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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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#2 ·
Interesting. sort of takes the fun out of it.
really all you can do is thin the pin in the center and hope for the best. maybe it would be better to make the pin larger than 7mm that way there would be more area/strength in the part of the pin that dont need to be thinned and also give more ingagment. I am wondering how that guy with that big .50 did his????
This is a build were a threaded insted of pinned trunoin would be nice.
I am relly suprised at how thin the barrel in the first place.
 
#3 ·
Other than to say it will do it I would be shying away from the 500Gr rounds. I really see no enjoyment in shooting that heavy of a bullet, do you plan on a muzzel break for it?? I wonder how this thing would be surpressed?? I have been pondering that possability with the 444???
 
#4 ·
What kind of 50 was it though? Was it a 50 AE, a 50 Beowulf, or 50 BMG? Because trust me, if he used a 50 bmg then he used a different trunnion. The round is almost larger then the trunnion's hole! 45-70 would be cool. But that is still going to be some ample pressure. Sure the chamber is going to be thick enough?

Post pics?
 
#5 ·
Would a sleeve threaded or sliver-soldered onto the barrel give you the meat necessary to install the barrel into a standard trunnion/standard barrel pin?
 
#6 ·
Biggun, I want to have the 500 grain rounds available to me. They are obviously overkill for anything that won't eat you, but I don't want to discount the use of this build for a home defense situation or in same applications that a .50 Beowulf would be considered... I fancy that the 500 grainers could be used in those "stop that vehicle" scenarios. Therefore, I would rather keep the 500 grain rounds on the table.


After looking at it more closely, I really do think I am OK with a thinner barrel pin. I'll have to insert a sleeve for the pin hole then drill it out closer to the top to ensure the chamber isn't affected. To keep it strong, I'll start with a bolt turned down to a barrel pin size and press it in, then drill it out at the top (not directly in the center). Since this will block the barrel, I'll obviously have cut the radius for the barrel to be inserted. That will give me a standard barrel pin arrangement with a smaller pin, and will avoid having to weld on the trunion. Then its a matter of finding some drill rod or other good steel for the new barrel pin.



Here's the way the threaded barrel is intended for the Winchester receiver:



If I think this through, the sleeve required for the trunion journal is going to actually have more material than the combined barrel and frame.

However it does not answer the question as to whether the barrel, by itself, can handle the additional loads. Typically, the 45-70 loads are limited due to the strength of the rifle.

So the question I really have is, if I were to use this in the heavier AK action, will the barrel be OK for use with the heaviest loads. I would think the answer is "yes" because "heavy" loads in this case are still in the range of the rest of the parts. I just can't see a MODERN 45-70 barrel being built in such a way that would cause it to open up like a banana if some bubba loaded a hot round for a "hey guys watch this" moment. However sustained fire may be different.

Honestly, the 350 grain rounds produce more chamber pressure than the 500 grainers. That is according to all sources, not just Lyman. Unfortunately the Hodgdon data doesn't list anything over 400 grains.

Now here's a question - given the same bolt size, how much difference will there be in bolt thrust for the larger, slower moving rounds? I seem to remember from the Chamber Pressure discussion that it makes a difference.


Numrich is out of Ruger Mk1 barrels :( I may phone them to see if and when they will get more in stock.
 
#7 ·
HC I think the formula for the bolt thrust for Bolt face ID id in the original 308 AK build thread It was the first or second thread in this calibur conversion section. If I recall there is a considerable increase in bolt thrust. remember You use the ID of the case for that calculation. (Ill see If I can find it maybe it can be a sticky or added to the specifications thread)

I was thinking that you reduce the ID on only one side of the trunion pin hole that way a steped pin could be used and be of full DIA on at least one side of the barrel an trunion. plug the hole and redrill it off center in the top half on one side only. (I wish I could draw a picture on the computer Of what IM thinking for You.)

The other thing that concerns me is how thin the breach is. I have concerns that accuracy may really suffer once the barrel quickly heats up and and any any warpage at the thin breach is going to cause signifcant barrel whip and warp at the muzzel. This build would be great on a threaded trunion and a bareel threaded to fit it. (lot of work just thing out lout here.

I hear what your saying about the 500 grainers. What barrel twist do you have?? will it even stabelize that heavy of a bullet? A 500 grain suppressed AK would be really cool.
 
#8 ·
What kind of 50 was it though? Was it a 50 AE, a 50 Beowulf, or 50 BMG? Because trust me, if he used a 50 bmg then he used a different trunnion. The round is almost larger then the trunnion's hole! 45-70 would be cool. But that is still going to be some ample pressure. Sure the chamber is going to be thick enough
It was a 50-110 shown here (link not working for some reason) Looks like a 45-70 but even bigger. If the barrel pin is going through a 45-70 chamber how did this guy do it? diffferant trunion or perhaps threaded. Dragonov?? I forget.

http://www.gunco.net/forums/f244/50-110-romanian-fpk-36134/

I wonder how difficult it would be to thread a standard trunion????
 
