Adjusting barrel to cylinder alignment

[Griz]

I have a set of "range rods" from Brownells for checking barrel to cylinder alignment. The "Match" rod passes smoothly into the cylinder on most of my guns, but I have one 686 that will only pass the "Service" rod. The Match rod clunks into the edge of the cylinder and won't go in. I also don't get the accuracy I'd like out of this gun.

How do you adjust the barrel to cylinder alignment? I have Kuhnhausen's manuals, but he only mentions checking it, doesn't say anything about fixing it.

[Toolguy]

Revolver tuning is the art of adjusting that which is non adjustable. It depends which way you need to go. If it's too far counter clockwise

(looking at the back of the chambers like you would hold it to shoot), the hand is usually pushing it too far. In that case use a diamond file

and file off the left side of the nose on the hand. Lay the file flat on the hand to get it parallel, then move over the nose, keeping the

parallel orientation. File off .001 at a time and try it in the gun to see where you're at. Most times one or two thou. will do it. When you are

done with that, file or stone an edge break at the top of the hand nose to remove the sharp corner. This will make the ratchets last longer

and make a smoother trigger pull.

If it's not going far enough, the hand needs to advance it more. The easiest way to do that is to get an oversize hand and a hand window file

from Brownell's. The hand is frame specific so you will need an L frame one. The file works for all frames. File the hand window wider towards

the center pin only until the wide hand slides in easily. File the vertical surface below the hand window to match. The hand runs up and down

in that slot so it has to be wider too. The hand nose will be too wide, so carefully work it down as described above. Measure the original hand

with a mike or calipers so you know when you're getting close on the new one. The new one will need to end up wider than the old one.

There are a lot more tricks, but I don't have time to write a complete course.

Once the cylinder is true to the bore, you will probably need to recut the forcing cone or muzzle crown or both. I just do both to eliminate

problems. Use the 45 degree cutter with proper pilot for the muzzle (you can chamfer chambers with it too with another pilot). Use the Brownell's forcing cone kit to do the forcing cone. I prefer the 11 degree one over the 18 degree one.

[Griz]

Since the timing seemed OK, I just assumed that it was out of alignment up and down, not side to side! I didn't even bother to figure out if it was high or low because I didn't have a clue what could be done about it. Thanks for opening my eyes and re-teaching me the old lesson about "assumptions".

[Tom E]

Am I misunderstanding something? I thought that once the hand had rotated the cylinder so the stop was engaged it had nothing to do with chamber/barrel alignment. It's held (loosely) in postion by the cylinder stop. The cylinder has rotational "wiggle" with the trigger back and the cylinder stop engaged. This isn't like a Colt where the hand locks things up. Am I missing something?

[Toolguy]

Depends on how loose the gun is. I can make them to lock up tight or have a lot of wiggle. I prefer just a very slight amount of cylinder

movement with the trigger held all the way back. Not too tight, not too loose. How loose with the trigger forward is irrelevant.

[Carmoney]

Actually, all of that is dependent on which generation of S&W revolver you're talking about. Warren's detailed post only applies to the older models. On the older guns, the hand (depending on the fit) may be literally pushing on the ratchet lug as the DA trigger pull is completed and the hammer begins its fall. This is why the old-school armorers made such a big deal out of range rods, holding the trigger back while checking for "clicks," etc., etc.

Most of that stuff is becoming outmoded now due to design changes in the guns. On current S&Ws (since sometime in the early '90s), the hand and ratchet engagement has been redesigned to allow the hand to disengage (it is cammed backward and up, away from the ratchet) after the cylinder is fully indexed and the cylinder stop is engaged. So as Tom E. correctly observes, at that point there is nothing holding the cylinder in place rotationally except the cylinder stop. On the newer guns, the hand is not contacting the ratchet lug as the hammer starts to fall.

On the newer guns, about all you can do to align the chambers with the bore is to ensure the yoke barrel is properly aligned with the center-pin hole in the frame. Most of the time they are pretty close to perfectly aligned, and if they're not, you'll know in a hurry because the cylinder will bind rather than spin freely when the cylinder is closed and the cylinder stop disengaged (by holding the trigger back slightly).

[Toolguy]

On all of them you can peen the cyl. stop window to move the stop one way or the other, use an oversize stop to tighten up the play or

file some off one side or the other to change where the cylinder stops and peen the cyl. cuts to tighten up the fit using a flat ended

punch on the flat side and the side of a hardened 1/4 inch dowel pin on the dished out side of the cut.

