I'd wait to talk to S&W next week.
There are a couple of issues to consider when replacing barrels in older 3rd gen guns, especially those with aluminum frames.
First, a replacement barrel has to conform to the same slide/breech face design. The older guns had what are called narrow breech face cuts, with corresponding narrow barrel tabs (the rear of the hood). Newer slides had wide cut breech faces, often called straight cut slides, and the barrels had wider tabs to fit the wide breech face cuts.
The narrow cut slides had the breech faces machined to form curved 'shoulders' right above the top of the chambered case, so the cut above/between them was narrow. This narrow cut extended up to where the barrel tab met the breech face.
The straight cut slides eliminated the curved breech face shoulders, making the 'machined cut' wider (straight) and continuing upward to where the barrel tab met the breech face. (They changed the extractor spring tension spec a bit at the time of the machining change, as well.)
So, a narrow cut breech face requires a barrel with a narrow tab, and the straight cut breech face requires a barrel with the wide tab.
Now, as the barrel cam lugs (on each side of the feedramp) run up & down within the frame cuts during unlocking & locking, they can develop peening and wear patterns in the frame which may interfere with a different barrel dropping in and functioning properly. Just depends on the barrel and the frame combination in any particular gun.
I tried to put a different (used) slide & barrel onto a different (used) 6906 frame one time. The slide wasn't a problem, but the different barrel just wouldn't run & hand-cycle smoothly within the well-used frame. The barrel lugs just wouldn't run down & up the corresponding spots in the frame. I ended up having to use the barrel which had been used with that frame, in the "new" slide, although it did require some fitting to work with the "new" slide. This involved some adjustment of the barrel hood & tab, while still maintaining proper tolerances.
It's really best left to a factory tech, gunsmith or armorer familiar with the older 3rd gen guns. (Some newer armorers may have never been in the position of having to replace a barrel, because the newer production guns have pretty much made it a situation where new barrels and slides require less fitting - or no fitting - than might have been needed with older guns.)
Besides, the factory repair tech will have more than one barrel available to try and fit to a particular slide & frame, so he can probably more easily try to find one which will fit and function better in your frame, using your slide, with whatever minor fitting may be necessary. (Of course, I'm speaking in generalities, as I have no way of knowing if they have many - if any - barrels of the different production styles of the 3913/6906 barrels available for repair at this time. You'll have to call and ask.)
It's important to have the barrel fit the slide, as well as move and function as intended within any particular frame. Smoothness and freedom of proper movement is critical to safe, optimal operation of the pistol.
FWIW, the condition and shape of the top of the frame cuts (which create the release point for the barrel to be lifted and moved into battery with the slide) are critical. If they become damaged, or go out-of-acceptable spec, the frame becomes useless and you can find yourself needing a new gun. I knew another armorer who had that happen with an older 4013 (made on the .45 alloy frame). They examined the gun and told him it was no longer safe to use, but since he was the original owner they replaced that gun with a new/different model (since no more 4013's remained available).
Just my thoughts, but I'd discuss this with the factory before spending any money on a barrel purchased elsewhere - and I'd let someone familiar with the guns, and experienced in making repairs, examine the gun and do the work.
__________________
Ret LE Firearms inst & armorer
Last edited by Fastbolt; 12-29-2011 at 11:27 PM.
|