629 tight cylinder gap

[329]

New to me 629-6 cylinder gap is a bit tight. The timing and action are both nice and seem stock. I noticed there was no visible light between the forcing cone and cylinder but it did not bind at all…until I got about 50 rounds of cas t gullets through it. Measuring the gap I get about .002- .003 depending on the cylinder rotation.


I am thinking of carefully stoning the forcing cone with a Diamond stone to .004-.005 to start.

Does this seam reasonable? My previous smiths we never this tight and I have had a couple whose cones were uneven from the factory but never made any adjustments.
From my limited time with this one it shoots lie a champ, far nor accurate than I will ever be.
Thanks!

 

[armorer951]

Before you alter the barrel extension be sure to check the "rear gauge" or headspace to verify that it is correct. Also check for excessive end shake on the cylinder assembly. End shake can develop from recoil with use, and is especially problematic in magnum calibers. If there is end shake over .002", you could shim the cylinder to move the cylinder back and open the barrel/cylinder gap without having to cut material off of the barrel.

I think your cylinder is "non-recessed", which means the headspace should be .060" - .068". (smaller is better)

If you determine that you have to remove material from the barrel to open the gap, it would be better to use a piloted facing cutter for the work. (Brownells) This would result in a better quality and more uniform 90° surface at the rear of barrel extension.

 

[steelslaver]

Unless you fire a bunch of rounds without cleaning it you will probably never have a problem. Non jacket bullets would cause enough fouling to bee a problem quicker than jacketed.

I have one of the tools amorer951 speaks about. I have also used a fine file that has the teeth ground off one side so it only cuts on the flat. The gun must be solidly fixed and you MUST hold and stroke one way holding the file dead flat to keep the face flat. I would only advise this to be done by someone who is good with a file and has some practice flat filing. On blue guns I place a thin piece of 309 stainless foil above the barrel shank to keep from making the frame above the barrel. If you use a diamond stone, even a 400 grit, one your going to be making a lot of strokes to remove even .002 of material. The more strokes the more opportunity to get your work uneven.

Unless you have problems I would leave it alone. Measure again every few hundred rounds.

 

[329]

Before you alter the barrel extension be sure to check the "rear gauge" or headspace to verify that it is correct. Also check for excessive end shake on the cylinder assembly. End shake can develop from recoil with use, and is especially problematic in magnum calibers. If there is end shake over .002", you could shim the cylinder to move the cylinder back and open the barrel/cylinder gap without having to cut material off of the barrel.

I think your cylinder is "non-recessed", which means the headspace should be .060" - .068". (smaller is better)

If you determine that you have to remove material from the barrel to open the gap, it would be better to use a piloted facing cutter for the work. (Brownells) This would result in a better quality and more uniform 90° surface at the rear of barrel extension.

Thanks for the reply. Measuring with feeler gages my end shake is between .001 and .002 and the headspace is a snug .060.

I was thinking of using the Diamond stone because 1. I don't have a pilot facing cutter and 2. The stone is realitivly easy to keep square and by going light it would take a lot of work to accidentally chane the forcing cone angle…almost like polishing as opposed to cutting. I would never be brave enough to file it

 

[steelslaver]

The forcing cone angle is inside the barrel and can only be modified using a tapered cutter on a rod with a tool that cuts inside. What you are measuring against and proposing to polish is the face of the barrel extension. Polishing ti may make it less apt to collect debi, but trust me it will take well over a hundred strokes to remove .001 with a 400 grit diamond. Been there.

BTW you can check flatness by closing cylinder holding it to rear and sliding a tight feeler gauge between cylinder and barrel. then put a dap of Prussian blue across the gauge on barrel side and then pulling it out. Blue will remain on loose spots and high ones will be almost clean.

But, once again with a .002-003 gap and .002 endshake I would leave it alone. Fire a some ammo through it and see if it drags.

If you are not confident with a file do not do that. LOL

A gunsmith with the correct tools should be cheaper than buying the 2 set.

