I know that the answer depends on a number of factors like ammunition.
But, what should I get for cyclic rate when shooting a C&R MG42 in 8mm with Yugo bolt with and without bolt stabilizer? I read that it makes no difference?
Also, with the same Yugo bolt, what cyclic rate should I get shooting with the 7.62"conversion kit installed? Does 7.62 shoot slower than 8mm or is this due to the bolts?
Pat
MG42 Cyclic rate question
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JBaum
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Re: MG42 Cyclic rate question
1000-1200 rpm is in the ballpark for most guns.
Other variables also influence the cyclic rate. The strength of the recoil spring, size of the nozzle hole, and how hot the cartridges are loaded can change the rate of fire. Combine the effects of all three and it's quite a bit slower or faster.
.308 generally shoots at a slower rate of fire than 8mm because it's a less powerful cartridge, but it can be the same rate as 8mm if you use a nozzle with a smaller hole.
Hot loads shoot faster than loads with lesser powder. 1/2 grain of powder can make a noticeable difference in speed.
The same bolt is used for either caliber.
Not using a bolt stabilizer in a rewelded post sample isn't too bad to do. When the gun blows and buckles the receiver, not much is lost other than time. Running a C&R gun without one is an insult to the gun. I recommend having tweezers and alcohol ready for people who do that. A good set of tweezers is essential for picking out the pieces of brass in your hands and arms. The steel receiver doesn't splinter, it just bulges and bends, and sometimes cracks. Safety glasses are a good idea too.
Every gun can be different depending on all the combinations of variables. The only way to know exactly is with a shot counter.
Other variables also influence the cyclic rate. The strength of the recoil spring, size of the nozzle hole, and how hot the cartridges are loaded can change the rate of fire. Combine the effects of all three and it's quite a bit slower or faster.
.308 generally shoots at a slower rate of fire than 8mm because it's a less powerful cartridge, but it can be the same rate as 8mm if you use a nozzle with a smaller hole.
Hot loads shoot faster than loads with lesser powder. 1/2 grain of powder can make a noticeable difference in speed.
The same bolt is used for either caliber.
Not using a bolt stabilizer in a rewelded post sample isn't too bad to do. When the gun blows and buckles the receiver, not much is lost other than time. Running a C&R gun without one is an insult to the gun. I recommend having tweezers and alcohol ready for people who do that. A good set of tweezers is essential for picking out the pieces of brass in your hands and arms. The steel receiver doesn't splinter, it just bulges and bends, and sometimes cracks. Safety glasses are a good idea too.
Every gun can be different depending on all the combinations of variables. The only way to know exactly is with a shot counter.
Re: MG42 Cyclic rate question
Thanks, I will never, ever run it without a bolt stabilizer. It was just a hypothetical question.
I just swapped the block on my Dillion 550B from 8x33 Kurz to 7.62. I reloaded 50 rounds using LC72 once fired brass with 42 grains of IMR 4064, CCI34 primers, topped with Winchester 147 FMJ. It is a moderate load. I shot this in my PTR91 without issues.
I think that I will shoot more 7.62 than 8mm. All with the great care.
Pat
I just swapped the block on my Dillion 550B from 8x33 Kurz to 7.62. I reloaded 50 rounds using LC72 once fired brass with 42 grains of IMR 4064, CCI34 primers, topped with Winchester 147 FMJ. It is a moderate load. I shot this in my PTR91 without issues.
I think that I will shoot more 7.62 than 8mm. All with the great care.
Pat
Re: MG42 Cyclic rate question
Real life rates on the MG42 vary from about 1100 to 1300 in 8mm and around 1000 to 1250 or so in 308. As noted the springs can affect the rate but not as much as you'd think. They can slow it down when they get weak but new strong springs won't necessarily speed things back up. The recuperator springs do make a big difference. When they get worn the barrel will hit the trunnion and not only damage it but will also reduce the rate of fire by a pretty good amount. As the parts wear more the gun will become less reliable til it does odd things like cycling a round or two and leaving a live one in the chamber with a light strike. Bob Naess has new springs and replaces them quickly. Definitely a good thing to do.
As for boosters the hole diameter will affect the rate of fire up to a point. Too big and the gun won't run right and too small and things start banging and breaking. The speed of the gun is related more to the friction in the system and overall condition. Taking any 3 guns and setting them up in the same cal will show you that the rates are usually in the 1200 rpm range though a little higher or lower is not unusual. 308 runs slower because the bullets are lighter so less recoil and also because the gas volume produced is lower. 8mm has heavier bullets at a speed not much less than the 308 and this means more recoil. Also much more powder gas volume so the booster makes a bigger difference. So having said all that you'll have to figure out your gun. Make sure the buffer spring is not cracked as the guns speed is more related to that one than any other in the system. Make sure you lube things. Like you noted, don't ever run the gun without the bolt catch. Don't run crap ammo.
Frank
As for boosters the hole diameter will affect the rate of fire up to a point. Too big and the gun won't run right and too small and things start banging and breaking. The speed of the gun is related more to the friction in the system and overall condition. Taking any 3 guns and setting them up in the same cal will show you that the rates are usually in the 1200 rpm range though a little higher or lower is not unusual. 308 runs slower because the bullets are lighter so less recoil and also because the gas volume produced is lower. 8mm has heavier bullets at a speed not much less than the 308 and this means more recoil. Also much more powder gas volume so the booster makes a bigger difference. So having said all that you'll have to figure out your gun. Make sure the buffer spring is not cracked as the guns speed is more related to that one than any other in the system. Make sure you lube things. Like you noted, don't ever run the gun without the bolt catch. Don't run crap ammo.
Frank