GTA

General Discussion To Gateway To Airguns => Airgun Gate => : raterminator July 03, 2006, 08:57:33 AM

: I would like to keep you updated
: raterminator July 03, 2006, 08:57:33 AM

on my efforts to correct the barrel droop problem which I mentioned before (Gamo 440, .22)

I used a plastic cup from paint spray can to make a shim for the rear ring. The thickness of the shim has already reached 1mm (0.040”) and it’s still shooting 2” lower of POI at 10 yards. How thicker can I make the shim before damaging the scope, unless of course 1mm has already passed that safety line?

: RE: I would like to keep you updated
: arathol July 03, 2006, 10:04:06 AM

Any shim is too much. Assuming the rings are aligned properly to start with, any shimming will cause them to be out of alignment. Rings that are not aligned will bend the tube, even just a thin shim like a piece of 35mm film can do it. 1mm is way too much. Correcting droop should be done either by bending the barrel upwards slightly (Beeman has done this for years) or by using adjustable or droop corrected mounts.

: Re: I would like to keep you updated
: raterminator July 03, 2006, 10:22:53 AM

Thank you Dave,
It worried me too, and I'm glad that you prove me right.

: RE: I would like to keep you updated
: July 03, 2006, 10:32:31 AM

You need a Bikerscum Barrel Straightener (BSBS)...


http://img.photobucket.com/albums/v309/Bikerscum/bsbs.jpg


 20 bux, will fix your problem.


 BS

: RE: I would like to keep you updated
: raterminator July 03, 2006, 01:11:07 PM

Hmm… I’m not sure if it’s a right lever point for bending. Wouldn’t it be right to move it closer to the breach?

: RE: I would like to keep you updated
: arathol July 03, 2006, 01:15:15 PM

Actually, that would bow the barrel. You want to bend the entire barrel from a single point to keep it straight. Right at the receiver block is usually best.

: RE: I would like to keep you updated
: July 03, 2006, 02:23:13 PM

Ok, so..... move the jack closer to the breech?

BSBS MK-II

 BS

: RE: I would like to keep you updated
: arathol July 03, 2006, 03:01:49 PM

yes, but you only need one restraint point on the barrel. The other should be on the receiver block or you'll still get a bow in the barrel. What you might want to do is restrain the block, slide a heavy pipe over the barrel and put the jack at the end of the barrel. Lots more leverage that way. Thats how I do it. Tweak it just a little at a time, and the barrel stays straight.

: Re: I would like to keep you updated
: raterminator July 03, 2006, 03:12:57 PM

I think it's more correct placement.

: Re: I would like to keep you updated
: July 03, 2006, 04:14:42 PM

The barrel in the pic was my Fast Deer barrel. It was bowed, in a more or less constant arc from end to end. I just assumed all droop problems were that way.... my mistake.


Thanks for all the tips.



BS

: RE: I would like to keep you updated
: July 05, 2006, 05:01:16 PM

raterminator - 7/2/2006  4:57 PM

on my efforts to correct the barrel droop problem which I mentioned before (Gamo 440, .22)

I used a plastic cup from paint spray can to make a shim for the rear ring. The thickness of the shim has already reached 1mm (0.040”) and it’s still shooting 2” lower of POI at 10 yards. How thicker can I make the shim before damaging the scope, unless of course 1mm has already passed that safety line?

A couple things to check:

Does the barrel lock up at the same angle each time?
If you push the barrel up realy hard before firing is the POI higher?
Is it drooped lower after the rifle is fired?

Bad lockup can sometime mimic the effects of massive droop...and in a way it is droop, but the causes and solutions are a bit different.