As close to zero as I can get. I don't like seeing any gap/light between the slide and comp. When I had access to a surface grinder I could get them to the point where the line between the two would virtually disappear when the pistol went into battery. But I will get it as close as I can, without it being an interference fit, with what I have. Probably have to hand work the last little bit because of the angles. What's that blue stuff the hand scrapers use? I could try that for the final fitment as Dykem dries too fast.
I'm already on my second piece because I started putting 3/8" ports in the first comp and realized that they are larger than I want. I will go to 1/4" ports with a 0.1" septum between to keep the pressure up as the bullet traverses all of the ports (3 or 4, probably 4). I have some 1/4" ball end mills coming later this week.
I hate this part because in milling a 1/4" wide by 1" deep port I have trouble getting the chips out of the way of the cutter. Patience...
I have always loved the way a profiled comp looks on a 1911. I'll be watching for sure. Looks like you're using the "Unique" slide. (I believe that's the correct name for it.) Will you be cutting the 'scallops' in the comp to mimic the classic slide lines?
A good friend has a Les Baer Monolith which uses the same slide profile. I didn't think I would like it, but it's growing on me.
I'm not sure yet, what I'm going to do with the profile. I like the look of the 'slab side', but would have to leave a gap on the bottom for the backward movement of the slide/barrel combo prior to coming out of battery. I'll probably have to sketch it up a few different ways and see what looks good to me.
I like the idea of the full profile for this 10mm Auto as this will help tame down the rearward slide velocity a bit.
Well, managed to get it drilled, bored, and threaded to .685x40. Bought a new boring head as I was having extreme difficulty in reading the one I bought from Shars. Didn't like the size/capability of the Shars 2" so I upped to a 3". It might be a bit large, but it works great...
The new 3/4x3-3/8 boring bar worked great. Uses a TCMT 21.51 insert.
Rick: Well, the piece of 4140 I bought kinda dictates the final shape. Never having done this, I asked my old mentor what size stock I should buy, and he said 1.5"x1" for a full profile. And it will work well. But had I wanted to pick up the profile of the extended dust cover, I would have had to start with 1.75"x1". Oh well, solves that problem.
I have the comp threaded on fully here and it is flush to the slide (no gap). I may have gotten the threads TOO good as I'm not sure there will be enough room for the Loctite, but time will tell. I cannot detect any play in the threads. It appears I will have about 5 to 8 thou between the breach face and the hood to work with to get the gap as minimal as I'm capable of. I've lost a bit of the fine motor skills over the last 20 years or so.
I thought I'd try one of those new fangled comp alignment reamers from PTG, but it measures at .416" which is WAY more clearance than I used to put in my competition garbage cans (round style). I was thinking more of like .408"? I've never had a bullet strike, but maybe I was overdoing it a bit. But I'll give it a go, and I guess I'll find out how efficient the comp is once I get to shoot it.
The last septum/front face of the comp is not to final dimension yet, and I will take it down to .2" once I get the comp-to-slide interface finalized so I can get the proper angle on it. Once fully fitted and profiled I don't think there are any external right angles anymore. Did I mention I've not tried one of these full profile comps before?
I've never run a profiling end mill either. Hopefully I won't break anything while I'm learning.
One of my first wide-body 1911s was built on a early aluminum para-ordnance .45 cal frame (steel didn't come out until almost a year later IIRC). The frame was rough, and the magazines pretty much junk, but I wanted to build a high-capacity gun for the USPSA sectionals in Mesa, AZ without resorting to 9mm major which the paid shooters were blowing up trying to get one to hold together. The .45 mags couldn't hold the 10mm auto, so after my mentor told me about a 'Centimeter' wildcat round, I decided to go with it and trimmed about 1000 pieces of 10mm brass to centimeter length. Used three chambers, .3" wide IIRC. Worked great, lots of shooters were checking out the gun and I even managed to get FTD on a couple of stages, beating Robby and Brian. Finished 3rd in Master Class. Not bad for a lefty shooting right handed (right eye is my master eye). Later when I was trying some really hot 'hunting' loads, a friend was shooting video and captured the muzzle of the gun actually dipping 'downwards' during recoil. But I also noticed that there was a significant amount of gasses following the bullet out the end of the comp. The 10mm Auto has a larger case, and more powder, so I figured that a extra port wouldn't hurt.
I went straight into the comp (90 degrees) with the barrel, so I had to angle the backside of the comp where it touches the slide. I did clean up the end of the slide slightly to remove some imperfections and tooling marks, but the angle is on the back of the comp. And as I like to fit my barrels a bit high for high(er) power loads I'm not sure 1 degree would be sufficient, so I ended up fitting the slide/comp interface by hand with files and sandpaper. Old School.
I am whining a bit, true, but I'm just ****** at the rolled edges on the slide flats and other imperfections in this thing. If I had a surface grinder I'd just thin the sides of the slide and comp a bit in an attempt to get rid of the lousy edges. I like those 'slice your thumb open' knife edges where the comp and slide meet.
Considering I fit this by hand, it's not too bad. I recently purchased a semi-full profile comp for another guys gun from a 'nationally known' gunsmith and the fitment was terrible, so I guess I shouldn't be complaining TOO much about mine.
I'm out of threads on the barrel. I've never attempted to pick up an existing thread before so I'm really not wanting to attempt that on the lathe. I guess I could look on Brownells to see if they have a .685" tap and die set. They probably do. That would be the safest route.
See that little block in upper left near the back of the slide? It is a piece I made that holds the lower barrel lugs centered in the slide for hood fitment (there's a longer one higher up in the pic that I bought from Wilson over 20 years ago, but it's a piece of junk). I use that and the rod to the right of that which holds the barrel in battery while I cut/fit the lower lugs (look in the first pic). The little block is damn near an interference fit in the slide and around the barrel's lower lugs/ramp so it works really well for lining up the slide flats and holding them there.
EDIT: I just checked Brownells and they do have the die, but it sure is spendy. But I went ahead and ordered it as it is less than half the cost of a new barrel should I screw that up.
It is not that difficult if you can get the part/barrel dialed in. Once that is done I set my cutter height and compound angle, engage the half nut and then loosen the tool in the holder. Run the tool into a thread and let is self adjust to the thread, tighten, and double check. Use some dykem on the threads and manually turn the chuck to verify.