[loboslanding]

There has been concern expressed over the ability of John's barrels to properly chamber 8mm surplus Yugo. We all know that John's work is second to none and I was having difficulty understanding the problem.

I have two new barrels from John that I got about 6 months ago and several ammunitionstore barrels. In an effort to understand for myself what the issue is I pulled some Yugo and Turk 8mm ammo and checked the chambers in both of John's barrels VS an ammunitionstore barrel with about 2k rounds thru it. I firmly seated the rounds in each chamber and measured the cartridge protrusion out the rear of the chamber.

Here's the results:
Yugo
John - 0.130
Ammostore - 0.138

Turk
John - 0.124
Ammostore - 0.131

I pulled the ammo and rotated it and reinserted it to make sure of accuracy in my sampling and it was consistent.

Both of John's barrels measured exactly the same protrusion which is testimony to his accuracy.

According to these measurements, John's barrels have MORE chamber depth than the ammunitionstore barrel after 2k rounds...John's barrels should run the 8mm Yugo. I see no need to do anything to these two barrels. If my gun won't feed using his barrels then it will be my problem in how I'm headspacing it.

Anyone having his barrels is welcome to post their measurements to compare them to mine.

As for me, I'm going to comfortably shoot the snot out of them.

 

[mrbullseye]

to everyone

look at a 98k mauser. the lands are tapered which is why there is no
problem shooting any 8mm rifle surplus ammo in it. try shooting surplus
ammo in a sporter rifle with a non-military surplus barrel. not good at all.
at one time both winchester and remington sold their bolt action hunting
rifles chambered for this round and surplus ammo was very dangerous to
shoot in it. been there, done that. the problem with these barrells is the
throating especially in john m barrells. look at the weatherby bolt action
rifles. they have long throating. so does the browning M-2. look at the
gewehr 88. they modified the lands in some in order to shoot the higher
pressure and larger diameter bullet. why does the velocity drop in a weapon
when many rounds have been through it. it is because the throat is worn.
the pressure drops somewhat which causes the velocity to drop also. the
yugo ammo is not necessarily a higher pressure load than the romo or turk.
just because one brand has less felt recoil does not mean is develops less
pressure. does the 5.56 or 7.62 nato develop less pressure than the yugo ammo
because of lower felt recoil? i am always amazed when i see written
"use romo 8mm ammo, it has less pressure than turk or yugo". want to know
for sure. then contact h.p. white labotories as they have the means to do
the proper testing on ammo.

 

[cal50]

Headspace is set from the shoulder of the cartridge to the base of the cartridge as we all already know. The problem that seems to be re-written about sounds more like a shorter throat or lead in angle. Like a target .22 chamber that engraves the bullet on chambering some of the aftermarket 8mm barrels sound short in the throat area and the bullet makes contact.
This would cause a problem when chambering a round to fire. An opposite example would be most ruger rifles or weatherby's (spell?) that have longer throats that it is hard to seat bullets out far enough to touch the lands.
If you want to know if your bullet OAL is the problem try the same measurement routine with a live round then pull the bullet and measure it again. If the numbers are equal then all's well. If they are different your throat is short or the angle is too steep. If the chamber and throat are chrome lined I hope someone has a carbide reamer to use. Or you could buy a cheap set of Lee dies and seat the bullets deeper.

 

[mrbullseye]

ouch

seating the bullets deeper without reducing the powder
charge equals higher pressure in the same round. oal
is very important. also never remove a 198 grain bullet
and substiute a 200 grain commercial bullet. there goes
that pressure rise again.

 

[Dave B - Great Lakes Arms]

I know of three guns that have experienced a KABOOM with the Yugo and McGuire combination.....all within a thousand or so rounds of starting to use them. I also understand the physics involved with chamber and throat dimensions and that is why I purchased a throat reamer to elongate my AmmunitionStore barrels.
So we are clear, I am not slamming Johns barrel becasue they are indeed of high quality.....they just make for a bad situation when used with Yugo and I agree with John in that regard and have heeded his warning.

