I know, I know, but I’m having fun. OK, last week I ordered a .270 Winchester rifle barrel (which has a .277″ bore) and I ordered .278″ and .315″ reamers. Yesterday the barrel and .315″ reamer arrived and I headed into the shop. I worked on it until 10PM before retiring for the night.
Now, when I was working on the 7.8mm conversion I had issues with the liner, so I figured the less I had to line the better. I put the barrel from the Maadi Helwan in the lathe and bored the first two inches from the breech to .432″. I cut the barrel at the end of the locking block and called it a night.
When I picked it up this afternoon I cut a section of the .270 barrel, chucked it up in the lathe and turned the barrel down to .590″ (about the diameter of the original barrel) then turned down one end to .432 to fit into the breech. I pressed it onto the breech/locking block with red Loctite, then bored through the block and pinned the barrel in place. I cleaned it up and blued the result with Oxpho Blue. The locking lugs had peened (as they seem to do on all Helwans sooner or later,) but this is meant to be a straight-blowback so I simply ground them off and filed them flat to the sides of the breech.
I put the .315″ reamer in the hand-drill and ram it against the belt-sander to create a reduced section to act as a pilot and then bored the chamber on the drill-press, checking carefully to make sure I got the depth of the chamber right. I also cut a feed-ramp into the breech with a stone grinder in a Dremel. Finally I cut and filed the barrel flush with the end of the slide because I like the look. I crowned the barrel afterwards of course.
I assembled the gun, inserted the magazine, hit the slide release and it neatly chambered a round! I was as gobsmacked as I was grateful; knowing it should work in theory is one thing; seeing it do it is another. As I expected the extractor is a bit short to pull cases from the chamber reliably, but allowing for that it was able to hand-cycle rounds from the magazine. YES! I’ll be making a new extractor to accommodate the narrower cartridge. Hopefully I won’t need to modify the breech-face.
One thing left to try. I chambered a round, aimed at the ballistic gel block and…
…click. Crap. I re-struck the primer and got another click for my trouble. Full of misgivings with worst-case scenarios racing through my mind I pulled the round and checked the primer. Nice, deep dimple. Bad primer. With palpable trepidation I loaded another round, pulled the trigger.
Whew! The slide recoiled far enough to cock the hammer and tried to load another round. It couldn’t of course, as the fired case was still in the chamber. OK, I knew I needed to fix that extractor. Polishing the chamber is also on the agenda… it’s a bit sticky on the fired brass.
So, it’s almost there.
So how did the 58gr. bullet over 2.2gr. of Unique do? Well, it had a significant bang and seemed to make the slide work- two more shots seem to verify this. It feeds from the magazine so that’s another milestone passed.
So What’s Next?
First thing will be the new extractor; I plan to make it out of tool steel and give it a spring-temper. Polishing the chamber after that. I expect I’ll need to modify the ejector; I’ll probably also have to alter the slide to accommodate that.
The next thing to address is ammo. I’ve got a set-up to cobble together ammo, but that’s not going to work for producing enough for ballistic testing. I also need bullets; I’ll probably convert some rifle-bullets. I also have a pal making me some molds for casting bullets. With the bullets cast hard they ought to be alright.
The smart thing to do would be to start with 5.7×28 reloading dies and work from there, so I’ll see about that. They aren’t common and can be pretty expensive, but hopefully I can come up with some.
The barrel is currently 4-1/4″ long; I intend the cartridge for more compact pistols but I have to work with what I have. I examined the possibility of shortening this gun to 3-1/2″ long, but I don’t like the odds of that working out.
Anyway, that’s where I’m at this evening. Good progress, but some distance to go.
Stay safe and take care,
Michael Tinker Pearce, 1 May 2022