Revolver Cylinder Reaming

[cigg52]

I just want let you guys know if you are needing your cylinder throats open up a little bit I sent my S&W 657 .41mag to a guy in Denver Co. I told him I wanted them opened up to .411. The total cost was $35.00. with shipping. I tell what guys, he did a perfect job, I checked and rechecked them 3 times and they were spot on. His name is TOM SOKOL, REVOLVER CYLINDER REAMING, 2810 DEXTER ST., DENVER, CO 80207. Ph# 303-618-4329

[Super Sneaky Steve]

Since I like Rugers and they can't seem to cut a proper .4525 hole I bought my own reamer from Brownell's with the guide bits. Easy job with a bit of Drilldo. So far I've cut my Redhawk, Blackhawk and Vaquero.

[DougGuy]

I do them for a LOT of folks on this forum. $30 plus shipping. The work is fast and professionally done. A simple PM gets the ball rolling.

[MtGun44]

Starting to sound like getting a tattoo. Seemed like a great idea at the time, but can't
be undone and may be a lifetime regret.

There are definitely guns that need reaming. There are also a lot of guns that are being
reamed to "make them better" when all that may be needed is a bit of custom loading.
Not saying you shouldn't ream a gun with real issues, but many are not too experienced
in the extremely precise measurement required to know what they actually have to start with
and also haven't made much effort to work with what they have. I wonder how many
measure the holes with a caliper "to .0001 inch" and decide they need their cylinder r
eamed?

Ream when it is needed, yes, but be careful of stuff than cannot be undone and make
sure of your precision measurement tools and skills.

Bill

[RobS]

Considering proper tooling and pilots, a bit of cutting oil along with patience cylinder throats are super easy to ream. A general but simple test is to slug the bore with straight/plain lead and then see if that slug goes through each of the cylinder's throats. If so then your revolver is likely fine for cast boolits but may not be optimal. Many here have shot revolvers here with success with cylinder throats that only take boolits the same size as the barrels groove diameter. It takes good load balance i.e. powder charge/pressure, alloy hardness and boolit lube. Heck even some have went as far as shooting revolvers where the cylinder throats were a bit under the barrels groove diameter and used a soft boolit and a quick powder to bump the base up or obturate so there isn't leading.

Having said that, I personally like to have my revolvers to have at least .001" over groove diameter cylinder throats. It just makes shooting cast boolits easier and accuracy is more attainable.

[fredj338]

Thanks. I am lucky, I have a friend that owns a grinding shop, does precision grinding on airplane parts & such. He has done two rev cyl for me, perfect to 0.0005".

[Shiloh]

I wouldn't measure them without a set of precision pin gauges.
Once the metal is gone, you can't put it back. There are stories of guys that opened them up with emery paper. These type of folks are called bubba's. Stay away from them!!

Shiloh

[Dan Cash]

I surely wish all the firearms experts would recognise that cylinders have chambeers and the chambers have the throats. Rant off.

[gwpercle]

I got to get me some of that Drilldo, at first glance it seems naughty. It would look good on the shelf with my can of Jig-A-Loo lubricant. Had to buy that for the name too.

[DougGuy]

I think the most misunderstood thing about cylinder throats, is how important it is that they are all the same size, as close as you can get them to within .0002" if possible.

When a revolver is fired, pressure builds and pushes outward in all directions the same. When the boolit begins to move, the movement, causes the pressure curve to respond in an expected manner. If there is a resistance to movement, it causes pressures to remain higher than if there was no resistance to movement, or a lesser resistance to movement. The pressure pushes the revolver rearward away from the boolit, and causes the revolver to move in the shooter's grip. We call this movement, i.e. the energy imparted to the shooter, recoil impulse. If the recoil impulse was the same from shot to shot, it's a fair and logical statement to say that each shot would go to the same point of impact on the target.

If the recoil impulse changes from shot to shot, it causes the revolver to move differently in the shooter's grip, and causes the muzzle to be pointed to a slightly different angle as the boolit leaves, which causes the boolit to travel to a different point of impact than previous shots fired. This is what is caused by cylinder throats that are different sizes. Looser throats dissipate pressure faster, cause less recoil impulse, tighter throats hold pressure longer, and cause more recoil impulse. This explains why a revolver with very even and consistent cylinder throat diameters will group more consistently than one with uneven throats.

