Author Topic: Quick shooting test (Read 464 times)

flakbait · « **on:** February 19, 2001, 01:31:00 PM »

I did this test offline, using all Bf-109 models with 5 times the normal ammo load. Since an MG 151/20 fires (unsynchronized) at 740 RPM I should have had 10 rounds left. I actually had, on average, 42 rounds left. I did this test by simply flying over a large expanse of water, where nothing could interfere with my FR. Just in case this is FR related. My FR stayed and locked at 26 for this test, even when shooting. I tested again around objects that would give me a slight FR hit, just to see what happened. I came up with 53 rounds remaining this time, giving me a firing rate of 697 rpm. In this case my FR was down to 17 flying near a field.

I hit B on my keyboard and started my stopwatch at the same time. I didn't let go of the B key until one minute was up. I got a hunch this wasn't right when a quick test (3 second burst) from the Fw-190's guns turned up an RoF of 440 rpm. 44 rounds were fired, devide that by 3 to get the number of shots per second (14.66666667) multiply by 60 to get the firing rate for one minute (880) and devide by two since two guns are firing.

Remember, the Fw-190 test was just a quick check to see if things were on the level. The same quick check with the MG-17s turned up nothing really surprising. I only did this check twice, but came up with 960 RPM. This looks about right for synched MG-17s, but since I only know the un-synched rate of 1,100 RPM it's only a guess.

I haven't checked any other guns yet, but probably will. Worst case means the RoF is off, best case means RoF is FR related and it's just me. Although I doubt the latter a tad since an FR of 26 should give accurate results. Either way the MG 151/20 on my end is showing up roughly 40 rounds per minute short. Anyone want to double check this?

-----------------------
Flakbait [Delta6]
Delta 6's Flight School
Put the P-61B in Aces High
"For yay did the sky darken, and split open and spew forth fire, and
through the smoke rode the Four Wurgers of the Apocalypse.
And on their canopies was tattooed the number of the Beast, and the
number was 190." Jedi, Verse Five, Capter Two, The Book of Dweeb

funked · « **Reply #1 on:** February 19, 2001, 03:01:00 PM »

http://home.earthlink.net/~jayboyer/b-20mmTabelle4.jpg

And you've got your best and worst cases switched.

[This message has been edited by funked (edited 02-20-2001).]

Tony Williams · « **Reply #2 on:** February 20, 2001, 02:25:00 AM »

Yep - RoF of the MG 151 was around 700 rpm, but in RL this could vary by around 10 percent anyway due to ammunition variations, gun wear and probably atmospheric conditions (affecting pressure and therefore recoil).

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website: http://www.users.globalnet.co.uk/~autogun/index.htm

Jekyll · « **Reply #3 on:** February 20, 2001, 03:47:00 AM »

Flakbait, I did similar testing a few weeks ago, and came to roughly the same conclusions. Lets see, the unsynchronised Mg151/20 fired at 740 rpm (from memory), and the synchronised Mg151/20 at around 660 rpm.

Testing in the 190A8 and A5 showed an average rate of around about 600rpm for the mauser, approximately 60 rpm too slow even IF both cannon in the A8 were of the unsynchronised variety.

But hey, its only a German plane, after all.

[This message has been edited by Jekyll (edited 02-20-2001).]

juzz · « **Reply #4 on:** February 20, 2001, 03:54:00 AM »

I think Pyro once said that the synchronised weapons in AH fire at about 15% reduced rof. So if they use 700rpm for the MG 151/20 as indicated in the pic above, 15% reduction = 595rpm.

Tony Williams · « **Reply #5 on:** February 20, 2001, 06:43:00 AM »

Quote

Originally posted by juzz:
I think Pyro once said that the synchronised weapons in AH fire at about 15% reduced rof. So if they use 700rpm for the MG 151/20 as indicated in the pic above, 15% reduction = 595rpm.

Not as bad as that - the synchronisation system of the electrically-primed MG 151 was very efficient. 650 rpm would be closer.

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website: http://www.users.globalnet.co.uk/~autogun/index.htm

flakbait · « **Reply #6 on:** February 20, 2001, 08:12:00 AM »

Funked, what do you mean by best case and worse case are reversed? At 26 frames a second the game is running a bit faster than a normal movie (24 fps). I've got an idea, run the same test I did and tell me what you come up with. Both on the Bf-109 and the Fw-190. If I'm wrong then this thread was just a confirmation things are running fine. If I'm right then something needs to be fixed. This isn't exactly a national emergency, or something along the lines of the Hispano Mk XXX Turbo-Laser debates. Just a goof that cropped up on my end.

