Barrel-to-Locking Piece Torque?

[CRUSADER]

Ok,
In my hunt for spare barrels, I decided to buy a few "Locking Pieces" without barrels from a seller on Gunbroker. Then I bought barrels without locking pieces from AJAX. I'm wondering what the best way is to screw them all together? How much torque? I'm thinking ... clean 'em up real good, heat 'em up some, screw 'em together with the aid of a strap wrench and bench vise, then peen the barrel into place and let 'em cool off, no? Sounds waaaayyy toooo easy, right? Or is it really that easy?

[bolex]

I have not done this but would assume that you would have to set the head space.

[CRUSADER]

Headspace!? - D'oh! That makes perfect sense. So...

1) Start to thread Locking Piece & Barrel together.
2) Insert "GO" Gauge into Barrel Breech.
3) When close, insert Bolt Head into Locking Piece, making sure that the Rollers are fully locked.
4) Crank the Barrel down tight ... real tight!
5) Peen the Barrel in place against the Locking Piece.

Does that make sense? Clearly, I am no Gunsmith/Waffenmeister. I'm just going by what "makes sense" to me as I look at all these parts, hahahaha!!

[mattcdavis]

Headspace is checked after the barrel is tight in the locking piece! Install barrel and torque to just guessing but a little over 100-125 foot pounds would be sufficient/hand tight then another 1/8-1/4 turn. Then install your headspace gauge's go and no go. Then if its not on the money remove the barrel and add shims or lathe down the barrel shoulder.(don't remove more than say .0005 at a time then retry! Yes it can be quite time consuming. Some rifles are more flexable than others. I have shot fal's that I have loose headspaced at around .005-.010 loose(slop/play) I thought it was too tight and filed a junk locking shoulder to try to fix cycle problems. (Was too small a barrel hole/gas port,drilled to .125 worked fine.) At that play it would really stretch the millitary(hard) brass but when I tryed federal commecial brass(soft) It would have case head seperations! I already have my apex bbl and my locking peice should be here any day! $80 barrels assembled is so COOL!

[mattcdavis]

In previous post said 100 -125 foot pounds and should have said OR hand tight and add 1/8 to 1/4 turn. similar to fal.

[mattcdavis]

Just got my locking piece and barrel stub apart today! had to use 15" cheater pipe on 6" pipe wrench with the locking piece in the vise. Easily 150 plus foot pounds to remove!

[CRUSADER]

eehhhh .... big "FAIL" for me so far, hahaha! The parts I got all have very short barrel remnants - only 3/4" or so. I ground two flats on the barrel remnant so I could lock that side into the bench vise. Before giving it the first try, I heated the barrel stub up. Not red hot, just pretty damn hot (all the oils boiled out and out and out!). Then I locked it down and put a steel prybar (only ~16") through the holes in the locking piece...and pulled for my life...near busted the vice clear off the bench, hehehe. No dice budging the barrel stub, though.

Soooo ... I re-mounted the vice and tried again ... no joy.

For strike three I tried a 3/4" x 5' iron cheater bar ... it folded like a cheap camera I swear I could hear the locking piece laughing at me!

I suppose I need a steel cheater bar or pipe, not iron re-bar



Screwing these back together is gonna be ... interesting

I need a barrel clamp - something that will not mess up the finish. I have a set designed for use with the AR15/M16, but the diameter of a MG42 barrel is way too big to fit it ... gotta figure out something else.....

I'm open to ideas

[gordie k]

Hi, well what you need yo do when its not moving is heat a small spot about the size of your little finger a dull red then quench in cold water use a 5gal. bucket some times you have to do it twice. Headspace on a 42 is totaly differnt.
remove extracor insert a 8mm or 308 live in bbl insert bolt set locking rollers you should now have between .005-.010 cl. between bolt face and bbl. if its zero mechine bbl,if more mechine bbl. collar. headspace must always be plus
gordie

[CRUSADER]

Thanks for the tip gordie k. I didn't heat the parts until they were red, and I didn't quench them in water. I just heated them again until they were damn hot (10 minutes from a crummy propane torch). Then I chucked 'em up in the vice and cranked on 'em with a steel 4' cheater pipe and a prybar. Both came right apart this time, no problemo.

I did notice that the barrel is not cranked in very much past "finger tight" ... only a few degrees. I took some photos. Both remnants in the photos are finger tight. It is easy to see the peening groove in the locking piece. If you look at the barrel remnants you can see where they were peened. I highlighted the peens with a black marker for clarity.

[falcom]

Since you have the stubs off .
What are the dimensions of the barrel threads?

Thanks in advance
Dave

[CRUSADER]

Since you have the stubs off .
What are the dimensions of the barrel threads?

Thanks in advance
Dave

You mean the thread pitch? If not, can you be more specific?

I have a pitch gauge at work - I'll check it out & get back to you.

Are you thinking about making new barrels? *cough*chromelined762*cough...hehehe

[CRUSADER]

OK - well, my thread gauge didn't match up with the threads on the barrel stubs at all ... hehehe ... could it be because I don't have a metric gauge?

Sorry dude!

[falcom]

I mean the thread pitch, the diameter at the threads and the length of the threads.
Thanks,
Dave

[redrivertactical]

omg....hella work....i just got my kit cleaned up and the slag removed....i shouldnt have to mess with the barrel lockin mech stuff but i feel for you bro. Just a thought, but you can contact your nearest plastics plant and try to lay hands on a solid scrap piece of the nylon plastic......maybe 6x6". Cut that in half cut, mold and shape the inside of the two pieces to your liking. This stuff is great because its soft enough that you can make a mold and its strong enough that it wont warp or damage the finish on metal parts if you put it in a vise. I used it when i worked at sundowner trailers to make ferrule molds for welding aluminum gate hinges on the trailers. It also has a good heat tolerance so it can actually hold your parts while you weld. Works great because you can easily lay hands on another piece and start over at square 1. I will definitely use that particular piece of material if it applies on my 42 build. Hope i helped you bro.