... 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.
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).
I wonder if there are any threaded barrel milled reciver stubs around that could be made to work in a stamped reciver. I have also been wodering if it would be possable to thread a pined barrel Yugo trunion. the thread size of a model 70 winchester would be close. Is a trunion to hard to thread with a TAP? I havent tried it yet. there is plenty af material to work with on a yugo trunion its not hollow like other trunions.
Here is a 458 WIN mag barrel stuck into a Yugo trunion. Yea Im watching this whole 45-70 thing close wish I had a carrier and bolt. I have a line on a *45-60* reamer and dies it will do pretty much every thing a 45-70 will do with modern powder and will fit a AK reciver mag well better IMOA
big gun,
I have a milled ($37 to the door) front section that Im making side plates for. the problem you will face is the 25x1.5mm (could be a 26mm, barrel stub is at work) thread of the trunion. there are sevral things that can be made to fit but it will need to be on the barrel side. ther is some meat on the sides of the trunion to bore out to 1.00" then use a bushing on the barrel or as Im thinking bore out the stub to 22mm and reuse the stub after welding it on the barrel. my plan is more work but will look like and use the threaded to keep the barrel in place. muttman
Hmm Im been thinking there might be some accuracy gains with a losely threaded barrel and a thread locking substance like locktight like some of the bench rest guys do to reduce tension on the barrel. or possably a barrel nut like the savage uses.
Some how forcing a barrel into a trunion then running a pin in buy force across the top half of the barrel seems to contridict everything spoken about building a accurate rifle regarding barrel tension and harmonics. although my varmit build does shoot damm good.
also have some ideas for a takedown gun. were did you find the stub for sale???
my main reason for the original post was to eleminate the barrel pin so close to the chamber on the 45-70 that HC Pookie is doing. turning a blank and threading it to fit should be doable. Plus a 26mm would allow a bigger barrel stub over a 23mm
keep in mind there is a 6mm slot cut thrue the top the trunion. I just put a spacer (.005" to keep the chunck of 4130 off the threads) in the slot and tig welded a pice of 4130 in then removed the spacer and the barrel stub. just leave me one so I can get my RPK made. muttman
HMMM very interesting bore out the threads and add a raised pin hole and you got a 35 or 36mm trunion possably. bore out the barrel and add a lowered pin hole and you could get down to a petty small barrel shank for a blowback project or any other cheap small ID take off barrel. numrich had 44 mag barrels 11" long awhile back for like $15 I got one but wasent sure what to do with it.
not completly sure what the slot is about?? it it length wise or across/side to side?? Argh always something!!!!
44 mag barrel
I need a couple of these to hold and fondel. maybe a .50-70 is in the works cant let HCPookie have all the fun LOL.
MUTTMAN was yours cut behind the lighting grove like the one pictured???
also these might be good for a blow back pistol or a 22 project
hc and big gun,
the slot is cut frount to back 6mm wide the reciver cut is just behind the rails and still has the D and E lettering on the right side lighting cuts are a good distance from the demill, the railes are in tact but short ( shorter than what is used on a stamped reciver) the barrel stub has a new crome lined chamber (7.62) with a 6mm slot cut in it that would work great for a blow back ak (good call big gun) if bored out. Im using the one I got for a miled ak that I would like to have.
I got 2 of them reciver stubs and cut barrel with sight block coming. I called the order in. they said they have hundreds left. if nothing else I will have two sight blocks to cut up and make varmit scope mounts out of. that way I will have a complete barrel assembly - trunion off my rommy kit when I do a varmit build I wont need to pull off all the part to get at it. he mentiond there was some STAMPED trunions with THTEADED BARREL STUBS FOR AROUND $90 hmmmm. Ill post pics when I get them of the cuts and all that. I got a couple ideas depending on exactly were the cut is on a way around it.
big gun
after reading the post on the 6.5mpc this might work with a swapable barrels 5.56/6.5 hmmmm . but this would be a latter mod for me. I should soon be able to order one more for my rpk build now that my barrel just came in. good luck on removing the pin on the sight block. still have not got it to move yet, an endmill is starting to look doable . if you do let me know what you did to remove the pin. muttman
I wont need the part around the barrel so I will just cut through the bottom of it and remove it. Im more worried about how this cut affects the strength of the trunion. I am going to do a blow back oistol at some point so I t should be usable for that at least. to be honest after looking at the 22 LR trunions I was thinking of just making a new blow back trunion from scratch.
id really like a unmolested screw in barrel trunion for a big bore project like the 45-70
big gun
tig it. there is plenty meat left in the trunion and that german steel is good. better than the bulgy stuff that we use at work. the only problem with the .22 trunion is I dont know what size and pitch the barrel shank is. over sizing the hole is not a problem but making something to fit is not that easy.
