View Full Version : 1911 Slide - to - Frame fit...Why?
March 28, 2012, 06:54 AM
I'm no pistolsmith but I have to ask.
To me, accuracy is exclusively a function of the precision with which the two features, the thing that the bullet comes out and the thing that holds the sights. So this means the barrel's lugs to the lug recesses in the slide and up front with the barrel to bushing and then bushing to slide. If the sights are mounted to the slide, you need only concentrate on these relationships, right?
In fact, I'd prefer to have a reasonable amount of play in the slide-to-frame.
Of course if your red dot is frame-mounted, then we do care about the aforementioned fit.
March 28, 2012, 07:35 AM
It is not the most important aspect of 1911 accuracy by far but you're not going to get match grade with sloppy frame to slide. The slide stop pin mounts in the frame. The barrel link connects it and the lower lugs. Lower lugs ride on the pin, drivng the barrel into the slide lugs. If you have loose slide to frame the barrel has more latitude to obtain a different relationship with the slide in lock-up.
More important to accuracy is the bushing foremost, lower lugs, and barrel hood to slide. And a shootable trigger of course.
March 28, 2012, 02:14 PM
Slide-to-frame fit is one way of ensuring that the lockup is consistent at each cycling of the action. Too much slop equals too much variability in the alignment and lockup of the barrel to the slide (particularly the locking lugs recesses). Some people make a big deal out of it, and it is important, but it is not the determining factor in accuracy.
March 28, 2012, 02:24 PM
FYI - Besides the locking lugs on top, and the link/ramp below, a barrel has two ends that should fit correctly for good accuracy - the bushing up front, and the hood at the rear.
Once the barrel is solidly-mounted to the frame, when in battery, the slide likewise needs solidarity with regards to it's fit to the same frame.
1 + 1 = 10 (ring).
March 29, 2012, 11:09 AM
Yes. That makes sense to me now, both the reason as well as the relative importance in overall accuracy. The slide-to-frame (and frame to pin and pin to link and link to link pin) plays a role in the position of the barrel in lock up.
I actually had an ulterior motive; to get a bit smarter about some of the options before engaging a pistolsmith to begin a project; that is to modify a Series 70 and turn it in to a Wad Gun for registered matches.
This feedback was very helpful., though I'm inclined to just shoot a Model 25 now that I see the extent of what can affect acuracy in an autoloading pistol.
I get it though; the gun's design gave reliability and durrability highest priority and we have been trying to make a precision target gun out of it ever since.
As a mechanical engineer, my mind naturally wanders to the obvious question; Why hasn't someone invented a fixed breech autoloader by now to truly approach the accuracy potential that rimfire autos enjoy? If someone has, why hasn't it caught on?
March 30, 2012, 12:40 AM
I'm no smith...
Are you referring to simple blowback type actions? If so, I know the .45 requires a locked breech/delayed blowback type action as the pressures are too high otherwise. This type of action also mitigates much of your felt recoil. I know that HiPoint and some Astra I can't remember have a 9x19 blowback pistol, but I think that's about as far as you can take it. Makarovs were made with fixed barrels and their accuracy is usually attributed to this unique feature. If you're talking about something else far beyond that, then I have no idea. I can hardly engineer a social event.
March 30, 2012, 06:59 AM
My first pass at a design would be to see if a gas operated system can be designed for pistols. Why invent something that already exists. If any of the multitude of gas operated centerfire rifle designs is scalable, start there.
Just a thought and totally useless as an option for me as I work through the decision making process of enterring Bulls Eye competitions with pistol or revolver.
But we may some day see it, and you heard it first mentioned here :D
March 30, 2012, 10:33 AM
Why hasn't someone invented a fixed breech autoloader by now to truly approach the accuracy potential that rimfire autos enjoy?
They did. It's called the Desert Eagle, and it is a gas-operated, fixed breech, magazine-fed, rotary bolt, semi-automatic handgun. It caught on just fine, but it's not cheap.
BTW, the 1911A1 configuration is entirely capable of very fine accuracy, but requires some work to be done in a very precise way. Trigger work, barrel work, frame work, and all have to be done precisely, usually by hand. Most production guns are not made to that standard, they would cost too much. Find a Colt Gold Cup and you will see how accurate a production gun can be. If you find a custom wadcutter gun, it will absolutely amaze you. One-hole groups at 50 feet is the norm, one-handed, standing.
You are talking about a custom match gun, you cannot compare it ti a beat-up military surplus gun. Not the same.
March 30, 2012, 02:01 PM
Fair enough. The cold NM is a good example. My only position is that those dozen or so steps that are generally agreed by all to be required to get that precision, are quite extensive and that is a function of accuracy not being the highest priority when it was designed. Whether accuracy was or was not a priority when the K-38 was designed I don't know, but the work required to get that fifty foot, one-hole group, at least for my unaltered K38, consists of the following; put bullets in it. :p
March 31, 2012, 02:13 PM
Maybe I'm nuts but isn't the HK P7 design a fixed barrel, gas retarded blow back design?
April 1, 2012, 04:46 AM
Consistency is the key to accuracy. Slop btwn moving parts means you don't get consistency.
April 2, 2012, 08:37 AM
When dealing with mechanical accuracy in a 1911 the slide to frame fit, at most, accounts for 5%.
The barrel and barrel fit will account for at least 80% of the mechanical accuracy, some claim more.
I would not be concerned with slide to frame fit unless the slide is so loose that it jepardizes the functioning of the gun.
Then if the slide to frame fit must be tightened the frame rails should be welded and machined back to tighter specs.
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