FD9E41FF2

I don't remember which one he covers this in but he talks about this very thing in one of them. They are all worth watching if you haven't seen them.

Jim

 

[rogn]

Scopes are also a potential cause of two grouping especialy if they are not in their center range of operation.

 

[AlanPF]

...That's the only load that did it. The other loads looke like "normal" groups...

I think you really need to do more groups. No 5 shot group can be called normal, or abnormal. You'll occasionally see statistical analysis of groups and you actually need about 30 shots to be able to draw a reliable conclusion.

 

[Elkbane]

Shooter,
I agree with AlanPF that you need to reconfirm this with more testing, but I had a similar experience with necked-up brass...and VLD's. I'd be looking for factors that cause differential pressure. Question: Is the base of the boattail when loaded below or above the neck/shoulder junction? Are you shooting them jammed or jumped? Reason I asked, in my case it was with Lapua 243Win brass necked up to 260Rem. On that brass, and using 130VLD's, I consistently threw off two really nice separate groups in any five shot group, but rarely one nice tight group. Jamming the bullets helped some, but did not eliminate the problem. I finally stumbled on the cause- it was my case necks, specifically the neck/shoulder junction, caused by my (poor) neck turning technique.

I had not trimmed the brass immediately before I cleaned up the necks the first time, so I had slightly inconsistent lengths. When I put them through the turner, I had some that cut into the shoulder material as it should and some where the turning cut just touched the neck/shoulder junction. This caused a "mini" doughnut to form inside the neck after a few loadings. The base of the bullet contacted this area (sometimes)and I could "feel" it hit when I was seating bullets (sometimes)- just a slightly snug feel on the bottom of the seating stoke (this was how I found the problem - seating pressure by feel). That difference was enough, on some of the cases, to induce higher pressure and a different POI. After carefully F/L sizing the brass, trimming it, expanding it again and and re-turning the brass for consistency, the issue mostly disappeared . I still got occasional slight flyers, but they were bearing length related with the VLD's, not from the brass. I found I had to measure/sort by bearing length if I really wanted them to shoot tight. I ultimately switched to Lapua Scenars and quit measuring bearing lengths altogether - not enough difference to matter.

Point is, I'd look closely at my case necks on necked up brass if I were you. It can be the cause of alot of small, difficult to diagnose ills....If the base of the boattail falls above the neck/shoulder junction, I'd disregard most of this, but you may still want to sort by bearing surface length and shoot a few groups - on a loaded round a difference in bearing surface length = a difference in effective seating depth and we're all pretty anal about that, plus the effect of differential friction down the bore.....
Elkbane

 

[gunner69]

This video will be helpful in consistently seating vld's. The video uses .284 win and berger 180 bullets


http://youtu.be/etgIVSSl8L8