Grouping problems

G

Gsjcky

New member
I can’t quit figure out what’s going on. Working up my load for a Christensen Arms Mesa in 300 WM. With Leupold scope, rings & bases. I’m getting two distinct groups at the bench at 100 yards. Any load I shoot, I’m getting a grouping at 12 o’clock & 9 o’clock with every load I try. Worked up to 70.9 gr IMR 4350 getting 3000 FPS with a Sierra 180 sbt. Same aiming point...... get 2 shots touching at 12 o’clock, then 2 shots touching at 9 o’clock about 1.5 inches apart.

My first thought was the barrel is getting hot, so I shot in 2 shot strings, letting the barrel cool between strings. Is the scope loose? If this is the problem, wouldn’t the groups be more random? Why am I getting 2 distinct groups?
Any thoughts?
 
They have a moa guarantee with premium factory ammo, have you tried any? If not follow their barrel break in(50 rds) and cleaning instructions. Action screws need to be at 65 inch pounds. It sounds like a shift due to stock fit or movement or bullet seating depth. Your reloads at least should duplicate the seating depth of factory ammo that uses the exactly the same bullet. Shoot 50 of your reloads duplicating factory loads, cleaning properly. If still having issues, contact them for a recommendation on ammo to test with, with a hunting rifle cold bore point of impact is most important.
Edit for inch pounds on action screws. Also make sure your bags are allowing the rifle to recoil straight back into your shoulder.
 
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Originally Posted By: spotstalkshootThey have a moa guarantee with premium factory ammo, have you tried any? If not follow their barrel break in(50 rds) and cleaning instructions. Action screws need to be at 65 ft pounds. It sounds like a shift due to stock fit or movement or bullet seating depth. Your reloads at least should duplicate the seating depth of factory ammo that uses the exactly the same bullet. Shoot 50 of your reloads duplicating factory loads, cleaning properly. If still having issues, contact them for a recommendation on ammo to test with, with a hunting rifle cold bore point of impact is most important.

Check action screws ^^^^ and try again.

Never claimed to be a good benchrest shooter, but, standard calibers I prefer to let the rifle forend lay on the bags &/light grip w/strong hand, thus allowing rifle to freely recoil. Works fine for me up to 30-06 or so.

When I acquired my first magnum (308 Norma), used same technique and couldn'd get under 2" group. Actually wore that barrel out trying. Rebarreled w/premium Douglas barrel and same thing. Then, for the first time, I noticed I was getting the same results as OP....two small, but separate groups.

Long story short, I learned that I had to change my bench rest technique on the heavier recoiling rifles and hold the rifle down on front bag, a tighter grip w/strong hand and pay closer attention to exact same cheek pressure and snug stock/shoulder contact....lo and behold the two groups re-united.

Not saying that's OP's problem, but it sure was mine some 50 years ago when I got that first magnum, and if I forget what I'm shooting and relax my grip, still get the double groups. (Even experienced same w/a light weight .308 recently that had to be held down to tighten groups.)

Regards,
hm
 
Are you using a scope rail? I had an issue with the fit of a rail on my Christensen Ridgeline. 300WM. Even with the rail bedded it would work loose in just a few shots. Closer inspection showed that the recoil lug portion of the rail that fits against the front of the ejection port was not fitting properly. The receiver was not completely square at the back with a slight radius on the left side. When the rail was removed you could see the marks where it been in contact with a very small corner of the receiver. A few strokes with a file and a new bedding job and I now have a 1/4 MOA rifle with the same loads that were around 1 MOA previously.
You also might want to try the Berger 215gr Hybrid bullets and H1000. Just seems to be "the" combo for a lot of 300WMs. My son has a Mesa 300Wm and it will also shoot the 215s into 1/2 MOA or better.
Good luck
Bobby
 
Sorry I haven’t got back sooner, but has been a long week at work..
I checked the scope base & rings for loose screws, but didn’t think about the action screws. I will check them before I try anything else.

I have Leupold 2 piece bases now, but maybe I should try a one piece base.
As for shooting technique....... That could be the problem. I will experiment at the range this weekend, and see if that helps.

Thank you for the advice. Much appreciated.
 
Having checked the mechanical possibilities mentioned above, try holding the rifle down on the bags tighter. I did notice, I mis-spoke in original post:

Quote:Long story short, I learned that I had to change my bench rest technique on the heavier recoiling rifles and hold the rifle down on front bag, a tighter grip w/both hands and pay closer attention to exact same cheek pressure and snug stock/shoulder contact....lo and behold the two groups re-united.

Anything you can do to keep rifle from bouncing on the bags will help shrink your groups.

Regards,
hm
 
You didn’t say, but you’re using a scope level during your shooting? Just a simple rotation of the rifle, though this would be a very consistent rotation, when lining up your shoots might account for the difference. Stock shape, it’s movement in the rest between shots and how you hold and line up the shot each time, might allow for a minor rotation changing POI.

Just a thought. Good luck.
 
Canting as mention could cause the problem. No offence intended, but I do believe its more the shooter than the rifle! Reason - that's alot of gun to get use to shooting..
 
Was at the range yesterday, shooter was having 2 distinct poi groups about 1" apart @ 100 yards. I told him how to adjust the objective lens(grads didn't match with distance). Next three 3 shot groups no vertical dispersion, all shots touching. Even at 100 yards with mid range power(18) parallax can be an issue, especially if there is a stock fit condition.
 
I’m beginning to think the problem could be in my bench technique. Unfortunately, with work and honey-do’s.......haven’t been to the range in 2 weeks. Hopefully that will change soon.
Thx for the input.
 
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