Will the real cyclic rate please stand up.

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May 16, 2006
I have heard claims about the U.S. M2 .50 cal had a cyclic rate that ranged from 700rpm to 850rpm.

So what was the real cyclic rate of this gun?

I have always thought it was 750rpm.
I fired them years ago and it seemed (giving space for the last 20 some odd years) a bit lower. Probably closer to 600 rpm.

I know some of the better gunners at the school (usually Seabees) could tap of single shots from the thing. Plenty of experience.

Also, it jammed all the time. Not a hard, break the thing down jam. More along the lines of a recharge it a couple of times and get to it. Could've been the guns, could've been the ammo but it was unusual to go through more than 20rds without a stopage.
The M2 was considered extremely reliable in its use on aircraft in WWII. As I have been searching further on this subject I seen some figures on cyclic rate as low as 550rpm.
Squeelig said:
I have heard claims about the U.S. M2 .50 cal had a cyclic rate that ranged from 700rpm to 850rpm.

So what was the real cyclic rate of this gun?

I have always thought it was 750rpm.

I think your rates are right for the M2, and at the end of the war the new M3 .50 cal boosted the rate to 1200rpm. This is the gun used on the F-86 in Korea.
I have a copy of a post war manual for 'Gun, Automatic, .50 calibre, M2' and the rate of fire is given as between 750 and 850 rpm. All kinds of things can affect the RoF of a weapon, from the build quality or factory it was made in, atmospheric conditions, ammunition quality, type of belting, type of ammunition being fired ect ect.

I think the lower RoFs were for the ground based versions of the "Ma Duece", somewhere between about 450-600, depending on the exact version and the adjustments made to the guns.

Interestingly, the US AN-M2 20mm (the US version of the 20mm Hispano Mk II) gives the RoF for the gun as 600-700 rpm. The RAAF ordanance guys used to competitively 'tune' the 20mm fitted to their Beaufighters, getting as high as 1,000 rpm in firing tests ( the winner with the fastest firing cannon got a crate of whisky). As the .50 Browning was quite suceptiable to armourers adjustments, I'm sure it could of been 'tuned' up to that level or maybe even higher. Reliability would be something of an issue though.
Also Air Gunners learnt that if they sent home and got bundles of pennies sent over they could replace the buffer pads with the coins.

That was one of the fastest ways to increase firing rates, although it was hard on the guns.
The original speed of the aircraft .50 M2 was around 700 rpm (the heavy-barrel ground gun did about 450-550 rpm). The water-cooled naval AA version also did 700 rpm. The aircraft M2 was 'tweaked' a bit around 1940 which raised its rpm to up to 900 rpm. However, as others have commented the actual RoF varied quite a bit depending on such factors as the age and condition of the gun, the installation and so on, so 750-850 rpm is normally quoted as the typical range.

Synchronised installations saw a big fall-off in RoF, with an average of 400-450 rpm being typical. This affected early P-40 and P-51, and the P-39/63 family. The big Browning appeared to have been particularly badly affected by synchronisation, others did not lose so much (the German guns in particular lost only about 10% of their free RoF).

The .50 M3 managed around 1,200 rpm but that saw little if any use in WW2.

A couple of articles on my website concerning the performance of aircraft guns in WW2:

Tony Williams: Military gun and ammunition website and discussion forum

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