advice on tightening groups

[rsbhunter]

Ok, shot my 260 AI varmint contour CBI bbl from NSS and then sent it off for muzzle brake, leade lengthened, nitrided.....and got it back, set it up, and shot it again.....It is super consistant....but at 100, i'm getting 1" to maybe 3/4" groups (very light wind, sunny, benched).......before and after the work.....this is fireforming, or once fired, neck sized cases....140 grainers...Berger, Sierra spitzers (hunting bullet) and Nosler custom comps...powder H4831SC, and RL17.....I'm going to try 48.0 grn.s of Win 760 per nosler manual with 100 gr Nosler Ballistic tip.....Now, those groups aren't bad by any means, but i was honestly expecting better...scope is tight, Sharp Shooter trigger set at 1-1/2 .B&C tact stock skim bedded, tang free floated, screws torqued to 45 in lbs. Anybody have one in this caliber?....maybe i need to stretch it out to 200-500 hundred yards? Any help would be great....Thanks, rsbhunter
before work, stock bbl

after work done...might just be a 1" bbl????

[rsbhunter]

Ok, shot my 260 AI varmint contour CBI bbl 1-8" twist from NSS and then sent it off for muzzle brake, leade lengthened, nitrided.....and got it back, set it up, and shot it again.....It is super consistent....but at 100, i'm getting 1" to maybe 3/4" groups (very light wind, sunny, benched).......before and after the work.....this is fireforming, or once fired, neck sized cases....140 grainers...Berger, Sierra spitzers (hunting bullet) and Nosler custom comps...powder H4831SC, and RL17.....I'm going to try 48.0 grn.s of Win 760 per nosler manual with 100 gr Nosler Ballistic tip.....Now, those groups aren't bad by any means, but i was honestly expecting better...scope is tight, Sharp Shooter trigger set at 1-1/2 .B&C tact stock skim bedded, tang free floated, screws torqued to 45 in lbs. Anybody have one in this caliber?....maybe i need to stretch it out to 200-500 hundred yards? Any help would be great....Thanks, rsbhunter
before work, stock bbl
after work Maybe just a 1" bbl?

[1Shot]

..Settle on RL17 powder & work on it...Jumping around from powder to powder is trying to fall on it out of dumb luck...

[ICUDIEN]

I agree stick with just one powder and one bullet. Try adjusting powder weight. Then adjust bullet seating depth( this is where I have gotten my biggest gains). Some might say to do it the other way but this way works good for me.

PS: 1shot I miss the bouncing butt.

[JCalhoun]

hunter;

You didn't mention anything about your technique.

Are shooting from a bipod, cast iron rest, sand bag? Is the platform moving any? How about breathing, trigger control, grip, etc.?

Has anyone else shot the rifle and had the same results?

[bigedp51]

Try changing the trigger guard screw torque settings up and down and see if this effects your group size.
At on time I had the web page saved for this tuning method but can't find it, sorry. But changing the torque does change how the barrel vibrates and thus group size.

[rsbhunter]

cement bench, steel pipe legs set in cement (gun club) san angelo front rest, sand bag rabbit ear rear bag...i have shot since in my early teens, started on 4 position 22 with a Savage Anschutz....(always Savage!!!).. so i know the fundamentals of trigger squeeze, breath control...sight alignment, etc...i understand about picking a powder, but i would think that i would get SOME variation with using three different bullets?...any way, i'll just keep working on it....if not, there will be a 260 AI for sale....rsbhunter

[racinready300ex]

How I work up a load. Is pick a bullet/powder combo based on what I want to do with the gun. I do two ladder tesst at 300 yards. If the results of the two look similar I move on to seating depth. Seating depth is huge. I generally work from a .01 jam out, then go back .005 either way.

I was working on a 178 A-max load, and my groups were something to the affect of .6xx, .8xx, .9xx, 1.0, 1.1xx just changing seating depth .010 with each group.

Shoot a couple 5 shot groups too confirm results.

If those bergers are VLD's are you jamming them? Most seem like a jam on VLD's. Also do some shooting at longer ranges. I have a 6BR that only shoots about .5-.7" at 100 yards, but shoots 3" at 600 most of the time, with a few in the 1-2" range.

