Cannon ROF Test Result

[EagleDNY]

Hi folks,
  I was interested to see how close the AH Cannons were to the real thing in terms of rate of fire, so I did some testing with a stopwatch and the results were quite interesting.  Each cannon was fired 3 times and the stopwatch times were averaged and then divided against the total ammo load to give the actual ROF of the cannon.  I'll post the excel sheet with the raw data in the forum if I can figure out how to keep the formatting intact.

The Results:
Hispano Mk.V (Tempest) 20mm Cannon:
Spot On historical data - ROF is 750 rpm.  (12.5 rnds / sec)

Hispano Mk.II (Spitfire/Hurri/F4U-1C) 20mm Cannon:
ROF is HIGH - 650 rpm on average (10.8 rnds / sec avg) - data from many sources on this cannon says the actual ROF was 600 rpm.

MG151/20 (Me109 / C.205 / FW190) 20mm Cannon:
Tests with the 109F4 and C.205 gave a 699rpm ROF (11.65 rnds/sec), and our test with the 109G14 came up with a 704rpm ROF (11.76).  The ROF of this cannon is at low end of historical data, but still near the 700-750 rpm that is indicated in the historic data for this weapon.

Type 99 (N1K1) 20mm Cannon:
Tested ROF was 493 rpm (Avg 8.21 rnds/sec) - I was surprised here until I read that the historic ROF of this weapon was 490-520rpm, so this weapon is also at the low end of the historic data, and is the slowest firing 20mm cannon tested.

HO-5 Cannon - here was a surprise - this cannon performed differently depending upon which plane I selected:
Tested ROF was 760rpm in the Ki-61 (avg 12.67 rnds/sec) which fit within the historic data for this cannon (750-850 rpm).  When tested in the Ki-84, the ROF jumped to 843rpm (avg 14.05 rnds/sec), which was at the high-end of the scale.  

Mk.108 (Me109G14/K4) 30mm Cannon:
Tested ROF was 602-608rpm (10.04 - 10.14 rnds/sec).  At the low end of the 600-650 rpm ROF indicated for this weapon, but within the scale.


The only cannon that seems "out of whack" with the data charts is the Hispano Mk.II with the ROF of 650rpm.  Everything else seems within published historic data.

EagleDNY

[Karnak]

The Ho-5s on the Ki-61 are in the cowl and are therefor synchronized, hence the lower RoF.

[1K3]

Hispano is over modelled!

(runs and hides)

[Nashwan]

Tony Williams said recently that the armourers handbook for the Hispano II gves the ROF as 650 rpm, so perhaps that's the source HTC is using (and perhaps it's correct, too)

[Tony Williams]

You have to remember that quoted RoFs were only averages, and there could be quite big variations from gun to gun, or for any one gun depending on the circumstances.

The synchronised RoF for the Ho-5 sounds high: the big Brownings didn't synchronise well, and typically lost 30-40% of their free RoF.

Tony Williams: Military gun and ammunition website and discussion forum

[Krusty]

What about MG151/20s that are synchronized? I'm thinking Fw190s here.

[Tony Williams]

Originally posted by Krusty
What about MG151/20s that are synchronized? I'm thinking Fw190s here.

The Germans had the best synchronisation system, particularly with the MG 151E and MG 131 as these used electric rather than percussion ignition. This meant that the synch system sent an electrical impulse which directly fired the cartridge - no need to wait for a firing pin to release and travel forward - so it gave them very precise control. The loss of RoF to synchronisation was accordingly only about 10%.

Tony Williams: Military gun and ammunition website and discussion forum

[Crumpp]

Waffengeber.....

[1K3]

by the our MG/FF cannon is the MG-FF/M right?  109Es started fitting MG-FF/M in summer 1940.

[EagleDNY]

Originally posted by Nashwan
Tony Williams said recently that the armourers handbook for the Hispano II gves the ROF as 650 rpm, so perhaps that's the source HTC is using (and perhaps it's correct, too)

Amongst the references I was checking was Tony Williams' site, which has the hispano II listed as firing 10 rnds/sec (ROF 600 rpm).  All the other references I found also had 600, so I'd be interested in seeing it.  

Tony's charts on the effectiveness of the individual cannon shells are interesting as well.  I can definitely agree with the assessment that the MG 151/20mm shells are only about 80% the power of the hispano rounds.  

EagleDNY

[Karnak]

Originally posted by EagleDNY
I can definitely agree with the assessment that the MG 151/20mm shells are only about 80% the power of the hispano rounds.

Averaged out of mixed belt, yes.  However a mine shell would be more destructive than a Hispano shell.  It just depended on what shell the MG151/20 hit with.

[Tony Williams]

Nearly all sources quote 600 rpm for the Hispano Mk II, but the armourer's handbook does say 650.

On another forum, there was an interesting contribution made by someone whose father had been an armourer in WW2 (Australian, IIRC). They had a competition to see who could boost the performance of the Hisso by the most. By doing a lot of careful polishing and adjusting etc he managed to win the competition with a measured RoF of 1,000 rpm. For Hissos straight from the factory, he reported that the RoF varied between 550 and 650 rpm.

US Hissos (AN-M2) officially did 650 rpm - when they were working....

Tony Williams: Military gun and ammunition website and discussion forum

[HoHun]

Hi Eagle,

>Tony's charts on the effectiveness of the individual cannon shells are interesting as well.  I can definitely agree with the assessment that the MG 151/20mm shells are only about 80% the power of the hispano rounds.  

Well, Tony's analysis systematically under-estimates chemical energy.

If you scroll down his page, you can see that he has contrasted his "rule of thumb" analysis with a "total energy" analysis, which shows that the mine shells are considerably more (not considerably less) potent than the Hispano API projectiles in terms of total energy.

I'm not sure which belting order Tony used, but with the 1:1:3 belting order (API:HET:HE(M)) specified in the Luftwaffe's Schießfibel for use against fighters, the firepower comparison is as follows:

MG 151/20 (MX): 1,4 MW
MG 151/20: 1,27 MW
Hispano V: 1,23 MW
Hispano II: 1,06 MW

(The MX shells were more powerful mine shells introduced late in the war.)

Regards,

Henning (HoHun)

[EagleDNY]

Yes, I see the data you are referring to in the charts.  I was looking at the "power" rating (16 for the MG 151 vs 20 for the Hispano).  Having flown both spits/tiffies/temps on the one hand and 109s & 190s on the other, I think the way the guns are modeled in AH gives about a 20% edge in destructiveness to the hispano (and the high ROF and ballistics don't hurt either).

Looking at the invididual damage ratings for the various types of ammo definitely shows the HE(M) round is the one you want.  I don't know what sort of tweaks HT can do on the gun models for each aircraft (I mean besides ROF - the Ki's seem to show that ROF is plane specific not gun specific).  It would be nice if the later model 109s & 190s got the benefit of the HE(M) ammo loudout somehow, or at least got the MG 151s firing at the high-end of the ROF range.  

I don't know enough about the reliability of the various sources to comment further on the 600 vs 650 ROF on the Hispano II.  Frankly, with the short clip on a spit, I think I'd almost rather have a 600 ROF for the extra trigger time vs fighters.  In a tiffie, I'd probably rather have the 650 ROF vs ground targets.  It is a small difference, but maybe that is a tweak HT should look at in a future patch.

EagleDNY

[gatt]

About 100rpm difference between the 151/20 and the Mk108 ... its incredible how much difference you feel in the game. Probably the muzzle velocity plays a big role here .... isnt it?