Inconsistant groups advise

[jonny315]

Hello everyone, I have developed a wild cat 6.5mm based off the 300 wsm case and shortened about 3/8''. empty case with water measures approx 65 grains and with a 143 eldx approx 60 grains.
once it is sized I fireform and anneal, then neck turn and trim. all cases seem to be within 1.5 grain of capacity once done.
My problem-
this has happened many times... I loaded up 3 rounds each of 56 grains and 56.5 grains of imr 8133 and shot .55 and .62 groups at 100 yards. about 50 deg outside and it was off a bench using a custom built tripod and sand bags.
Happy with the results I loaded up 2 5-shot groups of the exact same thing and went out this morning and shot 1.25 and 1.5'' groups at 100 yards. temp was about 45 deg. I have done this with retumbo and rl17. I just seem to be getting good groups but never consistent groups!
I have checked and my stock is tight, barrel is free from front to action, scope it tight, all oal match exactly and all cases are trimmed. I cleaned my gun, shot 3 rounds through it and tried grouping again and same results.
could I have just gotten an inaccurate barrel? I have noticed that as the speed increases when I do a latter test each 1/2 grain makes it move to the right from an inch to an inch and a half progressively.
any input would be greatly appreciated thank you.
jon

 

[L.Sherm]

How many rounds on the barrel?

 

[jonny315]

How many rounds on the barrel?

about 100-150, new when I started.

 

[Dusty Stevens]

Are you using wind flags and good rests?

 

[Zero333]

full length Size after annealing.

And try a different bullet and/or powder.

 

[Sandstorm]

What kind of stock is your action in...and have you used that stock with good consistent results in the past....
or is all this new...as in part's action stock etc..

 

[jrm850]

We talking hunting barrel or target Taper? Wood stock? Bedded? Barrel touching bolt? Scope base screws touching tenon?

 

[jonny315]

What kind of stock is your action in...and have you used that stock with good consistent results in the past....
or is all this new...as in part's action stock etc..

Its a new Winchester m70 that has been factory bed at the lug and tang, also has a supergrade contour with flutes. also it has a wood stock on it.
im going out and trying h4831 and rl 22 today.

 

[BoydAllen]

I think that you have the cart before the horse. IMO you need to either pillar bed the action, or have it done. Decades back, a friend asked me about a similar problem of inconsistency of groups. I pointed him at a good article on how to pillar bed and he did an excellent job of producing stress free bedding, which solved his problems. After that, he did all of his rifles with similar results.

 

[3Sigma]

I had the same issue with a 20 year old M70. I put it in a new B&C stock and skim bedded it... first 3 shots got better, but they still opened up when I shot 5.

My issue is the hammer forged sporter contour barrel... it heats up and warps a bit.

My solution was to change my load development methodology and go from 5 shot groups to two 3 shot groups, allowing the barrel to cool in between (using temp. strips to monitor). As this is a hunting rifle, 3 shots is good enough, and cool/cold barrel shots are actually most important, so it improved my performance and confidence.

It went from a 1.5 to 2 " gun to .75" @ 100 yds consistently. about as good as I can expect with a stock action and barrel.

Just food for thought. The new FN barrels have a good rep., but I read they are still hammer forged, and the fluting may exacerbate movement from heating.

 

[jonny315]

I think that you have the cart before the horse. IMO you need to either pillar bed the action, or have it done. Decades back, a friend asked me about a similar problem of inconsistency of groups. I pointed him at a good article on how to pillar bed and he did an excellent job of producing stress free bedding, which solved his problems. After that, he did all of his rifles with similar results.

that surprises me, I have gotten many factory rifles to shoot 1'' without bedding the action I didn't think bedding made that much difference

 

[Dusty Stevens]

that surprises me, I have gotten many factory rifles to shoot 1'' without bedding the action I didn't think bedding made that much difference

Makes a huuge difference unless 1” is all you are after

 

[Sandstorm]

I have found that a really awesome barrel in a ok stock caused the same kind of issues for me in the past,
however after custom bedded in the same stock shot light's out....consistently...your issues may not be the same but
sure reminds me if my issues.

 

[dolek]

Makes a huuge difference unless 1” is all you are after

+1 Dusty speaks the truth,it can make a huge difference . There are many variables involved,if you have a good bedding job you have eliminated one of the major issues.

 

[rwj]

Can anyone comment on how much of an impact the front rest and/or rear bag can have on group size? I’m noticing different recoil behavior when the shot breaks and don’t know if it’s primarily being caused by me or the way the rifle is supported.

 

[dstoenner]

If the butt of the stock catches on the recoil it will usually throw the shot high. For benchrest i use a used dryer sheet between the rifle butt and bag to make it slick for rifle to recoil smoothly.

David

 

[garandman]

What jumps out at me as possibles:

• Action bedding
• Temp sensitivity of powder
• I've had tons of great 3 shot groups. 5 shot groups are more telling of what a gun actually shoots, And 10 shot groups yet more so.

 

[jonny315]

What jumps out at me as possibles:

• Action bedding
• Temp sensitivity of powder
• I've had tons of great 3 shot groups. 5 shot groups are more telling of what a gun actually shoots, And 10 shot groups yet more so.

i went to a 3 shot group because i cant get a 5 shot under 1.5 moa consistently, thinking my barrel warms too quick!

 

[garandman]

i went to a 3 shot group because i cant get a 5 shot under 1.5 moa consistently, thinking my barrel warms too quick!

Barrel diameter ? Most barrels should be able handle 5 rounds.

 

[3Sigma]

Barrel diameter ? Most barrels should be able handle 5 rounds.

One would think... Mine is a sporter contour, but more importantly a hammer forged barrel that I believe has a significant amount of residual stress from the rifling process. I get a different POI if I shoot 3 x shot strings in a row - all up and to the right. It doesn't matter the load or bullet either. Once I started tracking barrel temperature it was an obvious relationship.

Eventually I'll replace it with a better barrel, likely a slightly heavier one as well, but that will have to wait until after deer season.