In essence isn't the way the gages work is if
* it does not not close on a go gage ( or any other ) and your in good shape
* but if it completely closes on a field gage you are out of luck- correct???
I wouldn't want to wait until one closes on a no-go as that might have been too long to have waited.
I might try and find a good 8mm and 308 gage to have for the future with these barrels getting harder to find- I have about 10 8mm and 5 308 now mo is betta.
Mark
mg42 308 blow up pics
No, not quite.
It must close and lock fully on the "GO" gage to insure proper positioning of the bolt to close fully and fire the weapon.
The "NO-GO" gage is the beginning of something bad that could happen and the bolt should not close and lock on the "NO-GO" this is where I would stop.
The "FIELD" gage is the maximum length before problems really start to happen and if the bolt closes and locks on that one then you are about to be in real trouble if you continue to use that combination then you might be looking for a new gun in short order.
Also remember if you have a MG 3 7.62mm NATO barrel;.308 Win. is not the same headspace so the gages could/would be of limited value for determining such.
It must close and lock fully on the "GO" gage to insure proper positioning of the bolt to close fully and fire the weapon.
The "NO-GO" gage is the beginning of something bad that could happen and the bolt should not close and lock on the "NO-GO" this is where I would stop.
The "FIELD" gage is the maximum length before problems really start to happen and if the bolt closes and locks on that one then you are about to be in real trouble if you continue to use that combination then you might be looking for a new gun in short order.
Also remember if you have a MG 3 7.62mm NATO barrel;.308 Win. is not the same headspace so the gages could/would be of limited value for determining such.
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JBaum
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With a perfect bolt and barrel extension, the cartridge can't fire unless there's a complete lockup as KMFDM explains correctly in his post.
That said, the world isn't perfect, rollers aren't perfect, firing pin holders aren't, and neither are barrel extensions or bolts. Get a couple parts at the extremes of their tolerances, and when the tolerances add up to something excessive in one spot, something bad happens. Each part can be OK individually, or with another part that's at the other extreme of the tolerance range, but add up a few parts that are each a little short the wrong way, and the ASSEMBLY is out of tolerance. Shortly after that, something embarrassing usually happens.
OK, I did this on anther thread a long time ago, but I'm not wasting time looking for it.
The GO Gauge checks the rifle to see that the chamber will accept cartridges made to the maximum specs. If it won't fit, the chamber is too tight for MAX spec ammo. That's not to say that it won't work for MINIMUM spec ammo, or ammo that you reload with the forming die set really tight. It's a gauge, not a guarantee.
If the bolt closes on a NO GO Gauge, it MAY have excessive headspace. It may still be within tolerances for cartridge specs. If the NO GO gauge will allow the bolt to close, it needs checked with a FIELD gauge . The maximum cartridge dimensions may fit in the chamber OK but the gun can still have excessive headspace if the bolt rollers extend completely to the outside edge of the grooves in the barrel extension and there's still a gap at the mouth of the chamber.
If the FIELD gauge allows the bolt to close, then it's extremely close or exceeds the maximum chamber size. The chamber in this case would be defined including the face of the bolt.
Slightly excessive headspace doesn't seem to bother the MG42 much. Too tight makes for blown up guns.
Buying a gauge or two is always cheaper than the result of not checking when you should have. Each combination of barrels/bolts need checked to be sure that the bolt face/chamber mouth gap isn't excessive, and to be sure that the locking rollers extend completely into the grooves of the barrel extension when the NO GO gauge is inserted. It's OK if they don't extend completely into the grooves with the FIELD gauge, but if they do anyway, it's time to look at the gap. I like the .003 " mentioned in another post, but will admit to running with more gap than that.
Nobody here would take a mixed assembly of Mauser or Enfield parts, put it all together and pull the trigger with their face 4" from something that would explode.... (alright, a few maybe, but most of you wouldn't). With the mix/match/different years/different countries of parts that are being assembled into MG42s, there's no difference. It's a dangerous thing to do, spending all the time rewelding and finishing a receiver while never bothering to check the chamber dimensions.