#9 ·
here is the formula for bolt thrust from the 308AK thread

--------------------------------------------------------------------------------

possorry for the long t just trying to get it easy to read, got some of the info from The Gun Zone -- .30 Caliber Ammo trying to do everything on the safe side hence the max proof pressures for the 308 stuff and the bolt head diameter instead of the true case head diameter

i got some good solid works 3D models of a romy trunnion today trying to run the force application on it as we speak (test how the lugs will hold up under different pressures applied from the bolt thrust)

not having much luck the software im using doesnt allow for heat treated steel so even the opperating pressures of the 7.62 x 39 arent giving safe results in the solid model stuff

ill keep trying and let you know what happens


Bolt thrust= area x psi

Area = 3.146 x ( (case head diameter / 2)^2)

Above is from http://www.riflebarrels.com/articles...g_strength.htm


7.62 x 51 NATO

"Proof" pressure = 67,500 psi
Bolt head diameter = .475

3.146 x ((.475 / 2)^2) = .1772

67,500 x .1772 = +/- 12,000

7.62 x 51 NATO = +/- 12,000 lbs bolt thrust max

308 Winchester

"Proof" pressure = 83,000 psi
Bolt head diameter = .475

3.146 x ((.475 / 2)^2) = .1772

83,000 x .1772 = +/- 14,800

308 Winchester = +/- 14,800 lbs bolt thrust max

7.62 x 39

Max "reload" pressure = 45,000 psi
bolt head diameter = .458

3.146 x ((.458 / 2)^2) = .1647

45,000 x .1647 = +/- 7,420

7.62 x 39 = +/- 7,420 lbs bolt thrust

6.5 Grendel

Case head diameter = .445
 
#10 ·
Yeah that .50-110 is really interesting. I forgot I didn't post the scan of the article I had and just put it up there... It does make you wonder if he just but a brand-new barrel from a blank.

It also makes you wonder how Meeper's .50 Beowulf SAR conversion worked.

If I had an un-cut trunion I could relocate the hole higher. That may be what they did - TIG the hole closed and re-drill it. TIG probably would not impart that much heat. I'm not going to do that because the notion of using a thinner barrel pin should be sufficient. Plugging the original hole should not be a major issue... I don't see a problem with my plan, other than making sure I get the hole drilled properly! ;)


I'm honestly not too worried about the barrel whip because of the taper the barrel has. The .45-70 is intrinsically a short-to mid-range round anyway, and past 250 yards you need good sights to keep it effective. That keeps it at most any effective range for whatever I can imagine I'd need to shoot at those ranges. It is pretty fat on the breech end, even though it is notched for the feed tube on the bottom.

I'm going to use a "fish gill" style compensator - think Barrett .50 - that pulls the gun away from your shoulder to help minimize recoil.


I may give this barrel to my dad and buy a thick barrel blank from Midway. I hate to spend almost 2x the cost vs. this barrel however. The twist is the "standard" twist for a 45-70 - I think 1:20 - and I think he has a Winchester rifle he wants to rebarrel. I'm going to make a chamber casting tonight.
 
#11 ·
I'm going to use a "fish gill" style compensator - think Barrett .50 - that pulls the gun away from your shoulder to help minimize recoil.
I think that it will almost be a must if you want to shoot it very fast.

that .50-110 cant have much for a pin even if it were raised.
I am sitting here with a 458 win mag barrel and my trusty Yugo trunion paper weight. It has a slightly larger chamber than the 45-70 I can assure you the pin will not enter the chamber if left as is. how thin can one go in that area I dont know. But think about this, on a chineese barrel with a 19mm trunion the pin groove gets pretty close to the chamber as well! this handel about the same pressures as you 45-70. You may be able to use it as is.
 
#12 ·
Check this out - I think I'll be OK.

This article discusses some Marlin lever action conversions. The author was actually able to stuff a .50 AE round into a Marlin - WOW!

What is Possible with the Marlin?

The big issue seems to be the behavior of a thin-walled chamber that causes bulging - due to the fact that the threads are inherently weaker than other designs. That will be eliminated because I'll lathe off the threads to prepare for a sleeve of 4130 steel. For a 1" AK trunion, that will mean I'll have about .4" around the radius of the chamber.

That thick a collar of steel in itself should have enough mass to eliminate bulged/burst chambers. It would certainly take 50,000 CUP and since it appears the barrel itself is made of a high-tensile steel, I should be OK even with those 500 grain slugs.

The only question that remains is whether or not I need to obtain a throating reamer to open it up for those larger slugs.
 
