S&W629-6 cylinder misalignment

[moritz83]

Hello everyone

I recently bought my first gun, an S&W 629-6 classic champion. It is a rather untypical model made for the European market only.

I love the way this gun looks, however, I think there is a problem. The other day, I was checking the cylinder to barrel alignment through the bore with a flashlight pointed at the recoil shield (of course I checked that the revolver is unloaded like 5 times). While checking, I pulled the trigger and held it down to simulate a shooting condition where the cylinder gets locked more tightly, but it doesn't change compared to the normal cocked state. I noticed that the alignment in the vertical direction is off a bit on all chambers. 2 chambers seem to be a bit worse, however this could also be a visual error from my side. This is not a classical timing error where the deviation would be in the horizontal direction, it is vertical. The cylinder seems to be a bit too high or the barrel too low. There is also a slight under clocking of the barrel (around 0.3 mm), but I could compensate for that by moving the rear sight a bit and I don't think it has anything to do with that.

I shot around 100 rounds of medium hot Fiocchi factory ammo through the revolver and so far and didn't notice any lead shaving at the forcing cone. However, I am afraid that I might get lead shaving if I try out more powerful hand loads. I also heard that barrel cylinder misalignment can cause larger groups, which would be not acceptable for a revolver made for precision shooting. The cylinder gap is very small on this 629 and in the range of 0.08 mm (0.003 in), but I believe the misalignment could still cause shaving.

Is there any way that a gunsmith could fix that? I read that some vertical misalignment can be fixed by gently bending the yoke in the right direction by tapping it. I might be wrong, but it seems that the whole cylinder is slightly canted upwards, which could be due to a bent yoke. I was always gentle when closing the cylinder and never hollywooded it, so it came like that from S&W.

Since I am from Austria, I don't think that sending it to S&W for service is an option, the legal paperwork is horrible and it would take forever. If a gunsmith can't fix that I would have to return it, which I would hate to do, I love this revolver otherwise.

I added some pictures of the slight barrel cant, the chamber alignment and an overall picture.

Thank you for your time!

Best
Moritz

 

[s&wchad]

Welcome aboard!

Nice gun! I don't see anything that would concern me. You say it shoots fine, so just keep shooting it.

FYI - I've found Fiocchi ammunition to be quite stout. I certainly would not recommend loading anything hotter. If you want to push the envelope, buy a Super Blackhawk or a Freedom Arms.

 

[moritz83]

Thank you for your reply and help

I will put out a few more rounds through the revolver then and see how it goes, I could also lend a revolver vice from a friend to mount the gun sturdy and check the grouping at 25 m.

FYI - I've found Fiocchi ammunition to be quite stout. I certainly would not recommend loading anything hotter. If you want to push the envelope, buy a Super Blackhawk or a Freedom Arms.

I also thought that the Fiocchi ammo is stout, but I was quite surprised. I have their standard 240gr SJSP which is listed at 1460FPS out of a 150mm barrel, which is 1540J and at the top limit for a .44 Mag load. However, my chrono only gave me 1180FPS, which is only 1000J out of my 165mm barrel. This is more in the medium to lower power range for a .44 Mag. I know that the cylinder gap reduces the velocity a bit, but never to such a large degree where I loose 300FPS.

Maybe this is a hint that the bullet is loosing energy when colliding with the forcing cone? But I can't imagine the bullet loosing like 500J without me noticing, the forcing cone looks completely fine and not damaged.

My plan was to load some hand loads with a maximum of 22.1gr of N110 powder behind a 240gr bullet. I looked at the Vihtavuori N110 load table, which gives a range of 20.4gr-22.1gr. I will start at the lower end and see how things develop, my goal is around 1500J of muzzle energy. These loads are still well withing SAAMI and CIP pressure spec, so the gun should handle them. I am not planning on using some insane +P .44Mag ammo made by buffalo bore, those are definitely in the Ruger only range.

 

[s&wchad]

A number of the ammunition manufacturers quote velocities achieved out of a fixed breech test barrel. You might get velocities like that out of a Thompson Center Contender, but not a revolver.

 

[stansdds]

It all looks normal S&W to me. I don't think you have anything to worry about with that Model 629-6.

 

[__steve__]

Nice first gun! 629 was my first too. Your barrel shroud is much closer to center than my PC revolver, which is my favorite and the most accurate. If it shoots good, and forcing cone looks good after several 100 shots, I would not be concerned, and they flex quite a bit during firing anyway. Tolerances don’t have to be perfect to shoot perfect.

 

[scruffy]

Most likely your getting parallax when looking down the barrel. Have never seen a revolver with the cylinder ir barrel tilted to give the impression of vertical mis-alignment. Enjoy your 629. They are fine guns.