One more thing... An MG42 CAN blow up whether it has good headspace or not. All it needs is a 1/100th of a second hang fire from a 40 year old primer to have it explode. The MG42 fires 25 shots a second. That means that it takes 1/50 of a second for the bolt to go back, and 1/50 of a second for it to go forward (figuring immediate ignition and no delay). Guess where the bolt and the cartridge are at 1/100th of a second after the firing pin hits, even if the cartridge doesn't explode. The BOLT CATCH helps eliminate bolt bounce... it doesn't stop it completely - nothing will. If the bolt happens to open 40 thousandths of an inch before the cartridge fires, the sidewall of the cartridge ruptures and all that powder gas has a new direction to go.
I don't think anyone here has less than $1,000 in their semi-auto, and I know I've got a LOT more than that in my full-auto. Any gambler will decrease his chances of losing whenever he can. I prefer to think of not using 40 year old ammo as decreasing my chances of something bad happening. That's a good thing.
That said, the world isn't perfect, rollers aren't perfect, firing pin holders aren't, and neither are barrel extensions or bolts. Get a couple parts at the extremes of their tolerances, and when the tolerances add up to something excessive in one spot, something bad happens. Each part can be OK individually, or with another part that's at the other extreme of the tolerance range, but add up a few parts that are each a little short the wrong way, and the ASSEMBLY is out of tolerance. Shortly after that, something embarrassing usually happens.
OK, I did this on anther thread a long time ago, but I'm not wasting time looking for it.
The GO Gauge checks the rifle to see that the chamber will accept cartridges made to the maximum specs. If it won't fit, the chamber is too tight for MAX spec ammo. That's not to say that it won't work for MINIMUM spec ammo, or ammo that you reload with the forming die set really tight. It's a gauge, not a guarantee.
If the bolt closes on a NO GO Gauge, it MAY have excessive headspace. It may still be within tolerances for cartridge specs. If the NO GO gauge will allow the bolt to close, it needs checked with a FIELD gauge . The maximum cartridge dimensions may fit in the chamber OK but the gun can still have excessive headspace if the bolt rollers extend completely to the outside edge of the grooves in the barrel extension and there's still a gap at the mouth of the chamber.
If the FIELD gauge allows the bolt to close, then it's extremely close or exceeds the maximum chamber size. The chamber in this case would be defined including the face of the bolt.
Slightly excessive headspace doesn't seem to bother the MG42 much. Too tight makes for blown up guns.
Buying a gauge or two is always cheaper than the result of not checking when you should have. Each combination of barrels/bolts need checked to be sure that the bolt face/chamber mouth gap isn't excessive, and to be sure that the locking rollers extend completely into the grooves of the barrel extension when the NO GO gauge is inserted. It's OK if they don't extend completely into the grooves with the FIELD gauge, but if they do anyway, it's time to look at the gap. I like the .003 " mentioned in another post, but will admit to running with more gap than that.
Nobody here would take a mixed assembly of Mauser or Enfield parts, put it all together and pull the trigger with their face 4" from something that would explode.... (alright, a few maybe, but most of you wouldn't). With the mix/match/different years/different countries of parts that are being assembled into MG42s, there's no difference. It's a dangerous thing to do, spending all the time rewelding and finishing a receiver while never bothering to check the chamber dimensions.
One more thing... An MG42 CAN blow up whether it has good headspace or not. All it needs is a 1/100th of a second hang fire from a 40 year old primer to have it explode. The MG42 fires 25 shots a second. That means that it takes 1/50 of a second for the bolt to go back, and 1/50 of a second for it to go forward (figuring immediate ignition and no delay). Guess where the bolt and the cartridge are at 1/100th of a second after the firing pin hits, even if the cartridge doesn't explode. The BOLT CATCH helps eliminate bolt bounce... it doesn't stop it completely - nothing will. If the bolt happens to open 40 thousandths of an inch before the cartridge fires, the sidewall of the cartridge ruptures and all that powder gas has a new direction to go.
