Advanced Marksmanship Can’t come up with an answer, need help

[PMCfighter]

I received a new build by Jim Hart. I have a couple of his rifles all set up exactly the same with different barrel lengths. Including 22”, 24” and two 26” rifles.

The one I’m having issues with is a 26” 1/10 bull, mag fed Rem 700 SA .308, with Timney trigger, H&S fully adjustable chassis with Atlas.

The issue I’m having is the gun JUMPS hard right. I am Right hand/Right eye. I have done everything I can think of to figure out what the problem is.

Subs, Super, can, no can , probe direct behind the rifle, canted / angled, seated, off hand, 168s, 184s, 196s. It absolutely doesn’t matter what I’m doing the gun takes huge jumps.

I thought it might be bad habits. So I buckled down hard really concentrated on fundamentals. Did everything step by step. Cleaned every 3 rounds. I allowed three random shooters to see if it was me and all three had the same issue.

I don’t have any issue with the other Hart guns just this one.

Sooo any ideas?

 

[sharpshot50]

Can you quantify what you are calling ‘huge jumps’? Are these jumps consistent in any way, e.g. always the third shot after a cleaning, etc.?

 

[Hobo Hilton]

Try a different stock......... That will narrow it down to a stock issue or an action issue.

 

[RTH1800]

Longer barrel is going to have longer recoil impulse. Exacerbated by use of high power optic sight.

 

[demolitionman]

Are you shooting off of a different surface than usual? Like concrete? Or a smooth bench? Maybe try laying prone on grass and see what happens....

 

[Erno86]

Between cleanings...my accuracy in my benchrest 223 rifle drops off at the 17th round mark.

May I suggest that you shoot at least 1 fouler shot after a cleaning before grouping & unless your breaking the barrel in...I would tend to think that cleaning after every third shot is a bit of an overkill for a smokeless rifle.

How heavy is the rifle?

Unless heavy enough...a 308 round will make the rifle jump around from recoil.

 

[PMCfighter]

Quantifying “huge jumps” the rifle is jumping 4-6” right with every shot.

No not on any new surface.
Shooting prone on the earth, seated and off hand

I have two of the exact same rifles and I am only having issues with this one. They are definitely heavy enough.
Further more the use of sub ammo should isn’t making a difference in the least.

 

[Hobo Hilton]

What is the guy who built it saying?

 

[AIAW]

Quantifying “huge jumps” the rifle is jumping 4-6” right with every shot.

No not on any new surface.
Shooting prone on the earth, seated and off hand

I have two of the exact same rifles and I am only having issues with this one. They are definitely heavy enough.
Further more the use of sub ammo should isn’t making a difference in the least.

The wording is confusing. You mean POI versus POA. or are you talking physical recoil "jumping"?

Checked Rail? Optic? Action tight in chassis?

Are you impacts keyholing?

 

[TheGerman]

Does it have a brake? Is it installed sideways?

 

[Long Range 338]

2 things to check if you haven't already are body position (making sure you are behind the rifle and the recoil impulse is straight backwards) and the other is the shape of the stock. If the stock has much drop in the comb it can lift the front of the rifle during recoil. For us to troubleshoot your issue, you will probably have to post a video showing rifle position, body position, and recoil impulse to narrow this down. You can also review some of Lowlights videos for the online training section.

 

[BOLTRIPPER]

The one I’m having issues with is a 26” 1/10 bull, mag fed Rem 700 SA .308, with Timney trigger,

that there is your problem...you got a bull barrel ........get a "cow" barrel

 

[vh20]

Almost sounds like something isn't concentric (bent barrel, bore misaligned, etc). Crazy idea, but worth a look I guess.

 

[Dthomas3523]

Between cleanings...my accuracy in my benchrest 223 rifle drops off at the 17th round mark.

May I suggest that you shoot at least 1 fouler shot after a cleaning before grouping & unless your breaking the barrel in...I would tend to think that cleaning after every third shot is a bit of an overkill for a smokeless rifle.

How heavy is the rifle?

Unless heavy enough...a 308 round will make the rifle jump around from recoil.

Properly driven .308 will not “jump,” regardless of weight.

If it does, it’s you, not the rifle.

 

[Milo 2.5]

Almost sounds like it is a left twist barrel.

 

[Downtown]

I'm really curious as to the answer. I don't think some of our suggestions are relevant, as he has two identical rifles and only one jumps. So not him and not things like stock fit. A really good question.

 

[SPAK]

Some questions:

Are you using a muzzle brake?

If you are I’d swap out the brake with one of the same caliber from another rifle that doesn’t exhibit the”jump” you’re seeing. See if that makes a difference.

Running suppressed?

You said subs do the same thing? I have a hard time believing that subs generate enough recoil to move the entire rifle 4-6”. Now if you’re saying that your reticle moves 4-6” on the target that’s different.

What caliber are the other rifles you have that do not exhibit the jump you’re seeing?

 

[bax]

I got nothing so I'm just spitballing but here goes ...

verify the twist, direction and rate. Maybe its really a 1:8, not a 1:10.

All the guns I had that hopped around on bipods were fast twist shooting light-weight bullets fast. But like the man said, it was probably me.

Can you pull the barrelled action and put it into a different stock? Maybe the recoil lug is not bedded correctly or isn't flat and the barrel is tilted to one side.

Swap bipods?

Remove the brake to change harmonics? You did say "can and no can".

Thinking about the hop itself, so what would make a gun do that? There is some force pushing the gun to the right. Could be your hand or because you aren't straight behind the gun but you already eliminated those.

As the bullet goes up the barrel, it will cause the barrel to twist. The untwisting torque might make it hop. If the gun is especially lightweight, recoil might make it jump into the air and drop somewhere - on the other hand, a 26-inch bull outta stay wherever you put it.
Try slower loads to change the barrel harmonics?

Is there a lot of drop at the buttplate so that the recoil tends to push the gun into the air or, at least, make it light on its feet?

Maybe the rifling was cut non-linear. Measure twist at the muzzle and just in front of the chamber.

When you down the long shiny hole, it looks straight, right? If is is bent, since the gun goes right I would expect the bend to be to the left. By the way, how does it shoot? are the holes in the target round?

When it jumps does it seem to torque or is the motion more straight - like a shuffle step?

Everything else I came up with involved fairies, witches, trolls, and invisible o'possum's. Oh, and friends with string and a wicked sense of humor.

 

[Snuby642]

A bipod loaded up enough to get barrel touching on a stock that is not stiff enough will do that but may not show up hand held or off a bag.

Load up bipod and have assistant check for clearance .
Quick free check.