THIS, and this alone, is why I say that it is more important that the cylinder throats all be even in size, than what diameter they actually are. You can very easily size a boolit to a specific throat diameter, you can even use ignition pressure to obturate it to a throat, provided there is enough pressure and the alloy is soft enough, but the main thing is with them all the same size, we have consistency, we have removed a variable and replaced it with control. We have a known common baseline that doesn't change from shot to shot because of cylinder throats.

[725]

What is the optimum relationship of cylinder throat to barrel groove measurement?

[DougGuy]

What is the optimum relationship of cylinder throat to barrel groove measurement?

.001" to .002" over groove diameter for the boolit is a pretty good relationship for the boolit to the barrel, and the throats would need to be at least the same size as the boolit to not downsize it on firing, best if the throats are .0005" to .001" bigger than boolit diameter. Having throats sized .0005" above your sizing die will allow for a tiny bit of growth which many alloys do with age. It's not uncommon to see boolits grow a couple or three tenths of a thousandth if they sit for a number of months after casting and sizing.

[725]

Thanks. I think I've got it straight now.

[cigg52]

How much barrel-frame restriction is acceptable in a revolver? .001-.002 ? This seem to me it would be just as important cylinder size in relation to the barrel groove diameter.

[DougGuy]

How much barrel-frame restriction is acceptable in a revolver? .001-.002 ? This seem to me it would be just as important cylinder size in relation to the barrel groove diameter.

That answer should be zero. In a perfect world, everything in a revolver should read like a funnel. Largest dimensions in the rear, getting smaller as it goes toward the muzzle, that way the boolit is constantly being sized down in each step, which provides a good seal in the bore, there should be NO constrictions anywhere in the boolit's path. You gotta think that shooting through tight cylinder throats or even a slightly constricted barrel, is the same as shooting through a sizing die.

Lots of shooters use firelapping boolits imbedded with abrasives to remove any choke at the threads, which if not too bad, firelapping or even lapping with a cold lead lap will remove the choke. If a choke is .003" there is the very real likelihood that the remaining rifling in the bore can become damaged by the time this much choke would be firelapped out. These need to go back to the factory generally speaking, because the choked part of the bore is out of SAAMI specs, and can pose a very real safety hazard due to extreme pressures if the revolver is used with maximum loads. Of course the cylinder throats should be of proper dimension before lapping.

And yes you are correct, this dimension is of critical importance. The only workarounds for this beside lapping or rebarreling or Taylor throat reaming, are shooting soft alloys with magnum loads, the boolit will in effect be bumped up in diameter to fill the bore by the pressure against soft alloy after it pass the choke. This is why you can shoot factory j-word ammo through a badly choked barrel and get away with it. This is what lets Ruger get away with it if the gun groups when they test fire it.

[cajun shooter]

They have some very good points being made on this thread. Having all of the cylinder chamber throats the same size is very important so that each cylinder gives as close as possible the same results. If the throats are smaller in size, then the revolver will have more recoil and cause problems for the shooter.
One of the best points made is to make sure you are not dealing with a kitchen table gunsmith. If he does not have a set of pins and the proper equipment to do the work, then run as fast as possible to get away.
I also agree with the posting that tells you that you may not need your cylinder to be reamed. I shoot in cowboy shooting and if one fast shooter has something done, then all the others have to have it also. Don't spend the time or money unless your firearm has proven it needs the work. Later David

[Char-Gar]

Starting to sound like getting a tattoo. Seemed like a great idea at the time, but can't
be undone and may be a lifetime regret.

There are definitely guns that need reaming. There are also a lot of guns that are being
reamed to "make them better" when all that may be needed is a bit of custom loading.
Not saying you shouldn't ream a gun with real issues, but many are not too experienced
in the extremely precise measurement required to know what they actually have to start with
and also haven't made much effort to work with what they have. I wonder how many
measure the holes with a caliper "to .0001 inch" and decide they need their cylinder r
eamed?

Ream when it is needed, yes, but be careful of stuff than cannot be undone and make
sure of your precision measurement tools and skills.

Bill

You are of course 100% correct! There are cylinders that need to be reaming and most that do not. Removing metal from your revolvers is indeed a permanent thing.

I am old enough to have watched fad, fancy and fashion among guns come and go. A bandwagon rolls by and folks jump on and load it down. All it takes is one person to write about some new improvement and do so with an air of authority and some tests to back him up and the game is afoot. Folks start to modify their guns before there is any proven need. Their new firearm comes out of the box just waiting to be improved by them. Quck, quick jump on before the bandwagon has rolled on to far to catch it!

