Hydraulic cylinder tubing

[Mike C]

One of the posts was talking about a good source of heavy wall tube for cannon barrels.  I have built a couple guns out of hydraulic cylinder tube, it comes with the I.D. Honed to a miror finish.  It is available in various alloys, some of it is 4130 or 4140 which is a good gun steel.  I just picked  up a peice of 3" ID 5-1/2" OD, it was a left over almost 4' long, got it for $20.  
Keep in mind that if you plan to do any welding especially a welded breech plug to use the appropriate filler material and process for the type of steel you are working with.  4130/4140 require preheat as well as post weld stress releif for maximum strength.  I do not weld trunions to the barrel itself as this will cause distortion of the bore, I machine a sleeve that the trunions weld to, after welding the sleeve is bored to shrink fit on the barrel.
Have fun,   Mike C

[Double D]

Mike C. Got any pictures?  Static pictures are nice. Belching smoke and fire preferred. Post them here.

Glad you posted here.  I have had some questions about using hydraulic cylinders. It's good to have some one with first hand experience.

Are those hydraulic cylinders heat treated?  Are they hard?  Are they easily machined such as turning tapers, bells and such?  

The preferred way to install breech plugs is to use a threaded and pinned plug. How hard is the bore of those cylinders? would I have problems cutting a thread?  Are those bores chromed?


How do those Tubes react to TIG welding vs stick welding. You metioned the problems with welding, and I assume you were referring to stick or MIG welding

The way I have installed trunnions in the past is to mill a flat the diameter of the trunnion in the side of the barrel. In the center of this flat is a threaded hole. I make the the Trunnion with a threaded stem. I screw the trunion in and then tig weld the trunion in place.  the lower heat of the tig weld causes less/no distortion.  I also don't do the final finish of the bore untill after the trunnions have been installed,  smoothing out any distortion.

Off course in your case you already have a finished bore to start with.