It looks like I'm not done with my commercial 30 carbine project yet. When we last had it out, the slide was hanging up on the disassembly notch in the barrel. The fit was loose enough that the slide would drop down a wee bit and hit the bottom of the groove head on. It simply stopped the slide and resulted in a partially chambered round and a bolt in the middle of it's travel. This happened with both the original banana barrel and with the new Criterion.
Swapping in the slide from the Inland fixed the problem. It fit much tighter to the barrel.
I took plenty of measurements from each slide as well as the barrel and studied the problem.

My slide has notches that are not as long as the GI unit and they don't poke out as deeply either. The GI slide was .020" narrower than mine.


It had .037" of slop side to side. That's rattly-clanky loose. Ugly. Being the enterprising sort that I am, I addressed the issue. Out came the pen, notepad, and dial calipers. I made lots of measurements of all surfaces involved. Once that was done, I got nasty with it.



ACK!! He did what?!?!? Yes! I butchered the slide. It's a cast piece and there was no way I was going to attempt squeezing it in a vise. Instead, I burned a little metal on the tabs. A little roughing in with a Dremel tool had the tabs reduced from lumpy bumps to over-sized guides. The various files came out to play and things started looking even better. I'd work the tabs a bit then stop for measurements. When they started getting close, I'd test fit the assembly and polish them with the Dremel.

After a couple hours of fiddling this is what I ended up with:



The slide now has .021" of side to movement side to side. That's a 44% reduction in slop. Because it has to be tilted while installing it's not possible to get a perfect machined fit. I also had to allow for some expansion of the barrel when it gets hot.
Gun barrels are fairly soft as far as steels are concerned. My welds are much harder metal. That's the biggest reason I worked with the polishing wheel to fit the tabs. The smoother they are, the less wear they will impart on the barrel. I also plan on adding a little of the high temp gun grease I use on my M1Aicon. Some of that in the rails will also reduce wear.

It still has a tendency to hang up on the notch. I beveled both ends of the left tab but it didn't completely stop the problem.
I know the tab on the back of the op rod is a bit under nourished.



Honestly, it's downright sloppy. I can almost pull the tab out of it's groove anywhere along the run. That's allowing the slide to rotate down on the left side.

Tonight, I'll attack the tab with the same mentality and see what I can do with it. Adding material to the top and inside of it will prevent the side from rotating and dropping into the notch. Fitting this end will be a wee bit trickier but I don't think it will take as long as fitting the front half.

My shooting group has a range day tomorrow. With luck, I'll be emptying magazines with impunity.


So, by a show of hands, how many of you firmly believe I've lost my mind?
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