[Balljoint]

This may be the web site you want for Savage Action Torque http://www.accurateshooter.com/techn...torque-tuning/

[gotcha]

RSB, Yer gettin' some great tips here!.............Like ICUDIEN & 300x I determine powder chg. 1st by varying 2/10th grain on sm. cases & fast powders to 1/2- 3/4 gr on medium case, slower powders. Make up 6 rnds ea. powder wgt. w/ one @ Max. Shoot 3 of ea. wgt. then repeat to prove the results of 1st sets of three. I know you shoot well & I'm sure your tightest group will repeat. Shoot all three shots THEN let cool. Next do seating depth. Start @ .040" off lands (6 each again) & lengthen in .010" increments 'til you're jammed .010" (Bergers DO like to be jammed) Repeat shooting procedure of powder wgt test. The seating depth test is usually an eye opener! After you get your best depth group, vary seating depth in .002" increments on either side of the best (Most accurate) seating depth. You may tighten the groups yet again. According to Berger their VLD's will sometimes shoot best waaaay off the lands. Like .050" to .080".... There's some info on their web site regarding this.... No need to shoot 5 shot groups dev. lds, if your 1st three shots are 3" what will 2 more shots prove? Shoot 3 followed later by 3 more @ different target & avg the six for group size. Big Ed & ball joint have interesting info but that comes AFTER you've got your best load. Good luck RSB, I know you can do it ;D Dale




'

[ShaneG.]

I have a 28" 8twist 260ai bull Criterion. I have not played with it too much yet with load workups. I have shot 140 amax's,140hpbt's and 95g vmax.

I have used 4831sc,MR2000 and shot one group with Superformance.This was with 140's and superformance it was the first load I tried with a clean barrel. Using a cheap front rest and rear bag prone and it was 90 and humid as you could get.
[img width=337 height=450]http://img.photobucket.com/albums/v392/sgregory/20110724154935.jpg[/img]
This group with 95g vmax and MR2000 first load tried with it using book 260 data at 3450fps.
[img width=600 height=450]http://img.photobucket.com/albums/v392/sgregory/20110724154922.jpg[/img]

I will say screw torque does make a difference here's 2 groups same load same day all I done was loosened the rear screw up a tiny bit. Afterwards I found out I had a crack running from front pillar to the rear. This is a .223 though.
[img width=337 height=450]http://img.photobucket.com/albums/v392/sgregory/20110724155023.jpg[/img]
here is the group fired right after tweeking the rear screw.
[img width=337 height=450]http://img.photobucket.com/albums/v392/sgregory/20110724155028.jpg[/img]

[rsbhunter]

I will check the seating depth, and do a ladder test....i will also try the rear screw trick.....maybe there is a bug hole hiding in there after all...Thanks for all the help, will STILL read all posts with suggestions.....rsbhunter

[jglover_81]

I read on here some time ago that someone suggested working loads up with the bullets touching the lands. One of the reasons was most bullets perform better closer to the lands (not all of them do). Once you find your best load if you have to seat the bullets deeper you don't have to worry about increasing pressure you will actually decrease it. The idea sounded great to me. I tried it on my 223AI and it worked very well! I'm working on it with my 243 also.

[racinready300ex]

I read on here some time ago that someone suggested working loads up with the bullets touching the lands. One of the reasons was most bullets perform better closer to the lands (not all of them do). Once you find your best load if you have to seat the bullets deeper you don't have to worry about increasing pressure you will actually decrease it. The idea sounded great to me. I tried it on my 223AI and it worked very well! I'm working on it with my 243 also.

To a point. Once you get farther from the lands you'll start reducing case capacity to the point it can cause pressure to increase.

[jsthntn247]

I have a 28" 8twist 260ai bull Criterion. I have not played with it too much yet with load workups. I have shot 140 amax's,140hpbt's and 95g vmax.

I have used 4831sc,MR2000 and shot one group with Superformance.This was with 140's and superformance it was the first load I tried with a clean barrel. Using a cheap front rest and rear bag prone and it was 90 and humid as you could get.
[img width=337 height=450]http://img.photobucket.com/albums/v392/sgregory/20110724154935.jpg[/img]
This group with 95g vmax and MR2000 first load tried with it using book 260 data at 3450fps.
[img width=600 height=450]http://img.photobucket.com/albums/v392/sgregory/20110724154922.jpg[/img]

I will say screw torque does make a difference here's 2 groups same load same day all I done was loosened the rear screw up a tiny bit. Afterwards I found out I had a crack running from front pillar to the rear. This is a .223 though.
[img width=337 height=450]http://img.photobucket.com/albums/v392/sgregory/20110724155023.jpg[/img]
here is the group fired right after tweeking the rear screw.
[img width=337 height=450]http://img.photobucket.com/albums/v392/sgregory/20110724155028.jpg[/img]

How many pounds did you have your front and rear action screws set to?

