1377 barrel

[crossliner]

That explains your problem then. If your 1377 barrel/band looks like this, then this it's problem.
http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,4523.msg51942.html#msg51942

This was my solution.
http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,4523.msg61234.html#msg61234

To keep the forearm from hitting the barrel band I installed a 2289 forearm. I could trimmed the original forearm , so it won't hit the barrel band.

I shimmed mine w/ CNC made delrin..

[1377x]

What are you using to hold the pump arm in place, if you are not using the stock plastic front sight?

P.S. If your are free floating the barrel, drill and tap the steel breech for a second and or third set screw.

Picture please.

i free floated the barrel on my disco pistol with just the one set screw no accuracy issues there.the barrel tilted up slightly still wasnt an issue

[smatjack60]

Think i may have found the problem,disassambled my gun. Noticed that the recessed hole for the screw that bolts the crosman breech to the tube had some burrs around it. With the stock bolt the pellets skipped right accros it. i had added a long nose bolt and every kind of pellet i tried hung up just as the pellet entered the breech requiring many attempts to seat the pellet,I,m wondering if this might have been derorming the pellets. I lapped the area to remove the burrs. Won,t know if this fixed until i reassemble

[1377x]

you are talking about the 4-48 breech screw recess
drop some candle wax in the hole.that should take care of the hang ups.if you need to remove the breech again just dig out the wax