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Prototyping a GP100 extended cylinder release


Fishbreath

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I sent my cylinder off to Dave Olhasso for chamfering, and was thinking about having him put an extended cylinder release on at the same time, but didn't want to spend the extra money to ship a gun for just that. Instead, I decided I'd draw one up myself, and 3D print some test articles.

 

A few days of testing later, and here's the final prototype.

 

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It cants a little bit inward, which I'd like to say was intentional to keep it out of the way, but is actually just an artifact of how I drew the part.

 

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To my surprise, the PLA I printed it in is actually strong enough to stand up to some light testing, although I wouldn't put much stock in it for live fire. (Nylon or Zytel might be sufficient, but I'm not set up to print in those yet.) I see why people like the weak hand reload now—much more efficient when you don't have to break your grip to open the cylinder! I'll have to give it some more practice, and see if I like it better than the strong hand reload given some drill time.

 

I have a place in mind to get these made in aluminum, or maybe even proper stainless steel, so once I hear back on required clearances/tolerances, I hope to have a metal one to install and test.

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It's a drop-in part rather than an attachment: below is a picture of the original release, and the CAD drawing of the part I printed.

 

The printed version hasn't broken yet, and I've been back in my daily dry fire routine in preparation for the 2021 season for a week now. It's made in a PLA+ plastic, with additives to improve its mechanical properties over standard PLA, but I suspect it's too temperature-sensitive to be trustworthy over the course of live fire on a hot day—it'll soften if it gets to about 125F.

 

I have a few on order with a 3D print shop in a variety of materials: ordinary nylon, glass-filled nylon, and a metal filament that mirrors the MIM process (printed as a green part, then debound and sintered in a furnace). Hopefully, one of those will be good enough for live-fire testing. If it is, and there are some volunteers with GP100s of various sorts, I'd like to send out a few freebies to see if they fit other GP100s without filing (or much filing), or if I designed a part that fits my gun only.

 

original-release.thumb.jpeg.4becd4ef07bbe9a34e1039282a45cbd5.jpeg

 

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I haven't made any progress on prototyping a further-extended release, but I did get a prototype part in the mail today, printed in glass-reinforced nylon. It's notably stiffer than the PLA one, and has fewer obvious printing artifacts because of the different printing technology used.

 

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Nylon is also substantially cheaper than metal options and substantially more heat-resistant than the PLA I can 3D print at home, so if it's strong enough to stand up to ongoing use, maybe I can get a few to sell.

 

Before I do that, though, I need some information on fit across multiple revolvers. Any volunteers with GP100s who could fit some free PLA samples and tell me if they fit, or where they don't?

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I have a metal prototype part, printed by a rapid prototyping shop in a metal filament that's kind of like MIM: metal powder in a polymer binder, which is then post-processed to remove the binder and sinter the part together.

 

It's not an unqualified success—it's not as dimensionally accurate as the laser-sintered nylon parts I've been using, I don't think, and interferes slightly with the hand depending on how tightly the pivot pin is screwed in. Still works, however, after a bit of filing, and the rotational force on the pivot isn't enough to unscrew it even without a spot of loctite (as the pivot had originally).

 

An alternate explanation is that the glass-reinforced nylon, though hard enough that it's difficult to bend the part perceptibly with fingers alone, is still much softer than the steel parts in the gun, and running the trigger a few dozen times simply laps the nylon to a perfect fit.

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  • 2 weeks later...
  • 1 month later...

I got my 3D printer set up for nylon, which means I can make production-ready plastic parts now. The most common feedback I got about the original design was, "Can you make a bigger one?"

 

ultralatch.jpg.a136923d60cfbd781cd498da8ec93213.jpg

 

So I gave it a try. I think I like it. We'll see how it goes in dry fire over the next few days.

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  • 4 weeks later...

The extra-large nylon paddle works well, but now that it's been moisture-conditioned by a few weeks at ordinary indoor humidity (as opposed to the drybox conditions of my house in the wintertime) and exposed to a hot day at the range yesterday, it's a little too flexible now—the paddle bends at the neck under thumb pressure, which probably means it isn't levering against the cylinder latch as well as it could be.

 

I went back to the glass-reinforced nylon one I had made from a 3D printing provider, and plan to investigate some more rigid, heat-resistant materials over the summer as I have time (both to try out different materials, and to get my 3D printer back into tip-top shape).

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I don't shoot Ruger, but I still find this project to be interesting on several levels. Good work, lots of great ideas and high level thought process. Keep on truckin!

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On 5/3/2021 at 5:18 PM, Toolguy said:

I don't shoot Ruger, but I still find this project to be interesting on several levels. Good work, lots of great ideas and high level thought process. Keep on truckin!

 

Thanks—an especially nice compliment, given its source!

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