When contemplating a used 1911 at a gun show, or even for peace of mind with a gun you have had for some time--
What can you look for in order to judge if the locking lug engagement between the slide and barrel is OK? Conversely, what sort of wear indicates bad fit?
And if it looks bad, how much should the price be reduced for the cost of having a gunsmith fit it properly? -- assuming its not too far gone to be fixed.
I highly recommend Jerry Kuhnhausen's book "The Colt 45 Automatic, A Shop Manual". The first volume shows how to examine a 1911 and check everything including lug engagement and what happens when it isn't right. Lots of pictures.
I second stans' advice on the manuals.
One problem comes that comes to mind is that, in order to determine exact depth of lug engagement, you'll need modeling clay and some graphite... assuming that the seller will allow you to run a test on the gun.
There are a few things to look for if he will let you do a quick field-strip. The inspection won't tell you anything about the exact mechanical engagement of the barrel lugs, but it will let you determmine if there are any problems.
Look at the front corners of the barrel lugs. They should be sharp and square to the bore axis. Any rounding off... radiusing on the corners... is indication of a timing problem. If the pistol has had a barrel hand-fitted by a smith, there MAY be a light, 45 degree bevel on the corners, but that bevel will be clean and well-defined.
Flanging is another sign of impending trouble. From back to front, scrape the lugs with a thumbnail. If you feel a burr or sharp edge, there's a problem. If it's slight, and without any damage to the front of the lug as noted above, it's possibly an easy fix... No guarantee... but possibly.
Even if the light flanging is due to a more extensive problem, catcing it before damage was done to the barrel and slide lugs makes it a viable project if the price is right. The fix can range from a simple link change or modification to machining the frame, to a barrel replacement.
Check the lugs inside the slide. If lug engagement is shallow, you'll notice a "stepped" shape on the rear of the lugs... but that's only evident if the gun has been fired enough to create the step(s) The barrel lugs may also show the steps on the front of the lugs... but it's usually in the slide that you'll see it first.
If there's a timing problem, the flanging on the rear corners of the lugs in the slide will be evident, just like on the barrel. Scrape the lugs from front to rear with a fingernail to feel for the edge.
While light flanging can be dressed and smoothed... and the cause corrected if caught in time, radiused and/or reshaped barrel and slide lugs will either put the gun into the "Wall Hanger" status... or the slide and barrel should be replaced if you intend to shoot the gun. It will likely function with this damage... but it won't function for very long... maybe 2 or 3 thousand rounds... and the accuracy will degrade pretty quickly due to the increasing fore and aft play in the barrel. Once the damage starts, it progresses quickly.
The touchy-feely advice is just what I was looking for; something you can check just by removing the slide without tools. The Kuhnhausen book is heavy reading and kind of presumes a lot of knowledge.
Now if someone would create a comprehensive index for his books, that would help a lot.
Yeah, I find the lack of an alphabetical index a bit annoying.
mfree asked:
Seems to me... couldn't you paint a little something on the lugs (the blue
dye they use to check rear end gear engagement for truck axles comes to mind)
and see how deep the lug engagement is by firing a few rounds
Dykem or Prussian blue on the front of the locking lugs will give a ballpark estimate... as in:
"Hmmm... Looks like about 75 or 80% of full depth."
...but it won't provide an exact measurement of lug engagement. The only way to know is to know... ya know?
The easy way would be to measure the engagement with a dial caliper. It should come up to about .50 + or- 2,3,4.
Dave said:
with a dial caliper. It should come up to about .50 + or- 2,3,4.
Grab another cuppa joe and come on back, Cap'n! Not lug depth... Engagement... Total overlap with slide lugs in-battery. Modelin' clay... graphite... depth mike...
The lugs in the barrel engage the grooves in the slide when the barrel is locked up. Factory guns have roughly the same engagement with about .025 to .030 of empty space between the barrel and the slide. The up and down is not as important as the fore and aft play in a standard barrel. When you have some slop all four ways, you cannot expect much accuracy or reliability in repeating the lock up. This is why we fit National Match barrels and bushings so we don't have any play in any direction. We fit these barrels in such a way that there is no play in any direction, but without the recoil system installed, they will pass the gravity test by locking and unlocking as you tip the gun up and down.