Lobo please be careful because what you are going to do is dangerous.

 

[loboslanding]

Just to clarify, headspacing on a 1919 has nothing to do with the shoulder...it is defined as the distance from the rear of the barrel to the face of the bolt. Read the GI manual on a Browning 1919...these are not bolt action rifles so the headspace relative to those does not apply here.

If the cartridge has the same protrusion at the rear on all the barrels then the round is fully supported and headspacing for a 1919 will be uniform.

If a chamber is too shallow then the cartridge will have too much protrusion and unsupprted case. I'm not finding that with John's barrels.

The problem is that many 1919 owners blow top covers with all the barrel mfgrs and usually for the same reason...headspacing or it's just plane old bad Yugo ammo...not the barrels fault. I think folks have blown covers with John's barrels and for some reason the barrel is getting blamed. I don't think so. It's either headspacing or bad ammo.

Again, the barrels I have do not have shallow chambers so there is no reason that they should not perform any differently than any other barrel.

So far I've not heard one reasonable explanation as to why someone thinks John's barrels are at fault. It was alleged that it was due to shallow chambers and the rounds were protruding too far out the rear of the barrel due to the slug engaging the rifling. Someone please show us one that has that condition. Measure your rounds protrusion as I did above and show where it is greater than an ammostore barrel or any other properly functioning barrel. Simply stated, if the round is engaging the rifling the protrusion will be greater than what I measured on mine.

BTW, anyone that takes out a new barrel of any caliber with surplus 8mm ammo and fires 1000 rounds thru it without checking the headspace after one or two belts is asking for trouble. With good GI components and ammo you can get away with it, but with 8mm you're taking a huge risk. If a gun makes it to 1000 rounds and then blows a top cover, what does that tell you? The headspace on new guns and barrels shooting 8mm most of the time require revisiting until it stabilizes. Maybe I've just been plane old lucky and haven't blown a top cover, but my headspacing gets checked more often than most...almost every belt or two.

I'm going to the range on 8-26 and I'm taking my 1919 and John's barrels and I'm going to run them first hand and see what happens. Hopefully nothing bad. I plan on giving it a slow run at first, as I do with any new barrel, and if it behaves I'll give it a good hard run with a Crankfire just as I do with my ammostore barrel. We'll see what happens.

 

[Dave B - Great Lakes Arms]

You have obviously not read the volumes of posts on this subject from multiple members and have no general understanding of the importance of the throat.

If you did read the posts you would know that a shallow chamber is NOT the issue with these barrels...it is the shallow throat. Throat and chamber are not the same.

As far as headspace....YES it is the distance from the shoulder of the case to the bolt face. Just happens that for military purposes the manuals are printed to reflect a distance from the barrel face to the bolt face becasue all the US GI barrels are chambered the same adn it was easier to make a guage that measure this gap. Can you guarntee that every manufacture of aftermarket barrels are chambering to the same dimensions as the US GI barrels....no you cannot.

Your theory on cartridge protrusion completely disregards the fact that the round is not fully seated in the chamber becasue the round is stopped short by the rifling on the bullet as a result of the shallow throat. Put a little thumb pressure on that round and then pull it out of the chamber and look at the marks left by the rifling on the side of the bullet. That is shallow throat and that casues over pressure and it doesn't matter if the case is supported at this point becasue the pressure is so excessive that the base will blow.

Who said they shot 1000 rds without checking???? Wasn't me, you made that one up yourself.

If you have not heard one reasonable explination perhaps it is that you are not a reasonable person. I know I have tried to make it as plain as possible but the truth is that this is a mater of physics and some people just don't get it.

The strange thing is that I really don't know why I care what you think or do.....
perhaps it is that people here take what you say as gospel and follow blindly....and it scares me for their sake.