 

[Protocall_Design]

The only way that could happen is if they mismarked a 627 frame as a 629. Then the centerline of the barrel would be .030" (.75 mm) higher than the centerline of the chambers. A .44 cal. range rod would tell you for sure.

 

[moritz83]

Thank you for all your replies!

A number of the ammunition manufacturers quote velocities achieved out of a fixed breech test barrel. You might get velocities like that out of a Thompson Center Contender, but not a revolver.

Yes, a longer barrel without a cylinder gap will definetly increase velocity. But the data given from Fiocchi also show the test conditions, they used a 5.9" (150mm) barrel according to CIP standards. My barrel is 6.5" long. The cylinder gap definetly causes some velocity loss, for a .357 Mag I know that a 0.006" gap causes a velocity loss of around 100FPS with a 6" barrel. This website is really useful for this: BBTI - Ballistics by the Inch :: Cylinder Gap Test

The 300FPS that I am loosing with an even longer barrel than the test condition seems weird to me. But yesterday a friend told me about a really weird incident with Fiocchi .357 Mag ammo. He said that he got cartridges with varying loads in a single box. He had noticably varying recoil through all the shots in the cylinder and some primers showed pressure marks while others clearly didn't. I guess factory ammo is not always that constantly loaded, maybe I got a less hot batch of Fiocchi.

I did another test today, I got a 10mm Aluminium rod and machined it down precisly to a flat surface at the end. I then tried to push the rod into the barrel while carefully pressing it onto the barrel side. I tried to see if I can feel any steps caused by the cylinder, but I felt absolutely nothing. Of course this is not as good as a precisely fitted range rod, but it still shows that the missalignment isn't bad enough to cause any shavings.

The only way that could happen is if they mismarked a 627 frame as a 629. Then the centerline of the barrel would be .030" (.75 mm) higher than the centerline of the chambers. A .44 cal. range rod would tell you for sure.

That is an interesting idea. But the missalignment seems to be a lot less than 0.75mm to me, so I don't think this is the case. A slight missalignment is there, but it is not big enough to cause a step, since the chamber is slightly larger than the barrel.

 

[__steve__]

The only way that could happen is if they mismarked a 627 frame as a 629. Then the centerline of the barrel would be .030" (.75 mm) higher than the centerline of the chambers. A .44 cal. range rod would tell you for sure.

That would make primer marks almost touching edge of primer.

 

[jaymoore]

Usually you can tell by the fouling in the forcing cone area and just forward if you have a misalignment problem. Last one with which I had any dramas was a 686. It shot OK at 25 yards but completely fell apart past 75. Fouling indicated bullet engagement was quite uneven, with engagement starting at about 1 o'clock midway down the forcing cone. No metal fouling at all at 7 o'clock in the forcing cone. Not so good if you want to stretch out to 200m... (It didn't spit metal out the cylinder gap, BTW.)
It may be caused by any number of factors, or is due to a combination thereof.
The main thing is whether it shoots well with SOME load. Jacketed bullets are more forgiving than cast. Cast are more forgiving than swaged. Generally.

 

[moritz83]

Good catch, so far I did not notice any irregular fouling on the forcing cone, the slight marks inside look pretty symmetrical, so maybe everything is fine.

I have another idea, my father is a machinist, so he could turn me a precisely fitted brass rod as a range rod. I am just unsure about the diameter of the rod for a tight fit, it is hard to measure with calipers due to the rifling. But I found some values here on the forum, which says that the diameter of a range rod for a perfect fit has to be 0.4166" (10.5816 mm). Does anyone of you know if this is the exact inner diameter?

 

[moritz83]

Did some more shooting with the gun and I like it a lot now I did some upgrades to it also, I installed a Wilson Combat Spring kit, polished the rebound slide and the surfaces where it rubs on the frame, and I also added some side plate shims to the trigger and the hammer. This improved the action a lot, the trigger is a lot smoother and lighter in both SA and DA.

I also added a Docter Red dot Sight since I prefer those over classical iron sights as a beginner, I only have to focus on bringing the red dot over the target instead of aligning the rear sight + front sight + target.

I also made my own weaker target hand loads with 18gr of N110 powder and 240gr Campro FMJ bullets. I managed to get some touching groups at 15m, but I also want to try 25m next time.

I also remeasured the Fiocchi factory ammo with a Magnetospeed chronograph. My guess was right, the optical chronograph was really horrendously inaccurate. It showed only 1180 Fps while the Magnetospeed shows 1430 Fps for the same Ammo which is very close to what is claimed by the manufacturer with a comparable test barrel. Those Fiocchi rounds are really powerful, the recoil is a beast compared to my target handloads. They must be really close to the pressure limit, 1500J is a lot for a 44Mag 6.5" Barrel Revolver.