Barrel feed ramp question

[mike56]

Put a deposit on a new XSE lightweight commander today.
While looking at it, I noticed that the feed ramp was not totaly smooth and round, but had a slight "trough" effect to it.

Looked at a few other new colt 1911's and noticed the same thing.

It is just a very different profile than the defender I had, which was totally smooth and even around the entire bottom half.
Is this normal?

[OD*]

Is this normal?
It's normal, Colt fans call it the "dimpled" barrel.

http://mysite.verizon.net/od45/sitebuildercontent/sitebuilderpictures/1911barrels.jpg
Original-Throated-Dimpled


http://mysite.verizon.net/od45/sitebuildercontent/sitebuilderpictures/dimpledbarrel.jpg
(Picture courtesy of Rio Vista Slim)

[mike56]

Yes, that's it.
Not going to get too concerned until I put some rounds through it.
Thanks

[OD*]

I wouldn't be concerned, it's a very good design that works well.

[TattooPaul]

It'll get those flatter tipped hollow points and wadcutters to chamber with less chance of hang-ups. Ball goes right on by.

[bradg]

I have a LtWt Commander XSE and have several hundred rounds through it. It definetley loves full metal jackets, no problem. Certain hollow points it does not like. The hollow points that work best for me are Winchester Rangers. Not cheap, but feed everytime. Hope that helps you.

[mike56]

Well, I was using the 230 gold dots in my Defender and USP compact.
Also, I reload alot of SWC for idpa and steel plates.
Can always have it throated/polished.

[1911Tuner]

That's known as the "Dimple Throat" and it's Colt's design. It pretty much splits the difference between the old "Hardball" ramp and the "Wadcutter" ramp to provide reliable feed with SWCs and wide meplat hollowpoints while maintaining maximum case head support. It works extremely well in 7 out of 10 guns. For the ones in which it falls a little short of expectations, it's usually due to the frame ramp being out of spec with the angle a little too shallow instead of correctly set at 31 degrees. When that occurs, about the only cure is to open the barrel throat to the wadcutter geometry...which often includes moving it forward about .010 inch and recontouring the whole ramp.

[OD*]

That's known as the "Dimple Throat" and it's Colt's design.
Funny you should mention that, I have spoken with and corresponded with Mike Scheidel who came up with the design, he didn't know what I was talking about when I asked about the introduction on the "dimpled" barrel.
Unfortunately for us (lucky for him) Mike retired from Colt (for the second time) last Thursday.


Hi Dan;
Kathy gave me a copy of your e-mail this morning and I told her I would call you. I did but apparently you were out or pre-occupied. Anyway, I apologize for taking so long to get back to you on the arched "serrated" mainspring housing question, but to answer it, no. The question was if we had one for the Officers model but I couldn't find one. Not current anyway. Colt had changed their computer bill-of-material system back in 1994 and only those models which were in production at that time were rewritten onto the new system. That simply means that I have no way of finding one unless I search the old bills in the vault and we only do that for the FBI or the BATF. However, if we had one back in the 80's, I think there would still be one hanging around somewhere in a current model. I could be wrong, but I haven't found one to date.

As for the barrel question, I'm not completely sure what you mean about the "dimpled" throat unless you mean the scallops on either side of the bore independent of the feed ramp. Those have been there for a few years. I increased them about 5 years ago I think, the same time we did away with carbon barrels on all standard production pistols. That is also when we did away with wide hoods except for the reproduction 1911 and 1911A1 which were introduced afterwards. I hope that answers you questions. If not, feel free to write back. You now have my e-mail address for another month.

Our best regards to Renita,

Mike

Michael E. Scheidel
Product Engineering
Colt Manufacturing Co. LLC
(860) 236-6311 X1679

[gbw]

Maybe slightly OT, but this brings up a question I've been meaning to ask:

What is the max. allowable distance from the breech face to the deepest part of the chamber (where the feed ramp is cut deepest into the chamber)? I'd assume this would include the max headspace and upper lug engagement slack.

I suppose if one were reluctant to release this value I couldn't blame them...the minute it's known, some bonehead (not this bonehead) will exceed it. Either on purpose, dangerously assuming that it includes a 'safety factor', or even more dangerously, by trying to use it all and just plain measuring or cutting wrong.

Still, it'd be interesting to know.

[1911Tuner]

I believe that the term "Dimple Throat" is a slang term that originated on either the internet, or in a gun shop by someone who didn't know exactly how to describe it...and it wound up on the internet. Whatever...Pretty sure the correct term for it is "Enhanced Barrel Throat" even though it's not the throat. It's the barrel ramp. The throat is forward of the chamber...aka "Leade."

FYI, neither is the barrel ramp a feed ramp...at least not if the gun is to spec.
It's more correctly a clearance ramp. The bullet nose shouldn't hit the barrel ramp during feeding.

gbw...The answer is...It depends. You can find what you seek in Kuhnhausen, Volume 1...but if you don't have it, I'll try to get back with a description/explanation soon.

[gbw]

I'm a little ashamed to admit I've never seen the K books....so I don't have it.

I suppose it could be calculated if one knew the specs for ramp angle, and the thickness of the chamber wall?

[OD*]

Dimple Throat" is a slang term that originated on either the internet, or in a gun shop by someone who didn't know exactly how to describe it
That's why I said "Colt fans." ;)

[deadmarsh]

It's a solid design -- never knew until now who actually designed it -- nice to know where credits due...


Dead

[1911Tuner]

What is the max. allowable distance from the breech face to the deepest part of the chamber (where the feed ramp is cut deepest into the chamber)? I'd assume this would include the max headspace and upper lug engagement slack.

You sorta answered your own question. The maximum allowable depth of the barrel ramp can vary...depending on a few other things...and still be perfectly safe. Or it can
be at minimum distance from the chamber face...and still be at risk of blowing a case head. The amount of case exposure ahead of the extractor groove and the web area of the case can appear to be perfect when a gauge or cartridge is dropped into the chamber, but if headspace is excessive in the wrong direction, it can cause a problem with bulged or burst cases. Go find the "Headspace" sticky and re-read it. It'll come to ya.

I hesitate to give a specific dimension because somebody will misunderstand it and rely on a static dimension...or worse, a cartridge case in the chamber to determine that they have safe headspace or a safe relationship between the depth of the barrel ramp and case head support...and damage a gun or themselves...or both. One dimension doesn't make for a good determination. There are too many related dimensions and tolerances to rely on one, and they have to be "in-snyc" and within spec to contribute to the whole picture.

Chamber depth...Distance from the chamber face to stop shoulder...Distance from the breechface to the stop shoulder...Upper lug engagement...Endplay/Endshake between barrel and slide...They all make up the whole.