I will recomend making your blow back trunion. it will open up a lot of doors for the build, i.e. the trunion and fsb will be welded getting rid of alingment issues of the barrel to trunion and fsb that I may get from my used 9mm barrel. now I just need time to get back on it.
I will recomend making your blow back trunion. it will open up a lot of doors for the build, i.e. the trunion and fsb will be welded getting rid of alingment issues of the barrel to trunion and fsb that I may get from my used 9mm barrel. now I just need time to get back on it.
Yea a blow back trunion could be as simple as a block of steel with a hole to hold the barrel in place and a barrel pin and rivet or better yet really deep screw holes.
I was kind of thinking of a custom trunion that didnt need a gas tube that does nothin, a copy of the german .22 trunion shown above. like mentoined then the scope could be droped down some and the trunion could be drilled and tapped for a weaver rail directly to it. In my mind I am thinking some thing that can be made with out buying a $200 kit. I was thinking just a bent tapco flat (no kit needed) a original FCG (really cheap and every one has them laying around no kit needed) a take off barrel or cheap blank in 9m ,45, 7.62 or out of a sunomi kit(no kit needed and cheap) a standard avaliable pistol mag with(no kit needed) possably a custom rear trunion with a rod to hold the spring and help guide the bolt. (no kit needed)
basicaly a tapco reciver with only a few original parts like the dust cover and trigger group. the hard part is what to use for a bolt???/ If there was a easy way use the sunomi bolt faceand extracter added to a hnad made carrer then we could get doen to only a very few AK parts and most of them are avalible aftermarket. with the high cost of kits it seems like it would be econmical not to be welding bolts and carrers together. basicaly im thinking a .22 AK bplt but hevier. if you think about it the bolt could be a sguare block with bigger rail groves and the bigger rails could be used in the reciver as well. would not have the classic AK look but would just Share the reciver shell FG. the 922 parts count would likely be no issue any more as the trunion, possably the bolt an trunion, barrel, could be US made , the gas piston would be gone, could likely then use original
I will start a new thread so not to high jack this one further.
Derailing my own topic, but I agree about making your own blowback trunion. I looked real hard at the Bizon assembly (still on my todo list!) and frankly the trunion is as simple as it can be - a rectangle with two big holes and some holes for the rivets! A chunk of steel that is about 1.5" wide x 1" long x 2" tall should work for that.
That steel will be really hard on cutting tools. I shaved the sides of a receiver stub for a trunion for someone a while back, and I had to carefully grind and file the sides. I would not want to see what it does to drill bits! Once you get past the surface hardness you should be OK, but the amount you would need to remove would not be enough to get past that point I think. Can't remember now... just remember doing it
The trunion doesn't have to be too hard - remember the locking lugs are the important piece and they apparently rely on surface area more than anything else. Think of how many locking lugs you've seen that get peened by mis-aligned rails or something. Heck, my Chinese 7.62 has peened lugs! Remember Winn's toothpick test - the trunion really doesn't even bear much of the recoil load. My point being, you could weld that hole up no problem. I for one don't like the idea of threads because it is a PITA to thread a barrel. At least with my setup, it would be.
That .22 trunion could probably work for a 5.45 trunion if the 5.45 bolt locks up.
Blowback really doesn't use the locking lugs, if you'll recall the Uzi or the Bizon bolt assembly, technically there is no carrier because the bolt and carrier are actually one piece. Since the 9mm is comparatively light, a chunk of steel with a recess for the case rim cut into it would work. It would be really easy to build.
OK back on topic...
Need a reamer. I don't know where exactly to find them cheaper than $100. Since I'm most likely going to build two different 45-70 builds, I can justify it since the rental fee alone would be nearly that much for 2 barrels.
I think that the barrel hole for the 22 trunnion is higher than a standard trunnion. The 22 bolt just rode on the top rails and didn't have a set of lower rails (IIRC).
Need a reamer. I don't know where exactly to find them cheaper than $100. Since I'm most likely going to build two different 45-70 builds, I can justify it since the rental fee alone would be nearly that much for 2 barrels.
