Rate of fire is what makes the p39s cannon so terrible. Its trajectory is actually pretty flat compared to the mk108s ballistics.
Seems like shooting can be a lot more involved than just eyeballing it if ya really get into it.
Yes, you can really learn some things about certain guns and the effects of your convergence settings by testing in this way.
I went ahead and did some quick tests with the P-39Q using only the M4 37mm gun. As Glz said above, it does fire "pretty" flat (especially as compared to the MK108 30mm), out to about 400 yards. However, there is still some "lobbing of the round" involved, especially at longer ranges.
I used a convergence setting of 300 yards. After observing fairly flat firing patterns at closer ranges, I started firing at targets at 600 yards and again at 800 yards at altitudes of 5K and 15K and speeds from 275 to 300 mph to determine the proper aim point at those various distances, alts and speeds. Once I knew the approximate aim point for those 2 ranges, I cleared the target, then fired 60 rounds in single shots to see what kind of dispersion I would get at those ranges (with the desired impact point being just below the bulls-eye).
In the screen shots below you can see what those bullet groupings look like. The screen shot is taken with the pipper on the proper aim point for that range. The targets were both brought in to 300 yards (after shooting the target at 600 and 800) so that the hits would be more visible. For reference, I also superimposed a Dora on the 600 target and a Dora and Lanc on the 800 target, so you can get an idea of what rounds would hit a fighter or a bomber at those distances.
My observations: Try to shoot in close. 200-300 yards is best. This is a good rule of thumb all of the time. If you are shooting at long range, you need to be aware that you are wasting considerable ammo.
With a clip of only 30 rounds for the M4 in the P-39, it probably isn't worth it. That said, if you can live with shooting a considerable portion of your ammo to get a kill, it can be done at longer ranges.
I would say with practice and decent aim you could reliably hit a fighter in level flight dead six ("extending from you") at 600 yards with maybe 40% of the rounds. At 800 yards, however, only 20% or 1 in 5 rounds fired would hit a fighter dead 6 profile (I estimated 12-14 hits out of 60 rounds in my test and that was aiming
very carefully). However, a Lancaster bomber could be consistently hit out to 800 yards. I didn't test at 1000 yards, but it might be something you could try, using the methods I just described, if you wanted to bomber-hunt in the P39-Q. Be sure to test at "bomber altitudes" as well. An easy way to do this is to select the TA (Training Arena) terrain for Offline mode and use the 20K or 15K bases in the bottom left of the map (Field 34, for example).
Another observation is that it is
important to be wings level when lobbing rounds out at long range. I've noticed this with the K4, but also observed it while doing this testing with the P-39. If you are rolled just a small amount (under 5-degrees) the lobbing effect will amplify this bank angle and cause the round to "sail" out to the left or right. You can see a few rounds outside the inner (20 foot) circle on my 600 yard target - these were rounds that sailed off to the left because I was "rolling into the shot" just a slight amount. Factors such as bank angle, nose-bounce and yawing are exaggerated with range, so it makes long-range sniping even harder and less efficient (another reason
not to try it without considerable practice and understanding of the waste of ammo that results).
Hope this is a helpful example of how to conduct and use this kind of testing.
<S>
Ryno
