Thread: .17 Mach IV Barrel

Well I managed to free up some workshop time yesterday evening and fitted up the .17 barrel to the CZ 527 action.





The barrel is 24" long and stainless steel with a bore that looks like new. I had it soaking in copper solvent for a few hours and none at all came out so it seems to be well looked after or it has possibly only run the molly projectiles it came with..

It was going to be a precise machining task for the simple reason I had to head space it without a chamber reamer as I dont have one or dont know anyone with one.
After closer inspection it had had an extended tenon bush fitted threaded in 1"-1/8x14tpi Whitworth which is a BSA .222 CFE thread but under the bush it is s M20x18tpi Sako Vixon tenon and this is what it was originally chambered in .17 Mach IV for and fitted on.





The CZ 527 thread is a shoulder less M25X1.25 which locks up on the rear face, this meant I could just turn the entire knox and tenon bush down to 25mm and clear off all the old thread, shorten off the rear contact face closer to the required headspace and re-thread it for the CZ.
I made up some go and no go gauges to work with my FL sizing die dimensions and took very light cuts from the rear face until it fitted up and head spaced perfectly.









I left the barrel at 24" for now just to see what velocity it could achieve but Im certain Ill cut it back to 20-22" once Ive had a play.
I had to make up a thread collar for the suppressor to square up against a shoulder for my M14x1mm suppressor as the barrel was only a fraction over 14mm out at 24". Will get away without it once trimmed back.