It seems to me that there is a bit of a misunderstanding about what the chamber on a 1911 style pistol should be like. Over the past several years I have personally examined dozens of pistols with barrels that have been professionally installed by competent pistolsmiths. Without exception, all the barrels inspected had the same sort of issues. Below is a short evaluation of some of what I have seen and my opinion on the way a chamber should be done based both on personal experience and how I was taught.
First of all it seems that none of the smiths that installed barrels that I have seen realize the chamber that is cut in the barrel when you receive it from Kart, Bar-Sto, KKM, or whomever, is not finish reamed. With very few exceptions, most barrels, whether in a semi-custom gun from any number of makers to full house custom pistols from the most famous of smiths, have not had this most basic of steps completed.
Finish reaming the chamber is a simple action that can be accomplished by even a neophyte with a small bit of training and any number of manufacturers' reamers. The two I recommend are Manson and Clymer. All that needs to be known is the depth of cut you desire from the back of the finished hood. On a .45acp, for example, it should be .905 to .908", using good calibrated calipers, from the above mentioned hood area. Of course this is based on having a hood to breech face gap of just less than .001". This will help make for good accuracy and reliability.
Perhaps most smiths don't realize the chambers are not cut. It is very easy to tell if one has been done or not. For example, every Kart barrel I have fit has a bump in the chamber from the factory. It is apparently part of their barrel making process that leaves a slight raised area in the chamber. The bump is not a problem unless it is not removed. If left as is, I believe it can cause broken extractors, failures to feed and eject, not to mention accuracy suffers greatly.
Second, there has not been a single chamber I have examined that has been polished. Perhaps people actually believe that the lubricity traits of brass mean you don't have to polish the corn cob rough chambers that come from most barrel makers. Or perhaps they think that after a couple thousand rounds the chamber will self polish. In either case they are, in my opinion, incorrect. I can totally understand a $500.00 bone stock pistol being this way, but a gun running from $1000.00 and up should be smooth and shiny in the chamber.
Finally, regarding 1911 barrel chambers is the throat area. Perhaps the second most misunderstood area of the barrel is the tiny ramp like space that leads the bullet into the chamber. Many people apparently fancy themselves as jewelers and feel the throat should be covered with as many facets as they can cut into such a tiny area with a dremel tool. Others seem to think the rougher it is the better it will function. Still others insist on over cutting it, rendering the barrel dangerous and useless, or making it so convex in shape that you couldn't feed a round if your life depended on it, as well it may.
The reality of the throat area is that in my opinion and experience, for the best in reliable feeding, this area should be slightly concave, not convex, in shape. It should also have neither rough spots nor facets. This is not a diamond, it is a pistol barrel. Furthermore, along with the aforementioned chamber, it should be polished to a mirror finish. The top edge of it should be SLIGHTLY rolled over into the chamber for those reloaders who like the short bullets. And unlike some barrel makers believe, it should never be rounded under on the bottom edge where the barrel meets the frame, but rather sharp and smooth.
Of course I could go on and on about the nuances and minutia of barrel chambers, crowning, leg fit, hood gap, etc, but I don't want to bore you with all the details that fitting a barrel correctly entails as we would be here for days. I simply wanted to point out something that I see on a regular basis that could easily be corrected with a bit of care and instruction.
Thanx for sharing your observations with us. They are both welcomed and appreciated.
I was especially interested in your comments regarding the barrel throat (ramp) leading into the chamber. The various vintages of Ordnance barrel drawings I have reveal an interesting progression over the years:
* ~ 1940: Convex ramp with 0.310R + 0.005 inch radius.
* ~ 1960/70: Same earlier convex ramp or a straight "Alternate Chamber Ramp".
* ~ 1980: Only the straight chamber ramp (no provision for a convex ramp)
Interesting because Army Ordnance seems to have phased out the convex ramp and you favor a slightly concave ramp. Interesting indeed!
I use a Clymer finish reamer. The biggest advantage I see it that is that it tapers the lans in the barrel throat. Obviously, it also lets you adjust headspace. To measure headspace, I use a "GO" gauge and feeler gauges to measure to the breaehface.
I'm curious, how do you polish your chambers?
I use a dremel with a felt wheel and polishing compounds that we get that are used in the jewelry industry for polishing metals. This compound does not have inert ingredients in it to mess up your bluing like many you purchase.
I also use feeler gauges to measure the hood to breach face gap when the slide is not on the frame, but use calipers to measure the depth of the chamber as I'm cutting it as this seems to be more accurate than "Go" gauges.
For years I've been hearing (on this forum) about handloaded ammunition feeding problems with Kimber 1911's being due to "tight chambered Kimbers". It's almost as if when a Kimber chokes on a handload the automatic fix is more crimp. I don't have a Kimber or even access to one for measurement purposes, so was wondering:
* Any idea if chambers in Kimber barrels are really tighter than others?
* If so, what's "tight" (knowing the SAAMI minimum ID at the stop shoulder is 0.474" for the 45 Auto/ACP)?