 

[jeffrefrig]

I had/have the same issues as you, and I left it alone and it has never given me a problem. I bought the gun used two years before this past Christmas. Now, between the .44 magnum and .44 special, I've only fired maybe 200-250 cartridges through it, but it's one of my most accurate, for me, handgun I own. Of course the K22 beats it, but not by much. Good luck.
Thinking it over, maybe only one year, but whatever!

 

[329]

The forcing cone angle is inside the barrel and can only be modified using a tapered cutter on a rod with a tool that cuts inside. What you are measuring against and proposing to polish is the face of the barrel extension. Polishing ti may make it less apt to collect debi, but trust me it will take well over a hundred strokes to remove .001 with a 400 grit diamond. Been there.

BTW you can check flatness by closing cylinder holding it to rear and sliding a tight feeler gauge between cylinder and barrel. then put a dap of Prussian blue across the gauge on barrel side and then pulling it out. Blue will remain on loose spots and high ones will be almost clean.

But, once again with a .002-003 gap and .002 endshake I would leave it alone. Fire a some ammo through it and see if it drags.

If you are not confident with a file do not do that. LOL

A gunsmith with the correct tools should be cheaper than buying the 2 set.

Yep, shot about 70 rounds mixed with 44 special and magnums. Both were lower velocity leas cast cartridges from Georgi Arms. Very dirty running rounds, especially the 44 specials which is where I had rouble closing the cylinder after about 30 rounds.. I may lighty stone and polish and take it back out. The only other 44 nag I have had that was this right was a Freedom Arms 83. Thank you all for taking the time to reply. Despite the occasional stickyness it is probably the best 44 mag I have owned. The wider trigger suits me well.

 

[Nick B]

Put one of those brass brushes ( tooth brush size ) in your range bag and use it if you feel the cylinder dragging .

 

[Doug M.]

If you end up shooting it enough to have trouble and decide to have the gap addressed, the odds are that you should not do it yourself unless you are an expert. Pay a pro, and don't cause yourself regret by doing something that will cost a lot to repair.

There is a reason I say my best gun smithing tool is a checkbook.

 

[Golddollar]

Back in the middle 1980s I bought a S & W Model 624 .44 Special that was brand new. I noticed that there was dragging by part of the cylinder on the forcing cone. Being that the gun was under warranty, I sent it back to the mother ship to get this taken care of. Even if your gun is not under warranty, I would recommend sending it back to the factory to fix up. With my gun, S&W fixed the problem I reported, and to the best of my analysis, went over the whole gun and massaged it. It just seemed a lot smoother in operation.

 

[racer19j]

I have a 629-1 with an 8-3/8 barrel. .0015 cylinder to barrel gap. Can shoot 50 xtp's without any issues. The face of the cylinder is almost perfectly square to the bore which is uncommon. Your issue may be that the face of the cylinder is not square with the bore so the gap changes with each charge hole.

 

[series guy]

I will have to be the odd man out here. I have had multiple S&Ws with tight barrel/cylinder gaps that drag or lock up after 20 - 30 rounds with cast bullets. I bought the Brownells kit and open them up a bit for reliable D/A shooting at the range. I have no time for a gun that needs cleaned during a bowling pin shoot. I have no issues with an .008 or .010" barrel/cylinder gap.

 

[steelslaver]

I will agree that a .008-.010 gap actually isn't an issue. Ballistics by the inch show why. The avast majority of B/C gap velocity loss is in the fist .001 For instance a Federal hydro shock from the same 6" barrel set at different gaps got
No gap=1359fps
.001=1304 a loss of 55 fps from that .001 gap
.006=1290fps a loss gap of just 14 fps with the additional .005

I find it hard to believe that another .004 is going to double that 14fps and even so most ammo will show over that for extreme velocity spread.

I to have the Brownell's tool set, but mostly because I use it when installing barrels. I always finish the last .001 with a fine file as the cutter leaves tiny chatter marks. The tool definitely shows me where any high or low is.