[Carmoney]

This conversation is interesting, but pretty esoteric. And perhaps somewhat academic.

If the cylinder spins freely without binding, and there is no gross misalignment of the yoke or obvious defect in the throats, forcing cone, or crown, the gun is going to be plenty accurate for 99.99% of the shots USPSA/IDPA/ICORE shooters will ever need to take.

For the few remaining people who are interested in shooting PPC and Bianchi with a wheelgun (sad, but true!), it may be a different story. But for the rest of us, achieving accuracy with a revolver is more a matter of load development and trigger control than taking the last micron of play out of the fit between cylinder and frame.

Or so it seems to me!

[Griz]

Bianchi

Guess what game I'm shooting

I need at least 3"@50 yards, ideally much less. I'm using a 627PC in open class right now that will do that, and I have an old 8-3/8" 686 with metallic sights that will do it.

I'm trying to move down to a L-frame for my open gun, but the new 686+ that I bought for the purpose can only do about 6"@50... This is the one that won't pass the Match range rod. No idea if fixing that will fix the accuracy problem but it's the first thing I see to attack.

[Toolguy]

For most purposes, I would agree this is above and beyond what is needed. Normally the cylinder stop is ok as is. If a certain gun needs

help or a particular owner wants the Nth degree, there are ways to get there. Just for the record, if I couldn't do my own guns, I would

be sending them to Carmoney. He gives the best value of anyone I know of.

[Allgoodhits]

Toolguy and Carmoney are class acts.

Could some of the accuracy issue mentioned be due to a bent frame, or yoke? Talking old school, I have seen Sandy Garrett of NVGW peen the cylinder stop notches, and I have seen him the old way peen (stretch) the yoke to take out endshake. I have also seen him take a pretty heavy lead bar and do some wacking to realign things. Scared the crap out of me the first time I saw it, but the results are amazing, when one has the knowledge, the time and skill to squeeze the absolute minimum groups from revlovers. To the above list add, that the customers has to be willing to pony of the KACHING ($) too.

Consistent less than two inch groups are achievable, just as Carmoney stated, in most applications today it is totally not necessary for the desired accuracy requirements, except BE, Bianchi and PPC.

MJ

[Griz]

Toolguy and Carmoney are class acts.

I greatly appreciate their expertise and advice... I also have a couple of stickshifts and a couple of Carmonized revolvers

Could some of the accuracy issue mentioned be due to a bent frame, or yoke?

Not impossible, but it is a brand new revolver, so it would have to have come from S&W that way. The only work on it has been a trigger job and I had the cylinder cut for moons (did this before test firing it... smart...)

I sat down last night to determine exactly which way the cylinder is out of alignment and discovered that I had some fouling in the throat that stopped the range rod before it could reach the cylinder... I didn't expect that since I've fired only 50 rounds or so since I originally checked it with the range rod.

I noticed when I was cleaning it with a jag and patch that the bore feels a little tighter in the area where it threads into the frame... I wonder if that is just the fouling or if S&W over-torqued the barrel.

[Toolguy]

That occurs in all revolvers except for the ones like Dan Wesson and the Smith ones with a shroud and tube barrel assembly. The area

that screws into the frame is squeezed down one or two thou. when they turn the barrel on further after it contacts the frame. That is

definitely detrimental to accuracy and can cause the barrel to get leaded up more, which in turn makes the problem worse. There are 2

ways to fix that. 1 - lap the barrel with abrasive until it's the same diameter all the way through, or 2- remove the barrel and face off

the back of the part that butts up against the frame until the barrel will tighten up straight by hand, then install with Loctite on the

threads. The cylinder gap may need to be slightly adjusted afterward. Some cast bullets will lead more than others. Jacketed bullets

eliminate the leading problem entirely. The amount of restriction in the barrel directly corresponds to how far off vertical the front sight

is when the barrel first contacts the frame. If the bullet is sized down too much going through this area, it is loose the rest of the way

down the barrel and not well stablilized. Leading in this area makes it even smaller yet.

A barrel that has good rifling, a centered and smooth forcing cone, an exactly concentric muzzle crown, and not overtightened will be

an accurate barrel. The rifling twist dictates what loads, in terms of velocity and bullet weight, will be accurate to what distance. The

slower twist, in the 1 in 16 to 20 range will need heavier bullets and/or higher velocity to shoot good groups at 50 yards. The tighter

twist in the 1 in 10 to 14 range will shoot most bullets at lower velocity and get good groups at 50. They also work really well with the

higher velocity too. Most factory Smith barrels are about 1 in 18.

