Huben Ring shaped indentations inside gk1 barrel

[subscriber]

A small bore tube can stand surprisingly high pressure, even with a thin wall. So, a stuck slug in a Huben barrel is not going cause a bulge from even 4500 PSI air pressure. Just think of a rimfire barrel and the peak pressure of 24000 PSI. Also, the thin brass rim of the case that handles the same pressure; albeit because the unsupported area is small.

What will bulge a barrel, is if a slug is stuck far enough down the barrel that the next one can pick up speed before running into the stuck one. That is like the difference between pushing another vehicle, starting with contact from zero speed; and running into it with a large speed differential from a distance.

 

[Asher]

Hmm. Well some of the indentation rings are near the muzzle but some are near the breech end. There's 4 total i think

 

[subscriber]

Is it possible that rapid fire can shoot some slugs at less than full pressure (or valve duration), so getting some slugs stuck in the barrel? That sounds hard to believe, unless a PCP is regulated, or has a plenum, or a depinger that uses a flow restrictor.

 

[Asher]

I also find it hard to believe especially since the fire cycle on hammerless AGs and the pressure spike happens so much faster than with many pcps that use a hammer and valve, but I really dont know how else they got there. Wish I could know for sure if any or all of them were there already to any degree but I never really inspected the barrel until I went to polish it over a year into owning it. It's accuracy hasn't always been this terrible which leads me to think that I did something to cause them. Just not sure what.

I've rapid fired my k1s and not had this happen, and polished my k1 barrels and the barrel of my aea challenger and they all saw improved performance

 

[subscriber]

It sounds like a bit of research is in order, to see if other GK1 owners have had the same problem.

 

[Asher]

That's partly why I made this thread.

Just got and polished the new barrel today.

Unfortunately my fears that the new barrel and magazine would be unkind to .254 slugs proved to be the case so now I've ordered the .2513 and some .253 AVS to see which one works. Then I suppose I'll have to order a reducer from corbin.

Unless anyone here wants to trade their gk1 barrel that likes .254 for one that likes a smaller diameter...

 

[subscriber]

The mag chamber diameter also matters. You don't want to struggle loading the mag, nor have projectiles drop out because the barrel like smaller projectiles.

You need to be sure that the barrel bore is properly aligned with all the chambers in the mag. Refining that alignment might help, in your case. From the video below, note the alignment screws and procedure, starting at 9:17 into the video:

 

[Asher]

The mag chamber diameter also matters. You don't want to struggle loading the mag, nor have projectiles drop out because the barrel like smaller projectiles.

You need to be sure that the barrel bore is properly aligned with all the chambers in the mag. Refining that alignment might help, in your case. From the video below, note the alignment screws and procedure, starting at 9:17 into the video:

Thanks, I already know how to do this. I do it a bit differently though. I put a slug into the magazine and push it into the barrel until only a mm or so of the slug is still in the magazine and most of it is in the barrel. Then I tighten the screws locking the barrel in position, remove the mag and slug, replace the mag and rotate it checking alignment on all the slots. Works great and I've done it to all the hubens I have owned