Series 70 Colt Collet Barrel Bushing Reliability


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GaryK
November 30, 2007, 03:10 PM
I have a Colt Series 70 Government Model that still has the collet bushing. It runs fine and is accurate. The gun has a lot of rounds through it and as of last night when I stripped it for cleaning the bushing appears to be in good shape. I have heard stories for years about their unreliability but never took it out because it never failed (why mess with something that works?). Has anyone had one that failed? Have I just been lucky or do they cause real problems?

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rcmodel
November 30, 2007, 03:22 PM
Yes I have seen several of them fail.
Yes I have had problems with them.
I no longer leave one in a gun any longer then it takes to get a solid replacement fitted.

Just replaced one about 4 months ago for a friend. His almost new gun broke a collet finger and locked up the slide jammed half open. Took a lot of beating with a rubber hammer to get the slide off. And that left some internal slide & barrel damage where the broken finger gouged into the barrel & slide.
Nothing serious requiring a barrel or slide replacement, but it needn't have happened in the first place.

I had been telling him since he bought the gun to replace it with a solid bushing.

There are known ways to modify & fit the collet fingers to prevent eventual breakage, but you can fit a new solid bushing while you are messing with fixing the collet one. And on a used gun, there is no way to tell if the bushing is just about ready to break, or will last indefinitely.
Some do, some don't.

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rcmodel

dfariswheel
November 30, 2007, 08:35 PM
The collet equipped guns that failed were traced to a mis-fit collet from the factory.

Jerry Kuhnhausen describes it best in the book "The Colt .45 Automatics: A Shop Manual, Volume One".

Basically, in a gun in which there is insufficient room between the collet and the slide, (undersized slide, over-sized barrel, or over-sized OD of the collet) the collet doesn't have enough room to spring open.
Unable to open, the collet "fingers" tend to bow instead of flex, and the strain causes the collet finger to break.

Kuhnhausen shows the "fixes" and the test for a possible problem which is to test the barrel for springiness when the barrel goes into lockup.

jwr_747
November 30, 2007, 08:52 PM
I have a Gold Cup with the collet bushing,one of the first one's produced,more rounds thru it than I can count.I had heard the stories of breakage ect.so several years back,when I worked for a living I had the bushing Magna-Fluxed,and some kind of X-rayed,no problems detected.now,several years later and several thousand rounds later,still going strong. jwr

GaryK
November 30, 2007, 09:22 PM
I had a Brown bushing that fit pretty well (2-3 thousands larger than the ID of the barrel end) so I installed it this evening. I plan on shooting it soon to see if the accuracy suffers. Dfariswheel yours (and Kuhnhausens) comments imply that the problems with collet bushings are more with the fitting and not in the concept. That is probably why some of them have worked so well for so long. I would interested to hear what some of the rest of you think.

1911Tuner
November 30, 2007, 09:24 PM
Okay. My 2% of a buck...

I've seen a few that lasted thousands of rounds before they let go. Seen several that failed early on. When they do break, the result is almost always the same. Gun locked up solidly. Best bet is to drill the slidestop arm off and remove the pin before trying to remove the slide. It minimizes the damage that rcmodel described...but it's never pretty, and sometimes the damage is beyond reasonable repair.

The collet bushing offers zero advantage over a correctly fitted solid bushing, and very little...if any...over a low-spec drop-in that requires minimal fitting to the slide. Usually just a little lapping and it's good to go. MGW makes a decent one.

Three questions that beg to be asked:

Why take a chance on expensive damage to a vintage Colt over a 25-dollar part?

If they're so good...Why did Colt drop'em?

Why don't we see the collet bushings on high-end custom pistols? (I don't know of any who use'em, though I'm sure there may be a few.)

ZBill
November 30, 2007, 10:18 PM
Would the MGW drop in work with my Series 70 9mm? The barrel contour/diameter narrows dramatically about 1 in from the muzzel.

Thanks, Bill

Jim Watson
November 30, 2007, 10:39 PM
Back when they were in production, several of us here shot them routinely with no problems. But if one does break, you have a mess.

