Kart in the Nork..

[saltydog452]

Rec'd a Fred Kart barrel for the Nork yesterday evening. This morning after the necessary caffene infusion, I tried to walk through the instructions provided by Mr. Kart.

His instructions, like most instructions, assumes that the reader is at least 'conversational' with the terms and that the reader is following the same train of logic as the writer. That ain't exactly true.

Suggestions as to fiting the barrel bushing were noticably missing. Following 'search' threads here on THR, I found lots of comments regarding fitting barrel to bushing, but not anything that I could find regarding fitting a bushing with a larger OD than the ID on the slide.

I've brought the fitting pads down to where there is only .025 left. The barrel is no closer to starting to approach lock up as when I started. I'm kinda confused as to just when I should start fitting on the barrel hood. If the hood is long, no matter how much the fitting pads are reduced, it would seem that the longer length of the hood would prevent the barrel from STARTING to get in lockup.

So, do you file a bit on the pads, then file a bit on the hood?

salty.

 

[saltydog452]

A couple of things that I have learned about fitting the Kart into the Nork..

First, Mr. Kart might well be able to fit the 'EZ Fit Barrel' in an hour but I haven't been able to do so in about 10 hours.

Second, my bride definitely does not like the smell of Dykem at 0600. 'Specially at he breakfast table.



The slide and barrel will now go into battery.

There is .003-.005 space on each side of the barrel hood between the sides of the hood and the sides of the slide.

The rear of the hood just gets friendly with breech face of the slide, not intimate. Minimal contact, the .003 feeler gauge provided with 'EZFit' Kit will not slide between the front of the breech face and the rear of the hood. As stated in previous paragraph, there is .003-.005 clearance on each side of the hood where the hood finds its way into recess milled into the slide.

Depth of the barrel lugs, where they are supposed to mate with the recess of the slide, are .050. I may be a little off in my measuring ability, but when the fitting pad height is at .025 or so, that don't leave a whole lot of room for barrel/slide lug ungagement on the first lug, much less #s 2 and 3.

There are still 'shiny spots' on the fitting pads at .025 height. Is the 'fitting' process supposed to stop when the slide goes into battery, or when the 'shiny' spots disappear? Before you reply, read on...

If I understood Mr. Karts analogy of the 'three leg stool' correctly, it would seem that the raised 'pads' on both sides of the barrel (which would show Dykem contact with the recesses milled into the slide) would necessarily have to have forceful contact with the inside recess of the slide.

With only .025 vertical raised depth of the barrel lugs, it would seem to this rookie, that there isn't a whole bunch of room for barrel/slide mating.

I dunno, your thoughts please??

salty.

 

[1911Tuner]

Kart/Nork Problems

Hey salty,

Sounds like you've run into a similar situation that I did recently with the PimpNork. Combined distance from the slidestop pin centerline and the top of the slide...underside...was more than the Easy-Fit system could compensate for. Remember that it doesn't rely on an oversized lower lug and slightly tall locking lugs to achieve the vertical lockup. (The barrel can lock anywhere on the arc...but will it do that and provide good lug depth of engagement?) Likely a tolerance stackup that...even though all separate parts were in-spec, the sum of the tolerances stacking up in the wrong direction threw the
whole dimension out of spec. In your case...which sounds worse than mine...it seems that you have at least one dimension that's out of spec in addition to the tolerance stack.

Kart's Easy-Fit system is very good, provided that your aggregate height from slidestop pin to top of slide is within spec. If so, the fitting pads will be nearly flush with the slots between the lugs by the time you get the gun to go solidly into battery.

It also presumes that the installer will fit the overlength hood horizontally to the first lug, and hope for the best on the other two. Again...if the location of the lug abutments in the slide are within spec relative to the breechface, your chances of having at least one more lug engaging horizonatally are pretty good...or are at such a place that with use and time...and lug deformation...that another one will come into play. (Equalize)

If all slide lug/recess locations are within spec, the Kart will fit to the first lug...which is the strongest one, being more supported. If the fit also provides good depth/overlap...you'll have a good lockup...even if the other two aren't kissing anything except air. As long as you don't get crazy with handloaded ammo pressures, it'll do just fine for a long time.

If, on the other hand, it turns out that the #2 or #3 location is such that filing the hood to allow the gun to go to battery on one of those less suported lugs...and leave #1 wavin' in the breeze...your lockup won't be nearly as strong. if it is, in fact, coming to bear on one of the less-supported lugs, you can face that lug back just a little so that #1 will come into the picture. Then you have two lugs online, with one that is well-supported.
If things work out just right, you can bring all three to bear. If you can do that...even with only .045 inch of vertical engagement per lug...you've got a pretty stout lockup. That's more total load-bearing surface than two equal lugs at full depth.

This is why, even with the Easy-Fit system...even if the slide is within spec...that it's important to gauge the slide to determine where each lug is
and how the barrel and slide will bear the thrust loading when the gun is fired.
Withoug gauging the slide, you don't know what kind of fit that you have, other than tight vertical and .025 inch of depth/overlap.

On the PimpNork, I had to order a hard-fit barrel and adjust the lower lug, and both the forward lugs to equalize...and on #3 I had to let it pressure equalize by firing it with a few near proof loads, since the closest that I could get it...and maintain the lockup that I wanted... was about .001 inch off the slide abutment. All three are taking an equal portion of the load with near full vertical engagement, and the lockup is about as strong as it gets.

Warning:

With modern barrels, pressure seating/equalizing more than about .002 inch can result in a cracked lug. Ya gotta get it close and ya gotta keep the lug faces as square as possible to prevent side-loading of the lug under pressure.
Also...Pressure seating/equalizing should be done with at least .045 inch vertical engagement. If you have less, proof-level ammo is not advised. Instead, use standard-pressure ammo and lots of it. Yeah...Dirty job, but somebody's gotta do it.