#13 ·
personally I wouldn't trust that bbl with anything hotter than a smokeless equilivanet of the standart load. lever action receivers are weak, and I don't think they would put a bbl meant for hot loads on a gun like that.
you really should make a threaded bushing for the breech, turning off the threads to press on a bushing will make the rear thinner. If you really want to test the limits of the round you should get a bbl blank. the 45 70 loaded for a strong rifle is a really potent round.
 
#14 ·
I'm thinking you're right. Everything I've read suggests 40,000 CUP is the confirmed limit for the Marlin 1895 rifle. I found this cartridge listing:

Garrett Cartridges Online - Products


... from the Leverguns forum discussion here (even Noah contributed!):

Paco Kelly's Leverguns.com :: View topic - NEED A STOUT 45-70 LOAD


The 50,000 CUP pressure limit is mentioned exactly one time, that of the previous post I listed with the Marlin wildcat conversions (forget the Smith's name).


I do honestly think the barrel would work, I really do. I would be willing to build it up just to test it out with a stump and string. However I would be faced with other challenges - the barrel sleeve, sleeving the tapered barrel for the barrel components, figuring out the best attachment for a brake on that thin muzzle, etc. etc. that are pushing me toward the "simple" route of getting a barrel blank and reaming to fit. And I'd have that question mark in the back of my head about reliability.
 
#15 ·
Yikes some of that 45-70 ammo is $185 a box!!!!! (how many boxes you getting LOL) I was looking at that 44 mag+P stuff with 45.00CUP. Its about what I want to load the 44??? to. Maybe I should be working on a a 44 mag instead.

IMOA you would be better getting a Chamberd blank in your choice of twist from some one an go with a heavyier barrel. Im not sur what you intended usage for this build (short barreld close quarters use or open range shooter or in between) but weight is going to be your friend here I shot my 45-70 this weekend and my shoulder is brused and sore..
I think you will also get better accuracy as well by having more material at the breach. as any warpage at that end is is going to be greatly magnifed at the other. bushings and all that cant help, not to mension the tension caused buy them. This is going to be a awsome build going with a optimum barrel is going to be safer, more accurate, and likely look better in the end.
Have you figured out the bolt thrust yet???
 
#17 ·
Yes I have and the pressures sound about right.

It is interesting to note that the Lyman manual has a 500 gr. load that doesn't even reach 40,000 CUP. I could probably work up to THAT load in the Marlin barrel and be safe. However I would like to have as much margin for safety as possible, and have the flexibility of those "hot" Hornady loads availble just in case I go on a dinosuar hunt.


One thing that will push 500 grain loads off of the list is how well it handles for recoil. If it does recoil heavily, even with the semi action, then it would be unusable for a home defense/tactical entry/SWAT/whatever kind of situation. It would even be unusable for dangerous game hunts, because if recoil pushes you so far away from your sight window that you are "searching" for that 2nd shot, then the critter is probably already on top of you.


At this point, I'm just going to call Green Mountain and profile their barrel. I think my lathe can handle it, but I need to get it in my hands before I can be certain. I don't want to turn if off-centered. If it doesn't then I'll need to find someone with a big enough lathe to handle the contouring for me.
 
#18 ·
Pookie, Would it be possible to make a collar that is pressed in? Then screw in the barrel from the front. Headspace would be adjustible using an external nut like the Savage bolt action rifles? And you've still got some extra protection around the chamber. Just a thought. I really like your work. Good luck, Greg
 
#19 ·
Sleeving the barrel at the trunion journal was my original plan, however it won't help this particular situation because I can't verify the chamber pressure can handle 50,000 CUP. It may be OK, however I am hesitant to proceed based on one gunsmith's research.

I doubt Marlin would answer me directly (I haven't asked them yet) about exceeding the Marlin rifle's chamber pressure since it would open them up to legal implications, so they will probably be no help at all. Better to err on the side of caution. If I had the time (and the motivation!) to build up a 2nd gun for testing, I'd do it just to see how it would act. That would prove it once and for all, but I don't want to risk destroying a gun - even for a test project - at this time. Maybe later! :)
 
#20 ·
barrel pin

instead of shimming it, or using a smaller pin, could you maybe drill for the pin a little higher up, using a virgin trunion.

I have read about 9mm conversions with small diamerter pins that broke.

recall the pin (and friction) is what holds in the pressure, just like the lugs on the back side.

the pin receives a beating every cycle.
 
#21 ·
I'd be curious to see a 9mm conversion with a broken barrel pin! Sounds interesting, because I can't figure out why a pin would break. I agree a higher-up pin would be the best solution, and it would be more like a pin setup in a G3 or VZ-58 that way. A smaller pin would then be usable.

