1911 OEM parts: why would they need to be "fitted"?

[Airman193SOS]

I'm looking at getting a few replacement parts/upgrades for my Kimber, and one of them is a flat mainspring housing with attached magazine well. In the listing it says that it may require "fitting" by a gunsmith. Now, if I already have OEM parts on the gun, why would replacement OEM parts not fit precisely the same way?

In other words, do I really have to consider the possibility of taking my gun to a smith, or is this based upon the possibility that I might try to add a Kimber part to a 1911 of a different make?

 

[highorder]

In the case of a magwell/speedchute, it may need some fitting or filing to align with the magwell of the gun. Mainspring housings also vary in width, etc. from model to model.

"Requires fitting" makes you aware that it may, uh, require fitting.

 

[jr_roosa]

That's the thing with 1911s, sometimes you need to do a bit of tinkering to get things to fit. Not all the time, but enough that parts have the "fitting" warning. Think about how snug the mainspring housing is. It would only take a few thousandths here or there to make it not quite go in.

It doesn't have anything to do with the brand. They just aren't made like an AR15 where any part from any rifle can go on any other and work just great. Remember it's a design from 1911, when machining got the part close enough for a highly trained person to fit it properly to the pistol.

-J.

 

[dmazur]

I have a little experience with 1911's, which includes parts that were "drop-in" and those that weren't.

I believe the AR-15's have created an impression that all gun parts should be drop-in. There should be standard drawings, and if parts are made to these drawings, why shouldn't they fit? And, for the AR-15, this is largely true.

Unfortunately, the 1911 was designed before CAD-CAM and there were actually "master copies" of the pistol that were given to manufacturers who were to build 1911's under government contract. The machinists took measurements off the masters and set up the tooling accordingly.

More recently, manufacturers of 1911 clones created versions of the 1911 that, while they closely resemble the Colt, may not duplicate all dimensions. Because of this, aftermarket parts may require fitting.

And, even with Colt 1911's, there are some parts that are just not made to close enough tolerances for "drop-in". These are the ones that usually require hand-fitting. Sears and thumb safeties are typical.

Finally, many manufacturers put "requires fitting by a gunsmith" warnings on all 1911 parts as a universal disclaimer, whether true or not.

So, aftermarket parts may fit your Kimber without "fitting", or they may not. Best answer is "it depends".

This is a general answer. If someone has experience with the exact part you're trying to install, they may be able to provide a better answer...

 

[Gunfighter123]

FWIW ---- the four 1911s that I own with Smith & Alexander {S&A} mag well/mainspring did not need to be hand fit to get them on the guns frame --- However -- after they were on the gun , most needed a very small bit of fileing for the new mag well opening to mate with the old factory mag well.

 

[9mmepiphany]

why would replacement OEM parts not fit precisely the same way?

what would lead you to believe that a part was OEM if it wasn't manufactured by the Original Equipment Manufacturer...i'm assuming you're referring to an aftermarket part since Kimber doesn't make a mainspring housing with attached mag well

 

[Onmilo]

There is so much variation in tolerence between various manufacturers of 1911 components that the idea of "tolerence stacking" where parts from a number of sources fit each others component pieces without hand fitting is nonexistent

I have yet to see a 1911 that will allow parts from a number of sources to be drop in assembled into a complete firearm.
All involve hand fitting to some degree.

The closest you will get to drop in assemble is to use ALL USGI parts on a USGI frame and slide and even then you will usually need to tweek a spring or stone a part to get it to fit and operate correctly.

 

[REAPER4206969]

since Kimber doesn't make a mainspring housing with attached mag well

Yes they do. I have one on my SW1911.

http://www.midwayusa.com/viewProduct/?productNumber=931019

Slid right in.

 

[9mmepiphany]

^^^
i stand corrected

why do they end the checkering panel 2 lines before the edge?

 

[REAPER4206969]

I don't know, but there are a lot of mainspring housings checkered like that.

 

[Airman193SOS]

I suppose it's my fault for not being clear, I have a Kimber and I'm planning on putting Kimber parts on it. I'm not talking about Wilson parts or other third-party manufacturers, that I could understand needing some work.

If I do that, buy OEM parts to replace OEM parts on the same gun, should I expect to have to take it to a smith? Are tolerances within the same company that variable?

 

[David E]

It depends on the part. If the mainspring housing without a magwell is the item, then it should slide right in.

Hammers, sears and thumb safeties will require fitting to function the best.

 

[Harvey]

Common sense and a small set of files is all that is required to tackle most any of the "drop in" parts, but unless you really know what you're doing, you'd best defer the more sensitive part groups to a competent smith.

Even the most mechanically inclined Joe might want to avoid the trigger group, and the barrel group from the link pin into the lugs. These are the two areas that require a thorough understanding of the gun's dynamics and timing.

But as far as the rest? ... simple cosmetics and better controls. Have fun.

PS: some shy away from the thumb safety, but in my experience, the OEM machining on the sear block generally works fine. And the catch at the plunger tube is fairly easy to tune with a file, if you study it carefully. Most of the ambi-safeties require a letting-in on the starboard grip panel (yuk), but there is at least one that uses the hammer pin for engagement. http://www.kingsgunworks.com/newcatalog/page03.html Nice application.

There are myriad grip safeties alleged to 'drop in', but you take your chances with frame fit and trigger block. Caveat emptor.

 

[Glockman17366]

All, repeat ALL, machined parts are made to a tolerance. The nominal dimension is the target, but there is always a degree of variation. This doesn't just apply to guns, BTW.
So, to get best performance from an aftermarket part (even if manufactured by the OEM), fitting may be required to accomodate those production tolerances (which includes tolerances on aftermarket parts). Those couple thousandths or even ten thousandths (that's .001" and .0001") can make a difference in the feel of the gun and trigger.

 

[Airman193SOS]

Fair enough. Thanks.