Range Report Vertical Stringing Advice

[CEL317]

I just got a new chassis - XLR Carbon - for my Tikka T3 .308 and I'm having an issue with vertical stringing that I never had before.

My load is:
Nosler Custom Comp 175gr
IMR 4064 42.7gr
Lapua brass
CCI 200 primers

The primers are a point of concern as I've only used GM210Ms but haven't been able to find them so I've had to substitute. But given the velocities I'm seeing I don't think that is really the cause. I did a magneto speed chrono on a different 5 shot test before I saw my 515 yard target as follows:
2632
2616
2626
2628
2627
AVG 2625
SD 6
ES 16

The groups were shot without breaking the cheek weld and and at the bottom of the breathing cycle.

100 yards - 3 shots

515 yards - 5 shots

Appreciate any advice/recommendations.


I am logical, rational, analytical, and direct. Just call me Sheldon.

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[redbullitt]

Load looks good. Your velocities look very nice, so at least it's not a velocity spread issue I don't think. I doubt the primers could cause that. I have had to switch primers before and never noticed anything like that happening.

You have a perfect vertical string on the close and far target, so I think you definitely can pull the trigger.
IF this has just started with the stock change I think we should start there. Check out EVERYTHING that was changed.

Simple first.
Is everything torqued properly and fitting to spec?
You have lots of adjustability there, make sure everything fits you well.
I have had an issue before where I changed stocks and I ended up with a bit of a cheek weld issue. It caused a similar issue to what you are seeing, so that may be worth a look.
Could you possibly be having a rear support issue? Sometimes we squeeze with the left hand at trigger pull and not realize it. That stock shape is different than a conventional one. It may take a little rearranging and getting used to.
Breathing can cause nice vertical stringing like that too.

Can this been duplicated by another shooter?

Possibly try shooting 1 shot. Break position, get up wait a minute. Reset and shoot another shot. Repeat. See if anything changes.
Try switching the stocks back too. See what happens. That may really narrow things down for us.

 

[40xs]

What redbullitt said, plus, I noticed you have a rather long pistol grip; Make sure it is not touching the mat as the rifle fires, as you don't want any other point of contact between the bipod and rear bag!

 

[OF&B]

Nice job on the ammo.

Bedding? Skim bed it or at least a dab behind the recoil lug?

 

[RobertB]

Seems to be in the stock. You know it is if the load is the same and it didnt do it before. I would check torque and seeing if your grip is mseeing you up like it was said before. But now going into a different grip style too might have some change. Have you played with your grip on the rifle?

Interested to see what others think. Good luck

 

[RobertB]

And maybe checking your scope base and rings since you just put it all together too.

 

[CEL317]

Thanks for all the suggestions. I had a friend make the same suggestion about shooting one round, break position, rebuild, and shoot again. I torqued everything to specs as I put it together, but I am not above tearing back down and doing it again. I am really thinking it is something I'm doing and not the stock (heard too many good things about the XLR to think it would be).

I didn't think about the grip possibly "grounding out" when I was shooting. I will verify that next time.

A little more background: before the group at 515y, I hit 6" steel to confirm I was on, then shot the 5 round string, and then shot steel circles - 6" (hit), 5" (hit), 4" (hit) - all in a row but breaking position between shots. Which leads me to believe the vertical stringing isn't happening every time.

Thanks again for the advice!

 

[RobertB]

My manners mini chassis had ti settle in as it stringed real bad and then settled in and was perfect. Wondering if yours is doing the same.

 

[CEL317]

After some experimenting I have come to the conclusion that it's my bipod - or more specifically how I use the bipod with the new chassis. It appears that I have to load the bipod more than I used to. Does this sound right to you guys?

100 yards
Moderate loading

Light loading

Heavy loading

515 yards
Heavy loading

This is my first pistol grip precision chassis so I think I have to adjustments to make to get the feel for it. Thanks for the suggestions.




I am logical, rational, analytical, and direct. Just call me Sheldon.

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