10mm Bushing Fit Questions

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Hi Gang,

Parts are dribbling in for my twin 10mm commanders project. I have some questions about my Colt stainless match barrel; to wit, the barrel shaft O.D. is 0.540 until about the last 0.562 toward the muzzle where it gently swells to 0.550. Being new to the 10mm I’m not sure what to make of the range of bushing I.D.’s I’m finding out there. I get it that many, if not most high-performance guns now use a bushingless barrel, but it's still a debate and I fall on the "wear out the bushing, not the barrel" side. Anyway, the bushings I can find on line seem to fall into three main I.D. camps; the 0.580’s, the 0.570’s, and the undersize “old Colt 9mm” -style at 0.489 – 0.500. Bushings don’t seem to be categorized by caliber in the 1911 parts groups but only as “government” or “commander” or “officer”, “defender”, etc. so by length and not so much by I.D. The barrel is overall a tight-ish fit in the Fusion slide that arrived for the evil twin with the aluminum frame. Although there is room for a bushing, it sure ain’t the generous (not to say sloppy) fit you normally see with a .45 barrel and slide without the bushing. So I’m fairly sure the Colt barrel profile is correct for 10mm but what do folks do for a tight bushing in 10mm? I’ve been all over the online vendors (Brownell’s, Midway, Sarco, Numrich, EGW, Fusion, and Dawson Precision) and no hint at all there. The closest I might’ve come is an RIA commander bushing at Hooper’s that also works for the 22TCI barrel (?), and a SIG/Sauer 1911 commander bushing that is a “gunsmith fit” item at Midwest Gunworks. I don’t mind inside/outside turning a bushing, but Kuhnhausen (Vol.-1, Book One, p.44) states a barrel’s total clearance of 0.001 is desirable for a service pistol; I’m not sure even a “gunsmith fit” bushing from say, the 0.570 group won’t be 10-15 times that with this barrel! Many thanks for your comments.

Cheers, and Best Wishes to the Forum for the New Year!

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[harrygunner]

EGW will cut a bushing for your barrel. Measure the outer diameter of the end of the barrel and provide that to them with your order.

FYI, when I had my custom 10mm Commander length 1911 made, I sent it to Bar-Sto. They milled the frame, made a ramped barrel for the gun and fitted a bushing to that barrel.

 

[edwardware]

@harrygunner beat me to it. Call EGW, discuss your needs. They've been quite helpful in the past, and do good work.

 

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Harrygunner and edwardware, thank you so much! I guess soon 10mm parts will become more ubiquitous but for now, it reminds me of when I built my first 9mm and had to adapt 45 parts and make yer own to suit! So EGW it is.

 

[harrygunner]

Thought I'd add more info. In your original post, you mentioned measuring the barrel diameter at a few locations. The muzzle end of the 1911 barrel has the greater diameter. It decreases a bit as you move toward the chamber end to allow the barrel to tilt during recoil.

That's why I said send EGW the measurement at the muzzle end for a tight fit when the gun is in battery.

One nice thing about the 10mm 1911 is only the barrel chamber and the magazines are "10mm specific". Everything else is a mix of .45 ACP, .40 S&W and 9mm.

So parts are readily available for your project.

Unsolicited advice, I went with a STI forged stainless steel Commander length .40 S&W slide. After researching many opinions of respected gunsmiths, I agreed with their collective opinion that the slide on a 10mm gun needs to be strong.

Don't know if this is on your list for your build, but I'd also suggest you add a flat bottom firing pin stop to your EGW order. You'll have to fit it to the gun. But it will slow the slide earlier in the recoil sequence. That effect makes feeding rounds off the magazine more reliable. A Commander length 10mm slide can move so fast ammo can stay in the magazine since there wasn't enough time to strip the round out the magazine. I also stayed with 18lb recoil springs.

My gun has fired real 10mm ammo with 100% reliability, once everything was worked out, for a decade. So, it can be done.

Hope you enjoy your project.

 

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Thought I'd add more info. In your original post, you mentioned measuring the barrel diameter at a few locations. The muzzle end of the 1911 barrel has the greater diameter. It decreases a bit as you move toward the chamber end to allow the barrel to tilt during recoil.

That's why I said send EGW the measurement at the muzzle end for a tight fit when the gun is in battery.

One nice thing about the 10mm 1911 is only the barrel chamber and the magazines are "10mm specific". Everything else is a mix of .45 ACP, .40 S&W and 9mm.

So parts are readily available for your project.

Unsolicited advice, I went with a STI forged stainless steel Commander length .40 S&W slide. After researching many opinions of respected gunsmiths, I agreed with their collective opinion that the slide on a 10mm gun needs to be strong.

Don't know if this is on your list for your build, but I'd also suggest you add a flat bottom firing pin stop to your EGW order. You'll have to fit it to the gun. But it will slow the slide earlier in the recoil sequence. That effect makes feeding rounds off the magazine more reliable. A Commander length 10mm slide can move so fast ammo can stay in the magazine since there wasn't enough time to strip the round out the magazine. I also stayed with 18lb recoil springs.

