Anyone try to remove barrel choke in a revolver?

[arlon]

I have a few revolvers that seem to have a decent amount of choke in them at the barrel threads. Playing with pin gauges almost all of my newer revolvers (80's to the present) seem to have some choke. Most of my older revolvers don't (mostly S&W). I have one Ruger 41 mag that passes a .400 pin gauge to the choke point and stops and takes a .398 to get through the choke. I don't see how that can be helping accuracy..

Is it really anything worth dealing with or is there an easy fix. First thing that comes to mind is fire lapping. Done plenty of that on older military rifles but never on a revolver.

[jcren]

Have firelapped a taurus 85 that had significant choke at the frame and roll stamp. Only ran a few coarse grit then switched to bullets "lubed" with jb bore shine. Worked well, accuracy improved and leading disappeared. Now slugging the barrel you can feel just the slightest increase in pressure at the frame.

[DougGuy]

If they are blued steel you might have a chance, stainless is very difficult and very time consuming to firelap.

[Outpost75]

The factory fix for this is a round-hole broach forced through the bore with an arbor press using plenty of cutting oil.

The carbide plug is 0.0005" under minimum bore diameter and cleans off the tops of the lands only, but does nothing for the grooves.

Done correctly it leaves a mirror finish, you won't feel any constriction on a tight patch, the gun will shoot better and will not lead.

This method was devised as an S&W fix to avoid the expense of pulling the barrel and refitting a new one, because the barrel torquing method and thread specs provided absolutely no guarantee that the replacement barrel wouldn't have the same defect.

Bean counters rule.

[cupajoe]

If its half a thou under minimum bore diameter won't it just fall through? I must be missing something.

[Outpost75]

If its half a thou under minimum bore diameter won't it just fall through? I must be missing something.

If there is no thread choke, that is exactly the idea. If the plug goes through gun "meets factory specs."

If it WON'T go through, then they remove the cylinder, yoke assy. and grips, dip the gun in oil, put it in the arbor press fixture and drive the plug through with the arbor press, then send the gun back to Customer Service for reassembly and return to the customer. Max. 15 minutes turn-around time. Bean Counters Rule.

Trust me. They got ALOT of these during normal assembly. SO they had to come up with a cheap way to move them through the system and accepted into the shipping department. They actually got enough of these in regular production that they developed a piece-work rate for fixing them on the assembly line.

They also had to handle the choked ones that made it out into the market and were returned, to process as quickly and inexpensively as possible and back to the customer.

[Wheelguns 1961]

Does anybody know anything about a taylor throat? I heard this was also a cure for thread choke.

[Petander]

Following.

I just found out my 2 1/2" -94 Mod 66 has a thread constriction. A "match" range rod doesn't want to go past the thread part.

[bob208]

how do they shoot ? if they shoot ok then they are not broken.

[Wolfer]

When I got my Ruger new Vaquero in 45 colt it had thread choke. I tried fire lapping for 60 rounds but didn’t help much.
Early one Saturday I fired up the lead pot and poured a lap. Using the Wheeler bore lapping paste I went to work. As the lap wore out I poured a new one. Took most of the day but I got it out.

Results before and after.
Before 50 rounds would lead the barrel enough accuracy fell off noticeably.
After, I may or may not clean my barrel after 500 rds. Gun was quite accurate before with a clean barrel. Just as accurate now clean or dirty.
Before.
8 gr of unique got me 950 fps
After.
It takes 8.8 gr of unique to get me 950 fps
I consider my days work to be a success and wouldn’t hesitate to do it again.

[Outpost75]

Does anybody know anything about a taylor throat? I heard this was also a cure for thread choke.

DougGuy may be someone to ask about this. My understanding is that it cuts a freebore to remove the choke. I don't know whether all the rifling is removed, or just the constriction at the tops of the lands. I have no personal experience with it, but people I have asked claim that it is miraculous... But I have yet to see "before and after" targets.

I used the round-hole broach method used by S&W experimentally in customer service when I was at Ruger, but felt that the method seemed a bit slapdash and jackleg. The preferred solution, of course was to avoid over-torquing the barrel! This was ensured by using a UNF-Class 2A thread, rather than a 3A, so that the barrels could be turned in by hand until the barrel shoulder contacted the front surface of the revolver frame. When turned in hand-tight the front sight cut had to align within 5 degrees of top dead center. If offset farther than that bringing the barrel into alignment would result in over-torquing and would cause a hoop stress at the root of the thread which would produce the thread choke.

During barrel shop set-up if the barrels would not spin up by hand to meet the assembly gage, the frame would get another light pass in a Blanchard surface grinder to take off 0.001" or so and tried again, then the whole rack off 100 frames corrected to match the gage for the batch of barrels being assembled that day.

To lubricate the barrel threads during assembly, and keep them tight while also sealing the threads against penetration of chlorinated paraffins or other external contaminants when the end user slobbered them with WD40 etc., the barrel shank was brushed with a service-removable Loctite product similiar to 242. Barrels would be turned into finish-machined frames prior to being sent to the polishing department. After polishing the barreled frames would go out to the shop floor to have cylinders, yokes and lockwork fitted, and be roll-marked and serial-numbered, then to proof testing, magnetic particle inspection, targeting and function rest, final cleaning and acceptance inspection before being scanned into the shipping department.