Hey, if I can do it, anyone can! I cannot see any way to tell what a 1911 barrel engagement at the counter in a gun store, but a quick check would be to press down on the barrel hood and see what kind of play you have. If it springs at all, do not expect much accuracy out of it. That springing means that the lower lugs are riding on air and the barrel link.
Johnny, why not with a dial caliper, used in the correct manner? Measure the depth from the top of the slide to the hood, back it out of lock-up and measure it again, do a little math, etc... It could go on all day measuring one of these things, but the test Dave described is probably as good as it's going to get at the sellers table or counter, and tells 90% of the tale anyway.
Bill said:
Measure the depth from the top of the slide to the hood, back it out of
lock-up and measure it again, do a little math, etc.
Yep. That'll work for a quick check. If I'm checkin' for engagement in a high-pressure/heavy use set-up, I like to use modeling clay to get a better idea of where #s 2 and 3 are. Stitch in time and all that. Also like to check for horizontal in case #3 is takin' the brunt.
Things are gonna get better, Bill... It'll take an effort sometimes and sometimes not so much, but you'll be back in the thick of things soon. Do what I did... Go buy junkers and put'em in shape to shoot. I did one a month for nearly a year.
My digital calipers have 2 ends. The rear end is a functional depth micrometer which gives virtualy the same numbers as my depth micrometer. If I had been a little smarter back when I bought the later I would have saved my money.
Here is how I check lug engagement:
Unloaded and fully assembled, place a piece of popsicle stick between the end of the barrel hood and the breechface. Slide is as forward as it can go, barrel is pushed up and forward but out of battery. Use depth rod of calipers to measure from top of slide to top of barrel at front of ejection port.
Remove popsicle stick, allow slide to go fully forward, barrel in battery, measure once again from top of slide to top of barrel at front of ejection port.
Subtract the latter from the former... voila! Lug engagement.
Hah! I'm not crazy, I knew it. That is the way I was tring to 'splain it, minus the popscicle stick. I se where that would give a more consistant reading as your not fighting to hold it in one place. I'll let the popscicle stick I use for slide/frame fitting do double duty, wait, I'll just eat another popscicle instead, yeah, that's what I'll do.
Sticks!
Yeppers... That'll tell what ya need to know on the first lug... but what's behind lug # 2 and lug #3?
I use modeling clay and mica or graphite... D'ruther use Plasti-Gage (tm) when I can get it, but it's kinda scarce, since auto machine shops don't use it that much any more. Plastigage for the barrel slots for slide lug engagement... Modeling clay in the slide lug slots for barrel lug engagement, since the lugs are usually shorter than the depth of the slide slots... and generally the front lug is a bit shorter than the center lug to let the slide get by it when it links down.
You may have to order Plasti-gage from your friendly, neighborhood auto parts jobber. Most of'em don't keep it in stock nowadays...
Another Great Popsicle Stick Trick! I am curious to know what the Tuner does with the information gleaned from knowing the engagement of the front upper lugs in the slide at lock up. What adjustments can you make, if any? I have ignored these enagagements forever and I feel I may be missing something here. Thanks in advance for your help.
I am an amatuer metal worker (retired interventual cardiologist) so I use tongue depressors rather than of popsicle sticks as I have an easy supply. I also have some brass shims. I do not have the best eyes and have a tremor so things that hold themselves in position are necessary for me even when I measure and recheck things - I just stumbled on to elite pistolsmith Chuck Rodgers technique.
Dave asked:
I am curious to know what the Tuner does with the information gleaned from
knowing the...
It started back when I was playin' around with "Buffalo Stomper" loads for our old Slabsides. I had a buncha pistols to play with, since I was in the habit of takin' in basket cases and makin' shooters out of'em.
250-280 grain hard cast bullets started after a guy gave me a couple of molds that he used for his .45 Colt revolvers...and had gotten too old to fool with. Nice, RN FP bullets that fed like grease thru a goose in most of my pistols... and I started bumpin' up the power charges so I could knock ballistic pendulums silly. I also got to noticin' a problem with some guns.
