What causes split groups

[JFrank]

There’s a good reason to inspect the equipment on a regular basis.
Weird stuff happens and usually it’s at the most inconvenient times.
Thx fellas

 

[dmoran]

From a loading perspective, inconsistent primer seating can cause split groups (typically when over seating / crushing the primers into the pockets to much).

 

[762plinker]

I had been having an issue chasing erratic shots lately and turned out my pic rail had come loose.Two weeks ago while at a range when I went to chamber my 8th round the bolt wouldn't completely close and I thought WTF?!Pulled the bolt and couldn't see anything but sticking a finger into the chamber I could feel a chunk of loose metal lying in the bottom of the chamber back in the case head area and had no idea where it had come from,once I got home I found where a chunk of the aluminum pic rail had sheared off from the screws coming loose(had used blue LocTite)and had gotten shoved into the chamber.I couldn't tell the scope had any movement just by feel but once I pulled it I could move the rail back and forth(screw holes in it were egged),and just enough that the recoil had sheared off that front little tip on the bottom of the rail that I guess helps position the rail and kind of helps secure it in place along with the 4 screws.Turned out to be a blessing as who knows how long I would've been chasing a load,and have since replaced the rail with a NF Extreme Duty steel one.I guess 450 rounds of 338LM(300 gr. Berger OTM's)and the weight(39 ozs.)of a NF 7-35 ATACR was just more than that factory aluminum rail could bear,beat the snot right out of it.

was at the 2000 yd match, and chased one of my guns all weekend..nothing consistent, but no obvious issues

until sunday after the match and when i picked up the gun the scope moved just a little. it was tight on friday, and loosened a little each day..never rattled..just not TIGHT...KRAPPOLA

 

[JFrank]

and a way lot of it in this video from bart:

the attention to detail and absolute precision of setting up the bench is eye opening.

Thanks buddy, I have fresh battle cry after watching the vid.

Bart’ is the Master.

 

[JFrank]

From a loading perspective, inconsistent primer seating can cause split groups (typically when over seating / crushing the primers into the pockets too much).

Timely mention, I’ve been experimenting with primer depth lately and recently set them a couple extra clicks in.
Thank you

 

[JFrank]

I just want to say thanks to you guys for the on going input, it means a lot to me.

 

[762plinker]

Timely mention, I’ve been experimenting with primer depth lately and recently set them a couple extra clicks in.
Thank you

DO NOT EXPERIMENT WITH DEPTH
1) uniform pockets
2) seat primers to the bottom of the pocket
3) apply a small crush in place..aprox .002
load and shoot

 

[JFrank]

DO NOT EXPERIMENT WITH DEPTH
1) uniform pockets
2) seat primers to the bottom of the pocket
3) apply a small crush in place..aprox .002
load and shoot

Added: my primer seating method actually mirrors your post…
The objective( my objective) is to determine the width of the primer seating window, without experimentation how do we learn ?

 

[762plinker]

Added: my primer seating method actually mirrors your post…
The objective( my objective) is to determine the width of the primer seating window, without experimentation how do we learn ?

how much are your/can your "experiment" with only 2 thou crush...plus or minus a half ??

 

[JFrank]

how much are your/can your "experiment" with only 2 thou crush...plus or minus a half ??

Well I’m not sure what the limits are just yet, that’s why I do a little trial and error.
Thanks

 

[JFrank]

Deciding to put in some work just ahead of a storm, and go to my local spot for some follow up on the great tips posted on the thread, thanks again guys.. on the right I had loaded a couple ladders, one with my normal primer seating depth another I added three extra clicks and a firm setting. Both groups measured 2 inches over 5 charges at 500 yds and looks to be the same basic node , I’m not sure what the take away is beyond a bit of wind today and shoot it again at 1 k ?

I also had been wanting to review Neck bushings, it seems to be a good time.
268 nk
L R - .265
R S - .262 3/4 vert ~ current
R S - .261 1/4 vert ***
R S - .260 2” vert

 

[762plinker]

typically groups split over subjects like is creedmore a contender or advertising?

 

[BartsBullets]

I’m asking for you fellas input on the cause of these types of groups, I’ve seen far too many with my name attached to the target.
These are 6mm rounds shot at 1000 yards Br.

All input is appreciated,

Thx ..Jim

Jim,

Out of curiosity, Did you check out the targets beside you to see if they had anything similar going on? If it’s already been asked I apologize.

Bart

 

[JFrank]

Jim,

Out of curiosity, Did you check out the targets beside you to see if they had anything similar going on? If it’s already been asked I apologize.

Bart

Not really, I didn’t even see my targets until a couple relays later. We get a little feedback while serving pit duty but that’s about it until results are posted.

I shot poorly.

 

[Bottom Fodder]

In my case it’s the shooter

 

[Jet]

Jim
Great advice above. Recommend you also consider shooting those 108s in a lower node. With H4895 try them around 29.8-30.3 gr. That will place you around 2900-2930 fps. 108s are happy in that node.

Good Shooting

 

[JFrank]

Thanks Rich, I was just thinking the same thing, I’ll load some up and report back.

 

[gunsandgunsmithing]

Lots of possible causes. I've seen tired brass do it too but I'd have to lean toward conditions above everything else, including mirage...until they are completely ruled out as the cause.

 

[JFrank]

Thanks Mike, yes we have plenty of changes, headwinds and mirage.
We know the conditions are the same for every one on the relay, unfortunately I’m the guy missing some let ups, shooting from behind the flags.
I don’t want to leave anything in the reloading room either.
I know I’ve picked up several pieces of great advice on this thread including tuning tips and Barts video is amazing, I hope im not the only one pushing the save button on a wealth of knowledge.
Thx again fellas
Jim

 

[Old Navy]

I've seen slightly loose scope rings do that. Also, being exactly between nodes. If that's it, either speed up or slow down a hair.

Thanks for that tip.