You know what...you are right...you know everything...Good Luck.

 

[cal50]

If the cartridge has the same protrusion at the rear on all the barrels then the round is fully supported and headspacing for a 1919 will be uniform.

If a chamber is too shallow then the cartridge will have too much protrusion and unsupprted case. I'm not finding that with John's barrels.

.

I don't think so.

Your using the chamber as an OAL gage. Proper head space means the cartridge is fully supported. If the bullet is makeing contact with the throat area it is pushing the cartridge shoulder away from the chamber shoulder. If it is excessive you might get a round to fire out of battery or a kaboom. If the barrels are held to the tolerance that the GI headspace gage is used and your using GI spec ammo youe should be good to go.
When your using an aftermarket barrel (mine too) and your useing different ammo then a stack up of tolerances is in play.
If it measures the same OAL with and with out a bullet in the case your headspace is the same. If it's different then your stopping on the ogive of the bullet and your headspace is different. AN extreme example would be a deep chambered barrel and a long seated bullet. They may protrude the same length from the barrel but I guarantee you the case is unsupported IF the bullet is contacting the throat.

 

[ohioblacksheep]

Just a Thought.

Does any one know how much presure the 1919 is capible of handling with the bolt locked in place? With as much mass as there is in the 1919 I would think they would be rated way higher than any bolt gun..Do you think there could be enough pressure built up to make it unlock itself out of battery? ...Lou

 

[Ouchman]

I will state the obvious once again. A simple chamber casting of your bbls. will make it obvious what is going on. It will clearly show the differences. About as plain and simple as comparing two cartridges.

 

[belt fed frog]

not all cases are equal

here is something no one has mentioned and that is the case it`s self not all brass(steel too) is the same while the external is dimentioned the same the internal is NOT some cases have a thicker web in the base of the case and it would seem that some yugo is thin in the web area and this is causing blow outs yes there is some truth to the leed (throat) issue but in 50 cal single shot rifles we get the most accuracy with very little back set from the lands on the order of .015 - .050 in a lot of cases , long free bore (leed /throat) is a major issue in the accuracy of AR -50`s and Barrett`s this is in large part due to liablilty issues and decreases the accuracy of the rifle significantly ,so they shoot no better that 1-2 MOA at any range it really shows up at 1000 yards

food for thought guys

 

[MD4ZZZS]

8mm Yugo In John Mcg's

So Far I Have Fired Around 500 Rounds Of The Yugo 8mm With Headstamp "50", Never Had Yet Encountered Any Case Separation Or Misfires. I Did'nt Follow The Headspace Tutorial. What I Did Was Screw In The Barrel As Far As Possible And Test For Timing Or Functioning Of The Trigger And Sear. Screw Out The Barrel A Notch At A Time Until The Trigger And Sear Are Functioning Right. This Way, I Am Sure Of The Ammo Being Well Supported By The Chamber And Not Having An Excessive Gap Between The Bolt And The Barrel.
Don't Know If It Is Another Way Of Doing It. But It Is Working So Far.

 

[acmech]

My cases were splitting vertically near the shoulder, and here is what I found with Johns new chrome lined barrels. First of all, John didn't make them someone else did so his skills aren't being smeared, second they aren't throated deep enough.

If you can see the picture, I blackened the bullet with a marker and put it into the chamber, I pushed it in hard and I let it wobble around since it didn't fully seat. The rifling is contacting the bullet before it is seated, this can be observed by the "ring" that is rubbed off of the bullet. Someone else here has done the same thing and posted a similar picture. Also the yugo rounds were sticking out of the barrel about .010-.015 more than on my ammostore barrel. The rounds dropped all the way in on my ammostore barrel and the cases didn't split on me when shot out of it. I have no idea why your measurements are different when I went through 2 of Johns barrels and got the same results. I didn't fire the second barrel, but the measurements were the same so I sold it. I didn't want to shoot a barrel that had the bullet jammed against the rifling, and setting the headspace at 0 clicks from lockup was the only way I could fire yugo ammo to minimize the splitting which forces the bullet in but also puts the brass where it can be supported. Your talking about the possibility of serious pressures here. Oh, and I found a note in the box of my replacement barrel, it was returned because the buyer found it wasn't throated deep enough for yugo ammo he was smarter than I was and checked it before shooting it.

