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My 45-70 barrel arrived...

5K views 61 replies 10 participants last post by  muttman 
#1 ·
... and I'm not sure how I can make it work in this Yugo trunion.

Issue #1:

Notice that the chamber is threaded, and that it is thin enough that a normal-sized AK barrel pin would cut into the chamber.

I think the correct answer is to shim the pin hole in the trunion, and drill it for a thinner barrel pin like those found on a G3 or VZ-58. That would let me pin it, and keep the chamber intact.

Thoughts on a "skinny" barrel pin?

http://pookieweb.dyndns.org:61129/45-70/4570_win_barrel/win_barrel.htm

ETA - The barrel is cut so that the Winchester tube magazine lays against it... well when the barrel is rotated into the alignment where that is on the bottom, the threads reach up to about 1/3 of the barrel pin hole. It is too close to call - the chamber may not be cut into, but I can't be sure. If it is not cut into, I do know that the wall of the chamber will be *very* thin. Only the barrel pin will support the chamber in that case. Therefore, perhaps a not-so-skinny barrel pin would be better... ?


Issue #2:

Pressure will increase if the bullet is forced into the rifling - correct? Therefore, I wonder if the 500 grain loads, being longer, need to have the throat reamed?

I have yet to make a cast of the chamber, so this is speculative at this time.

Lyman measurements:

500 gr jacketed RN COL: 2.93" --- !!!
350 gr jacketed SP COL: 2.71"
400 gr jacketed FN COL: 2.55"

So that's .4" longer for the 500 grainers. These are intended for a Ruger Mk 1 or similar bolt-action style "heavy frame" rifle that is capable of the higher pressures the 500 grain loads produce - up to ~ 39,000 CUP according to the Lyman book. Even higher with the (hot) Hornady loads. Compare this to the average mid-30's CUP pressure of the lighter loads. (the Yugo / RPK / PSL trunion design is rated for up to 45-49,000 CUP found in the 7.62x54R).
 
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#57 ·
big gun as you can see from the photos I have repaired the slot cut in the stub. Im still working on the side plates as time permits.
the fsb sight will move all the way down there is no windage adjustment like on a euro rpk but I have eyed the same setup on a chicom rpk.

muttman
 

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#59 ·
chuck the reciver in the padded vice and use a pipe wrench in the stub. I used a 8" to un screw. just the oposet of a FAL. lock up starts at 10:00 to 10:30. if yours is like mine then the slot was cut after the barrel was instaled witch is good.
BTW, on the reciver stub did they leave the full and auto ( D&E) marks on the left side?
 
#60 ·
Mines got after the barrel was installed. both have the selector marks and one has half the detent groves. both have the ejector intact.

not sure what you mean about lock up ocuring? and the Fal referance (Ive never played with one)

If they werent cut/sloted they would be ideal for a big bore build. a 50 beowulf or 45-70 comes to mind.
 
#61 ·
The one I did for a Galil was loctited in place. Took a long cheater bar, some sheet metal to protect the trunion from scratches and to make the wrench fit without galling the trunion.

Like this:



 
#62 ·
hc,
I used some alum. jaw guars to hold the reciver. the alum. left some strecks but a trip to the caustic tank will remove the stains. ther was no locktight on the threads just macinal (sp) lock from the barrel ring.

big gun,
pic 1 is of a FAL the barrel has a ring the butts up to the reciver and locks it in to place after 110+ lbsft is used. on a kit build the reciver stub is removed from the barrel with slot is cut to open up the reciver threds and a cold chisel is used to open up the slot, breaking whats left of the threds then the reciver can be removed from the barrel with out damage. pic2 is of the ring on the barrel. Im planning on boring out the stub to 22mm and cutting the barrel down to 22+mm for a press fit then set head spacing and tack weld stub to barrel then cross pin the three (stub, barrel, reciver). at 22mm this will give me a .15x" wall on the stub and still keep the barrel DIA. in the safe range.
you should get a fal they are realy easy to convert to .243 or somthing based on the .308 case. muttman
 

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