I keep looking at YouTube channels that talk about semi-autos for bear protection.
One of the channels is from Buffalo Bore ammo. Tim the owner of Buffalo Bore, talks up the 45 acp +p load as sufficient for this purpose.
He praises the 45 Super but only mentions its use in a 45 1911 or a HK made pistol.
I have a first generation Sig P220ST and wonder if its strong enough to take a 45 Super load with a switch to a 24# recoil spring.
Does anybody have experience in this?

I don't live in Grizzly country or even plan on going anywhere to encounter "old Grizz". I'm just looking to find new purpose for the P220ST on occasion. I would not want to do anything that would harm it.

As I always now say, this is no sort of recommendation, but I did see a friend fire a few rounds of 45 Super with his non-ST P220 and nothing bad happened—as far as I know. I thought it was risky, but had/have no reason for that other than the cartridge was much more powerful than what the gun was designed for.

I personally would be much less concerned with a steel frame pistol. Although I haven’t seen many reports of SIG Classic line aluminum frame guns failing, it’s usually because of rails cracking and separating from the frame. I do not know, though, if the gen1 P220ST differs in frame design from current models.

As you probably know, the P220 pistols chambered for 10mm have steel frames, and although it seems that most commercial 10mm Auto loads these days are loaded to pretty wimpy levels hardly exceeding 40 S&W, presumably the guns must be capable of handling the real deal. I’ve never tried to compare a full-power 10mm load with 45 Super, but that might be something to do.

And now that you mention it, I do have a DAK P220ST that I could try some of the Super in. We do have mountain lions and black bears in our county and possibly where I walk in the remote areas.

At one time I was thinking of getting a 10mm P320, but decided against it based on the pitiful state of 10mm ammunition. But a more potent P220ST—? The worst (probably) that could happen is that I’d end up with a broken gun that my heirs wouldn’t have to deal with.

In your situation, though, I would only ask Why? if you don’t need it.

A quick search [I'd never heard of 45Super] makes the 45S sound like a +P variant of 45ACP?

The Brave summarizer says 45S is around 28k PSI, with 10mm having slightly higher velocities.
10mm for better penetration, 45S for larger wound channel.

Since you have the 220 already, if you have 45S availability, sounds like the way without having to convert or buy a 10mm for similar performance.

But, I'd look for some more knowledgeable sources to verify the 45S is safe in the 220.
I'd think if the 220ST can handle 10mm, and if the web seems to say the G21 or 1911 can do 45S with just a recoil spring change, it [the 220ST] should handle 45S as well.

Although people tend to look at chamber pressure when trying to decide if a load is okay to use in an autoloading handgun, unless pressure is high enough to blow up the gun, what actually matters is slide speed because that’s what affects the frame and slide. Slide speed is mostly dependent upon projectile momentum.

A way to compare momentum is to use the power factor formula: bullet weight times velocity divided by 1000 (the last to get a more manageable figure). That doesn’t give us a physics classroom result, but for comparison of one load with another it’s fine.

For comparison, I asked the Internet (trigger alert) for hot 10mm and 45 Super loads. One 10mm load was a 220 grain bullet at 1200 feet per second; that produces a power factor of 264. One 45 Super load was a 230 grain bullet at 1130 fps for a PF of 260. Another 45 Super was a 255 grain hard cast bullet at 1075 fps, PF 274. Even at the outsides, the PF of the hotter 45 Super load was only about 4 percent greater than that of the hot 10mm.

Thanks for your insight.
The failures I read about had to do with the standard P220 splitting at the rail. The P220ST is a tank but I don't want to needlessly sacrifice it experimenting with it.
I doubt I would get any unbiased advice from Sig as I'm sure they will follow the liability line.

I just find it fascinating that without buying a 10mm pistol I could easily swap a recoil spring and have a round that could match or exceed the 10mm in performance in a pistol I already own.

I will send an inquiry to Tim Sundles at Buffalo Bore and see what he has to say about the P220ST and 45 Super loads that he manufactures, or the 45+P loads that he makes.

Maybe an email to Grayguns?
Since they did the work for the 10mm 220ST, maybe they'd have some insight on fhe 45S too.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Great idea!

I would think that adding a comp would mitigate a lot of issues. Its what is required to safely run 45S in an FNX Tac 45

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I do have a comp for the gun and the longer barrel from the P220 Sport.

I took the advice mentioned here about contacting Bruce Gray, I heard back from his shop today.
They advise to NOT fire the 45Super in the P220ST.
There advice comes from the use of the 24# recoil spring. The 24# spring is not the problem on recoil but is a problem when it slams the slide shut. It was also mentioned that racking the slide with a 24# spring would be diffucult.

I was told that Bruce has several .400 Corbon barrels in stock and this might be a better approach.