ACCURACY- WANDERING GROUPS

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  • Last Post 05 May 2019
joeb33050 posted this 04 May 2019

 

ACCURACY- WANDERING GROUPS

 In the past, I have shot groups almost exclusively, seldom for score. Lately I have been trying to learn to shoot score, for the 50-yard rimfire matches at the club. The targets have 25 bulls, 1 shot per.

 The group center moves relative to the aiming point as I move the rifle from target to target; with no relationship between rifle movement direction and group center movement direction that I can detect. This has happened for as long as I can remember, but doesn’t matter in group shooting.

 I have no guns with "bench rest" 3" wide forends.

 I began with my ancient and reliable Hoppes front rest, with a Stoney Point Universal Front Bag, (4.75" L X 2.5" H X 2" W), and a Protektor rear bag. The front bag is attached to the Hoppes rest with double-sided tape and the Velcro holder straps. The front rest is free to turn left and right, the top piece is free to rotate on the shaft. Everything else is locked down. Coarse elevation adjustments are made on the Hoppes front rest; fine elevation adjustments are made by sliding the gun forward and backward. Windage adjustments are made by moving the rear bag left and right. I put baby powder on both front and rear rests frequently, to eliminate friction and stickiness.

After a lot of experimenting and several contraptions, it looks like the front rest/bag is the culprit. I went to the Don Baker front rest. With a sled on some rifles, a half sled on others, and tilt eliminator and a brass screw/acorn nut on the Ruger Charger; most of the wandering group problem seems to be gone.

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joeb33050 posted this 04 May 2019

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joeb33050 posted this 04 May 2019

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Ken Campbell Iowa posted this 04 May 2019

hi joeb ... do you have a weight limit ?  if not, put lead or brass into your stock, front and hollow buttstock .  mass is your friend.

even with the magic of plastic stocks, i would worry that factory bedding is good enough ...  i would re-bed everything again just to gain confidence.  sometimes confidence is enough difference, the only difference.

even the bench is part of the resonant system ...  we found that even moving our elbow on our 4 inch thick poured concrete bench changed zero .... and consider that moving a 4 ounce barrel tuner ( nut ) 0.002 inch backward moved both the impact and our group size.

when we were shooting high level 22lr bench, we had a couple guys shooting "" pistols "" ... they never quite won a match, but scared the heck out of us ... they could get in the top 5, which is really as good as winning .  they used a rest pretty much as yours, except they used a front bipod, but let it slide on a baby-powder flat plate also.

the good news::  in competition, you don't have to be perfect, you only have to outshoot everybody else ... they are fighting mother nature's little tricks, the same as you.

i attach a pic of a benchrest that we built ... the gun is never moved on the rest ( except for the reset of the slide from recoil ) the whole upper carriage of the rest pivots and tilts to aim at the next bull.   on zero-backlash adjustments, btw.  the locating screws were needle-sharp micrograde carbide .  the rod caddies were a product of ours, powder coated;  lester bruno bought the whole run, nice guy.  

we might have over-obsessed, but it was interesting. as soon as i get through plinking, i might get back into obsessing . 

enjoy your target posts, guilty pleasures of lurking, i guess.

ken

 

 

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mashburn posted this 05 May 2019

Ken,

The liberals are going to put a lawsuit on you people for contaminating that cornfield in the back ground with lead. Send me a couple of bushels, I'm short on lead.

Mashburn

 

David a. Cogburn

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