Home Forums Hunting & Shooting Ask The Gunwriters Double Grouping

I know this has been discussed before, but what tends to cause double grouping.

My 6.5 PRC just started doing it . 2 groups about 3/4" apart.

Checked guard screws, bases are epoxied. Scope rings (Leupold QD) torqued 22 in. lb.

This rifle usually would put 5 in .40-.75"

Lety

My Tikka in 6.5 Creed does the same thing with Accubonds, Three touching, and two touching about 1/2" apart. No idea, it does not do that with other loads.

Ive seen loose scope mounts cause double groups......something to look at!

What scope?

On my Tikka a Meopta Meopro 4.5X14X44. Doesn't do this with other loads. Not really an issue, just over MOA. Plenty good for Minute of Deer.

John,

It's a 3.5 X18 Swarovski



Lefty

I have had rifles do that if the clearance holes for the action screws were not in line with the screws and they were touching.Might try drilling them out a tad

I did everything you could in an attempt to get my Pre 64 model 70 to quit two-grouping. It was bedded 3x, full length, floated, etc. Re tighten every screw, new scope mounts, relieve magazine box, relieve action screws, bolt lug engagement checked. New scope. Tried every load known to mankind. Consulted several of the Campfire Illuminati. Nothing worked. My rifle still shot two half inch groups an inch and a half apart. It was more than accurate for “normal” shots on deer, say, 300 yards and in, but it drove me mad.

Finally my rifle revealed to me that she just plain hated Nosler bullets....despised them. I never suspected that and failed to ever consider that little point. That was it. Sierra Gamechangers? Berger VLD’s? Quarter inch groups.

leftycarbon,

I haven't found ANY scope brand to be free of occasional problems--which is why when a rifle starts giving me problems that don't go away with easier fixes, one of the first things I try is another scope.

How many 5 shot groups did you shoot that followed the same pattern?

The last 5 or 6 groups. 2 different loads. Today two shots in a bug hole at 11 0 clock and three in a bug hole at three 0 clock. About a inch between them.

Pulling scope tonite and putting my40X Br scope on.

Once I've eliminated scope problems for double grouping, I start looking for to a bedding problem. There might be two slightly different ways the rifle is sitting in the bedding. Haven't seen it happen with well bedded rifles but have seen it happen with un-bedded Tikkas that finally shoot the bedding a tad loose and have seen it with a Ruger a gunsmith bedded way too tight for me--was very hard to separate the action from the bedding and that gun would double group. When I rebedded it the issue went away.

I ran into that when I mounted an allegedly AirGun compatible Weaver rimfire scope on my Air King. Moved it to a real .22 and it stopped. The Air King uses opposing pistons to make it "recoilless", but there's a lot of movement as the action slides around during the process.

Well It's not the scope.

Double grouping and 2 &1 with my 40X BR scope.

LC

Factory rifle or custom? If a custom, who’s barrel is it?

SS custom #4 contour. Not saying mfg at this point.

LC

From what I’m gathering from your post is that this is a new occurrence with 2 new loads? Loads before shot well?

loads that shot well do not now


Lefty

Gotcha....

I think i read where deeper bullet seating may help prevent double grouping. May give it a try.

I have noticed that half the time with my rifle and half the time with other people at the range I help..... the problem is lose scope base screws.

Never lose ring to base.
Never lose ring cap.

This was a mystery to me for years, until figured out it is caused by oil creeping into the crack between the base and the receiver and then recoil can shake it loose. Never happens in 22s or 223s. Not enough recoil.

Excellent point. I tend to mount scopes pretty well--which is why the first suspect is the scope itself!

Looked at bedding Looks good but I did see some small pieces of bedding compound at the bottom of the recoil lug recess. Cleaned that up last nite. Checked clearance on bbl float all good.
On most of my sporters I bed the first inch or so of the bbl tenon. This one is fully floated from action forward.

May be my next step to bed it about 1 1/2"


Wind stops will shoot it today.



Lefty

A very good chance that those little pieces of compound were keeping the rifle from seating fully into the bedding. One of the reasons I like good clearance all around the recoil lug, except the back side of course. A loose fit make it less likely to get shavings and easier to clean out if any debris finds it way in.

Well the wind finally slowed down and got the rifle out to the range. Cleaned up the bedding of the recoil lug checked that the 36BR scope was mounted tightly and fired four 4 shot groups using Berger 140's.

Biggest group was .90 smallest .35. Bit of wind also.

Reason for everything.


Lefty

This can work but if there is much throat erosion chasing the lands can help sometimes. This has happened to me when a proven load started to group poorly for no apparent reason. I was looking at all the other possibilities to no avail and then seated longer and the problem went away.

Try shooting 10 shot groups.
When I worked at Federal we shot 4, 10 shot groups and then take the average.

10 shot groups are just too exhausting. No one wats to do that crap anymore. By the way, the op found out his rifle bedding was the culprit. A tweaked/torqued receiver or one with poor bedding can always be an issue. Hence the reason i always say proper bedding is the foundation for a consistently accurate rifle. Others have been saying the same schidt for a hell of a long time. And yet, you still have guys with improperly bedded, or not bedded at all rifles, and expecting them to drive tacks day in year after year. Let me tell you folks, you are living in a fantasy world. A pipe dream, if you will..

I had this happen with a rifle that was a known shooter. It took me a while but finally determined it was the scope. I sent the Nightforce in and they repaired it. It turns out the glass is bedded and the bedding had worked it's way out, so the glass would shift. Upon return, back to one group. Something to check out.

tansinator,

Thanks for that info. As I noted earlier in this thread, my first suspect when accuracy problems crop up in a usually reliable rifle is the scope--either the scope itself or the mounts. (

Have also seen two problems crop up simultaneously, which can be really confusing--one reason I try not to mount a new scope on a new rifle.

With the hard kickers, best to bed the scope base and action, or epoxy the base on the action, will come off with heat later on if you need for it to.

Heavy scopes move bases and rings.

Another issue, a guy should chronograph his load when the rifle is new were he works up a load. 500 rounds later, a loss of accuracy will be certain if you are not chasing the lands. Also, you will need to add more powder to bring up the velocity where it was when the barrel was new...often this is an easy fix.