The lugs were gettin' beat all to hell-and-gone in some pistols... slide and barrel lugs... but others didn't seem to know the difference. Soooo... I started checkin' things, and I saw that as long as the forward barrel lug... #3... was sittin higher in the slide's slot than about .040 inch... and the middle lug... #2... was about .050 deep... with full engagement on #1, the guns would stand up to the heavy bullets at 800-850 fps waaaaay longer than when the engagements were in the "average" range, with a lot of air above the barrel lugs... even with good slide lug contact in the barrel slots. Not too critical with standard .45 ACP pressures and 230-grain bullets... but a lot moreso when the pressures and recoil forces go up. I figure that some of those loadings were pretty... adventurous. I sheared a few barrel lugs in those days... but GI barrels and slides were cheap at the shows, so I pressed onward.
Then... when I started welding barrel lugs up and fitting them so as to get a full mesh engagement... slide lugs in full engagement with the barrel slots, and barrel lugs in the slide slots as close to 100% as I could get'em and still let the barrels link down far enough to let the slide pass over'em... the guns would stand up to about triple the number of those rounds.
I even lowered the saddles a little to let the barrels link down farther so I could set the barrel lugs deeper into the slide, but ran into a point that linkdown timing was more the limiting factor than lack of clearance. Of course, the forward lug was the fly in the ointment due to the fact that it's sitting higher than the other two when the barrel is in linkdown. No matter how much clearance I got at the back... the barrel would fall only so fast. I could get very close to full mesh on the middle lug... but not the forward one.
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Dean... Your dial caliper indeed has a pretty good depth mike on the bottom, and as long as you're dealing with tolerances that are typical in the 1911 and other pistols, you're golden. Most dial and vernier calipers are accurate only to within plus/minus .001 inch..but if you need to split that into tenths of a thousandth, you need a depth mike with a vernier scale for a more exact measurement. The wider, more stable base on the mike also makes it easier to consistently center on a radius than the bottom of a caliper. Unless you're well-practiced, you can take 3 such depth measurements and come up with 3 different results with a caliper. Not a critical point on a 1911 pistol, but as you begin to work with closer tolerances, you'll see the difference quickly. If you're truly bitten by the bug, it's natural to get the equipment and dabble with making your own tooling, jigs and fixtures. It's a never- ending quest that borders on mental illness. Welcome to the world of a toolmaker... my world.
Thanks for that information, Tuner. We were working in two different worlds so I now know why I ignored that factor. I built guns out of new parts with NM Barrels and bushings, quality links and pins, properly polished upper surfaces in the slides, and ready for any kind of hot load that my clients want to destroy their gun with. I also knew how to break the upper lugs on the barrels so that they would not batter the slides. I quickly learned that quality is remembered long after price has been forgotton and my end users always got what they paid for. I have never had a Custom Caspian come back in 20 years, so I must have done something right. Several of my own 1911's have been chambered for 10mm Centaur and 400 Cor-bon and have had thousands of very hot rounds leave the muzzle with no problems that I know about. I still load up 255 grain cowboy bullets for my 1911's just for fun so I have done my share of high pressure work. That's only an extra 25 grains from hardball so I have never worried about battering lugs with them. That do tend to have a nice big BOOM when you shoot them that I enjoy!
We were working in two different worlds...
Yep... Bein' a po' boy with a shootin' addiction, I'd buy a clunker for 50 or 60 bucks... beat the rails down... weld up the lugs...sometimes the rails too... square up the hammer hooks... add a little prep and a little buff and shoot the thing 'til it wore out or busted and start all over.
Wish I had all those old GI pistols now... They'd be worth a mint. I'd be willin' to bet that I've shot 50,000 bucks worth of slides and frames to destruction... but it was a hoot while it lasted. Even shot a barrel in half once...
One semi-complete 1918 Colt... 70 dollars
15 hours cost of my labor in the rebuild (1969 dollars) 30 dollars
NOS and used GI parts... maybe 10 dollars (but I doubt it)
The look on my face when I realized that it was the barrel that went downrange... Priceless!
Tuner - How many rounds did it usually take you to tear up your lugs?
I have a Custom Open STI .45 with a ramped barrel which I use for pins. It was built with the Captain's type of lug treatment. I have used multiple different hot loads with 230, 255 and some 270-280 bullets trying to get an advantage. It has about 35,000 rounds through it and no sign of wear yet on the lugs. It runs fine.
John - I was not expecting any trouble until you posted. I guess I should watch things closely.