You would be better to buy it cut your two barrels and ten sell it for 75% of what you paid.
If and when you pull this build off if the carriers and bolts are still avaliable (are they) others will want to build one. you could likely rent it or ream a few barrels to off.
I was kind of thinking the same for the 444????build.
I got the milled trunion stubs with cut barrel and RSB with the trunion cut through. they are slightly pitted but both have the lightening grooves intact . there are groves on bolth sides not just one like the yugo. the rsb is pretty beefy looks like it could be bored out to at least .800 these would be good for a 308 take of barrel or heavier 7.62x39 target barrel or possably the 444??? HMMM
the trunions are both stamped LEHR right by the serial number what does that mean?????
as far as the groove cut through the barrel and trunion it is .229 right through the top of the trunion it is a milled slot and was done before the RSB was installed this was not part of the demill it was done prior to assembly. Man I wold love to get one that wasent cut. barrel was 6" long would have made a pistol.
im thinking for a blow back pistol the old barrel can be bored and the milled gap could filled with a spacer an possably be cross bolted instead of pinned. it could certainly be welded for a blow back. Im not to sure about using these welded up for a gas operated system the temper will certainly be affected. the stub is 1.342 wide it will mill down to stamped trunion size with out getting into the barrel bore. I cant tell what the actual thread size is.
big gun,
Im not sure what the LEHR is for eather but my guess is a code for drill/prade guns. yes the slot was cut then the fsb was instaled but the fsb pin is not that easy to remove I have bent and shot out sevral push pins from the press. call me a sissy but I now stand by the leg of the press.
the one I got had a flip up sight cover like on a rpk (for 300m ?) . Im using this one for a milled ak. after tiging in a scab on the 6mm slot the reciver is still hard and will work as a reciver. the hard part for me is figgering out the corect set up on the lathe to cut a 26x1.5mm theread for a sleave on the barrel. so far the best I can do is 1.6 pitch. I may change up and bore the barrel stub out and tig in a scab and slide it over the barrel and pin it in after headspacing.
when I bring the reciver home from work Ill post some photos of what I have completed so far. muttman
My sightgoes to 800 meters and looks like any other sight. except it it 8000 not 1000 lik the yugo. interesingly one has red numpers one has white an the numbers are slightly differnt sizes.
you might have to throw some heat on the area around the pin and then try to remove it. im goint to try to save them because there is enough materal to bore these out for a reminton take off barrel I think. or at least with out having to take the barrel down much. these will be perfect for my 308,243, and rechamberd 30-06 to 308-39 projects.
on my varmit build I just cut the ring off the doner barrel becuse I was planningto weld on a new sleave any way.
if you look in the fsb there is a slot cut in the bottom to take the "hook" from the lower side of the gas tube. the hook helps lock the tube in along with the lever/arm at the top of the fsb. if you cut the part off that the barrel goes thrue the slot will not be there. my problem is my rpl barrel is way bigger (1.00"+) at that point then the stanbard 23mm and I was thinking of cutting off the ring off of the fsb and welding a new bigger ring in and cutting a new slot for the gas tube but the over size barrel will put the tube highter than standard. muyyman
the flip up sight is just a pice of spring steel like banding and locks in the top of the sight. Ill get a good photo to document it. I like the 308 fsb idea I will be turning my rem. barrel this week.
Ill try some heat on the fsb and see what happens. I may make a large push pin with a 3mm tip to get it started. btw what do you use to cut a notch in the the frount for the gas tube hook on the bottom of the tube.
on my varmit build the gas tube is suspended by a little tab welded to the tube with a bolt running through it into the RSB. the screw is bottomed out in the threads so the tube can float. I think I just ground the bottom of the tube down untill is cleared the barrel. its been three years since I did it. I was working on it till 4 am about 4 days straight back then to have it done in time. Id pull it off and look but that would require pulling the scope and its dialed in and Im hoping to shoot some coyotes with it soon.
bottom line is on builds like this and builds like possably the 45-70 you will have to remove or modify what ever is in the way removed. I wonder if Hcpookies 45-70 barrel will be a small enough OD to allow the use of normall block???? the tromix 444 marlin used factory parts.
I just used a Dremel to cut the slot before welding it all up. I would clamp the cutoff RSB top to the new bottom and try to lock the gas tube. If it didn't, just unclamp and cut some more.
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