PS at the factory the final gap used to be set with a file. You can do very precision work with one IF you know how and have practiced at it.

If the OP wants to borrow my tool with cutter I will lend it to him for postage back and forth and a deposit.

Or he can rent one from 4Dreamerrental
Revolver Forcing Cone Tools 44 Caliber (11 degree) - 4D Reamer Rentals

 

[dogdoc]

Stoning is not the way to open gap. Lathe or brownells kit (what I use) is way to go. I too find most cylinders are not perfectly square to barrel on smith revolvers. I used to worry about it but have found it really does not matter in spite of what most say. You can often notice slight differences with naked eye if rotate the cylinder while looking at the barrel cylinder gap.

 

[steelslaver]

Stoning is not the way to open gap. Lathe or Brownells kit (what I use) is way to go. I too find most cylinders are not perfectly square to barrel on smith revolvers. I used to worry about it but have found it really does not matter in spite of what most say. You can often notice slight differences with naked eye if rotate the cylinder while looking at the barrel cylinder gap.

Ya, I have set some up in a lathe and the face is often about .001 out from one side to the other. I have set them up both using a indicator on the OD and on 2 centers and there is often some variances.

Here is another interesting thing. I have a set of pin gauges and have found variation in both throats and chambers on the same cylinder. First found it when I went to ream a factory new 44 mag cylinder to 45 colt. My reamer with a .429 pilot would not go in al the throats. 2 were .429 and 2 were a tight.428 and the other 2 were an easy .428. Checking I found an older one at .429, .430. When you are reaming them from 44 to 45 you can tell by how much effort it takes and how much material is being cut. But then I also have 2 Clymer 45 colt reamers and one is just a tiny bit bigger than the other.

 

[series guy]

Collectors take great pride in tight tolerances and if your primary interest is collecting with an occasional trip to the range to shoot 10 or 20 rounds of factory ammo then the tight tolerances will most likely work well for you. While I never abuse my guns and actually shoot nothing but my reduced power handloads I expect my revolvers to be good for 100 or 200 rounds of double action shooting without binding up or needing cleaned. A .004" barrel/cylinder gap is not conducive to that.

 

[Mike-AK]

New to me 629-6 cylinder gap is a bit tight. The timing and action are both nice and seem stock. I noticed there was no visible light between the forcing cone and cylinder but it did not bind at all…until I got about 50 rounds of cas t gullets through it. Measuring the gap I get about .002- .003 depending on the cylinder rotation.


I am thinking of carefully stoning the forcing cone with a Diamond stone to .004-.005 to start.

Does this seam reasonable? My previous smiths we never this tight and I have had a couple whose cones were uneven from the factory but never made any adjustments.
From my limited time with this one it shoots lie a champ, far nor accurate than I will ever be.
Thanks!

I'd leave it alone. With the endshake measurement you note, you will be at 0.004" to 0.005", which is excellent. If you decide not to, use the right tool for the job...a facing cutter. You will also need a plug gauge to check the forcing cone depth after shortening the barrel stub. If the cone is not deep enough after cutting, you will also need a forcing cone cutter. This is not a job done with stones.

 

[steelslaver]

Removing .002 of the barrel extension will hardly have any effect on the size of the forcing cone opening.

 

[Mike-AK]

Removing .002 of the barrel extension will hardly have any effect on the size of the forcing cone opening.

It will shorten it by 0.002". If a plug gauge shows the minimum dimension already, then the cone would need to be deepened by 0.002" to be correct

 

[Protocall_Design]

Forcing cones just aren't that finicky. Most of them aren't right to begin with, usually trending to the small side. Often they are rough and/or off center. You can recut the forcing cone and square up the back face of the barrel (almost always angled) with the tools mentioned above.

If you want a gun that works with a tight cylinder gap, you can square up (on the lathe) and polish the cylinder face and back of the barrel. Then the carbon and lead has nothing to hold on to, and will get blown out of the gap with every shot. You will have to keep a close eye on the endshake, though, and keep it tight, since it won't take much to close the gap.