S&W vs Ruger

[kwilfong]

Hey guys,
Info I gathered here was very helpful in sorting out the leading issue I had with my Blackhawk 45 Colt. Turned out the "Ruger thread choke" was the problem & lapping the bore solved it.
I just got a pristine S&W M24 & I'm wondering if "thread choke" is ever an issue with S&W's? Years ago I had a couple M29's & a 624. The 624 was a much better shooter for me than either of the M29's. I'm wondering if "thread choke" may have been an issue? I've always loaded #429421 mostly with Unique; 7gr in SPL & 9gr in Mag but some 22gr #2400 in the Mag.

[dubber123]

I have quite a few S&W's, and most seem to have some degree of constriction. I'm slowly getting them all firelapped.

[45fan]

Hey guys,
Info I gathered here was very helpful in sorting out the leading issue I had with my Blackhawk 45 Colt. Turned out the "Ruger thread choke" was the problem & lapping the bore solved it.
I just got a pristine S&W M24 & I'm wondering if "thread choke" is ever an issue with S&W's? Years ago I had a couple M29's & a 624. The 624 was a much better shooter for me than either of the M29's. I'm wondering if "thread choke" may have been an issue? I've always loaded #429421 mostly with Unique; 7gr in SPL & 9gr in Mag but some 22gr #2400 in the Mag.

Kwilfong what exactly is "thread choke"? I recently bought my first revolver a S&W 629 classic, I have yet to cast or reload for it yet but plan to. I would like to know what this is so I know what to look for if this is something common.

[gandydancer]

I will let some one else explain better then I can. I believe it has to do with the screwing in of the barrel to the frame and will cause a tight spot or thread choke just forward of the forcing cone. fire lapping most of the time will clear it up nicely. I did this to two of my ruger black hawks and it worked out well.

[drklynoon]

My impression is that groove diameter vs. cylinder throat diameter and throat choke problems are inherent to newer guns, mainly Rugers. I haven't run into a sever thread choke problem with a smith but I don't own any newer ones. A simple explanation to thread choke involves a barrel of limited crush strength being screwed into a rigid frame. Some guns are worst about this than others.

[stubshaft]

I have had both Smith & Wessons and Rugers with thread choke. The problem was that in MY Rugers (all 6 of them) the cylinders were smaller than the bore diameter and I had to have them opened up. Not a big problem and it resulted in much better accuracy.

[kwilfong]

Thanks guys!
I'm headed for the shop to cast a batch of 429421. My pot is full of pure lead & I'll run a few of those for slugging & lapping(if necessary).
By the way; does anybody know when Lyman switched from stamping their molds from Ideal to Lyman? I have some of each.

[dubber123]

FWIW, I don't think pure lead is recommended for firelapping. I have always used wheel weight metal, and had great results each time. Good luck.

[MtGun44]

Thread choke is due to overtightening of the barrel slightly when assembling the pistol - they
are clocking the front sight and if tolerances are off just a touch this can happen. It is
fairly common to all revolvers, unfortunately. The way I fix it is have my gunsmith remove
the barrel, face a few thousandths off of the rear face of the barrel shoulder so it will clock in
with no torque. He then reinstalls the barrel with red loctite. This has worked on several
pistols with no issues. Removal takes warming the joint with a torch, but hurts nothing.

He currently holds a number of national and international first place positions in revolver
competions (Bianchi and PPC) with guns he has built, so really knows his stuff. Unfortunately,
he does not do it as a business, only for friends. Not trying to drum up business for him, just
pointing out that this is a viable solution, too.

Bill

[kwilfong]

My Blackhawk was thread choked enough that it very obvious when pushing a lead roundball through the barrel from the muzzle. Rather than fire lap, I used a couple of my soft 45/70 bullets that I use in BP cartridges. Drilled through them & attached to a cleaning rod with a bushing to protect the muzzle, & hand lapped the tight spot.
The Smith isn't bad but the barrel is a little tighter at the muzzle & breech than in the middle, so I guess I will try my hand at fire lapping, & I'll use ww alloy.
Thanks again!

[44man]

NO PURE LEAD FOR LAPPING BOOLITS. Air cooled WW boolits are best.
Not all guns have a thread choke. Ruger had tight threads so the bore was constricted, nothing to do with sight alignment.

[kwilfong]

Got it! The batch I ran this morning are water dropped; 17-18 Bhn. Is that too hard for fire lapping?

[44man]

Got it! The batch I ran this morning are water dropped; 17-18 Bhn. Is that too hard for fire lapping?

