A friend recently mentioned that he had tried out some “sub-sonic 9mm ammo” that was supposed to be good for use in USPSA Production class shooting. He asked me what I thought, which resulted in the following response.
Before I comment on subsonic ammo, a few words are in order:
As a competitive shooter, one of the key reasons for reloading is to work up a tuned round specifically to work with one’s tuned pistol to produce shots with little felt recoil that still achieve minimum power factor for the division one is shooting. In our case (Production division) everyone is scored Minor Power Factor (MinorPF), so there’s no advantage to loading higher than that. Minimum MinorPF is 125. This is Mass (bullet weight in grains) times velocity divided by 1000. So, if you are shooting 115gr bullets at 1100 feet-per-second that equals a PF of 126.5, or just over the minimum for Minor. Most factory ammo is hotter than this, which results in a higher PF but also much greater felt recoil. Shooters desiring less recoil and more control can achieve this by trading velocity for bullet weight.
I shoot 124gr bullets with a relatively small amount of a hot powder (TiteGroup). At 1050fps, this makes about 130pf, which is comfortably above the minimum yet is significantly softer than typical factory ball ammo. The fast-burning powder makes the recoil impulse less, especially with the heavier round. Now, with this round I can switch to a lighter recoil spring, which means less force to cycle the gun, less wear and tear and again, less recoil and overall movement of the pistol. All this adds up to a highly controllable shooting experience. Just watch my muzzle flip versus yours in our videos.
So, what about subsonic 9mm? Any round traveling slower than 900fps (roughly) will be slower than the speed of sound but in order for that round to be “legal” in Production, the bullet weight has to make up for the low velocity. The common 147gr round made by many/most manufactures of 9mm ammo is in fact often subsonic right from the factory. For reloaders, you simply reduce the powder load accordingly and voila, the softest shooting 9mm round possible. Dave Sevigny shoots 147gr bullets, as do many of the top-level shooters. The only down side is that the slide takes longer to cycle and you will probably have to go with light recoil springs if you want the gun to function correctly. So are these the best rounds to use as match ammo? As with most of life’s questions, the answer is “it depends”. I tried loading some 147gr rounds and found them very easy to shoot but the difference between those and the 124gr rounds was negligible yet the cost was substantially greater for the heavier rounds. So for me it’s not worth it to shoot the 147gr bullets at this point. When I’m straining to get to GM status perhaps I may change my mind. However, this has nothing to do with the subsonic nature of the round per se.
Re: the use of a particular round for Match Ammo: Personally I practice with the exact same ammo that I will shoot at matches. The only difference in my “match” rounds is that I make those with the best brass I can find (usually once-fired, name-brand cases) and I typically take a bit more care in the loading and inspection than I do with “practice” ammo. However they are the exact same bullet, powder (type and weight) and primer. I think that using different ammo for practice versus matches would be counterproductive.
So, there you have it.
Indeed.
Firearms4u 
In the second italicized paragraph you write “Most factory ammo is hotter than this, which results in a higher HF but also much greater felt recoil” but just above that you had said that production division always scored MinorPF — if that is so why would you get a higher HF?
Secondly, the lower velocity would increase drop to the target. Am I right in assuming this is negligible at the distances involved?
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Hi Peter
I must apologize. The reference to “HF” was supposed to be “PF”, or Power Factor. I have corrected the text accordingly. “HF” usually means “hit factor”, which is the term used to refer to USPSA scoring.
The gist of the matter is that if you test most factory ammo it will give a PF well in excess of the 125pf rating needed to achieve MinorPF. Most factory ammo will yield a 140-150pf, and even higher for the heavier rounds made with heavier bullets. Since Production class is always scored minor, there’s no point in loading above the minimum. In fact it is best to load as close to the minimum as you can. The idea is to achieve the softest, most controllable round you can, provided it cycles the gun properly, is stable in flight and of course, still makes 125pf. I’ve seen rounds loaded too soft that would not fully cycle the action and/or allow the bullet to fly erratically.
Your second point is correct. The amount of bullet drop at typical USPSA distances (10-75 ft.) differs very little between the rounds we are discussing, especially given the relatively tall A zones on our various targets.
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