What causes two groups seperated vertically?

[Mordamer]

I have consistently been shooting tight groups with my rifle. The problem I'm having is that there are two tight groups. I just shot 7 shots at 100 yds with 3 of the bullets making about a .3 MOA group. 3/4" below this group the other 4 bullets made about the same size hole. I have had this happen consistently and I'm wondering if it is me or the rifle? I had previously shot 5 round groups under 1/2 moa at 100 yards with this rifle.

Rifle: 700 sps tac .223
-Epoxy bedded

Scope: SS 10x42

Ammo: Hornady 75 gr. BTHP handloads
-remington brass
-Remington 7-1/2 primers
-25 gr. varget
-Bullets seated jammed about .005"

Has anyone had a problem with shooting two groups like this?

 

[ponchair]

Re: What causes two groups seperated vertically?

Im gonna have to say it's you.

This is typically a natural POA problem. Keep the same cheek placement, after every shot, don't move your head at all, just load another round, and repeat.

 

[Mordamer]

Re: What causes two groups seperated vertically?

Thanks for your reply. I am somewhat relieved to hear someone say it is probably me. I haven't changed anything with the gun in a long time and would hate to have to try and find a problem with it. I'll work on my shooting and see if I can't stop the problem.

 

[glock24]

Re: What causes two groups seperated vertically?

I used to have this problem also. The benchrest guys call this "split groups".

It is definately shooter error. Things I now watch for;

1. Removing or shifting my cheek on the stock, or removing my cheek while loading rounds

2. Parallax error in the scope

3. The front sling stud hitting the rifle rest during recoil (if shooting from bags)

4. Holding the buttstock up with my arm to change vertical adjustment instead of letting it ride naturally down into the rear rest. Vertical adjustment should be done with the front rest, or by sliding the rear bag fore/aft on the bottom of the buttstock.

 

[bohem]

Re: What causes two groups seperated vertically?

The initial impression is shooter error, although if you're using 2 different brands or lots of brass that have a large difference in capacity internally then you can do this as well.

A friend of mine was shooting the same load from his AIAW 338LM at 400yd for some load testing back in the fall. He accidentally mixed a couple of Norma cases in the Lapua brass and it did exactly this.

2 distinct groups, both appreciably small (about 3/8 MOA) but separated by appx 5 inches vertically.

 

[turbo54]

Re: What causes two groups seperated vertically?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ninja Pirtle</div><div class="ubbcode-body">Im gonna have to say it's you.

This is typically a natural POA problem. Keep the same cheek placement, after every shot, don't move your head at all, just load another round, and repeat. </div></div>

That is an AMAZING signature. Damn.

 

[Mordamer]

Re: What causes two groups seperated vertically?

Thanks guys! From reading your comments I realized I had been taking my cheek off of the stock after every shot. I'm testing some new loads and I just got a chronograph and I was looking at the brass and looking at the chronograph after each shot.

I just went out and shot another 5 shot group without taking my cheek off of the stalk and without moving my trigger hand (left hand shooter right hand gun). The group was a nice cluster that was just about .75 moa. I'm happy with that for now because I was shooting around 1.5 moa before hearing your comments. Never thought that taking my cheek off of the stock would make that much difference.

Thanks again for the tips.

 

[ponchair]

Re: What causes two groups seperated vertically?

Glad it worked out for ya.

 

[Kalman]

Re: What causes two groups seperated vertically?

I've been doing this sometimes. I'm sub 1/2 MOA if I don't do it, but spreads out to about 1MOA if I do. I'll try keeping my head on the rest and see what happens. I think I need to get something kind of raised cheek rest on my rifle.

 

[BOLTRIPPER]

Re: What causes two groups seperated vertically?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kalman</div><div class="ubbcode-body">I've been doing this sometimes. I'm sub 1/2 MOA if I don't do it, but spreads out to about 1MOA if I do. I'll try keeping my head on the rest and see what happens. I think I need to get something kind of raised cheek rest on my rifle. </div></div>




good idea..............