Friday, February 03, 2006

What about .45 GAP?

In my post "Why no .45 from Browning" I mentioned that I would kill to have a Browning HiPower in .45acp; but unfortunately you can't do it without making the pistol just a bit larger, and a good bit stronger.

A commenter posits the question:
"What would making a BHP in .45GAP give us in terms of

1. modifications to the design

2. Ballistics compared to the .357SIG and .40S&W


Which is a pretty good question, because the point of the .45GAP, is to allow for a .45 caliber pistol, with standard .45acp ballistics, in .40S&W sized frames.

The immediate tradeoff of the GAP is of course you lose a round in capacity to the .40; and that's if your slide has enough clearance, and enough strength with the thinner metal over the sides that it would necessitate.

It's no coincidence that Glock came up with the .45GAP, because it has some of the strongest pistols ever made, and theres PLENTY of clearance and thickness of metal in it's slides.

The problem is the case head dimensions on the GAP are still too large to feed in a standard BHP breech face. The Browning slide is about as thin as you can get for the .40. I'm not sure exactly how much wiggle room there is left in the .40 BHP slide for this; but it can't be much.

Hmmm... though with the external extractor it may not be as big a deal as in say a 1911, and the .45gap is still a low pressure round in comparison to the .357 sig...Honestly, I'd need to know the metalurgy a bit better, but I don't think it would work. The early production .40's had slide cracking problems already (though they were fixed with improved heat treating).

So, to chamber the .45GAP safely and reliably, we'd still need to thicken the slide just a bit (call it .05" probably).

The thing is though; I don't think the .45GAP would even be an improvement over the .40S&W

How can that be? Pressure. The .45GAP is very near it's pressure ceiling giving .45acp ballistics out of a much shorter case than the ACP. There isn't a lot of room voer velocity improvements, even in the lightest bullet weights.

The same is not true of the standard pressure .40S&W. In fact theres a HELL of a lot of overhead in the round; presuming a gun designed to handle it.

Given this, a hot and heavy +p .40S&W gives a lot more energy (165gr at 1250 fps 572ft/lbs) than the hottest .45GAP factory load (185gr at 1050fps for about 450ft/lbs).

Actually (and this is proven in street statistics, not just ballistics numbers) +p .40 is a better stopper than standard pressure .45acp in light bullet weights (say 165gr .40 vs 185gr .45). Theres only going to be a 20gr difference in bullet weight at that point, and only a .05 diameter increase with a velocity around 1050fps and 450 ftlbs ... Yeah, I'm giving the edge to the .40.

Now this is just taking standard pressure loadings of the .45gap vs. +p loadings of the .40 so is that fair? Well, yes; because there isn't a lot of headroom for the .45gap to push without running into serious pressure problems so there ARE no hot +p loadings, and there won't be (because there CAN'T be).

The same isn't true of the .45 ACP; which in +p loadings stomps over the .40 quite handily.

In a modern, properly prepared gun chambered in .45acp with a fully supported chamber and a heavy recoil spring, you can get 1050fps out of a 230gr bullet without too much of a strain (there are factory loads available), and handload up to 1150fps at the same weight if you are careful (though I wouldn't recommend it - SuperVel used to do it, but it was well over max pressure).

We can make more direct comparisons to the .40S&W by going down in bullet weight to the lightest standard .45acp (or .45GAP for that matter) at 165 gr. which is also the heaviest standard bullet for the .40.

With a bullet that light and a properly prepared gun, you can push 1350fps out of the .45acp without danger (from hot factory loads no less) for almost 670ft lbs, and handloaders have taken it to 1450fps (and 770ftlbs) but I think they're nuts. This is in comparison to about 1150fps from the .45GAP, and 1250fps for the .40.

The GAP comes off even worse in comparison to the .357sig. The only advantage the GAP has over the .357 is bullet weight and diameter. Of course thats a significant difference (about 40gr minimum, and up to 115gr maximum and .09 inch), but I'm still giving the advantage to the .357 over the GAP.

Considering the track record of ballistically identical loads to each, there is no question as to which is the better stopper, AND you'll have 1 more round of the .357 available to you.

I won't say the .45gap is useless, clearly it has decent defensive potential. What I think it is, is the new .41AE. Sure it's good, but it's redundant and doesn't give any advantage over the other options.