 

[Dave B - Great Lakes Arms]

here is something no one has mentioned and that is the case it`s self not all brass(steel too) is the same while the external is dimentioned the same the internal is NOT some cases have a thicker web in the base of the case and it would seem that some yugo is thin in the web area and this is causing blow outs yes there is some truth to the leed (throat) issue but in 50 cal single shot rifles we get the most accuracy with very little back set from the lands on the order of .015 - .050 in a lot of cases , long free bore (leed /throat) is a major issue in the accuracy of AR -50`s and Barrett`s this is in large part due to liablilty issues and decreases the accuracy of the rifle significantly ,so they shoot no better that 1-2 MOA at any range it really shows up at 1000 yards

food for thought guys

#1 Red Text.......pure speculation, can you show proof of this?

#2 Blue text.......you may note there is a significant difference between "Little backset from the lands" and TOUCHING THE LANDS This makes a HUGE difference in case pressure. In the new chrome barrels the bullet touches the lands upon chambering.

I agree, for a MATCH rifle....with consistant MATCH grade ammo....that is being shot for ACCURACY.... you do indeed want as little throat or freebore as possible.....but then again we are NOT talking about a match grade gun and accuracy is not the objetive. People...these are MACHINE GUNS....albiet semi auto in many cases but they are still machine guns by design and you must follow rules set fourth for heat and ammo inconsistancy....that being looser tolerences and room for heat expansion and such. These barrels have ZERO....NADA....NONE....ZIP throat or freebore when used with Yugo ammo. This is not a safe combination.

 

[mrbullseye]

message getting through finally

as stated before. look down any mauser barrell from the breech
end. see the tapered lands. see the throat. now look down a
john m barrell. are they the same. you tell me. no taper and no long
throat spells high pressure. make a chamber cast as stated before.
pressure stays in normal range as long as bullet moves forward before
touching the lands. maybe when a john m barrell has a lot of rounds
through it the throat will start to wear and increase which will then
help keep the pressure down. all this info is in a lot of reloading manuals.
remember when 50,000 psi lets go you are in for a real surprise. i would
also see if a bullet will slip into a fired case. if it does then chamber is
large enough. if the bullet will not slip into a fired case then you have a
really tight chamber. whoops, there goes that pressure spike again.
i will use a ammuntionstore barrell when it comes and make sure the throat
is where it should before i fire yugo or turk ammo. i was going to buy a
john m 8mm weapon but decided not to for obvious reasons.

 

[Dave B - Great Lakes Arms]

I went ahead and bought a throat reamer for 8mm from Brownells. When my AmmoStore barrel came in I gave her a throat job. Just got done doing a cast of it...I mean literally like 2 minutes ago. Looks good and free so the Yugo should be no problem. I did not cast it before reaming as a visual inspection led me to belive it could use a little lengthning and I wanted to try the reamer anyway.

 

[loboslanding]

Guys I ain't trying to come across as the know it all of anything here. I'm just penning what I measured. Some comments were made that have caused me to go look at it again from another angle. I must be missing something because if the rifling is interfering then it should show up in the measurements I took between the two different barrel mfgrs. So maybe I am dense, but here's what I did to test my approach.

It's said that the projectile is hitting the lands and causing the round not to seat completely and in the photos it certainly looks that way on those chambers. I took the same loaded Yugo round I used for yesterdays measurements and unloaded it. I removed the projectile, the offending object, from the equation and reinserted the empty case into the chamber...no difference in measurement. I used another loaded round and took the measurements again and no difference.