After careful and thoughtful load development, your gun does not please you, then and only then, should you ask the question why?

After years on this site, I have noticed several things;

1. Many folks just don't know how to shoot a firearm well.
2. Many folks are clueless about how to develop a good cast bullet load.
3. Many folks are anxious to spend more money on their guns.
4. Other folks are willing to take their money, doing unnecessary improvements.
5. Most folks that post here are just posting theory or repeating what they heard or read from somebody else. They lack the depth of experience to truly understand and evaluate what they are posting.

I feel reasonably certain I will draw fire from several quarters for saying what I believe to be true, but that is just part of life I guess. As always folks should read my disclaimer below!

[Harter66]

I have had in my possession a 75-76' Security 6 357, a 76' BlackHawk 45 Colts , a 43' Colts 38 and a 47' S&W 38 . Only 1 , the S&W, had all 6 throats close enough to be considered to be 1 tool cut. The Colts had a pretty rough life and had 1 that was out of round at the throat 361x357 ,but the other 5 were close enough to not mess with. The 2 Rugers however displayed 1 at a lower minimum dia ,2 of small nominal dia ,2 of a larger but nominal dia and 1 at near a maximum dia,subjectively in terms of modern manufacture .

As I recall the 45 was .4515, 4523,4523 ,4532,4533 and 4541 paired to a 451 by 442 bbl. The result was very regular 6" 50 yd groups with 2 out layers and 4 pretty close in the middle. When finished the throats were 4537 to 454 the high flyer is gone and 6 shots from 6 chambers are always inside 3",2 with the more particular hunting loads. The 357 didn't show up the high and low flyer like the 45 did but it did close groups by getting the 357 throat matched up to the 359 hole.

My belief is that the tool heating and cooling and the piece heating and cooling are dictating production dimensions in the later guns where the older guns had the throats finished by hand with rather than drilled 123456,reamed for throat 612345 and chambered and throated 561234. The result is that number 6 is cut with a hot tool and carries more heat (big tool ,small hole) while 1234 are cut with tools of nominal temperature and a fairly stable piece temperature number 5 gets finished with a cold tool and has the longest cooling time. (small tool big hole.) That's my theory about the bits being off and the best I can do to show it.

I had a Taurus 66 for a while and after much thought about its gross target displays I'm inclined to think it may have had a correct 357-8 bbl but 355-6 throats alas it was before my cast awaking so no measures were taken.

In the end you have to measure and decide if reaming will likely correct the problem or not .

If I had a 357 that was thread choked to 354 it would go somewhere, likely back to its assembly point.

[dubber123]

To this I could add that many people are cheap, and not too energetic. I sometimes display both qualities, but I try not too. Many people just won't spend the time or money to do something right, but will spend much more time defending their sub par equipment. If your stuff needs fixing, fix it.

[DougGuy]

I don't think tuning cylinder throat diameters is a fad, nor a passing cycle, it is taking a known variable, and bringing it into alignment by having all the throat diameters the same as we can make them. I have not seen the instance where reaming throats to half thou over the cast boolit diameter, has been anything but favorable. I do not think you could create a scenario where this would be a detraction and not a noticeable improvement. We are talking a specific set of dimensions, not your kitchen table mechanic with a drill and a roll of emery paper.

I use two diameters for .44 caliber, depending on the existing throats and what size boolit the shooter wants to use, one reamer finishes right at .4317" after reaming and honing, the other finishes right at .4327" after reaming and honing. I found that there are a great number of Ruger cylinders produced by gang reaming 3x throats at a time, where the 3 cutters are chucked up in a triangular arrangement that plunges 3 throats, indexes one hole, and plunges the remaining 3. In this fashion, each reamer cuts a pair of holes, adjacent to each other. As the reamers wore, Ruger swapped them out with new reamers but not all at once. They replaced the most worn one with a new one, and as the other two wore, they were replaced. With this arrangement, you have 3 different sized cutters, and therefore 3 pairs of throats, each pair a different diameter than the others. This is very typical for 70s and 80s SBH for instance.

Some of these cylinders have one pair of throats that my .4315" reamer will simply slide right through, and it will take a bite on the other throats. This is not good. I stepped up and got a custom reamer ground to my own specs that specifically addresses these exact .44 cylinders. The only way to fix them, is to bring all the throats to the same diameter as the largest throat, and size the boolits to fit those. NOW, we have a much more consistent cylinder, which will immediately show improvement in the groups it shoots, and can be documented with a chrony as well. Provided all other variables are carefully detailed i.e. weighing each charge, same COA, same neck tension, same crimp, etc..

