CBIs and Air Rifle Accuracy

mobarron · Post by **mobarron** » Mon May 17, 2010 12:03 pm

For the past 5 years or so our rifle team has been using the recommended CBIs (clear barrel indicators), a piece of bright nylon filament inserted in the breech and pushed into the barrel so that it clears the muzzle. Our shooters pull these out from the muzzle when they are ready to shoot and often drop them on the floor of the range.
This year we q;uestioned the accuracy of the rifles (2002s) and have sent four back for servicing. We have gotten them back and find the velocity uniform but overall accuracy wanting. We're bolting the rifles down to a heavy piece of steel, using individually packed R-10 pellets and getting 10 shots groups ;that are in the two pellet diameter range.
We've been wondering whether there is something wrong with our locking the rifles down firmly or whether we might have damaged the crowns of the barrels with the CBIs. Our 2002s are about eight years old and it's hard for me to believe that we have shot out the barrels.

Guest · Post by **Guest** » Mon May 17, 2010 12:47 pm

I'd be suspicious of what the CBIs are collecting on the floor, and subsequently being put into the barrels.

jhmartin · Post by **jhmartin** » Mon May 17, 2010 12:56 pm

1) CBI's ... not just recommended anymore ... required

2) CBI's should be wiped off before inserting in the gun ... ESPECIALLY if they are being dropped on the floor ... placed on the mat or hung on the OH stand is better, but train your shooters to wipe them off anyway. Seems that if the gun is not theirs, they don't treat it as such.

3) Just because R-10's are expensive does not mean they are the best pellet for the rifles. Have you checked other pellets/sizes? Try H&N's, Vogels & such in 4.50 and 4.49 sizes. Some of our guns that shoot 4.49's very, very nicely, shoot 4.50 R-10's just like you are describing.
(Some of the best that ever shot in one of our 2002's were H&N 4.49 pellets in the green Diablo green tins ... inexpensive sporter pellets ... sadly we cannot get those anymore ... we use Vogel 4.49's now)

Rover · Post by **Rover** » Mon May 17, 2010 3:41 pm

I think jhmartin nailed it.

talladega · Post by **talladega** » Mon May 17, 2010 4:18 pm

clamping the gun to something will not allow the gun to recoil properly. i did this with my air rifle to test accuracy and was getting horrible groups like you but then I noticed a slight vibration of the whole gun after each shot.

so what i did was shoot the shot. then just rest my hand on the gun just enough to stop it from vibrating. once i did that, the groups were down to .177 sized holes.

RobStubbs · Post by **RobStubbs** » Tue May 18, 2010 5:46 am

talladega wrote:clamping the gun to something will not allow the gun to recoil properly. i did this with my air rifle to test accuracy and was getting horrible groups like you but then I noticed a slight vibration of the whole gun after each shot.

so what i did was shoot the shot. then just rest my hand on the gun just enough to stop it from vibrating. once i did that, the groups were down to .177 sized holes.

There should be no recoil with something like the 2002, so clamping it (properly) should be fine. I too agree that pellets need selecting for the gun as not all work. And really don't let the kids drop the CBI's on the floor. They should be taught to respect the guns and not risk putting anything dirty in them.

Rob.

jhmartin · Post by **jhmartin** » Tue May 18, 2010 8:14 am

I differ with Rob a bit. I feel that there is indeed recoil with an air rifle. Not very much, but a bit.
I use a Black & Decker "WorkMate" folded up and sandbagged (shot bagged really) to a hefty gov't style desk. The workmate seems to have just enough give to it to resemble a return to battery rest ... seems to work for us.

On the CBI's .... ask the kids:
1) What do you do with the pellets you drop (spill) on the floor? If they are picking them up and shooting them .... (deleted due to Political Correctness Censorship)

Same applies to smallbore cartridges ... what do they/you do? Even if it's a whole, brand new box of Eley EPS Red ..... (of course they'll NEVER have just one box on their OH stand when this happens)

Me .... I hand them a new box and go out hand begin kicking my truck tires till my toes say "that hurts!" and then go back in .... :-u

JSBmatch · Post by **JSBmatch** » Tue May 18, 2010 9:16 am

The Anschutz 2002 doesn't have a recoil absorber fitted, unlike the 9003, so there will be a tiny bit of recoil similar to a pre charged pneumatic.

I carried out my pellet tests with a 2002 from a sand bag bench rest and got a one hole group. Not as accurate as a vice, but it gave me confidence in the pellets.

JSB

Anschutz · Post by **Anschutz** » Tue May 18, 2010 10:26 am

I have shot a pcp Feinwerbau and Walther and there is definitely a slight recoil with them both.I can normally tell when everything has gone ok with the shot, relaxation, trigger release,follow through etc as it's then that I see a slight jump in the foresight. Colin

talladega · Post by **talladega** » Tue May 18, 2010 4:12 pm

RobStubbs wrote:
talladega wrote:clamping the gun to something will not allow the gun to recoil properly. i did this with my air rifle to test accuracy and was getting horrible groups like you but then I noticed a slight vibration of the whole gun after each shot.

so what i did was shoot the shot. then just rest my hand on the gun just enough to stop it from vibrating. once i did that, the groups were down to .177 sized holes.
There should be no recoil with something like the 2002, so clamping it (properly) should be fine. I too agree that pellets need selecting for the gun as not all work. And really don't let the kids drop the CBI's on the floor. They should be taught to respect the guns and not risk putting anything dirty in them.

Rob.

Well it's not recoil like you get with a .22

I have a Steyr LG100, it doesnt recoil as in make the barrel bounce or anything. It's just there is a slight vibration of the barrel and stock when its clamped in my test rig. I will be able to get rid of the vibration by doing some modifying of the rig. But with how it is now, if I load the gun and shoot it, and then load another one and shoot without stopping the very slight vibration (you can barely see it) after about 10 shots or so the grouping is a hole that is the diameter of 2 pellets.

All I would do is just barely touch the gun for a second or two to stop the vibrating and then grouping would be back to perfect single pellet sized holes.

mobarron · Post by **mobarron** » Tue May 18, 2010 5:10 pm

Talladega: We would be interested in your modification of your test rig. Our is a heavy peice of U-shaped steel that we have drilled for 1/4" T-shaped bolts that we slide on the accesory rail and then hold with nuts. It's clamped to a desk that is bolted to the floor. So it's very solid. We have a piece of 1/8" to 3/16" rubber between the stock and steel but we may still be getting vibration and we'll try dampening it between shots. We're at a point now where we need to get a broader selection of pellets.

talladega · Post by **talladega** » Tue May 18, 2010 11:38 pm

my test rig is a piece of railway track with a steel piece welded to it that the rail of the gun slides onto and 3 bolts are tightened.

I need to add some extra metal to strengthen it a little as I think the steel is flexing a little bit.

Sort of hard to explain. Once I get it done it should hopefully work better than it does now. Currently it is quite time consuming to test ammo.

Guest · Post by **Guest** » Tue Jun 01, 2010 12:34 pm

I don't shoot 10 meter any more ( eyes have had the course) but I do use my 2002ca for benchrest at 25 yards. Thing drove me nuts as I would get 2 or 3 shots to poa and then there would be a shift sometimes more than a pellets worth. This with a 36 power scope mounted. The velocity spread was less than 5 fps over the course of 50 shots, various brands of match pellets. The current crop of 4.49, 4.50 were just not making the grade. I did try a different scope, and various changes to the action /stock connection to no avail. Switched to 4.52 dia. pellets, the difficulty now seems to be resolved.