17 is about right but water dropped will have the boolits harden with a little time. It is best to air cool. Use them before they get harder.
Lapping charges are very light with a boolit just clearing the barrel so there is no bump up. The boolit must engrave to the bottom of the grooves. You want to lap the lands and grooves evenly.
Too soft has the compound imbed into the boolit when shot. Keep the compound on the surface, sharp edges wear and the farther down the bore, the less it cuts.

[Lance Boyle]

Thread choke is due to overtightening of the barrel slightly when assembling the pistol - they
are clocking the front sight and if tolerances are off just a touch this can happen. It is
fairly common to all revolvers, unfortunately. The way I fix it is have my gunsmith remove
the barrel, face a few thousandths off of the rear face of the barrel shoulder so it will clock in
with no torque. He then reinstalls the barrel with red loctite. This has worked on several
pistols with no issues. Removal takes warming the joint with a torch, but hurts nothing.

He currently holds a number of national and international first place positions in revolver
competions (Bianchi and PPC) with guns he has built, so really knows his stuff. Unfortunately,
he does not do it as a business, only for friends. Not trying to drum up business for him, just
pointing out that this is a viable solution, too.

Bill

I have a friend and rifle smith who barrels his personal rifles the same way with the red loctite and a relatively light barrel torque into the action for less stress. His rifles shoot bug holes.

[kwilfong]

17 is about right but water dropped will have the boolits harden with a little time. It is best to air cool. Use them before they get harder.
Lapping charges are very light with a boolit just clearing the barrel so there is no bump up. The boolit must engrave to the bottom of the grooves. You want to lap the lands and grooves evenly.
Too soft has the compound imbed into the boolit when shot. Keep the compound on the surface, sharp edges wear and the farther down the bore, the less it cuts.

Thanks 44Man! I really appreciate the way you folks share info here!

[kwilfong]

44man: Do air cooled bullets not harden as much over time as water dropped bullets? This whole precipitation hardening thing is new to me. I only recently discovered it when I tried to lube/size some 260gr .45 SWC's that had been cast with a mix of ww & linotype & sat around for a year. I ran some thru the lube/sizer shortly after casting & it was OK. Then got the same batch out after a year & was afraid I was going to break the linkage on my Lyman 450 so I got the LEE size die for my old Rockchucker & ran them thru that 1st. (I was experimenting with really hard boolits before I figured out the tread choke problem)
& while I'm picking your brain (and I really appreciate your & everyone else's advice!); my plan for fire lapping the M24 is to load about 20 of the 429421's with a very mild powder charge & fill the lube & crimp groove with #400 lapping compound. Should I plan on cleaning the bore between shots?

[dubber123]

Not 44man, but I'll take a stab at answering a few of your questions. An air cooled WW boolit will make it to about 14 BHN pretty quickly, a water dropped one can reach a BHN into the high 20's, I have had heat treated water quenched ones approach 29 BHN. How long it takes to fully achieve maximum hardness is often debated, but I find you are at least 90% there within a week.

For firelapping, it is best to roll the boolits between two steel plates to embed the material in the driving bands surface. Just putting it in the grooves will likely negate most of the cutting effect, as it will just hide out in the grooves for the ride out the barrel. I imagine you could use any two pieces of a hard, flat substance to roll the boolits. You load them into fired, but unsized brass. Don't make up too many to start, as the boolits tend to be fat after rolling them, and in combination with the unsized brass, may be hard to chamber, so you may have to do some "fiddling" with the combination. The load should be as slow as you can get it, Bullseye is a favored powder to use. Be prepared to tap a few back out of the bore until you get the charge weight down. Until you get your load worked up, I'd recommend checking the bore after each shot. You only clean after each cylinder is fired. This really can work wonders, good luck, and have fun.

[kwilfong]

Great info dubber! Makes perfect sense to roll the bullets between hard plates & use unsized cases so as not to scrape the lapping compound off. Not cleaning between shots will leave some compound in the bore. Is 400 grit about right?

[dubber123]

I have always used 320 grit, as it is what I have. Some get their knickers in a twist over it being too rough, but I will say the bores are way shinier after than they ever were fresh from the factory. Maybe a hand lapped high end barrel from a custom barrel maker might have started smoother, but the finish I see left by the 320 grit beats what the factory did on any of my S&W's or Rugers. If it makes you feel better, you could shoot some with a finer grit at the end to do a final polish. You should be aware that this won't likely be a "6 shots and done" deal, I've usually had to do 3-4 cylinder fulls minimum, depending on how bad it was to begin with. Have fun.

[44man]

Dubber has it right.
Don't expect instant cutting, it can take many, many shots and Ruger steel is tough.
I use LBT compound and it seems pretty course. Never found a need for smoother. 400 grit will have you shooting a year.