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viper2788 · Member

Once sighted in, accuracy is excellent - however a day or two later my POI would change requiring me to set my zero again. How do you guys go about this? Or better yet, could someone explain to me the science behind barrel configurations? I did some research but its still all a bit confusing to me as I simply lack experience.

I've heard of many people adding an additional barrel band near the front, but that doesnt seem to work too well as you have multiple contact points throughout the barrel. Well, at least it didnt work too well for me. So then I tried using a single barrel band mounted all the way down near the fill cap... worked better, but still changed a little over time. Free floating the barrel isnt an option for me as the barrel is just too thin, and im sure it'll get banged up sooner or later... esp with an extended muzzle brake.

I sort of have a new plan, but thought I'd share and get some input before I start investing. This is the setup I'm going for:

I'm planning to order 2 sets of the TKO "drilled barrel bands" which come with additional set screws. I was thinking of fully securing the barrel and air tank with the band near the breech(after boring it out to fit the wider diameter), and only securing the the air tank with the front band(at mulpitple locations), which will be located just by the muzzle brake, leaving the barrel just sitting in the band but not secured. what would you guys say?

Also, if anyone have found simpler solutions that work, please share! thanks.

SMP · Silver Status Member

The POI shift you are experiencing is possibly-probably coming from the expansion and contraction of the tube. This is common. pressure, temperature and temperature differences ie sunlight on one side will cause it.

One way to get around it or minimize it is a semi float. Use a barrel band that is larger than the barrel but supports the barrel useing a non rigid material. Bob uses O rings that sit in a groove inside the band...I believe you can buy these just not sure where.

I like a full float with the barrel inside a protective tube and the tube is held by bands(seen often in match guns) but thats some fairly intensive work

viper2788 · Member

Thanks for the info. So you think I'd be alright if I went with my plan, with adjustments to the front band as you mentioned? The reason I want a band near the breech is because I heard somewhere there is just a thin screw securing the breech to the rest of the gun, so I'm hoping that the rear band will secure that tightly without causing too much expansion issues.

SMP · Silver Status Member

Sure I think your plan for a band near the breach would work fine. I wouldn't be too concerned with the integrity of the breach. It is held by two screws one at the rear of the trigger assembly and another through the center of the breach. It is quite secure. But adding a barrel band near the breach wont hurt anything.

For POI and other accuracy issues it is from the center of the barrel and forward that counts...This will be where you would use the semi float band.

rsterne · Moderator

My Disco suffered from POI shift as the pressure in the tube changed.... My solution was to tighten the lower setscrew tight on the air tube, but with the upper screw only "just" touching the barrel .... It required blue loctite to prevent it from loosening further....

Bob