Blurr...

Pics... pics... pics....

And looking forward to this build!!

Cutting off the receiver stub from the barrel is fairly straight forward. I used a dremel cutoff wheel to slice through the bottom where the bolt carrier rides. Once I could barely see threads, I got a big cold chisel and BFH and with a couple whacks, the cut had cracked the rest of the way. I had to drill out the barrel pin 3/4 of the way through before I was able to pound it the rest of the way out. I should have waited until I was at the shop and used the drill press, to keep the bit from going off center, but since I'll be using an oversized barrel pin when I reassemble, it's not that big a deal.

When I chucked the barrel up in the lathe with the chamber in the live center, I noticed that the cut for extractor was causing it to spin slightly off. So, I grabbed my NO-GO guage, which has a nice hole drilled in the center of the back and front, and used that to keep the barrel centered... and it worked!

I cut alittle more than I thought on the second pass, and when I checked I was already alittle under the dimension I wanted, but not too far along where it would cause major problems.





I took alot of pounding to get all these pins out, and I still can't get the gas system parts to budge off the barrel either; even after soaking with penetrating oil overnight, and using a torch to try and loosen them up. I'll have to use the press at the shop to break them loose.



and here's the barrel rough cut at 17"



I may try my hand at fluting it to shave alittle weight, which I'd rather do than just reducing the OD by turning it off in the lathe. I'm also going to try cutting the sling and cleaning rod mount off the gas tube front bracket, and contouring it to match the other side. Kinda like this:


However, I think the next step is going to have to be modifying the carrier to fit so I can check headspace and get the barrel installed.

Blurr,

That is a great idea to get that barrel centered!

I like this build so far... and look forward to your progress!

I have wanted to do an RPD.... so this interests me alot!

So, where and how much to trim the bolt carrier rails... that always seems to be the question. DSA told me over the phone to trim the bottom of the rails, however in Mathews SGN build, using a DSA receiver, he trimmed the top of the rails.

I took a look at my parts to see how they matched up, and here's what I found:

Original receiver stub that I took the barrel out of, with bolt in place. There is barely a difference in height from the bottom of the bolt to the top of the rail slot in the receiver (pictures are upside down as the finished gun would be)


Compared to the same bolt in the DSA receiver, there is much more of a step between the two


and viewed from the rear; original receiver stub


and DSA receiver. I turned the bolt around because I was having a helluva time getting the camera to focus the other way.



So, it looks like trimming off the top of the rails will keep the bolt riding at the propper height and in line with the barrel. How much to trim though? I've heard .025 and .043 thrown around alot.

Original receiver railway height is


Original rail height of bolt carrier is


which leaves .0015 per side for clearance. The DSA rails are


so to keep the same .0015 per side, we minus .003, which gives .212 for final desired rail height. Continuing with the math I never thought I'd use after high school: .2305, being current carrier rail height, minus .0185, would yield .212. So, I guess .025 would give Plenty of clearance. I'll trim .018ish and see how it fits, and then go from there.

Here's the visual difference between .025 and .043



Another interresting thing I didn't realise until tonight. The firing pin has alot more free movement than I thought. This is it at full rearward travel


Hopefully tomorrow I can get to the shop and get alittle progress made.

Finally made it to the shop today. Last day of vacation (labor day doesn't count, so I got an extra monday off).

Before we start on the bolt carrier rails, lets make sure we do things in order just incase the ATF knocks down the door to try and catch me at the right time for them

We gotta get rid of the sear notch, and the hammer hump that hits the firing pin when the bolt locks.






now that we're safe, we can really get to work.

It took alittle while to figure out how to hold the carrier in the mill vice. Nothing some tetris with set-up blocks can't fix.




Took off alittle more than I planned, but it's hard to shave off a tiny bit, and the carrier fits just fine without toomuch slop.


I ended up having to shave off the top of the carrier in front of the bolt because it was hitting the receiver underneath the barrel.


While I was at it, I shaved the back of the carrier flush, to get alittle extra room for the striker.


Now it was time to mark it for the striker / firing pin extension.


All set to drill, if I could just figure out how I am going to support this thing... if I had a standing drill press with a hole in the table, it would be easier. Using a milling set-up in the lathe would probably also be more secure, but I didn't have either of those options. And there's no way I could hold the carrier in the mill vice with the piston haging off it... so I set out to remove the piston.
Experience with AK pistons paid off. Just gotta sand or file to find the hidden circle. The flat spot on the top of the piston made it easier.


I center drilled it about 1/8" down.


and then used one of my (old broken pin punches) starter punches to tap it out.


Look at all that cosmoline... and beefy threads too. Since I went trhough all this, maybe I'll make a stainless gas piston to help with 922r.


Well, now that it's shorter, I can atleast lower the mill table enough to be able to drill the other end. Still not psyched about lack of support... I just know something is going to go wrong.


lining it up, and center drilling




and of course, the pilot bit wanders off... I was informed this is one of those times when explatives are allowed


I whacked down the paper thin metal that lifted as the drill came to close to the top. Atleast it's still centered left and right.

I found a small file that just fit the hole... yep, deffinetly not straight.


After alot of filing, I was able to get the now egg-shaped hole lined up.


So, to fix the extra space issue, I took a brass punch, and spun it down on the lathe until it was just the right size for the hole. Then I used a dremmel cut-off wheel and let it remove any material that it could take out with the slightest pressure.


Time to weld that up. I put a little piece of copper around the roller to keep the splatter off it.


Here it is with some turds of metal patching the hole. I forgot my welding helmet, and had to do the "close your eyes and zap a spot" method.


It cleaned up well enough.


Alittle more filing to smooth the hole out so the drill rod slides easy, and then it's off the drill the retaining pin hole.


I had to replace the piece of drill rod with the brass punch because the drill kept walking it out of the hole. While pulling the drill back out, it bound up on chips and snapped. Atleast the hole was done and I could punch it out from one side.


That's all the pics I have for now. I was cutting it close, and barely had time to clean up before I left the shop for the day.

I was also able to get the gas system parts pressed off the barrel... I have never seen things pressed so tight on a barrel before that did not also have solder or a hidden pin/screw also holding it on. I will most likely have to polish those areas of the barrel just to get the back on.

Next step I believe is getting the barrel done and reinstalled so we can set headspace and trim bolt flaps.

Well?