Fitting oversize slide stop with help from John Harrison

GRPfan · 2025-09-21T14:12:27-0400

John Harrison, in addition to being one of the premiere 1911 gunsmiths ever, is truly a gentleman, always happy to help. He customized my favorite pistol, by far, with a retro project I commissioned in 2006, which you can read about here (photos, of course).

Harrison retro customized SA Milspec

When my son graduated from college I sent him an SA Marine Corps Operator (third iteration, sadly discontinued) and asked him to do whatever he felt necessary and here was his invoice list.

Harrison Invoice said:
H-D Extreme Service oversize firing pin stop, carbon steel S-70, fitted

Machine for "bow tie" clearance cut on frame bridge VIS

Harrison Design Extreme Service extended magazine catch, blue

Installed HD Extreme Service tool steel ignition set featuring slotted Commander hammer finished in IonBond DLC, basic trigger job, 4-1/4# trigger pull

Extreme Service Hammer Strut

H-D Extreme Service extractor, carbon steel S-70

H-D Extreme Service 11 pc. pin set 4140 bar stock hardened to 40RC, blued

Wolff 16# Gov't model recoil spring

Wolff X-P firing pin spring

Wolff plunger tube spring

Wolff #2 reduced power magazine spring

The gun shot wonderfully, you haven't lived until you've experienced a John Harrison trigger job. But just because I wanted to try some projects, I fitted one of the radial-bored barrel bushings John sells last year, and that project was very much fun and very effective. A few years ago I had installed a Wilson Combat Bulletproof slide stop, also, but the gun was so tight it was difficult to start to rack the slide, and while after a couple hundred rounds it began to function well but would not quite go 100% into battery. It wasn't dangerously out of battery, but you could not put the safety on without tapping the slide to get it to go that last maybe 1/32".

I read some threads here and elsewhere about other who had this problem, and most responders suggested getting a new slide stop rather than trying to fix it. I emailed John about it wanting to get a slide stop from him, but after I explained the problem, he sent me this reply, and I quote."

John Harrison said:
Well, John, the fix is to have the correct diameter slide stop shaft, to work with your frame, slide and barrel. From what you’re telling me, all you really need to do is to shoe-shine sand the outside diameter of the shaft from about 12 o’clock around to about 3 o’clock With 12 being straight up and three being straight toward the rear.

I hold the slide stop between my pad, advice jaws, reaching from the tip of the shaft to the other side of the slide stop, with the shaft oriented to allow me to sand with a strip of sandpaper about 1/2” wide. You don’t have to sand all the way through the length of the shaft, just the section where the barrel feet are touching. Something around 180 to 220 grit will work fine. Just sand a little, wipe it off and test fit it And keep doing that until you reach the point where you have free operation.

If you don’t wanna get into that and just wanna replace the slide stop, if you can measure the pen, diameter, accurately, like with a micrometer, I’ll be glad to see if I can pick one out. That is just a hair smaller and send to you.

But honestly, if it were my gun, I would sand it.

Best Regards,

John Harrison

Harrison Design
770-419-3476

1911 Parts - Shop.HarrisonCustom.com

Many of the other threads I read suggested it is difficult to reduce the pin on a slide stop evenly and it's easier to just get a new one. John's email immediately made perfect sense to me--the area he's suggesting sanding is the part of the pin that contacts the slide lugs. No need for the pin to be perfectly concentric, just don't sand the part that fits in the frame holes. So, I did just that and it worked out perfectly. I went slow, four trips to the vice, got it nearly where I wanted it, then put 50 rounds through it yesterday and today touched it up with some 320 paper and it is just perfect now. Here are some photos of it.

I imagine this is a pretty simple and stupid project to be posting in here with the level of expertise here, but I was so grateful to John for explaining it in a way that made me confident I could do it. John turned this into an amazing pistol, I just had a little fun, but I can confirm it is more accurate than my buddy's Garrison which I also shot yesterday.

With the parts, I know have about $1,800 into this gun, and with inflation since 2017, I'd guess that's about $2,300 in 2025 dollars. But, this gun, IMO, is about 95%+ equal to a Nighthawk or Wilson, at about half the price. I own a Wilson, and have owned a Nighthawk, so I'm not talking through my hat here. Sincere thanks to John Harrison. His parts are loved here, please continue to use them.

megafiddle · 2025-09-21T22:52:20-0400

Nice job.

Interference of that type can be often be due to just a tiny amount of extra metal, possibly less than a thousandth. If this were a barrel that was being fitted, the lower barrel lug would be fitted to the slide stop pin instead. But since the barrel had already been fitted at the factory (to whatever extent they do that), sanding the slide stop pin is a reasonable solution.

I would check that the barrel lower lug is fully engaging the slide stop pin when fully forward in battery. Remove the barrel and insert the slide stop pin into the link. Position the slide stop lever to the rear, just as it would be when assembled in the gun. Make sure that the slide stop pin will swing on the link into firm contact against the rear of the lower lug.

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GRPfan · 2025-09-22T11:18:49-0400

@megafiddle Done! Looks fine. And agree, I doubt I took more than a thou off in this operation, two, tops. I don't know how much this may have improved accuracy, probably not a lot, I think most improvement comes from the tight barrel bushing, but this is a wonderfully accurate gun, that's for sure.

passx · 2025-09-22T11:26:22-0400

I generally dykem blue or use a sharpie to mark the lower barrel lugs to check for the slide stop pin contact. I believe that most accuracy is achieved through a tight barrel bushing where I try to fit the I’d to about .0005in loose on the barrel and as close to a line to line fit on the od and still get the bushing in and rotate it..

You also want as tight a fit between the barrel hood and the breech face and still get the barrel to properly engage the barrel to slide lugs .
IMHO, the slide stop pin is a big part of the slide to barrel lug engagement , the pin works against the barrel feet to hold the barrel in the slide lugs, the barrel link length is part of this as well. If you get it right the slide will move freely and go into battery easily.

It all needs to work together, get it right and you’ll have a nice running very accurate gun.

One thing I’ll add is when I sent my 5” SS Range Officer back to Springfields Custom Shop for poor accuracy and bad fte’s and ftf’s, they did an accuracy job on it ($430) where they put in a new match barrel (whatever that means) along with a new tightly fit barrel bushing and a new tighter slide stop . The gun came back (and still is) way more accurate that me but I had to press the muzzle against the bench to break the slide to rack it. Should’ve sent it back but I played with the link a bit for length and pin fit and got the slude to work pretty well still with great lockup..

The only problem I had was there was a distinct catch/hesitation in the slide function and what I found was that the slide stop was a MIM (poor quality) part that had a large mold line on the pin that caused the bump. I polished this down and had a really nice and smooth slide action and with care and much measuring was able to keep things very tight fitting. Now about 10k rounds later this gun is still way more accurate than I am capable of delivering. One of my absolute favorites ! Again you need to look at everything.

GRPfan · 2025-09-22T12:05:16-0400

Thanks, @passx I appreciate the response. This place is such a great place to learn. I had that "catch" as you put it, hard to rack the slide, but now it's perfect and pin to lug contact is good. And the WC bulletproof part has a great reputation. I got the radial bushing from John Harrison, those are also well thought of. This thing is a tack driver, just tested it with 50 rounds after my fix, shooting off my backpack and it's very accurate now.

I think this gun is DONE!

Fitting oversize slide stop with help from John Harrison

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