Funny cause I was just thinking I started this about a year ago last night and had better get my butt into gear. I have a 17hmr ar15 upper, sgn-9, and suomi build "on going" as well.
tired of idiots
mole, my 17hmr upper is canceled. after A LOT of research the 17hmr is prone to OOB problems.....you may want to reconsider
I actually debated it for quite a while before deciding to go ahead with it. I've shot a remington 597 17hmr and was pretty impressed with it (when it would cycle, the mags suck). I was trying to find an easy to make a delayed blow back design for it, but couldn't find anything. If anyone knows a simple delayed blowback design I'm all ears! The reported injuries I could find were for leftys which would make sence because their head and body would face the ejection port. I'll try it out and if all seems well, I'll keep it as a 17hmr, if not I'll rebarrel to 22 mag. What are you doing with your 3/4 scale one? It'd be a shame not to use it, perhaps a 22 mag or lr?
Originally Posted by vz58
A simple delayed blowback can be an op rod and piston attached to the bolt pulling forward with some gas pressure from the barrel (behind the piston). The WW-II German VG-1 and the later H&K P-7 Squeezecocker pistol did this biased gas pressure thing.
The gas piston can also be a shoulder on the barrel and the cylinder surrounding the barrel blows forward pulling on an op rod or slide. This is much like the VG-1 carbine.
A set screw valve on a gas block or valve gas vent on a sleeve will allow variation of the delay pressure so you can tune it to your favorite station !!!
Combined with a fluted chamber this system will operate with most any size ammo. I don't believe that the .22 HRM would need a fluted chamber.
I finally got around to melting some aluminum in the propane forge. I had a few hours so I fabbed up a small crucible and fired up the burner. I used a set of 3' bolt cutters to break up the head from a briggs & stratton lawn mower into several pieces that would fit in the crucible. After a half hour the crucible was red and the aluminum was melted. I poured it into a large steel ring that was laying on a steel plate to make a round button about 3.5" in diameter x 1" thick. I plan on using the aluminum button to help test out a fly cutter I plan on using to repair the two broken gears on my sheldon lathe I'm restoring. I still need to make a mold and try casting some simple parts. Here's the button made from a b&s head next to a tecumseh head.
sorry to say that is not right u can heat treat aluminum casting. the proper term is call precipitation hardening.. this is were t6 for example comes from when clasifying aluminum
Originally Posted by kernelkrink
ex 7075 ---- aluminum chemical composition
if t6 is added it meas that is was heat treated as per t6 specification
u can then anodize the aluminum for increase surface wear resistance