When I first decided to convert one of my 1911s years back, the recommended steps were easy enough to understand: stronger recoil spring to absorb the extra power, stronger firing pin spring to prevent doubling, and maybe a buffer cushion system to protect the frame. Lately I've noticed people mentioning an additional step: a flat-bottomed firing pin stop. Can somebody fill me in on this: exactly what do they mean by that and how exactly does it help?

I think I'd actually call it the firing pin retainer - it's the flat plate at the back of the slide that holds the firing pin (and extractor) in place. It has a curve on the bottom back edge to lessen friction against the hammer when the slide goes back. The theory is that a square edge will increase friction some when rubbing against the hammer during firing, and so slightly lessen slide velocity. I'm not sure that I buy it, but that's the idea.

Thanks a lot, Tom! Your explanation makes it quite clear, and I think I agree with your analysis. Makes me think I'm OK with the springs and buffer.

The use of the flat bottom firing pin stop plus a heavier main spring will delay the initial rearward movement of the slide when the cartridge is fired. This acts to delay unlocking of the barrel and slide and also reduces the need for obscenely heavy recoil springs.

For the Colt Delta Elite (10mm Auto), it was recommended to have a 1/16" radius on the bottom of the firing pin stop, a 25 pound main spring, and an 18 pound recoil spring. This created slide to frame impact and barrel to slide stop pin impact forces similar to firing standard 45 ACP loads. I would think this would be a good setup for 45 Super as well.

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VCDL, GOA, NRA

The firing pin stop upgrade absolutely does what it's supposed to do and it (in concert with a heavier hammer spring) can slow the slide velocity more and better than any recoil spring is physically capable of doing.

And just to clarify - I don’t think it’s actually “friction” that the stop provides; it’s more that having a non-rounded profile changes the mechanical advantage so that the hammer gives more initial resistance to the slide as the slide comes back.

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Uvidíme se později, aligátore.

I looked into this some years back, but unfortunately received so much conflicting information on the subject, along with crooked gunsmiths who were actively trying to discourage D.I.Y. conversions, that I ultimately ended up just buying a H&K USP45 instead since those can fire .45 Super without any modifications required.

One thing that a lot of folks claimed back then which is less common now is that you need a ramped barrel with a fully supported chamber to safely fire .45 Super, but that may have been more nonsense being spread by crooked gunsmiths to discourage D.I.Y. so that folks would hire them to do conversions instead.

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Shooting Comfort is bilateral.

When J.M. Browning designed the M-1911, he initially designed it with a flat bottom firing pin stop. It was the cavalry that complained about it being too hard to rack the slide to chamber the first round from the magazine while controlling the horse that lead to the generous radius we see on the M-1911-A1 and nearly all commercial production 1911 style pistols. The original M-1911 also used a 14 pound recoil spring, but with the change in firing pin stop design, a 16 pound recoil spring was required.

Barrels with a fully supported chamber and integral feed ramp in the 1911 came from IPSC/USPSA competition shooters loading the 38 Super to meet the 175 power factor required at the time for major caliber scoring. All too often, those over-pressure 38 Super cases would suffer case head rupture with the standard, unsupported, 1911 barrel.

Does the 45 Super require a fully supported chamber? Probably not and the large diameter chamber often cuts into the top portion of the supported barrel's integral feed ramp, giving it marginally little more chamber support than a standard 1911 barrel. I would recommend using Starline 45 Super brass as its case head is stamped "45 Super", making it easier to distinguish Super loads from standard 45 ACP loads. Their 45 Super brass is made from a different brass alloy and is heat treated to further increase its ability to withstand 45 Super pressure levels.

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VCDL, GOA, NRA

That makes sense - thanks for the clarification.

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I converted my Colt Government 1911 Mk.IV Series 70 many years ago by going the heavier hammer spring, recoil spring & EGW small radius firing pin stop route too.

I've never fired any commercial 45 Super ammo but I can tell you at what point in working up 45 Super loads using HDY 185gr XTP & Power Pistol that the Starline 45 Super brass will start to bulge because of inadequate chamber support.

Years later when I got the 3rd Gen bug I found my M4506 had no issues handling the same loads that bulged in the Colt.

Starline brass is strong enough but there's no replacement for chamber support.

A heavy hammer spring in a 1911 makes little difference in trigger feel if you started with a good trigger but in a 3rd Gen you can feel the effect of a heavy hammer spring right away.

Fortunately only a little extra spring is needed in the 4506 for 45 Super.
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Waiting for the break of day

Does the flat bottom firing pin stop not cause excessive wear where it meets the slide? I always find myself polishing the radius to improve function. Maybe that isn't always a good thing to do.

Rosewood

The firing pin stop fits in the slide, so it should not cause any wear to the slide. Does it cause wear on the hammer shank? I do not think it will so long as there is not a sharp edge on the bottom of the firing pin stop and there does have to be the tiniest bit of a radius, hence the 1/16" radius recommendation.

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VCDL, GOA, NRA

Your image on the left shows a very small radius, but your image on the right incorrectly shows a 1911-A1 style radius stop as "non-radiused".

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VCDL, GOA, NRA

I had a crainial air explulsion, I meant would it cause extra wear on the hammer and itself?

Rosewood

As long as there are no sharp edges and a tiny radius, no. Well, it could if you are using a cheap hammer than is made of a softer grade of steel.

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VCDL, GOA, NRA

The two slide stops in the image half on the right was (originally) meant as a comparison of a new (non-radiused) EGW slide stop (left) -vs- a factory slide stop (right), if I remember correctly, now that I look at it closer?

It was taken a long time ago & I've slept since then.

I though I had some better pictures but these are all I could readily find.

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Waiting for the break of day