PPC-Style Ball Bearing on Yoke - Purpose? Effective?

[CoronaGold111]

On many PPC-style revolvers there is a little ball bearing & notch / detent thingie on the yoke. Obviously it is there to improve results downrange, but what is the exact intent and how effective is it?

It seems like the idea is to make the chamber and barrell alignment more consistent? But I have a hard time believing that springy little bump makes ANY improvement during live fire.

Who has the trigger time to tell me whether it makes any real difference? Thanks.

 

[burneyr]

On my PPC revolver the yoke ball/detent was placed there to serve as a replacement lock point. With the addition of bull barrels, the ejector rod bolt is usually deleted.

Also, S&W uses a ball detent lock on the X frame revolvers and the new-ish 66-8 revolvers. It's a bit different than what is commonly used on PPC revolvers, but it also deletes the ejector rod center pin bolt lock.

 

[RetCapt]

I do have the trigger time. That said though, I can't tell you if it makes any difference in grouping ability relative to the forward anchorage point on the tip of the extractor rod.

Unless someone has done a comparison test on the same revolver, but configured for a latch at the tip of the extractor rod, then configured for a yoke mount latch, then each version bench rest tested for comparison of group sizes, your question can't be answered. If anyone has ever done any such testing I have never seen any such mention.

There are two advantages to the yoke mount:
1. Using a bull barrel underlug as the forward part of the yoke mount is simpler to machine than adding an extractor rod tip anchorage on the bottom of a bull barrel. These yoke mount underlugs were available already fabricated. Bill Davis was one such supplier.
2. The extractor rod tip latch assumes the extractor rod is perfectly round. Any deviation from this can become a source of binding.

Once these fabricated underlugs became commonly available, they became the preferred method of forward latching. The gunsmith who built my PPC revolvers went to them, and retrofitted both of my revolvers. He thought them to be a superior system.

About PPC revolvers: Between practice and matches, they get a lot of rounds put through them. But these are .38 cal wadcutters, so very light loads. These are not rounds that have the intensity to loosen revolvers. Thus. the durability of yoke mount latch systems was never really tested in PPC applications.

The subsequent manufacturer use of such systems would seem to suggest that durability is not an issue.

On my PPC revolvers, regardless of which forward latch system was used, neither was a limiting factor for scores.

The limiting factor was me.

 

[WR Moore]

One factor not mentioned is how much of an issue extractor rod drag on the yoke can be if it's locked at the far end. Extractor rods that are actually straight and concentric to the hole bored through them are tough to find. In a defensive/duty gun, this really isn't much of an issue, a minor bit of bind as the cylinder rotates often isn't noticed or significant. OTOH, when you're trying to keep all your rounds in the X ring at 50 yards, variance in the trigger motion can be a big deal.

Yes, you can make sure the extractor rod has minimum runout and dress the high spots on the OD down, but it's a pain. The ball detent makes life much easier.

 

[Protocall_Design]

The effectiveness of the aftermarket crane ball detent is very dependent on the skill of the installer. I have seen many that did little or nothing, due to the ball being staked in too deep, giving very little latching force, or the detent being poorly cut, allowing the crane to move sideways.

A properly done one holds the crane tightly closed against the frame.

 

[Sevens]

I have five examples of true PPC revolvers. Four are built on S&W K-frames and one of them is a Ruger Service Six with a Python barrel and serious action work. It was done by Bill Davis and is so marked.

Of these five, only two have a ball detente on the yoke lockup. Neither of the Bill Davis guns have it and my one custom PPC revolver that was built by an unknown gunsmith does not have it either, however that revolver does have a traditional lockup at the front end of the ejector rod while neither Davis gun locks up anywhere except the rear of the cylinder.

My two other PPC revolvers are both Travis Strahan creations and both have the ball detente on yoke lockup.

I've shot them all to good effect. The Ruger with Python barrel shoots extremely high but all of them are one-hole guns and I love them.

With my small sample size, I am not convinced that it's necessary to have to ball detente on crane lockup.

 

[armorer951]

I competed in PPC back in the 1970's and 80's, and built many PPC revolvers for other competitors during that same time period. (back when dinosaurs roamed the earth)

As others have stated, I too am not sure about the potential aided accuracy from this particular style of lockup. It seems this would be hard to quantify, although the ball detent, if properly installed, does hold the crane in position better than the S&W traditional front locking lug system, particularly in terms of side to side movement. Arguably, this could take some of the stress off of the cylinder and yoke assembly, and put the cylinder in a position where the cylinder and barrel are in alignment more consistently. Obviously this all depends on the skill of the builder.

For me, at least, this detent lockup system was also considerably easier to install than trying to configure a locking bolt system on a bull barrel, particularly when an underlug or counterweight was used.

