Accuracy Tuner Pistols

[size=57]Today I worked on two old Clark 45 longslide pistols. One was built by Clark in 1969 on a commercial Colt frame/slide; had matching numbers. The next pistol was built by Clark in 1972 was GI US Army 45 frame and the slide had no markings/bare. The number on the disconnector rail of the slide did not match the frame; had Clark Tigertooth Stippling on front strap and MSH. I bought a used Clark from Clark back in 1989 that was mismatched! So they are out there like this directly from Clark.[/size]
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Both pistols used accuracy tuners. The 69 pistol appeared to have one piece barrel. The 72 had a two-piece sleeved barrel. Both pistols are high mileage California guns; BE is shot here year round with as many as 4 matches a month if you drive a little. [/size]
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The 72 pistol unfortunately was severely worn at the slide locking lugs and the barrel upper lugs. 50% of the lugs had deformed/sheared off. There were raised burrs on the barrel lugs. Possible that an old soft GI slide was used and just didn’t have the heat treatment to give it a longer life. The original owner of the pistol was a longtime master BE shooter who shot into his 80’s before he passed away. [/size]
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So the reason I’m writing all this is to say; if you have a pistol that uses an accuracy tuner, please make sure you do not tighten it down too much on the barrel. Unfortunately the tuner pushes the barrel down out of the locking lugs of the slide. This gives less surface area for lockup engagement. Result is pistol comes out of battery faster and prematurely wears lugs. Also if your frame to slide fit has loosened up since being built (peened rails) if you tighten the accuracy tuner down to compensate for loose frame rails you are bringing the barrel further out of battery and will increase/induce more lug wear on the barrel. Eventually you will shear the lugs. On the 72 pistol I could move slide to the rear approximately 0.020” before the barrel would start to move to the rear with the slide. This is because the gap between the hood and breech face and the worn locking surfaces of the barrel lugs and slide lugs would allow this. On a newly built match pistol you will get 0.0005”-0.001” or 0.002” of slide travel before slide lugs push barrel to the rear. You can see this is quite a large difference.[/size]
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So that nice cheap used pistol might not be such a good deal  [/size]
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If you own a accuracy tuner pistol and have it re-barrelled with a Kart, the tuner can be left off the pistol because the Kart has enough extra material to be fit correctly and doesn’t need it.
Jon[/size]

Jon;
Did you post pic's ?
If you did, they did not come through(on my end anyway).

You made me go out to the shop and check my 11/68 long slide with a tuner
I am coming up with .0055" of slide movement before the barrel begins to move.
Anything to be concerned about ?

I know it is a two piece barrel with a welded up hood from the looks.
Could you explain the concept of the two piece sleeved barrel ?
Is it sleeved the whole length ?

The barrel and slide lugs are good and square and shoots well.

I have never touched the tuner and probably never will.

Thanks;
Clarence

Hi Clarence.
Just to double check is it 0.0055" (5-1/2 thousandths) or 0.055"?
Two things taking place possibly. If you take slide of frame and push barrel forward toward muzzle while lugs are in battery, most older pistols will have a lot of play/slop. If you take a feeler gauge and measure it you will see how much the slide can move to rear before contacting barrel lugs (keeping it simple because other things can take place). So in the case of the two pistols I described this was taking place before the barrel started to slide to the rear with the slide. At some point approx 0.010" to 0.040" the barrel will start to drop/unlock allow slide to travel all the way to full recoil. On a modern built BE pistol there is minimal play fore and aft between barrel and slide and better bottom lug lockup.
The 2 piece barrel is full length from muzzle to hood. Sleeves are either done from hood side using existing barrel lugs or done from front with new upper lugs machined into new narrel portion. Clark typically machined his own lugs.
Jon

My measurement is .0055 (5 and a half thousands).
That is where the lugs start to push the barrel from full lock up.

Thanks for the info.

The measurement should be slide barrel travel until the barrel unlocks from the slide. At that point the barrel should remain stationary and the slide move fore and aft. It should be more than .0055 inches.

Unfortunately many pistols have been built with almost zero lockup: unlock almost immediately. Result is accuracy loss and more recoil. If you had a really good pistol to shoot side by side with an older vintage pistol there is a night and day difference. I have a client that I've built 5 pistols for, for that reason alone.
Jon

I guess it all depends how you look at things in general.
To Wobbley, the measurment is still .0055"

What is your desired spec ?

Clarence are you saying your slide moves to rear .0055 then barrel starts to drop from barrel lugs? Or that your slide moves 0.0055 then the narrel starts moving to the rear with the slide and then drops later?
Jon

Of course the barrel drops later, shit, how else does it work.
Thanks

Never mind Clarence. As long as your happy.

Sure would be nice to see the pics. Easier to see what ya'll are talkin about

For me I prefer .090 or better. My Clark hardball gun moves at least that much before the slide is free of the barrel. For a typical 45 the slide will move about .070 til the bullet leaves the barrel. There will be a small movement between the slide and the barrel while fully locked but this should be only a thousandth to two. Otherwise the gun won't lock. Some small clearance is required otherwise the mechanism won't work.

I just love the internet.
No one knows what the hell the other one is saying.

Yah Jon.
I'm happy

gaaack! My mistake, you're talking about the free play between the barrel and the slide while still in lockup. My bad. On your case it is probably how the ancient and honorable smith built it. Only way to tell is to see if there's much peening of the lugs in the slide or barrel. Unless you know what to look for might have a smith take a look at it. So long as it shoots ok and doesn't get worse, it should be no issue.

At five and a half thou there should be some perceptible end play, at 0.002 hardly noticeable at all.

Hi Jon,
Keep up the discussions!!!
Some of us learn quite a bit and understand.
I have learned a lot from you and Jerry.
Thanks,
Wes

What's a tuner?  How does it work?  What does it look like (pictures)?

Thanks!

Here is a picture of a rib with a tuner. There was a device adjusted my the two screws circled in the image that would keep the barrel lugs in contact with the slide stop pin. Great idea to keep pistols in tune but it was never truly intended to substitute for proper fitup. Unfortunately some smiths tended to rely too heavily on these and their accuracy jobs didn't last because their fitup was poor to start with. http://www.guntalk-online.com/images/tunerrib2.JPG