Ruger Base Pin Assembly – The ExhaustNotes Blog

By Joe Berk

One of the very few areas in which the Ruger Blackhawk design can be improved is cylinder shaft retention. I experienced this problem many decades ago on a Ruger .357 Blackhawk, and back in those days, the easiest thing to do with a problematic firearm was to sell it (that’s not so easy these days). I don’t want to sell any of my guns, especially my 200th Year Ruger .45 Colt Blackhawk. It’s the one you see in the photos above and below.

Before I go too much further, let’s address terminology. The Blackhawk cylinder rotates around a shaft that Ruger identifies as a base pin assembly. That’s okay, I guess; Ruger makes a lot of guns and they can call their parts whatever they want. I tend to use more precise and descriptive terminology. I call the part the cylinder rotates around the cylinder shaft, and that’s what I’ll refer to it as in this blog.

To get the point of this blog, I had a problem the last time I had the Blackhawk on the range (which was only the second I had fired the gun). I shot my 850 fps, 5.9 grains of Red Dot, and 200-grain cast bullet loads (which is a mild load), and suddenly, the gun would not cock. On closer examination, I found that the cylinder shaft had jumped forward. It was the return of a condition I had experienced on another Ruger Blackhawk back in the 1970s and then had completely forgotten about.

The cylinder revolves around a shaft that is held in place by a spring-loaded, frame-mounted lock. Under heavy recoil, the cylinder shaft wants to stay where it is due to inertia as the gun recoils. The spring-loaded lock engages a notch in the cylinder shaft, and it’s supposed to prevent that from happening. Sometimes, though, the recoil is too much. The spring-loaded lock is cammed out of place by the cylinder shaft inertia, and the cylinder shaft slides forward in the frame.

The left arrow points to the cylinder shaft. The right arrow points to the spring-loaded cylinder shaft retention pin. To remove the cylinder, push the retention pin to the gun’s right, and the cylinder shaft can be pulled forward. This allows removal of the cylinder for cleaning.

Under recoil, the cylinder shaft’s inertia can cause it to displace the cylinder shaft retention pin, and that allows the cylinder shaft to slide forward in the revolver frame (as you see here). When that occurs, the revolver hammer cannot be pulled all the way to the rear to cock the gun.

When the cylinder shaft slides forward in the frame, the spring-loaded pin at the other end of the cylinder shaft moves forward, too. It shifts to a position that interferes with upward motion of the revolver’s transfer bar when attempting to cock the gun. You can see the area of interference in the photo below.

When the cylinder shaft slides forward in the revolver frame, a spring-loaded pin on the end of the cylinder shaft moves with it. When that occurs, the cylinder shaft’s aft end pin no longer pushes on the transfer bar (indicated by the red arrow). The result is that the transfer bar is no longer held to the rear. When attempting to cock the gun, the transfer bar’s upward motion is blocked by the firing pin.

The transfer bar is designed to prevent the hammer from contacting the firing pin if the trigger is not pulled. This feature prevents an unintended discharge is the gun is dropped. The transfer bar is normally pushed to the rear by a spring-loaded pin in the back of the cylinder shaft, but when the cylinder shaft slides forward, that no longer occurs. The result is that the transfer bar (no long held to the rear) catches on the firing pin, and the gun will not cock.

The Fix: The Power Custom Base Pin

So what’s the fix to the cylinder shaft moving forward in the revolver when it recoils? That would be a product called the Power Custom replacement base pin (note that Power Custom uses Ruger’s terminology for the cylinder shaft). I bought one and this blog focuses on the good, the bad, and the ugly (and which, with a nod to Clint Eastwood, somehow seems fitting for a blog on a part that goes into a Western-styled six shooter).

The Power Custom replacement base pin (upper component) and the stock Ruger cylinder shaft. The little pin on the right end of each is what pushes the transfer bar to the rear, preventing interference with the firing pin when the revolver is cocked. Note the Power Custom’s larger grip on the left.

Installation

When I started to remove the Ruger’s cylinder shaft so I could install the Power Custom part, I discovered something I had forgotten. The ejector rod subassembly has to come off to allow cylinder shaft removal. Without doing so, the cylinder shaft cannot move far enough forward for removal.

A fully-extended cylinder shaft. The ejector rod and its housing had to be removed to remove the cylinder shaft.

The screw that allows removing the ejector rod housing.