Pretty obvious, and just an "old coot's" opinion here, but I believe most of the accuracy of these revolvers came from using high quality barrels (Douglas, Apex), and the attention to detail with respect to the configuration of the barrel extension and the forcing cone angle.

When professionally built, and using the proper ammunition, they can be a joy to shoot, even out beyond 50 yards.

Carter

 

[Protocall_Design]

I agree with everything that armorer951 said (as usual), but would add that a lot of the tight groups from 25 to 50 and beyond, were greatly aided by the tighter-than-factory barrel twist that these custom barrels have.

Most of the factory S&W barrels are 1 in 18-3/4", almost 1 in 19. The custom barrels were 1 in 16, 1 in 14, and 1 in 10. I never saw a 1 in 12.
All the ones I built were 1 in 10. The factory barrels (that I've shot) wouldn't shoot a really tight group with a low velocity (750 - 850 fps) wadcutter bullet, but the custom barrels would shoot 1" to 1-1/2" groups at 50 all day with the same light wadcutter load.

I have always thought that the bullets out of the factory barrel were spinning just fast enough to be stabilized at the muzzle, but went under the required rpm before reaching the 50 yard target. I wish S&W would have made their twist rate more along the lines of 1 in 10 or 1 in 12 across the board to shoot light target loads better. If you use higher velocity ammo (1100 fps or more) in the factory barrel, the groups will tighten up nicely.

 

[JohnHL]

I have a model 29 "Classic Hunter" that my now deceased shooting buddy bought new in the late '80s.

Immediately after purchase, he brought it to Nu-Line guns and had them install the crane/yoke ball lock.

This was before the "Endurance Package" upgrade was done by S&W on the 29/629.

The reasoning at the time was that heavy loads could cause the cylinder to unlatch and open and the ball lock was intended to prevent that.

John

 

[BillBro]

Mine was done by s;w and its cut all wrong and does nothing. The PC no less.

 

[RetCapt]

This has evolved into a fascinating thread.

A few responses and comments to follow:

For WR Moore. Your post starts out "One factor not mentioned..." I did in fact mention this factor. It is #2 in my post directly above yours. I did not go into more detail because I did not think it necessary given that this is a knowledgeable group who can connect the dots.

For Sevens. I have seen one Davis PPC revolver built on a Smith K frame with no front anchorage at all. It was a very early version that Davis built for a fellow CHP officer. It may have even predated when Bill Davis went commercial. Given the only use this revolver saw, as a wadcutter target gun, it did seem logical at the time to assume the single rear locking point would suffice. While I was not convinced a ball/detent mount was/is necessary, especially in a wadcutter gun, the almost universal use of them by PPC gunsmiths once they were available was sufficient proof to convince me. These gunsmiths, certainly not me as a shooter, were the experts and I respect their opinions.

For Armorer951. Your comments concur with my gunsmith, Greg Roberts, who was in Santa Cruz at the time. That is why he went with the Davis underlug yoke mount units once they became available. He also felt that the barrels were the critical component. He used Douglas barrels for blue revolvers and Atkinson for stainless. He said the Atkinson barrels were more expensive but contended the additional expense was worth it in the end revolver. I concur with your statement that they are a joy to shoot. I am long retired from LE, and had quit PPC competition long before that, but I still enjoy shooting my PPC revolvers.

For Protocol Design. Your comments on barrel twist rate reflect everything I have ever read on the subject. Somewhere in all this I had read that Colt used a faster twist rate which contributed to their (claimed) tighter grouping ability. IIRC Roberts used 1 in 14 twist rate barrels.

For JohnHL. Your account of your buddy having a yoke mount ball added to a Smith 29 further resolves my speculative question about durability.

Overall, an unusually informative thread.

 

[RWJ]

Another thought

My early 80s Lou Ciamillo gun was built with a 1:10 Apex barrel with 10 lands and grooves, and would shoot any reasonable quality factory or reload, including some of my old reloads using the old 3-D HBWC, to a B-27 X-ring or smaller from a Ransom Rest at 50 yards. Somewhere around 100,00-125,000 rounds, the recess detent for the ball started to show a little wear, and some slight lateral play. A center punch just outside the detent edge tightened it right back up to Lou's specs, and that gun still sits in the safe, ready if I ever get the urge again.

 

[Protocall_Design]

The Colts had a 1 in 16 which did help with target load accuracy. They also had a tapered bore that went from .357 at the forcing cone to .355 at the muzzle. This was done by hammer forging the barrel over a mandrel. Each different length of barrel required a different mandrel to be the right size at both ends.

 

[WR Moore]

I've lost the book somewhere in the house, but while the twist specs for the older Colt duty type guns was 1-16, for the Python and another model, they used 1-14. Per the same book (by Charlie Askins), Colt always used a 0.354 in groove diameter for .38 Spl/.357. Can't recall (didn't pay attention) to what they may have used for .38 S&W and it's kin.