I don't think anyone here has less than $1,000 in their semi-auto, and I know I've got a LOT more than that in my full-auto. Any gambler will decrease his chances of losing whenever he can. I prefer to think of not using 40 year old ammo as decreasing my chances of something bad happening. That's a good thing.
.003" or more over a field gage; interesting.
I hope you don't mind me asking because I am genuinely curious about that. So here they are "machinegun style" as it were. Also not meant to flame but to satisfy my curiosity on this particular weapon.
It sparks this series of questions in me then. If it goes over the gage and closes could it not have too much lock and make the gun work harder battering the curved piece/trunnion and reciever more because you have gone past the acceptable limit (As I was taught the "FIELD" gages are there for a reason)? I am sure the mentioned process works because most militaries build in quite a "Dummy Factor" into their stuff, but the gage is there for a reason and it isn't always headspace: on the M240 (DShK 38 and a few others) machinegun it is also there to protect the locking surfaces from unnecessary battering. Same with the timing on an M2 machinegun. On the MG42 series; is the barrel still moving forward when the next round fires? Or has it come to rest? If it is designed to be moving then you may have eliminated that factor and make the gun work harder wearing out components sooner than necessary. Perhaps being over in the headspace could also allow a higher chance for bolt carrier rebound on a cartridge that has a hangfire creating a higher incidence of possible problems above mentioned?
25 shots a second is fast (1500rpm)-but that is in an MG42 without a bolt stabilizer correct? Which is a potentially unsafe practice if memory serves correct and has a much higher incidence of out battery fire. Especially with ammo that is marginal. Also that rate of fire assumes no wear on parts and springs and correct german spec. ammunition. Using brass cases slows MG3's down a little from my obseravtions, I have never tried it in an MG42 though.
20-22 shots a second (1200-1320rpm) seems to be about the norm for stabilized guns if I remember correctly, and it also makes for a very low incidence of out of battery fire. It would seem slowing one down just that amount makes for a big difference in reliability all the way around.
Also as for tolerance stacking on parts that is already factored into production and finished product and the use of the gage is there for that reason also and it is also there for worn guns and parts. The presence of bad headspace does not automatically mean the barrel is bad (as you probably know)-that is just the starting point for troubleshooting the whole locking system.
I hope you don't mind me asking because I am genuinely curious about that. So here they are "machinegun style" as it were. Also not meant to flame but to satisfy my curiosity on this particular weapon.
It sparks this series of questions in me then. If it goes over the gage and closes could it not have too much lock and make the gun work harder battering the curved piece/trunnion and reciever more because you have gone past the acceptable limit (As I was taught the "FIELD" gages are there for a reason)? I am sure the mentioned process works because most militaries build in quite a "Dummy Factor" into their stuff, but the gage is there for a reason and it isn't always headspace: on the M240 (DShK 38 and a few others) machinegun it is also there to protect the locking surfaces from unnecessary battering. Same with the timing on an M2 machinegun. On the MG42 series; is the barrel still moving forward when the next round fires? Or has it come to rest? If it is designed to be moving then you may have eliminated that factor and make the gun work harder wearing out components sooner than necessary. Perhaps being over in the headspace could also allow a higher chance for bolt carrier rebound on a cartridge that has a hangfire creating a higher incidence of possible problems above mentioned?
25 shots a second is fast (1500rpm)-but that is in an MG42 without a bolt stabilizer correct? Which is a potentially unsafe practice if memory serves correct and has a much higher incidence of out battery fire. Especially with ammo that is marginal. Also that rate of fire assumes no wear on parts and springs and correct german spec. ammunition. Using brass cases slows MG3's down a little from my obseravtions, I have never tried it in an MG42 though.
20-22 shots a second (1200-1320rpm) seems to be about the norm for stabilized guns if I remember correctly, and it also makes for a very low incidence of out of battery fire. It would seem slowing one down just that amount makes for a big difference in reliability all the way around.
Also as for tolerance stacking on parts that is already factored into production and finished product and the use of the gage is there for that reason also and it is also there for worn guns and parts. The presence of bad headspace does not automatically mean the barrel is bad (as you probably know)-that is just the starting point for troubleshooting the whole locking system.