[Wheelguns 1961]

Thanks for the reply! It is always interesting to read your posts.

[arlon]

how do they shoot ? if they shoot ok then they are not broken.

That Ruger shoots patterns. Only worse gun I've had was a S&W 625-8..

[Wheelguns 1961]

That Ruger shoots patterns. Only worse gun I've had was a S&W 625-8..

Does the gun lead just past the forcing cone? If you are thinking about firelapping, visit the beartooth bullets website. You will find alot of information about firelapping revolvers there.

[cupajoe]

Outpost,
I thought you were referring to the bore diameter at the choke point as being the "minimum bore diameter". I understand now. Thanks

[John Taylor]

Found out that rifle barrels will shrink the chamber a bit when installing. I always short chamber new barrel and take a little out for headspace after the barrel is installed ( bolt guns). Most of the time the reamer will take a little off the chamber wall after the barrel it torqued.

[dtknowles]

Now I think I understand why I like Dan Wesson Revolvers so much :-)

Tim

[contender1]

Fermin Garza did an excellent write-up about bore lapping for thread choke. I think it's on the Gun Blast site,, as well as the Single-Action Forum by Lee Martin. If you can't find it,, go to the SA Forum, and ask "2 dogs" (Fermin) where to find it. I printed my copy long ago.

[Gtek]

I have a very nice Stainless R that has been sitting here for years due to the how should I approach this issue. Having gauge pins and slugging confirmed the choke this side of .002", with cylinder to muzzle ID being okay. The latest mental was to remove grips and stand vertical in padded vise, cylinder swung and internal frame/holes taped over. Source a tube that fit bore and create stop externally that would place tube about a 1/4" from restriction/frame line. Cheap plastic artist brushes and starting with Clover coarse, get a brush full and insert brush from bottom of slip tube and insert until bristle tips flush at bottom. Having light oiled bore insert tube to correct depth, extent brush and paint interior area to cone, retract brush and remove tube. Everything here to make up some pure round balls, slugs, when I need them. Flush one in muzzle then using brass rod with muzzle guide push one through and one to two more then repeat all above several times. Stop, full clean, pin gauge, visual. Keeping process until pin gauge is just about clearing then switching to fine grit to finish clearing dimension. Having in the past mixed results with fire lapping and really wanting this revolver to be okay in the end. Understanding that this process could take a few possibly to a full day event or even days. Hopefully not a waste of time when finally attacked.

[Petander]

Does the constriction "choke" give up when the barrel is loosened / removed?

Following what Outpost75 wrote,can Locktite be used instead of torque?

[Outpost75]

Once barrel has been removed, most of the stress is relieved, but some constriction remains. The barrel can then be lapped to remove the remaining choke. The barrel threads may need to be chased to permit turning the barrel up mostly by hand except for the last 5 degrees or so before final sight alignment. Use "service removable" Loctite 242 as a thread lubricant and sealer during reassembly, so that excessive barrel torque is not needed to keep the barrel tight. Remington uses the same product in asembling barrels on their 700 bolt action rifles.

https://www.loctiteproducts.com/en/products/specialty-products/specialty/loctite_threadlockerblue242.html

Loctite Threadlocker Blue 242 is designed for the locking and sealing of threaded fasteners which require normal disassembly with standard hand tools.

The product cures when confined in the absence of air between close fitting metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and vibration. Loctite® Threadlocker Blue 242 is particularly suited for applications on less active substrates such as stainless steel and plated surfaces, where disassembly is required for servicing.

Prevents rusting of threads
Can be removed with hand tools
Prevents loosening of metal fasteners caused by vibrations
Protects threads
Medium strength
Locks threads

[arlon]

Thanks for all the thoughts. I'm leaning towards some sort of hand lapping with a slug of soft lead. I just think this Ruger would shoot a lot better if this issue was fixed. It also had t cylinder bores that were a lot tighter than the others, evened all of those out. Gun was made in 1985 but as new when I got it last year. Certainly don't want to send it back to Ruger, no telling what would happen.

[Petander]

Outpost75,thank you very much again.

I'm familiar with both blue and red Loctite.

[Outpost75]

Outpost75,thank you very much again.

I'm familiar with both blue and red Loctite.

If you clean the barrel threads and the threads in the frame very well, see how easily the barrel turns on by hand. You might not need to chase the threads and get lucky, which would be very nice!

[John Taylor]

I do quite a few liners on old guns and find that several will have barrels that don't come up tight, blue Loctite fixes the problem. Had a Ruger come in several years back that the customer said the screws kept coming loose so he used red Loctite. I could not get it apart so I could not do any repairs without breaking something first. The grip screw would not come out because the nut side was spinning in the wood.

[oconeedan]

Make sure you also check the throats of each chamber in the cylinder.

[PBSmith]

Is there a critical date/period before which thread choke was NOT a problem with S&W?

Do Colt revolvers sometimes have the same problem?

[Outpost75]

Is there a critical date/period before which thread choke was NOT a problem with S&W?

Do Colt revolvers sometimes have the same problem?

My pre-1970 S&Ws do not have this problem, nor do my Colts of that era and earlier.

[Tracy]

I have a GP100 that had a noticeable constriction. I've been firing full power jacketed bullet loads through it in hopes that it will help to polish it out. Seems to be working. When I first got it, leading was an issue with any type of cast bullet loads. After a few hundred jacketed bullets, that has improved.