My gun has fired real 10mm ammo with 100% reliability, once everything was worked out, for a decade. So, it can be done.

Hope you enjoy your project.

harrygunner you are a pioneer of the 10mm solving these problems 10 years ago! When I floated my build plans in my siiick firearms thread, I was being provocative to stimulate responses in case my critical assumptions were in any way questionable. I got back very little information but some support and caught some heat and approbation. Your post changes that and now I have more questions. This Colt 10mm barrel is the first one I've ever seen with a slight swell at the muzzle -all the rest, including my Colt 9mm have been straight tubes. Your post has it that the relief back of the muzzle is to give the barrel a chance to angle up and down/down and up again through the recoil cycle. I've always believed that the loose-fit straight-through bushings and the tighter fitting, relieved-angled bushings took care of that. I thought the lump at the muzzle was a "gunsmith fit" feature but the lack of anything remotely close to a 10mm bushing defeated that idea, so your explanation appears to have merit. I was surprised to hear of your STI slide; I've wanted STI parts but can't find them offered (at this time, anyway) at their website. Same goes for Colt and S&W parts (scandium frames!). Every name brand barrel, like Colt, I've had to purchase as a scrounged part from a jobber dealing in used, surplus, and production-overrun parts, like Numrich or Sarco. I've been building 1911's as a stress-reliever from my professional career, now retired, but have not had access to gunsmith resources and buy retail like most, I suspect, here do; and as just another consumer I take what's offered on the websites or make my own to suit. I appreciate your suggestion about the square-base firing pin stop and had already factored it into my orders, but I caved to conventional wisdom and purchased 22-lb recoil springs and 19-lb mainsprings to protect against battering from the dreaded 10mm round. Yet your post states that you have fired real 10mm ammo for 10 years in a commander with commander-beefed-up (from a government model's normal 16-lbs in 45 ACP) 18-lbs recoil spring! That's awesome. I mooted that idea as a theory in my thread, but had no idea, until now. Many thanks. So, the dwell is all; does my notion of drilling-out the hammer pin holes on the aluminum frame and replacing them with screw-in steel bearings to prevent egging around the hammer pin make sense to you? Seems like an easy fix to me, and slide-stop egging shouldn't be an issue with no frame-battering due to the dwell. Anyway, thanks again for the opportunity to talk real problems with a knowledgeable correspondent.
Cheers,
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[harrygunner]

To my surprise at the time, I was a "pioneer" in 2007, in spite of the fact that the Dan Wesson CBOB in 10mm was sold back then. I lived in California at that time, a state with the "logic" that one could buy a "safe" gun, then have it modified into the "unsafe" gun you wanted in the first place.

I've realized that after fleeing California for the U.S.A., I still would have had to consider having a custom Commander length 10mm 1911 made since there are few available today.

I should state my motivation. I wanted a 10mm 1911 with features that made sense for me. Didn't want to build the gun and was willing to spend whatever was needed to make that happen. So, I learned enough to make up for the lack of experience with that type of gun in gunsmiths that had good reputations for .45 ACP Government length 1911 smithing.

Looks like the latest move from the .40S&W to the 9mm has affected parts availability. I'd find the strongest slide I can find. The issue is the stress on the breech face of the slide. You have to shoot quite a bit of ammo before that manifests itself.

Bar-Sto will make a ramped 4.25" 10mm barrel for you. Also see what Kart offers.

There's a lot of, IMO, irrational concern about the "power" of the 10mm. 1911 frames didn't fall apart because of the 10mm thirty+ years ago. Cracks occurred because Colt cut square holes at stress points. Any aircraft designer would be tarred and feathered if they specified cutting square holes anywhere. In fact, the 10mm made all 1911's a bit better. The .45 ACP 1911 built this morning has a round cut at that spot on the frame that failed thirty years ago.

I also have the opinion that the need for stronger recoil springs is Internet sustained fake news. Another effect of the overstatement of the power of the 10mm. The slide is stopped by the abutment on the frame that was designed for that purpose. The recoil spring is intended to return the slide to battery. The recoil spring does slow the slide as it moves rearward. But the change in slide speed goes as the square root of the change in the recoil spring's Hooke's rate. Less effect than some might imagine.

The standard 18lb Commander length spring works well with the lower mass of the Commander length slide, keeping it from returning too fast.

Increasing the spring rate for the mainspring does make sense. That plus the flat bottom firing pin stop helps slow the rearward movement of the slide more efficiently.

I built on a forged steel frame and don't have experience with aluminum frames.

Are you aware of http://10mm-firearms.com ? Some members have built custom guns themselves. There may helpful info there.

Some chronograph results with Underwood ammo:

180gr XTP180gr XTP : avg 1271 ft/s 645 ft-lb
180gr GD : ave 1314 ft/s 689 ft-lb
200gr XTP : avg 1183 ft/s 620 ft-lb

Not bad for a 4.25" barrel.

A few photos of my 10mm carry gun I had built -

 

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Beautiful gun...that's what I aspire toward making. Thank you for the link, too.