Besides, when I chambered the rounds yesterday and seated them firmly I checked for striations on the slug and saw none. I also had seated them so firmly that I had to use pliers to remove them.

Unload a round and try it for yourselves. Post the difference here and let's see what kind of variations we're getting.

I do know that John recalled some earlier barrels for chamber issues and perhaps most of the issues are from that era and do not pertain to the vintage of the one's that I have.

The whole problem I'm having here, whether it's with John's barrels or any other, is the issue of kabooms due to out of chamber ignitions. Those have been occurring ever since we started shooting 8mm in these guns. I still cannot understand how a firing pin is dropping on a round when the bolt is not locked up and I do not believe that this ammo is causing such pressures as to unlock a bolt...it would have to almost sheer the breach block to do so which tells me the breach block is possibly not locked into the cam properly when the fp drops. And while on this subject I'll toss this out. I've gone over a few builds where the cam block was jammed in between the sideplates and irregardless of whether the retaining screw was "backed off" or not would have made no difference in allowing it to move to ensure the breach block does lock up properly. Most of the time when I see this it's due to the front couple of rivets not having enough countersink on the inside and the cam block is jammed by the protruding rivet head. I really believe in having a lot of slop in the cam so the breach block will lock up no matter how hot or dirty the gun gets. This corrosive residue ends up right there in the cam and mine get pretty gummy pretty quick so I build 'em sloppy loose. Just a thot and observation.

And just so I'm making myself clear, I'm not telling anyone to go shoot any combo of barrel and ammo without checking it first.

MD4ZZZS, the way you are headspacing is perfectly fine and is at 0 clearance...very tight headspacing. I headspace with one click out beyond the way you're doing it for 8mm and the gun runs fine. That is typically too tight when I run '06 and the gun heats up, but this junk 8mm has such a wide range of rim, case length tolerances and OAL that I run the headspace really tight on my 1919 and '28. By running such a tight headspace, if I get a round where the OAL is too long then the bolt won't lock up and fire so I eject the round and toss it.

 

[belt fed frog]

just saw a few diffrent cases in half length wise and you will see the diffrence ,try it on diffrent lots and you will find some variation ,some times extreme it also is related to brass composition wether it is "long " or "short " brass alloy , i have found great variation even in US mil brass in both alloy and cross sectional specs

take it for what it is worth i have been at this for VERY LONG time

 

[loboslanding]

belt fed I agree. There are significant variations in OAL in this stuff and some are really long. I don't personally want my chambers or set my headspacing to accommodate the long stuff. I headspace pretty tight and the long one's won't chamber so they get ejected...I don't try to fire them. I save them up and when I get enough of them will one day run them thru a seater die and reuse them. I let my gun do the sorting cuz I'm too lazy. Yeah, sometimes I get belts with stoppages for either deep primers or long rounds, but as long as no one is shooting back I don't mind cycling the bolt a few times.

 

[BEFU]

8mm solution

OK, so what it sounds like to me:

1. when John M 8mm barrel comes in, check it for throat length and make sure lands are not touching the bullet on Romanian ammo. Can also check Yugo, but probally not a good idea as if it is not touching, it is overly close or a long round would touch. Use this chrome barrel with Romy only.

2. Buy a ammostore barrel when they are back in stock for the $140 or so. Check it also for proper throat on Yugo. If good, shoot the cheap Yugo. If not, ream it out as it is not chrome lined. shoot the crap out of it and have fun, save chrome barrel for better ammo.

You could always ream out the john m barrel, but why? I want a chrome barrel so it last, not one with plain steel in the throat area where it will wear first. So keep it in good shape, and shell out the money for the ammostore barrel, it is only $140. Eventually all the Yugo will be gone, so then I have a good barrel for the available Romanian.

Sounds like a simple plan to me.

Anyone disagree other than having to have two barrels?

And yes, check headspace again, and again, and.......

Brian