New m53 build

[roadrunner]

Spent the morning setting up and joining my receiver . Ended up using uni strut jig for tacking while rotate jig was mounted for stringlines. After tacking removed assembly from uni strut and welded between centers. Really nice to be able to rotate and weld oppsing sides to counteract pull. Didnt see any significant warpage. Copper backer jig kept the inner walls flush. Mounted the recup. and slid a rail in to check for clearance. Fit is good but have to finish up D-holes to nest rail. Top cover closes nicely after a little relief on side bumps. Next is the biggy. Install barrel and see where rails line up. Overall a productive day. later guys

[42rocker]

roadrunner
Really like the posts and the pics. Good new ideas in use. Looking forward to the range pics. I think that you will be happy. Nice job.

Later 42rocker

[roadrunner]

Been a month since I got a chance to work on my project. Finished the d-holes and fitted rails. Trimmed the tips a bit on cam end. "new mg3 rails" Line up great and centered on cam piece. Going to rivet rails but decided to weld buffer tabs. Made an alignment/heatsink jig for tabs. And same for faux rivet heads. Liked oakrodents idea but dont have a magna spot. Will be plug welding tabs and rivet heads. Also 4 outer spot welds as on original will be plug welds. Still lots to do. 15 deg. bevel on slot next. etc. Good to be back at it. RR

[42rocker]

Glad to see some more posts. Looks like nice slow and stead progress. Looking forward to seeing you finish this.

Love to see a few pics of the jigs that you used by themselves. And your thoughts on using them again or what would you do to improve / change or whatever.

Thanks Again for sharing.

Later 42rocker

[roadrunner]

Sure, I'll do that when I'm done. Being a toolmaker by trade I probably make more jigs than really neccessary but It gives me peace of mind knowing that things are located properly and cant move or slip . Plus they will speed my next builds. I have two more kits to do. Plan on mg3 clone, mg1 and an 8mm old school style. Been working on a plan for a 2 piece milled billet mid section utilizing these new mg3 rear sections. later RR

[roadrunner]

Made some rivet bucking tools today and tried on a few rivets. First one I got a little too hot and the head pitted a bit but second worked out better. only have one more spare. Used 5/8 ss hex stock and 7/16" bolts with 5/8" heads which fit perfectly in the rails. Ground radius into air chisel tip with a dremel stone while spinning in the lathe. matched to factory rivet head. Not using air hammer but bit was handy and hard. Hopefully have the rails mounted this weekend.
RR

[gunnut]

Damn! can't hardly wait for your next installment. You'v got some ingenious methods in use here, which I'm gonna try and copy on my M53 build.

[roadrunner]

Last week I mounted my buffer tabs. Jig worked perfect. Left tabs and jig .003" long in the front and after shrinkage only a kiss with a dremel cutoff wheel was needed for a nice tight fit. Big rail mounting plans for the weekend were taken up by family events but did manage to plug weld faux buffer tab rivets. After welding I removed copper jig and ran tig torch in a circular motion over tops, rounding them. Will do some more clean up for appearance. Then beadblast. Contemplating a matte black teflon coating process when finished. Theres an outfit less than 100 miles away that does it. Might be just the ticket for an Alaskan outdoor mg3 clone. RR

[jamesob]

did you have to modify the bushing to get the right bushing depth or did you just put the bushing in until the angled parts mated up? this is were im at right now but my measurements are a little off if i just put it in until the bushing angles mates up.

[crash520]

RR,
with your elevated attention to detail, id be very interested in what your thoughts for tooling would be on a MG34 reweld! have you thought of doing one?

VR
C

[roadrunner]

Jamesob, I think your referring to the barrel bushing right? What I did was make some v-block pads for my c-clamp. If you look at my assembly pic. ready to weld you can see them. Figured the width needed and added .015" As you tighten c-clamp split bushing is forced forward and bushing is tight on front and rear angled surfaces. Also must note, v-blocks are aluminum allowing a bit of moosh factor after forward travel is reached to squeeze center tight. Measured barrel bearing projection and retraction and was good. Just laying bushing in shroud will not draw it forward firmly enough in my opinion. Crash, How are ya? Sure I think about it but man those parts are costly. RR

[42rocker]

Nice work. Pointed this tread out to several folks that are starting on theirs in a few months. You have taken several good ideas from this site and done a great job on reworking them and showing how to make things easier and dare I say better.
Stay warm up there.

Later 42rocker

[roadrunner]

Thanks Rocker, Hope to finish this project soon. Been playing mr. mom alot lately. "it a good thing" but have more access to the pc. than the shop. More than happy to answer any questions I can about the project in hand.
Later guys, RR.

[roadrunner]

Another month gone by. Managed to mount my rails today. Must have installed with screws and removed a couple dozen times along with recup. Before I was happy with alignment. Then drillet to full size. Recup. removes/installs easy now. Had to make it a bit looser fit in the semi blocker. Was zero clearance tight. Ended up using tig torch to heat rivets at low amperage. Then form while tungsten burns into leg. . Set up a torch holder after that. Still it would be better with two people as rivets cool fast.
Fitted fcg to receiver. Had to mill about .020" from rec. bottom to mount. Made for a flatter surface too. Ready to assemble it to grip now. Welded up bolt extension and it centers within rails onto buffer very nicely. Also bolts slides down rails and into barrel effortlessly. It should I spent enough time centering each end.
Question, I read that mg3 top cover spring should be removed for semi build. I want to use starter tabs with cover closed. Cant you just hold back c/h, pull tab to second click and let go? Really want to add a bolt hold open that is independant of c/h. Dont like it slamming forward with bolt too much.
Next up mount ratchet plate and finish fcg. Didn't expect to spend over six month on this build. Really about a 40 hour project. RR

[42rocker]

Super Nice work again.

**** In review I noticed the diagrams at the start of this thread -- Note the rivet holes change position from mg42 to mg42 -- therefore you might be 1/32 to 1/8 inch off using rivet holes to measure from. Watch out for that.
That pad area was the area that the builder used to drill and install the rivets, I don't believe that they used a set jig. If you compare one set of holes in a set of rails to another set you might notice what I'm talking about.

If you can redo everything in 40 hours I think that a few companies might want to hire you.

Later 42rocker

[roadrunner]

O.K. maybe that is a bit optimistic. Tomorrow I am dedicating to my project. Got the o.k. if you know what I mean. But for now "Go Packers" RR

[42rocker]

Good Luck

Later 42rocker

[marknct]

RR
Did you take a measurement between the existing rail rivet dimples on the front stub? My samples between the dimples run 1.900 to 1.908. The rail/ bolt assy runs 1.900/1.902 which means no clearance. I haven't seen anybody talk about bumping the dimples back out. The BRP sections should show 2.00 between them giving .05"/side which would leave room to shim. These stubs never measured 2.20 from what I see. The norm is -.05" with one showing -.03".
Anybody have thoughts on this?
Did you find a target clearance for the bolt to rail?

[42rocker]

Just noticed that Brian - brpguns.com just posted some new measurements and stuff in his dimensions pdf, we might all want to go and double check his latest stuff. I know that there is some new stuff in there that when I have time I'm going to be looking at a lot. Like trunnion / camming area measurements.

http://www.brpguns.com/content/42saprints.pdf

Good Luck with your builds.

Later 42rocker

[roadrunner]

That is what I discovered also. I used new mg3 rails and when installed it was zero clearance between pads. Had clearance with old yugo rails slid in. Anyway, I milled appx. 5/8 section on bottom of rails above pads about .020" deep so mg3 rails sat flush with inner frame. Have .036"-.045" front to rear bolt clearance. Sorry I didnt document this better. RR