* Or is the "tight chambered Kimber" just one of those urban myths that never seems to die here in cyberspace?
The bump in the top of the Kart chamber is from the letters being stamped. I can't account for the other bumps I've seen in their barrels recently... but I agree that they all need to be finish reamed. If for no other reason than to cut a proper leade. Kart's is too short and too abrupt.
Concave barrel ramp. Indeed! The barrel ramp is a clearance... not a feedway or bullet guide. That's why they were widened for SWC bullets... to provide that clearance for the bullet shoulders.
Overcut ramps that compromise head support? Absolutely. Seen it done in some pretty expensive semi-customs from some respected shops. Even seen it in full- blown customs... just not as prevalent. I most often find it either in pistols that don't have the correct feed ramp angle and geometry, and the "smith" starts cutting on the barrel ramp in order to relieve the 3-Point Jam that results from the bullet nose being directed straight into the barrel ramp, or... Dremel Dan has decided to remove the step between the top of the feed ramp and the lower edge of the barrel ramp and blend them smoothly together so the gun'll feed better, by gawd... and in so doing destroys even a proper ramp geometry. So, he attacks the barrel ramp in order to let the bullet nose skid across the top instead of hitting the center of the ramp. It does feed... but it also very often bulges or even blows cases.
I also like to see a little headspace and a small clearance between the hood and breechface. I like .003 inch there, but that's just me.
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The bump in the top of the Kart chamber is from the letters being stamped.
I can't account for the other bumps I've seen in their barrels recently... but
I agree that they all need to be finish reamed. If for no other reason than to
cut a proper leade. Kart's is too short and too abrupt.
I thought Kart barrels were advertised as being short chambered and needing a finish reaming after fitting.
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I thought Kart barrels were advertised as being short chambered
They are sir. But it is interesting that there are people out there that seem to believe that they are finish reamed as they come... ugh...
Then there is that stamping issue... I would agree with that except the bump is not always in the top. But I can totally see how that could be in many of the Kart barrels I've cut...
The single most often encountered issue with new barrels from all sources is taper near the shoulder. Even without pushing the reamer deeper to adjust final headspace or clean up the leade... whenever I drop a reamer in one, I get chips almost without exception. Don't know what that's all about, but it presents a problem with lead SWC bullets.
I take a little different approach to barrel fitting than most pistolsmiths. Accuracy isn't my primary concern. In most cases, the accuracy is enhanced to some degree... and sometimes greatly... over the OEM barrel, but chasing 1- inch groups at 50 yards just ain't my passion. The practical difference between 3 inches at 50 and 1.5 is of no consequence in a duty pistol or an IDPA gamer. As Jeff Cooper once noted:
"Absolute accuracy in a fighting pistol is a lot like top speed in a pickup truck. Interesting but irrelevant."
I shoot for dead reliability, and the accuracy is what it is. Mine will shoot better than I can prove without a sandbag rest... and with my eyes these days... probably better than I can prove with one.
I don't like to see the barrel fitted so tightly in the vertical plane as to force the slide upward into hard contact with the frame rails. I also like to see .003 inch of vertical and side play between the slide and frame. I'll fit the barrel to remove that vertical play... and then go back and loosen the barrel fit gradually until I just get it back.
The result with a good barrel is usually around 2 inches at 50 yards, give or take a tenth... and that's about twice as accurate as it needs to be for a defensive pistol that will most likely be used at less than 10 yards. If the range happens to go as long as 25 yards, that equates to an inch at that distance. If I can't hit what I need to with that level of accuracy, I can't do it with anything.
I also like horizontally equalized upper lugs, especially for hard-use range beaters. Not as important with carry guns that see limited use, but very much so if the gun is going to have to endure tens of thousands of rounds every year.
I have installed several of the Ed Brown 5" Drop-In Match Barrel/Bushings (Part #925-45) in various 1911's of late. In every case, the chamber was perfectly on-size and the correct depth.
The title is misleading because this is ANYTHING but a drop-in barrel. The rear barrel groove is semit-finished and it takes a lot of fitting to get the FP centered and the lug engagement correct.
However, I prefer this to the easier-to-fit Kart barrels, that require chamber work after fitting.
Leade entry diameter differences have always intrigued me. The SAAMI specification for this is 0.452 + 0.004 inch and its minimum value (0.452") will just accommodate the first little bit of a 0.452" cast lead bullet.
However, the minimum dimension for an Ordnance barrel (plain GI, not NM) works out to be 0.4513" at the leade entrance which won't accommodate a 0.452" cast lead bullet. I have one such GI barrel and it's fine with 0.451" OD Ball ammunition - but not with the larger lead ones.
With all the different 1911 barrel makers around the world, many may use Ordnance drawings. I've often wondered how many "GI" drop-in barrels exist with leade entrances too small to satisfactorily chamber lead bullets, but my exposure to different 1911 barrels is quite limited.
Had you ever noticed this?