[ShaneG.]

Not sure of the torque. Front one was fairly tight and when I loosened the rear it let the tang lift up a little bit then the group shrank.

[CharlieNC]

Last year I was talking to a "famous" benchrest rifle builder to get some tips about loading. He said the top three important factors is to find a bullet your barrel likes. I've been working on a 25-06 and getting little improvement until switching brand of bullet; night and day improvement vs minor effect of powder, etc.

[jsthntn247]

Not sure of the torque. Front one was fairly tight and when I loosened the rear it let the tang lift up a little bit then the group shrank.

Sounds like you need to be the rifle.

[rsbhunter]

Well, i loaded up some Bergers with H4831SC, maybe not the fastest powder, but it's a starting point, the Bergers are set at 0 clearance, in other words, just toching the rifling....if this doesn't work, i'll try backing off in .010 increments, and if THAT doesn't work, i'll try the same deal with RL17, and then H4350....then on to other bullets...I really appreciate the help guys!!!!!rsbhunter

[scottw9120]

just curious, what type of powder thrower are you using and have you trimmed length of case. I went with expensive thrower and made sure case length was same helped most.

[tammons]

Assuming you have your rifle set up properly, IE bedded, action torqued properly etc. if you are trying to shoot one hole groups,
I would start with a known accuracy powder for that round and get some Lapua Scenar Bullets and load them jammed about 15 thou and work up a load.

Scenars have shot tighter than most other bullets I have tried. Bergers 2nd.

RL17 is great for the extra speed but its temp sensitive so I would start with something else if only shooting target.

+1 on weighing your powder, IE each load by hand.
Top shooters use a scale that measures down to one piece of powder.

I just got my hands on a .02 grain electronic scale.
Even a RCBS chargemaster rounds off a good bit.

Also every rifle I have run for accuracy loads, for VLD bullet I always started jammed about 15 thou. Flatbased bullets jumped about 10-15. and work from there.
Can remember where I read that but it works for me.

[jsthntn247]

I'm not a professional gunsmith, but I have bedded a bunch of rifles. If your front action screw is tight and you loosen your rear action screw and the tang comes up causing groups to shrink, you have a improperly bedded action. It sounds like you are binding the tang which can cause accuracy problems. I would address this issue before I burnt up 200 dollars worth of bullets and powder.

[rsbhunter]

I am using a rcbs chargemaster, that i have checked against a beam scale(sounds backwards, doesn't it) and it wasn't my gun that the tang lifted on, but it is something to watch.....My stock is bedded(skim) as it is a B&C tactical ...Now, NOT to start a war, and i honestly do believe that the torque does effect accuracy, but if a rifle is bedded with say, Devcon (very hard and stable) once the action screw is contacting the trigger guard (steel one) how much compression can varying amounts of torque change the "seating" of the action/bedding material, given it is a "mirror" image of the action? Not the same thing, but in engines, the torque is actually a measurement of the bolt, or fastener "stretch, not the compression on the material its self. I always thought that if a bedding job was done correctly, that once the screw was "tight", that it was there, as much as it was going to be....now, i will NOT argue with Stan Pate,(or anyone on this site) read the article, and the man knows his guns....so i will bring my Fat Wrench with me to the range, and honestly try some different torque settings..... just had some thoughts....rsbhunter

[JCalhoun]

hunter;

I believe you are correct about the torque and bedding idea. I only snug my action screws and check them periodically.

How hot are you letting the barrel get before taking a break?

[rsbhunter]

Not hot at all....i shoot a three shot group, then the bbl cools to warm...not much above ambient air temp....i have a major fear of overheating a bbl...i shoot alot of close to overbore cartridges, and i am always cautious about the heat factor...cheaper to let it cool down, than to rebarrel... I have loaded some 100gr nosler ballistic tips...maybe it likes lighter bullets...but it is 1-8".....rsbhunter