Too much cylinder gap?

[MK11]

A local gunsmith converted my 4-inch model 64 to a 3-inch by adding a model 65 barrel. Shooting Winchester 130 grain FMJ and Herters 158 grain FMJ, function and accuracy were fine at 15 yards but the flash and sound were like 110 grain .357. The same ammo in my factory Model 13 had both softer flash and report.

I don't have any other revolvers with such a noticeable cylinder gap--is this the reason? Is it a problem?

80191

80192

[WDR]

Your gunsmith, isn't.

[JCN]

Yeah he needed to clearance the barrel so it could make an additional full turn in but looks like he was lazy and took the easy way out. You’re going to lose a lot of velocity from that gap as well.

[MK11]

That’s what I was afraid of. Is this an easy fix?

I went local after Pinnacle Performance was unresponsive to email or voicemail. Lesson learned.

[WDR]

That’s what I was afraid of. Is this an easy fix?

I went local after Pinnacle Performance was unresponsive to email or voicemail. Lesson learned.

I'm not a gunsmith, but the barrel should be able to be unscrewed, shoulder set back, and then gap set and forcing cone cut for a proper gap. I'd be a bit concerned what the "gunsmith" may have screwed up when he swapped the barrels (did he use proper tools to hold the frame, etc).

[OlongJohnson]

I went local after Pinnacle Performance was unresponsive to email or voicemail. Lesson learned.

Next time, go Sokol.

[Malamute]

The 357 cylinders are roughly 1/10" longer, and the barrel correspondingly that much shorter where it comes through the frame. The gap should be .003" to .010" (3 to 10 thousandths of an inch), you have roughly ten times the max amount.

As was mentioned, the barrel needs to be turned back a thread or two and fitted so it torques correctly, then fitted for gap, and it can be set on the narrower side to reduce flash etc, yet not bind if it gets hot.


Or, you can wait and get the correct 38 spl barrel, yours is worth something to people wanting to build a 3" 65.

Your gunsmith should not have charged you to screw your gun up and not say anything. He should have refused the job if he couldnt do it correctly. Its probably safe to shoot, but going to be nasty in the blast department, as you found out, and probably spit badly with lead bullets.

[Outpost75]

Over 0.010" cylinder gap and you are very likely to stick one of those low velocity 130 FMJ range loads in the barrel. This was a common problem with the Army Ball M41 load shooting in worn out WW2 Victory models. Customer Service maximum barrel-cyliinder gap is pass 0.008", hold 0.009", although S&W now allows 0.010" as within new commercial spec.Back when I was inspecting guns for the feds in the 1980s that would have been rejected.

Expected Delta-V with standard. pressure lead bullet .38 Special is a. loss of 10fps for each 0.001" increase in "front gage" beyond Mean Assembly tolerance. With jackets and plus-P you can expect more, with 15 fps per 0.001 being a good approximation with slower-burning powders.

Normal factory fix to correct OFG or " open front gage", the factory term, is to refit a "plus" cylinder 0.005" longer than Mean Assembly Tolerance. Common gunsmith fix is to set barrel back a thread and to refit after correcting any excess head clearance or end shake.