MG34 vs MG42 question


#1

Quote from “7 days in January” by Wolf Zoepf, p.56:
"Practical rates of fire were 120 rounds per minute for the MG-34, but 250 rounds for the MG-42, cyclic rates were 900 and 1400 respectively"
Author blames a sudden switch to new MG-42 for runnng out of ammo.
Question 1: What is “cyclic rate” vs “practical rate”?
Question 2: How did they achieve higher rate in MG-42 if both shoot the same 7.92x57? My understanding is that the actual length of a cartridge determines how long the bolt has to travel back.
Remember, I know little about MG’s, make it simple to comprehend, thanks.


#2

Vlad - Cyclic rate is based on how many rounds would be fired in one minute if you had a feeding mechanism of sufficient capacity to hold one minute’s worth of firing, and you held the trigger down exactly one minute.

Practical rate of fire is how many rounds a well-trained team operating the gun can get off in one minute and still properly engage targets. It is somewhat more subjective because it depends on the feeting mechanism being used with the gun at the time (remember, the MG 34 and MG42 had several different feeding devices that could be used), the skill of the firer in trigger manipulation and ability to engage targets effectively and quickly, the skill of the person feeding the gun, and even, I would think, the weather. In a driving, cold rain storm the gun would not be in as much danger of overheating as it would, say, in the North African desert at the highest point of temperature of the day. There are lots of other factors I am sure.

I will not get into the mechanics of having one gun fire faster than another. It is basic design engineering, but I am not familiar enough with the intricacies of either of the German guns to say.

It is interesting that a German source says the practical rate for firing the MG34 was 120 rounds per minute. Despite its slower cyclic rate of fire, the Browning M1919A4 has about the same practical rate of fire when fired with six-round bursts (not difficult to do pretty consistantly with practice). Of course, the MG42 had a practical rate of fire somewhat more than twice that of the Browning. I have never been convinced that meant much in the real world, but then I have never faced an MG42 in combat nor fired a shot in anger with the Browning, so I am the last one to have a rigid opinion on that.

edited for spelling only


#3

Cyclic rate is the mechanical ability of a machingun to fire with average ammunition. Practical rate takes into consideration time to reload, change barrels, the ability of the arm to absorb the heat generated by firing, etc… The MG-34 has a rotating bolt while the MG-42 used roller locks. Rotation vs. linear movement. I beleive that the difference in the two locking designs is why the cyclic rates are different. The barrel change for the MG-42 is quicker than the MG-34, so that improves the practical rate of fire. The barrel of the MG-42 swings out to the side while the MG-34 requires the whole receiver to rotate to allow the barrel to be changed. Never heard of the MG-42 running at 1,400 RPM. Usually, it is quoted at 1,200 rpm.

AKMS


#4

Here’s wikipedias take. Pretty much what John and AKMS said.

There are three standard measurements of rate of fire for automatic weapons:

Cyclic rate
This is the mechanical rate of fire, or how fast the weapon “cycles” (loads, locks, fires, unlocks, ejects). Measurement of the cyclic rate assumes that the weapon is being operated as fast as possible and does not consider operator tasks (magazine changes, aiming, etc). When the trigger is squeezed, the rate at which rounds are fired is the cyclic rate. Typical assault rifles have a cyclic rate of 500


#5

We had an instructor in gunsmith school who was a sniper in Europe during WW-2. He was of German heritage and spoke the language. He was used many times as a battlefield interpreter. he said he asked many MG 42 gunners why they used worn out barrels thinking they could not get new ones. Was told by the gunners they preferred the worn ones because they scattered the bullets better! He found the gunners did use mostly short bursts with the MG 42.

Gourd


#6

Interesting. I’ve heard that due to the high cyclic rate of the '42, the beaten zone was already too big and this was considered one of the weapon’s failings. Saw a WWII period U.S. Army training film that alluded to this. Maybe it was just propagands to help green soldiers face this beast with some confidence…

AKMS


#7
  • @ sksvlad: The cyclic rate [or the rate of fire] of a weapon is only a theoretical notion which cannot be applied in reality. I would like to give you this example: in army using the 7.62mm AKM [the Romanian made PM-63] I fired a few times one full 30-rds box magazine using the “automatic-fire”. In less than 4 seconds all the 30 cartridges [7.62X39] were fired, the rate of fire of the 7.62mm AKM is about 600 rds/min. After only 3-4 seconds of firing the barrel was very HOT, you could not touch it without to burn yourself. Can you imagine to have a 600-rds magazine and to fire all the 600 cartridges in about 60 seconds??? The barrel would not resist too long to spit 10 bullets per second for about 60 seconds. Even after firing the 7.62mm AKM using short bursts of 3-4 rounds [the 30-rds magazine will be empty in less than 10-12 seconds] the barrel becomes hot enough to burn your skin. Liviu 04/22/09

#8

Ditto to what Liviu just posted; I’m translating a copy of Monetchikov’s “History of Russian Automatics” now, and he says that in practical use, the AK/AKM were only expected to be fired in bursts of up to 5 rounds, and even the LMG versions, the PK/PKM, were only expected to be fired in bursts of up to 15 rounds.


#9
  • @ SDC: This is very true and that Russian author is 100% right. Firing only “automatic-fire” ruins very fast the barrel and the amount of ammunition needed would be too big for each weapon. Liviu 04/23/09

#10

I had a friend in the Marines who was an armorer at the School of Infantry. He got to fix all of the machineguns that the students abused. Saw more than a few examples of MG barrels that were ruined by overheating. The best one was a .50 Browning barrel that got so hot that it sagged under it’s own weight and a projectile went out of the top, leaving a 2" long gash in the metal. One M-249 SAW got so hot that even with it being fired from an open bolt, a round cooked-off in the chamber before the bolt had time to lock. I have the rear part of the ruptured case in my collection of oddities along with the projectile that was removed from the bore. The lead core melted out of the rear of the jacket, leaving the steel “penetrator” to rattle around inside the jacket. The green paint on the tip (M-855 ball) burned off, leaving a black residue. I’ve been told by experienced machinegunners that during night fires, when the M-60-E3’s lightweight barrel gets really, really hot, it turns cherry red and you can see shadows of the projectiles going down the barrel.

Google search for the video of a guy firing drum-after-drum through a full-auto AK. The wood handguards literally burst into flames after a few hundred rounds…but the AK keeps firing at cyclic rate…

I got my Hungarian AKMS clone so hot after firing seven thirty-round magazines as fast as possible (semi-automatic), that the lacquer finish on the handguards began to bubble. That is hot!

AKMS