As long as the slide lugs are at about 100% engagement in the barrel slots, and the gun will used for standard-pressure .45 ACP ammo, it'll live long and prosper... assuming that the barrel lugs are in spec and equalized in the load bearing... but you knew that already.
When I planned on "something more"... High pressures and/or heavy bullets, I wanted all the barrel lug in the slide recesses that I could get. Most of the time, I had what I had. If the height of the barrel lugs didn't engage at least 75% of the depth of the recess in the slide, I didn't use it for those applications, and stuck with more or less standard ammo.
Of course, that would vary a little on the #3 lug, since there was the issue of the slide havin' enough clearance on that one to keep from beatin' up the front corner... so I usually had to be happy with whatever I got on that lug. The #2 lug could get deeper and still allow for clearance.
If I was determined to use the gun for that kinda thing... a toy mainly, but also for a defensive gun to be carried into "Bear Country", I'd start by fitting the barrel slots to engage the slide lugs at 100%... and check the barrel lugs for depth in the slide. If it wasn't what I wanted, I'd have the lugs welded and light in with a file until I got the barrel fairly centered up in the slide again, assemble the gun and see if it would go to battery... and cut a little off the tops until it would go.
Then I'd remove metal until the barrel was centered vertically, blue the tops of the lugs, and remove metal from the lugs until they just cleared... remove another .010 inch from the front lug, and about .005 from the swcond. Blue the lugs again and test-fire the gun with a light load and spring to check for signs of interference at the front corners... and adjust accordingly with emery cloth in small increments. At that point, I lightly broke the corners of the barrel and slide lugs at 45 degrees and tested the gun with full-power loads. If there was no sign of rolling or flanging, I had a gun that would withstand a good amount of use with the heavy stuff. Final step was lappin' it all in with Du Pont Rubbing compound... we didn't have J&B then... and it was cheap and worked prety well.
Much of it was probably unnecessary, and may not have added enough life to the guns to make it worth the effort... but I had time on my hands and liked to do the work... so I did the work... mainly for my own use, but I did a few for other guys too, and it seemed to work out pretty well.
Interesting. I like just the right amount of lock-up so that the slide rides over the barrel smoothly when it fires and unlocks with a minimum amount of damage to the barrel hood. I have found it to be a varible in every gun I have built. I never do anything the the grooves in the slide where the barrel lugs ride. I like them to be nice and sharp to prevent any back and forth movement. Different Strokes for Different Folks, Huh, Tuner? If I had to use one dimension, I would say to get it as close to .050 as you can with a plus or minus of .004. I would be glad to stand corrected if there is a better ball park measurement I should use.
Dave said:
Interesting. I like just the right amount of lock-up so that the slide
rides over the barrel smoothly when it fires and unlocks with a minimum amount
of damage to the barrel hood.
Yep... We're *almost* on the same page, Cap'n. For high-stress applications, I like all that I can get, and don't consider light scuffing to be damage, though there's sometimes a fine line there.
quote:
I have found it to be a variable in every gun I have built.
Surely! Maximum engagement isn't as hard to get with a "Hard Fit" barrel due to oversized/undersized dimensions. 95% of my experience has been with whatever barrel came with the gun... and those variables that fell outside of my self-imposed parameters were corrected inasmuch as possible. It was "Old School" fitting, to be sure... and inferior to how it's done today... but it was all I had or all I could afford at the time. Money was short. Time cost me nothing.
quote:
If I had to use one dimension, I would say to get it as close to .050 as
you can with a plus or minus of .004...
Roger on the different strokes.
.050 plus/minus .004 is a good fit, but I'd always try to get it down to .050 inch, plus .004/ minus none. If I could get .055 inch without hard contact on the hood OR either lug, I was in heaven, and would routinely spend hours holding a .001 inch tolerance. That's the toolmaker curse, though... In that field, an .008 inch tolerance (plus/minus .004) is a football field. We tend to think in terms of tenths instead of thousandths. i.e. plus/minus .0001 inch, or even less.
I don't worry over tolerances that close with standard Hardball-Spec ammo though... just for certain applications... and I don't fool with things like that these days anyway. When I was playing with it, I was an apprentice toolmaker, and combining practicing my trade and playing with my toys... and it didn't seem like work at all. Win-Win!