The point of the collet bushing was to tighten up the guns without handfitting. The problem was, they DID have to fit right or they would break or bind with the slide out of battery. I have seen binding but not breakage.

The reason the S70 9mm and .38 barrels have the funny contour is to reduce the recoiling mass while using the same collet bushing as the .45. A standard bushing will work.

dfariswheel
December 1, 2007, 12:52 AM
"Why take a chance on expensive damage to a vintage Colt over a 25-dollar part?"
No real reason, other than the collet offered enhanced accuracy out-of-the-box without having to buy and fit a custom part.

"If they're so good...Why did Colt drop'em?"
Expense.
The collet bushing was significantly more difficult and expensive to make, and did require more care in fitting the slide, barrel, and bushing.

"Why don't we see the collet bushings on high-end custom pistols?"
Because few custom makers actually make their own bushings. They buy bushings and fit them, which is much cheaper than actually manufacturing a bushing, especially a complicated part that requires careful heat treating.
Then to, a custom fitted bushing is as good as a collet type at a cheaper cost.

Among companies that did use collet bushings was Bar-Sto.
Their bushing worked differently than the Colt design, and was a seriously great accuracy enhancing design.
"Back in the day" people wanting the best bought a Bar-Sto barrel with the collet bushing. If you had a Bar-Sto unit, you were a SERIOUS 1911 shooter.

Jim Watson
December 1, 2007, 09:16 AM
As I recall from Dean Grennell, BarSto quit making collet bushings because people kept yanking the bushings off the flared muzzles and breaking their fingers. Since the BarSto design really worked on spring fingers, it was not critical as to fit and really did what it was supposed to; increase accuracy without hand fitting.
The Colt Mk IV design works like a draw collet and depends on the reverse tapered barrel expanding the bushing snug into the slide bore. Which does require a correct fit, which their design and machinery could not always achieve without handwork, defeating the original purpose.

1911Tuner
December 1, 2007, 09:22 AM
No real reason, other than the collet offered enhanced accuracy out-of-the-box without having to buy and fit a custom part.

When they were correctly fitted anyway...and when they weren't, as Jim noted...they could make a real mess of things.

The Colt Mk IV design works like a draw collet and depends on the reverse tapered barrel expanding the bushing snug into the slide bore. Which does require a correct fit, which their design and machinery could not always achieve without handwork, defeating the original purpose.

Exactly my point. If it requires hand-fitting anyway...why go with something that could cause a problem if it's not "Just so" in the execution.

Again...I've seen too many that let go after working for many thousands of rounds. Not pretty.

esq_stu
December 3, 2007, 02:37 AM
almost new gun broke a collet finger and locked up the slide jammed half open.

this happened to me; slide froze closed at the range, but I had the gun at least 20 years before it happened

ZBill
February 14, 2008, 07:52 PM
I have a Colt Series 70 in 9mm that I installed a EGW Prefit Bored Bushing in last evening having read about the possible failure of the collet fingers. The only fitting required was minimal filing on the lug on the bushing that goes into the cut recess groove in the slide.

The barrel to bushing fit is very snug as is the bushing to slide fit. I need a bushing wrench to remove the bushing unless I file a little more.

My question: Can anyone provide insight as to whether I should leave the lug/slide lock up tight enought to require a bushing wrench or file some more off so I can just use my fingers to turn the bushing?

Shot it today and the accuracy is great.

Thanks for any input, Bill

rcmodel
February 15, 2008, 03:08 PM
I would fit it loose enough you can turn it with the magazine floor-plate.

That is neither so loose it rattles and you can turn it easily with you fingers, or so tight you have to use a bushing wrench.

Your bushing wrench is in the butt of the gun, as long as you still have a magazine.

http://i81.photobucket.com/albums/j219/rcmodel/KTOG/1224.gif
rcmodel

BigG
February 15, 2008, 03:30 PM
The collet bushing types usually need the slide retracted to release the fingers so you can turn the bushing for field stripping.

