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Old 12-28-2011, 06:17 PM
snubbiefan snubbiefan is offline
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I have a follow-up post here based on something I have just learned.

I purchased a pile-of-parts from a used 317. I haven't a clue as to how many rounds the parts have seen, but for the price of all the internals I received...it was a bargain. Everything but the frame. I decided I would stick the cylinder in one of my newer guns just for giggles. Yoke and cylinder changes are suppose to be a factory performed fit, but I tried it anyway.

I believe that excessive end-shake is going to be the first problem that will be observed in an alloy cylinder. My main concern had previously been the yoke-rod, but this older used yoke and rod were dimensionally identical to my new rod. My (relatively) new cylinder fits either one and the BTCG is the same with either yoke .004-.005, as well as the end-shake. When I installed the used cylinder on either yoke, end-shake was way out of spec. and very obvious. With the cylinder pushed forward, I could barely insert a .0025 feeler to gauge the BTCG. With the cylinder pushed rearward I had a BTCG of around .012. The yoke rods being the same....the wear is on the bearing surface at the back of the cylinder and I would imagine this shows-up rather quickly in an aluminum cylinder. One of my 317's has around 1,000 rounds through it and I can already feel a bit of end-shake as compared to my wife's 317, which has been little fired.

Would the gun shoot...you bet it would. Was it accurate...yes and it shot about like the newer 317. I could tell no difference at all. The end-shake issue can be corrected with bearings, but I also learned this morning that it may also be necessary to re-finish the interior bearing surface of the cylinder as the yoke-rod cuts a grove in the base of the cylinder. A simple bearing installation may fix the problem temporarily, but the real fix is to machine the inside bearing surface of the cylinder prior to the installation of any bearings (shims).

The older cylinder also exhibited slightly more "wobble" than the newer cylinder, so I expect the inner cylinder bore is somewhat worn and not the yoke rod, as it performed the same with my newer cylinder.

What does all this mean to anybody....I don't know, but it may make for interesting reading for anyone concerned with aluminum cylinder longevity. I am sure the main concern from most shooters is..."will it blow-up". That should not be the main concern. I feel like these aluminum cylinder guns will require more and better lubrication in the rotational area where the cylinder comes into contact with the yoke-rod. That is where your wear will be.....not in the chamber bores, but in the cylinder-to-yoke-rod fitment.
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