Removing the ejector rod subassembly was easy enough to do, and after doing so, I pulled the original Ruger cylinder shaft and replaced it with the Power Custom part.

The Good

The Power Custom replacement base pin (which replaces the original cylinder shaft) has a tighter fit in the revolver frame and the cylinder. The Power Custom part has a diameter of 0.2492 inches; the stock Ruger cylinder shaft has a diameter of 2.480 inches. I could feel the decreased cylinder wobble as soon as I installed the Power Custom part. Theoretically, this should translate into improved accuracy.

The Power Custom replacement has a different, larger-diameter, stepped grip. There’s more to grab onto when you want to slide the cylinder shaft forward to cylinder removal.

The Power Custom grip contains a set screw that can be tightened against the revolver barrel (which I did not use). The idea is the tighter fit and the set screw act to prevent the cylinder shaft from being inertially driven forward under recoil. Power Custom recommends using a drill bit through the set screw hole to spot face the barrel, which would give the set screw a better place to seat. I didn’t like that idea, and I didn’t tighten the set screw on my gun.

A set screw on the Power Custom base pin assembly. I opted not to use the set screw. Note the slot in the Power Custom part for the cylinder shaft release, and note that it is unmarred.

Finally, although the Power Custom base pin has a larger grip, the overall part is shorter in length than the stock Ruger part. This allows greater ejector rod travel, which is better for case ejection. Sometimes with the stock Ruger cylinder shaft, the cases aren’t fully ejected due to carbon fouling in the cylinder, and spent cases have to be pulled manually from the cylinder after they are partially ejected. This shorter overall length is a good idea, I think.

The Bad

I already mentioned the set screw business above, and Power Custom’s barrel spotfacing recommendation. I didn’t like the idea of having to use a set screw.

Power Custom provides a tiny Allen wrench for use in tightening the set screw. With the stock Ruger cylinder shaft, the cylinder shaft can be moved into the cylinder removal position with no tools, and should the need arise, the cylinder can be removed in the field. With the Power Custom part, an Allen wrench is needed. I don’t want to carry around a tiny Allen wrench. Is this a real concern? Maybe. In the last 50+ years, I have had to remove Blackhawk cylinders a time or two while wandering around in the boonies. To me, this is a disadvantage.

This brings us to the principal bad, and it’s my fault (for reasons I’ll explain momentarily): The Power Custom base pin did not reliably stay in place under recoil in my Blackhawk. Note my comment above: I did not tighten the set screw in the Power Custom base pin. If I had, it probably would have stayed put. And on the plus side, it doesn’t jump out of position nearly as often as the Ruger cylinder shaft does.

The Ugly

Once the new Power Custom cylinder shaft was installed, I grabbed some ammo and headed to my local indoor range. How did the Blackhawk shoot with its new cylinder shaft? From an accuracy perspective, I could not tell the difference. This is a 10-yard target, depleting a box of my reloaded .45 Colt ammo in the process.

Thanks again, Command Sergeant Major Hickman! My point of aim was at 6:00 on the orange bullseye. At 30 feet, the revolver was shooting high, and the rear sight was all the way down.

During my indoor session on three different targets (using up a couple of boxes of the 5.9-grain Red Dot reloads), the new Power Custom cylinder shaft jumped over the retainer twice. If I had tightened the set screw against the barrel, that probably would not have happened, but to mention it one more time, I don’t like the idea of having to rely on a set screw to hold the cylinder shaft in place.

When I returned home, I pulled the Power Custom base pin. I could see that it had deformed slightly in the groove that engages the mating retention feature in the revolver frame. I then pulled the extractor subassembly to get a better photo.

A gouge on the new Power Custom cylinder shaft. It wasn’t there when new (see earlier photo of the new part). I believe the Power Custom base pin steel should be heat treated to a higher hardness. The part’s softness and not using the set screw is what allowed this to occur.

My conclusion is that the Power Custom base pin should be heat treated to a higher hardness. If it had been, it would not have deformed when forced against the revolver’s cylinder shaft retention feature. But that may be irrelevant. The Power Custom base pin’s principal locking feature is the set screw, and I didn’t use it. And as I mentioned above, while it did shift forward a couple of times, it doesn’t exhibit this behavior nearly as often as the stock Ruger component does.

I emailed Power Custom about the deformation I noted in their cylinder shaft, and to the company’s great credit, they put a replacement base pin in the mail to me the next day. That’s great customer service.