Jim K
February 15, 2008, 05:08 PM
I replaced a lot of them "in the day" and I would say the percentage was about 10 percent broke on their own and 90 percent broke because people kept fiddling with them to "loosen" or "tighten" them.

Jim

GaryK
February 16, 2008, 10:31 AM
I did not notice any difference in either accuracy or function when I replaced the collet bushing in my series 70 Colt with an Ed Brown prefit bushing. If what you guys say is true I suspect that I might have saved myself some inconvienence and a wasted trip to the range for the $20.00 cost of the bushing. Thanks.

grendelbane
February 17, 2008, 06:50 PM
Why take a chance on expensive damage to a vintage Colt over a 25-dollar part?

Tuner, I have to take offense to that remark. I have 2 Colts in my collection that came with collet bushings, both of them purchased new. The Gold Cup was my first .45, purchased in 1979, and the .38 Super Gov't model was bought in 1983.

I just turned 52 last Friday, so by definition, nothing that I bought new can ever be described as "vintage".:neener:

I propose that you use the term, "BITD", (Back in the Day), as it sounds much better to my ears.

For the record, I never had any problems from the collet bushing, though after changing barrel and bushing on the .38 Super it has become much more reliable and much more tolerant of different profile bullets than it was before. The Gold Cup still has a collet bushing, though I may change it soon. Doesn't matter too much since I rarely ever shoot it.

SlamFire1
February 20, 2008, 05:57 PM
I have a series 80 M1911 Colt that has the Collet bushing. It is a standard length M1911. I have wanted to replace the thing, just for the reasons described, don't want a seized pistol.

However whenever I have tried to drop a GI or NM bushing on the end of my barrel, well the barrel is too big. This series 80 pistol has a flared barrel.

So, is this Ed Brown replacement bushing a true drop in?

"Solid Barrel Bushings
All spring type collet bushings are subject to breakage and are replaced with the solid type as a rule with professional gunsmiths. We offer a drop-in replacement in blue and stainless that will work on most 1911 types with little or no fitting, and an oversize gunsmith fit version, also in both blue and stainless. Specs: Heat treated alloy and stainless steel. Drop-In: .581 ID, .699 OD. Oversize: .575 ID, .705 OD."

http://www.edbrown.com/cgi-bin/htmlos.cgi/004710.1.336756611113096900?

rcmodel
February 20, 2008, 06:18 PM
Most Series-70 barrels measure around .578" to .579" at the muzzle.
So, the .581" drop-in should fit perfectly.

The .575" over-size would be too small and need to be fitted to your gun.

Ideally, you should measure yours first and see if the .581" will fit it or not.

http://i81.photobucket.com/albums/j219/rcmodel/KTOG/1224.gif
rcmodel

SlamFire1
February 21, 2008, 11:50 AM
I should have measured my barrel diameter before posting that question. That I will do next.

Thanks.

SlamFire1
February 25, 2008, 08:54 PM
I measured my barrel end and it is very close to .579. Even though I measured it with a Mitutoyo Digimatic Micrometer, I don't have calibrating blocks, so I could be off by a .001 or so.

I called Ed's Browns, they consider "normal" clearance between a bushing and the barrel to be .002". Though they said the bushing will work if you can just get it one.

Also said that it won't make much of a difference in accuracy. They said barrel fitting (or "fit") was more important.

My series 80 is accurate enough, it least three inch groups at 25 yards, maybe better. Not awful.

outerlimit
June 8, 2008, 01:44 PM
The collet bushing types usually need the slide retracted to release the fingers so you can turn the bushing for field stripping.

I have one with the collet bushing and have to do no such thing. I just push in on the plug and turn. I installed a 18.5lb Wolff recoil spring, but this doesn't seem to have made it much more difficult.

The gun only has about 100rd's through it, but I'm a little concerned since there's always such a big deal made about the collet bushing and it seems when they break, they break hardcore.

Since the barrel has the collet taper groove towards the front and obviously was originally fitted at the factory for this bushing, I'm a little leary of replacing it with a solid aftermarket part of unknown quality or origin though.

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