I don't see this as a fad or a here today gone tomorrow thing at all. I see it permanently affixing it's place in the scheme of improving one's revolver to shoot to it's best ability. What does Beartooth Bullets have at the top of their page about firelapping? Something like "Ruger, America's best known do-it-yourself gun kit" or something like that. It's fine tuning. It's accurizing on a very affordable scale. It's all good.

[fatelvis]

A good, easy way to check your cylinder/groove relationship:
1) Slug your bore and determine what size boolit you need to fit it well. (.001-.002" over groove diameter)
2) Cast a boolit and size it to that needed diameter.
3) Open your cylinder and drop the unloaded, sized boolit down into the chamber, just as if you were loading a cartridge.
4) Boolit should baaarely fall through the mouth of the cylinder under it's own weight, maybe requiring a few shakes to the revolver, or a gently push with a pencil eraser to fall through. If the boolit falls through without barely touching the walls, the mouths are already pretty large. If you need to force the boolit through the mouth with any more than hand pressure with a pencil or similar rod, the mouths may need reaming. I have found Rugers to need reaming frequently also. (i.e. Vaqueros and Blackhawk)

[TXGunNut]

You are of course 100% correct! There are cylinders that need to be reaming and most that do not. Removing metal from your revolvers is indeed a permanent thing...

After careful and thoughtful load development, your gun does not please you, then and only then, should you ask the question why?........

I feel reasonably certain I will draw fire from several quarters for saying what I believe to be true, but that is just part of life I guess. As always folks should read my disclaimer below!


Well said, both of you! I find these threads interesting because someday I may buy a Ruger that may actually need a little machine work, glad to see that we have folks here that know how and why it's done.
My 45 Colt RBH's cylinder throats seem to measure close enough to what they should but I don't have the equipment to do that job properly. I do, however, have a good enough shooting technique and loads to demonstrate that the gun will do everything I'm capable of doing on paper and game. At one time I was a pretty decent pistol shot and this old gun stoked with hunting loads would almost keep up with my match guns in the accuracy department. It works and I'm too tight to spend money fixing stuff that doesn't need it.

[4rdwhln]

I Have wondered about this on my smith 686 for a while now. I am able to shoot 2-3 inches at 25 yards. and 4-5 inches at 50 yards of a rest and a bench. However at 100 yards I can barely keep them on a 18x14 sheet of tagboard. I feel that If I do my part I should be able to shoot an 8-10 inch group. I do not have the best eye sight and I do not get to shoot as regularly as I would like.
My load is sorted and fully prepped brass with 14.5 grains of 4227 and the Keith style 358429 currently cast of mostly wheel weights and some added sn. These are sized at .357 and lubed with old Rcbs lube. They shoot clean with no visible leading after 50 or so rounds. The same gun shoots the 158gr xtp to 3 inches or so at 50 yards with max loads of 4227. I have checked and the .357 sized slugs will not fall thru the cylinder, even with some force. I feel that this is a good candidate for reaming. I pretty much only shoot cast, however the ability to increase knockdown by a stout loaded jacketed is nice to have.
I do not think reaming the cylinder will suddenly make me able to shoot 1 inch groups at 100 yards but I believe it could help improve my chances to keep em in the black.

[Char-Gar]

What kind of sights to you have on your handgun! If you are talking about factory square notch rear sight and a red dot or a scope those are entirely different equations. Small errors in sighting with factory sights get magnified the farther the target from the sights. It doesn't take very much variation in sight picture to make the groups spread out at 100 yards.

I doubt very very much that reaming your cylinder will make a significant change in your 100 yard groups.

[MtGun44]

Other things to try are a different lube and a different alloy. I have historically been
able to get 4" groups at 100 with my most accurate handguns with 6" bbls and standard
open sights, rested, of course. I expect that I might improve on this somewhat with
a scope or red dot, but have only a few guns with them mounted.

Good luck with your guns, I have reamed exactly one pistol so far out of many that
I own. It was a BH convertible in .45 Colt/ACP and both cylinders had throats that
were .449 and .450, while the groove diameter was .4515. It shot acceptably with
jacketed loads, but not great and tended to throw a few well out of each group with
cast. After reaming to .452 and polishing to about 1/2 a thousandth more it
shoots very well with .452 or .453 cast boolits.

Bill