What causes split groups

[JFrank]

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

 

[dcali]

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.

 

[F Class John]

Start around 33:00 or a hair earlier if you want more context but Jack Neary talks about reading and interpreting groups as well as the bullet holes themselves which includes double grouping. He alludes to what @damoncali says above regarding powder charges, pressures and being between nodes.

Maybe this will help IF it's not a mechanical issue.

 

[JFrank]

Thx John,
I’ll add my 1K tuning group for that weekend, I chose 30.8 thinking the temp might rise later in the day and I didn’t want to break out, however it looks like i chose poorly.

 

[Northridge]

Deep Creek is Notorious for double grouping when we get “quick” bleeps of head winds in you face then gone then back again. Not always on sever days… often in colder months with heavy “pockets” of air in same casual scenario result will be the same just more compressed.. tune of choice based off your ladders wasn’t a bad decision Jim IMO

Shawn Williams

 

[lawman29]

Deep Creek is Notorious for double grouping when we get “quick” bleeps of head winds in you face then gone then back again.

I've shot Fclass several times at deep creek. Saw the vertical - scorer had a piece of pink surveyor tape hanging off the spotting scope stand that told the story.

 

[jelenko]

Deep Creek is Notorious for double grouping when we get “quick” bleeps of head winds in you face then gone then back again. Not always on sever days… often in colder months with heavy “pockets” of air in same casual scenario result will be the same just more compressed.. tune of choice based off your ladders wasn’t a bad decision Jim IMO

Shawn Williams

Ah. Causing the much higher than wide group?

 

[JFrank]

I’ve shot some decent groups at DC and had some real stinkers too.
My last four targets were frustrating to say the least.

 

[Ranger188]

Head or tail wind or bad scope.
Reticle shifts.

 

[DaveTooley]

I've done that shooting a heavy gun. I shot too fast. After pushing the rifle back to battery against a stop the barrel was still vibrating from the impact. Cost me the Nationals once. I knew it when I finished my group. Lesson learned.

 

[Northridge]

Head or tail wind or bad scope.
Reticle shifts.

Though a thing that can happen not likely the culprit.. “a lot” and I’m talking a lot have left Deep Creek with “broken” scopes… usually on or after the most pristine of morning with that Deep Creek “flag flicker” or burp in your face . Give me a 3rd relay to start my day on them morning 1st and 2nd relay are going to have some kick ass targets then the lane next to you has a “broken” scope and a dude scratch’n there head Lol

Shawn Williams

 

[Northridge]

Ah. Causing the much higher than wide group?

Based off his pre match ladder, and tune decision being “stood up” or on end isn’t surprising knowing the days conditions we shot in …

Shawn Williams

 

[Northridge]

Thx John,
I’ll add my 1K tuning group for that weekend, I chose 30.8 thinking the temp might rise later in the day and I didn’t want to break out, however it looks like i chose poorly.

Jim question, was this ladder shot off a clean bore? & did you clean rifle after for Saturday morning? Or did you roll in to Saturday with Fridays ladder fowling on bore?

Shawn Williams

 

[tom]

Shoot next door to a muzzle brake by chance? Next time you sit down beside one, watch your reticle when they shoot. That vibration is harmonics that your rifle didn't start. It's related to what Dave mentioned, but either way you want your fire control to start your harmonics that you tuned the rifle around.

Tom

 

[JFrank]

Jim question, was this ladder shot off a clean bore? & did you clean rifle after for Saturday morning? Or did you roll in to Saturday with Fridays ladder fowling on bore?

Shawn Williams

Shawn, I shot two ladders , both shot after a few/maybe 4 foulers and both showed about the same node. I cleaned up Friday night and made up a few extra fouler/sighters for Sat.

@tom I had not given any thought to vibration from muzzle breaks but I will take note next time.

I’m always concerned about recoil management and returning to battery on the X yet find myself making small adjusts to my rest during strings and wonder just where that’s coming from.

 

[Northridge]

Shoot next door to a muzzle brake by chance? Next time you sit down beside one, watch your reticle when they shoot. That vibration is harmonics that your rifle didn't start. It's related to what Dave mentioned, but either way you want your fire control to start your harmonics that you tuned the rifle around.

Tom

So many variables, muzzle over a personal bench bench has a similar affect I find with or with out a brake . example before shooting pound on bench top with your fist while recording optic cross hair spring or rebound.. shoot one shot then return to battery then pounds on bench again rebound response will often be different after shot. Then repeat you’ll find this to change through out string. Another change in response comes from one shot body preloading bench then next your suspended over bench affecting bench respond differently… running a fan on a bench with out a isolator of some sort causes continues harmonic or noise… each bench will handle differently also I find..

Shawn Williams

 

[chop house]

I’m always concerned about recoil management and returning to battery on the X yet find myself making small adjusts to my rest during strings and wonder just where that’s coming from.

this drives me nuts (not that you are doing it, that i have to do it too). i suspect it is one reason most of my rifles shoot better than i do.

 

[JFrank]

Thanks fellas, there’s a lot of wisdom in these few posts, I’ll be processing each line individually and hopefully it will all sink in. Besides the DC range conditions “getting revenge” on with me for the few times Ive snuck in a small group, there are times when I think I’m my own worst enemy with regard to table manners and recoil management and this is an area I need to focus on a bit more.


Jim

 

[chop house]

there’s a lot of wisdom in these few posts,

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.

 

[Diverjeff]

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.