Tony, either way the RoF looks off. My quick test showed an average of 440 rpm for the Fw-190. That's only about 200rpm short. FR varied between 17 and 21, which should be fast enough.

If indeed the game depends on frame rates to fire at the specified rate, then we have the rubber bullet problem WB 2.6 had. Bullet strikes depending on FR; if your FR was low or average you'd get about half the damage someone running a faster machine would sustain.

-----------------------
Flakbait [Delta6]
Delta 6's Flight School
Put the P-61B in Aces High
"For yay did the sky darken, and split open and spew forth fire, and
through the smoke rode the Four Wurgers of the Apocalypse.
And on their canopies was tattooed the number of the Beast, and the
number was 190." Jedi, Verse Five, Capter Two, The Book of Dweeb

-lynx- · « **Reply #7 on:** February 20, 2001, 08:33:00 AM »

Can someone please explain how this syncro stuff works?

Say, ShVAK firing through 3 bladed prop should be firing at 1/3 of the engine RPMs, should it not? I cant get this ROF from an AH's La5...

funked · « **Reply #8 on:** February 20, 2001, 08:49:00 AM »

Flakbait, I read your post wrong, sorry.

Jekyll, how do you insist on a 740 rpm figure in the face of contradiction by a primary source and a guy who has forgotten more about automatic weapons than you and I will ever know. Oh yeah, I forgot, you saw it on the web so it must be true.

funked · « **Reply #9 on:** February 20, 2001, 08:55:00 AM »

We already covered all this. http://bbs.hitechcreations.com/smf/Smileys/default/Forum9/HTML/001368.html

The ROF for MG 151 are correct, notwithstanding any frame rate effects which I have not been able to measure.

funked · « **Reply #10 on:** February 20, 2001, 11:21:00 AM »

PS I need to read before I post. I think flakbait's main thrust here is that we have some kind of rate of fire decrease with low frame rates. If this is happening we need to document it and it needs to be fixed. I'll try to duplicate it.

Tony Williams · « **Reply #11 on:** February 20, 2001, 01:46:00 PM »

To

Quote

Originally posted by -lynx-:
Can someone please explain how this syncro stuff works?

Say, ShVAK firing through 3 bladed prop should be firing at 1/3 of the engine RPMs, should it not? I cant get this ROF from an AH's La5...

It doesn't necessarily work quite like that. The US 1930s synchronisation system only gave one opportunity per prop rev to fire, so if the prop was spinning at 1,200 rpm (typical) and the gun was firing at exactly that rate, in theory the rate of fire shouldn't be affected. On the other hand, if the gun could only fire at 1,000 rpm then the firing rate would become slower, and somewhat irregular.

In practice, of course, the rate of fire of any particular gun would vary, and so would the propeller revs, so the RoF of a synchronised gun was not constant.

I have some data from postwar RAF studies which shows that for a 600 rpm gun, a loss of around 6% could be expected on average; it would be double this for a 1,200 rpm gun.

The actual loss of rate of fire depended on the synchronisation system. The US one wasn't very good (well, the USAAF made very little use of it) and neither was the Soviet one; the 12.7mm UB managed up to 1,050rpm unsynchronised but only 800 rpm synchronised. The German system was much more precise (it used direct electrical contact to the primer) so resulted in less of a reduction.

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website: http://www.users.globalnet.co.uk/~autogun/index.htm

Lephturn · « **Reply #12 on:** February 20, 2001, 01:57:00 PM »

Funked:

My only note is that you should make sure you have NOT disable V-Synch. That is, V-Synch should be enabled. I'd be interested to see if enabling or disabling it would change the results.

------------------
Lephturn - Aces High Chief Trainer
A member of The Flying Pigs http://www.flyingpigs.com

Check out Lephturn's Aerodrome!

"Nothing is so firmly believed as that which we least know." - Michel Eyquem, seigneur de Montaigne. (1533–1592)

Pyro · « **Reply #13 on:** February 20, 2001, 04:05:00 PM »

RoF on the 151/20 in here is 700. Synched guns are using a standard 10% reduction. If that rate isn't being met or is varying with framerate, the gun could be set up incorrectly. I had that problem on the panzer's MGs that was fixed last version. I'll take a look through the planes and make sure none of them have that same problem.

------------------
Doug "Pyro" Balmos
HiTech Creations

LLv34_Snefens · « **Reply #14 on:** February 20, 2001, 04:10:00 PM »

If there are no limits on the fire per prop rev like the early US versions, wouldn't the actual loss of ROF be more a function of the ratio of entire prop-dish that are blocked by the propellers (at the position the guns pass the dish) than their rpm?

As I see it this holds true if one of either ROF or rpm is high enough. Question is if the ROF's and RPM's we have are at that height.