[Griz]

Some cast bullets will lead more than others. Jacketed bullets eliminate the leading problem entirely.

Other than whatever they used at the factory, the only bullets this barrel has ever seen are 125gr Zero JHPs, and only about 100 of them total. The fouling that stops the range rod now is copper fouling judging by the blue sludge coming out on my patches.

[Toolguy]

The range rod is being stopped by barrel constriction, not fouling. That much is definitely an accuracy killer. I shoot the exact same bullet

for my match loads and hardly ever clean the barrel. They print very small groups at 25 and 50 yards.

Edited December 4, 2009 by Toolguy

[Griz]

The range rod is being stopped by barrel constriction, not fouling. That much is definitely an accuracy killer. I shoot the exact same bullet

for my match loads and hardly ever clean the barrel. They print very small groups at 25 and 50 yards.

I also run the same loads in my other guns and get great accuracy. l never clean the barrels other than snaking them occasionally.

When I first got this gun, I fired a few groups, was unhappy with the accuracy and checked it with the "Match" range rod and it passed through the barrel with the cylinder open, but wouldn't enter the cylinder with it closed and cocked (the Service one would). That's what prompted this thread...

I have since fired another 50 rounds or so and now the Match range rod won't pass through the barrel at all, that's why I think it has to be fouling (perhaps in addition to a constriction which probably caused the rapid fouling).

I had originally intended to rebarrel this gun and I'm starting to come back around to that plan. It will have to be my 2011 Cup gun if I do that.

[Toolguy]

It doesn't take much to pull the barrel, trim a couple thou. off the back and reinstall with Loctite. The barrel will spring back to normal diam.

once the pressure is off of it. Maybe you can find someone in your area to do that.

[Carmoney]

It doesn't take much to pull the barrel, trim a couple thou. off the back and reinstall with Loctite. The barrel will spring back to normal diam.

once the pressure is off of it. Maybe you can find someone in your area to do that.

That sounds like a good plan to me.

Hey, maybe this explains why I sprayed frickin' bullets all over the place at Nationals this year.....I think I must have a constriction! A constriction.....yeah, that's the ticket.....

[Allgoodhits]

It doesn't take much to pull the barrel, trim a couple thou. off the back and reinstall with Loctite. The barrel will spring back to normal diam.

once the pressure is off of it. Maybe you can find someone in your area to do that.

That sounds like a good plan to me.

Hey, maybe this explains why I sprayed frickin' bullets all over the place at Nationals this year.....I think I must have a constriction! A constriction.....yeah, that's the ticket.....

Some constrictions are best resolved from the point of entry, some from the point of exit. I prefer those used form the point of entry. Many shooters, and gunsmiths I know have good results using Correctol from the point of entry. Unfortunately, it is a delayed correction, plan accordingly. YRMV

[lrjet]

Taylor Throat for squish and hope Smith comes out with aftermarket cylinders with .001 difference in center line to charge holes.

[Griz]

UPDATE: I finally rebarreled. After I unscrewed the old barrel, the match rod will pass through it.

I installed the new barrel using the tool from Brownells to set back the barrel without a lathe. I set it back until it was about 1/12 of a turn or maybe less from lining up, then added loctite and turned it the rest of the way. I checked the the newly installed with the match range rod and it slipped right in, no constriction, no bumping into the edge of the cylinder.

I cut the barrel to cylinder gap so that the cylinder will turn with a .004" feeler gauge between the barrel and cylinder. I figure I can always trim it a little more if that is too tight.

The real test will be shooting it for accuracy when the snow melts off of the access road to our range.

[9146gt]

Brian, They claim it will be 58 tomorrow in Charlotte.

Tom

[Griz]

Brian, They claim it will be 58 tomorrow in Charlotte.

Tom

I'll be there!

[Griz]

I just shot it for accuracy and it's a real tack driver now

At 25 yards, off of a bench rest, all of the shots were going into the same hole. One 5 shot group that I walked down to look at closely had a one-hole 4 shot group that measured 1/8" and a flyer that bumped the group size up to 1/2"... I'll take that.

I didn't feel energetic enough to set up at 50 yards in the shin-deep snow, so I'm hoping that my 25 yard results will extrapolate into a 1" group at 50... Even if it turns out to be 2", it's still good to go for NRA AP.

[Toolguy]

Congrats Griz! Good job!