damaged barrel threads

[jesseskinner]

Bought a 9mm sti open gun on BE back in 06. It was built on sti short block by previous shooter less than 10k rounds allegedly...seller stated that the barrel had the comp come loose before...bought it had tons of fun for one season won a couple plaques with it... comp came loose again so I lock tightened it with high strength...came loose again and I wasn't happy with the thread engagement (from either inspection) so I talked to a Smith who claimed to have a jeweler who could fusion weld it so off it went...came back with a bigger bill than expected but I was willing to pay for no more drama...fast forward a few practice sessions and it was loose again.Out of desperation had the welder I use to weld 700 bolt handles (even though barrel was Ss and comp carbon) TIG it, no love there either. There is no apparent baffle strikes but the barrel threads are under 50% engagement when measured with thread mic, barrel still shoots good and comp still works.

I am thinking about breaking it out and seeing if I could salvage the barrel /comp. Does anyone see a problem with turning down the barrel, fitting egw cone comp, and either black lock tighting it or using rocksett...All work would be done one one of the lathes in my shop....

Any problems with this plan? Any suggestions?

[APL-G35]

What about installing the comp and then drill through and make a pin to pin it it place. It would need to just barely engage through the threaded portion to eliminate loosening. If done right you could make it almost seemless

[Iceman2733]

Is the barrels threads what is incorrect or the comps threads? You could always use a set screw with the comp. Also what loctite are you using on the threads? With engagement issues a stronger grade might not help but lots of people including myself use 272.

[jesseskinner]

It this the barrel threads that are damaged comp appears good but I have not made a tight fitting mandrel to confirm it... do not feel that chasing them (barrel threads)on a lathe would help as the pitch diameter has been reduced too much by multiple loosening with ccontinue shootin...272 is what I previously used but if I get it back together I will probably use the black grade for permanent installs of sleeves in engine blocks or rock sett like I have used on suppressor mounts and muzzle breaks on rifle barrels...

[BrianATL]

Get the green loctite don't have the number handy and drill and tap a set screw

[Sudden Death]

My vote is replace your barrel and get rid of your problem, sounds like when the barrel was threaded they took to much off the OD therefore the depth of the thread does not go into the matting threads on the comp and it works loose, this may have been caused by the threading tool tip was broke, the kept cutting the threads to where the comp went on, which ended up being to shallow

[jesseskinner]

Betting that the that Sti's threading tool was sharp as you can visually see the threads being taller at the back of the barrel and noticeably shallower at the front but I still thread mic'd it to see how bad it was (bad). Yes I could buy and fit a new barrel and be done but if a 30 dollar cone and a little lathe time get me back in the game....just looking to see if anyone saw a problem with converting the factory bull barrel to a cone comp (I am more of a rifle Smith, turn around ar and bolt gun barrels from blanks all the time, make chassis stocks etc.)...I will make a threaded go no go mandrel from brass or 12l15 to ensure that the comp threads are ok...really would like to salvage the comp as the French border cuts extend out onto it as well as being tired of it wanting a diet of $100 bills...

Edited June 9, 2014 by jesseskinner

[jpl]

Loctite 680 is what I use on my builds. Turning the barrel down, threading it for the conversion cone and using your comp should work well. I use a bushing barrel with a cone and Beddell's comp on my 4 1/2" open guns. Works fine and lives a long long time.