I have a beloved S&W Stainless 645, but it doesn't get much use. I had a chance to take it to the range the other day and noticed that while it was very clean and properly lubricated, it had a problem reseating itself occasionally between rounds. It fed just fine and I could easily reset the remaining 1/8th inch with slight pressure, but that's clearly not the way its supposed to be.

I could not find any evidence of burrs or other damage which would cause it to hang up like that. Weak spring? What should I look for?

If it is clean, lubed and worked ok before it might be time for a new recoil spring and perhaps mag springs while you are at it.
645`s are great pistols. Hope you get it going into battery again.
Jim

Could be an ammo issue also. Depending on overall length of the cartridge, the gun could be headspacing on the bullet.

Did you clean the chamber thoroughly to ensure there's no fouling in there?

A tight extractor will cause that problem too. Make sure that's clean and lubed also.

Usually either a tight/dirty chamber or a weak rebound spring (or maybe some really old thick oil if it hadn't been shot for quite a few years). That or SWC bullets seated out a little too far.

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H Richard
SWCA1967 SWHF244

If it were me ...

I'd replace the recoil spring with a factory spring, especially if it didn't match the measurement in this:


Then, I'd preferably replace the older metal-based 645 mags with current 4506/66 mags (improved lips, followers and butt plates). Or, at least replace the mag springs.

Inspect the front end of the recoil guide rod and make sure it's not peened (mushroomed), which could slow the slide/barrel from returning into normal battery.

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Ret LE Firearms inst & armorer

Thanks guys for your input. I do appreciate it.

I went back to inspect and deep clean again. (Long time military and I can't stand my weapons to be in anything but armory ready condition. Its the stainless version so inspection is easier.) The weapon was cleaned again before going to the range and experiencing the difficulty. I couldn't find any residual carbon or old residual oil at all. The light coat of oil appeared to be optimum with no thick residue anywhere.

I had never considered that I need different springs for different ammo. I've never replaced a thing except to substitute PacMar grips and still have the original stock spring in place. Its been pampered and has really had relatively few rounds put through it since I bought it nearly 30years ago.

I inspected the recoil rod and it looks straight as an arrow with no damage or mushrooming of any kind. I measured my factory recoil spring at 5-13/16" which doesn't square at all with the spring spec shown above. (Thank-you). I think I'll go find a replacement spring, visually compare, and see how she does with it.

Thanks guys. I'll let you know.

That could just be your problem, a spring for light target loads not having enough oomph to fully close the action and seat the bullets.

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H Richard
SWCA1967 SWHF244

Try Wolff Gunsprings, Im sure they have what you need.
Jim

The factory lists a set of both recoil springs.

Factory Part# 193020000 RECOIL SPRING SET (20071 & 20161)

Retail price in 2013 was $2.50 for the set, or $1.45/each for the separate springs. Shipping costs more than the cost of the spring set.

FWIW, #20071 is the wadcutter spring, and #20161 is the standard spring.

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Ret LE Firearms inst & armorer