I have ordered a Shilen barrel blank and will use that instead of the Marlin barrel on my first build. It is HEAVY too. I'll soon be shipping it off to the smith with a big lathe :)
 
#28 ·
I'd be curious to see a 9mm conversion with a broken barrel pin! Sounds interesting, because I can't figure out why a pin would break. I agree a higher-up pin would be the best solution, and it would be more like a pin setup in a G3 or VZ-58 that way. A smaller pin would then be usable.

I have ordered a Shilen barrel blank and will use that instead of the Marlin barrel on my first build. It is HEAVY too. I'll soon be shipping it off to the smith with a big lathe :)
I saw it in an advertisement. Some dude was sellign his FAIL build.

The picture looked like he used about a 3/16 pin. (or possibly smaller)

Stick with "bigger than a 1/4" and you should be fine.

The barrel pin takes the pressure from the firing also, just like the lugs, except not as much, due to the friction between the barrel and trunion.
Still, over time it takes a beating both ways. (the bolt slaming home also)

Bigger is better, as long as you don't cut into the chamber. :hatprop:

The barrel pin, if set in there tight will help support the chamber.

Sounds like you need to use a virgin trunion and drill as high as possible. Try to not go smaller though, if at all possible.
 
#22 ·
I wondered if the bolt wasnt slaming into the barrel or something when I read this. barrel pin will hold up to 308 loads in a Siaga and i assume the 30-06 is pined as well.

if it holds up tp those rounds it will hold up to any 9mm build unless something is built wrong or the pin is not the same as an original.

I have ordered a Shilen barrel blank and will use that instead of the Marlin barrel on my first build. It is HEAVY too. I'll soon be shipping it off to the smith with a big lathe
SWEET!!! this will make a good shooter. how long are you going with???

BTW have you seen the latest SGN there is a article on using 45-70 roe a bunch of differant rounds very interesing the 45-60 would be a good one IMOA
 
#23 ·
I wondered if the bolt wasnt slaming into the barrel or something when I read this. barrel pin will hold up to 308 loads in a Siaga and i assume the 30-06 is pined as well.

if it holds up tp those rounds it will hold up to any 9mm build unless something is built wrong or the pin is not the same as an original.





BTW have you seen the latest SGN there is a article on using 45-70 roe a bunch of differant rounds very interesing the 45-60 would be a good one IMOA
on the 9mm build, one cause was the barrel was too small (no press fit) or the wroung type of steel used for the pin i.e. dawl pin. that type of pin will not take a side load if there is some slop with the barrel to trunion fit.

the SGN artical is a bummer for me. I had high hopes for a 9x54r bolt gun but now I see their is a round that is close to mt idea, 9.5x54r I think.:pissed:

muttman
 
#24 ·
Oh, so poorly built... no wonder! Good building makes all the world of difference.

I think you mean 9.3x62?... that's apparently a big round in Europe. There is another Russian/Euro round, the 9.3x74 I think. Definitely a big game gun! US_Dragunov has been eyeing a Russian TIGR in that round. Wouldn't that be cool? :)
 
#30 ·
Oh, so poorly built... no wonder! Good building makes all the world of difference.

I think you mean 9.3x62?... that's apparently a big round in Europe. There is another Russian/Euro round, the 9.3x74 I think. Definitely a big game gun! US_Dragunov has been eyeing a Russian TIGR in that round. Wouldn't that be cool? :)
Yeah...the Europeans have a couple of cool cartridges that really haven't made it big over here yet. The Russian TIGR/SVDK clone that I am doing is 9.3x64. I have the mags and a bunch of the parts but still need to collect a few more before I really get started on it. Oh yeah...and I am getting one of the actual military scopes designed for the SVDK.:)

The Finns used to have a law that citizens could not hunt using military cartridge dimensions. So, the Finns (having a large number of Mosin Nagant parts, actions, etc) rebarreled the Mosins into 7.5x54r, 8x54r, 9x54r, or some odd variation of caliber, but all based on the 54r base case.
The main round that I think you are talking about is the 9x53R (same as 54R....just in Finn speak....lolol). This is the same cartridge that the Russian Saiga-9 is chambered in. If Izhmash decides to start making these again you will see some come our way most likely.

 
#25 ·
HC have you considerd leaving the muzzel end A larger OD than the rest of the barrel and going with a integral brake/magna port?? the gas block and FSB could be pressed on from the rear if planed out in advance. It would look pretty cool and save some weight on a already nose heavy gun.

On my next varmit build and the last, the barrel steps up after the trunion area so intalling parts from the rear is no proplem.
 
#26 ·
The Finns used to have a law that citizens could not hunt using military cartridge dimensions. So, the Finns (having a large number of Mosin Nagant parts, actions, etc) rebarreled the Mosins into 7.5x54r, 8x54r, 9x54r, or some odd variation of caliber, but all based on the 54r base case.
 
#27 ·
I'm not really interested in a magna-port type of deal. I realize it will be front-heavy, but then again I'm going to have a mag full of heavy ammo that will offset the weight :)
 
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