Bull barrel lockup

[dth122]

I'm working on my first 2011 build using a Rogue Tac slide and 9mm Primed bull barrel.  Generally speaking, it's like a Kart EZ-Fit.

 

I've run into a question on the barrel fitting process.  The hood seems to fit well.  Hood length is 1.311" and I'm not seeing any light between the hood and breech face.

 

The guidance I've seen is that I need at least 0.038" of lockup before I start filing the lug fitment pads.  However, I only have 0.027" of lockup.  My problem is that I can't find interference anywhere.   The hood back and sides look clean and the lugs look clean after some aggressive cycling of the barrel in and out of lockup.

 

Is there someplace else I should be looking for a better fit?  Or should I go ahead and start working on the pads?

 

I don't want to file the pads and end up taking them down too much while my lockup problem is somewhere else.

 

Any thoughts?
 - Dave

 

 

[ltdmstr]

If you're not binding on the hood, and don't have contact at the lugs, I'd check the slide bore where the barrel contacts the bottom.  If the barrel is springing, that's probably where you need to remove material.

[Aircooled6racer]

Hello: Look in the grooves of the barrel on the sides. Also look at the front of the barrel on the top about 3/4" in from the end of the slide. Lastly look on the bottom of the barrel near the end of the slide. I would also try to get more lockup than that. Thanks, Eric

[stardust tommy]

use (cande)soot to mark your barrel, insert the barrel in the slide and tap the barrellugs with a soft hammer. remove the barrel and see where you make contact.

 

 

 

.042-.045 lock up is needed

[Bakerjd]

I've used plumbers putty before to see where the binding is. Make a little ball of it and stick it in the lugs on the barre and slide. Then test fit. 

[assaulter]

Likely springing.  I rarely fit a Bull barrel that doesn't need to be adjusted at the muzzle end.

[dth122]

Took me a while to look at this.  I totally agree with everyone that I need more lockup.  That's why I'm concerned.

 

Incidentally, what's the best way to measure?  I can tell it's too little by eye.  I've measured from the top of the slide to the top of the hood, in and out of battery.  Is that the best way?  Or is there something more reliable and repeatable?

 

Plumbers putty comes back clean... I don't see any any of it making hard contact around the lugs.  The only area of contact seems to be the fitment pads.

 

I agree that it's likely springing.  Is there an easy way to identify the contact points?  I haven't tried candle soot yet, but I can't see any interference around the top of the muzzle end of the barrel with dykem or sharpie.  I could start filing down that area in general, but that seems unscientific.

 - Dave

 

[Denato1]

first I would check to see if a deprimed case primer hole lines up clean with the hammer pin hole.  If it needs to move up then File tiny amounts 3/4in back from the front of the barrel on the top. very small amounts stack up quickly in that area so go slow.

[assaulter]

I use a rubber mallet and moderately tap on the bottom of the barrel lugs.  You'll hear it ping each time because the barrel lugs are slapping the slide lugs.  You'll also easily see the marks left and the top of the muzzle end.  As you get closer to fitting you'll notice this "ping" goes away because the springing is no longer pushing the barrel out of lockup.  Measure your lockup at the top of the slide to the top of the barrel hood.  If your dimension changes when you are pushing it into lockup and releasing the pressure you know it's still springing.

[Benevolence]

I had this same issue and it was quite frustrating. I marked the points of contact in the thread below, but essentially you end up with a pivot point at the top of the barrel, about half way back, with the other two points of contact being the bottom of the barrel with the slide, and the barrel locking lugs trying to engage the slide locking lugs. You've got to either raise the pivot point (remove material from the top of the barrel), or lower the other limiting point (bottom of barrel with slide). I ended up electing to remove material from the slide (where the front & bottom of the barrel rests on) to allow the locking lugs to move up. As lmtdmster said; if it's got some "springy"ness to it then it's likely that.

 

 

[dth122]

Thanks everyone for the suggestions.  I ended up taking a little bit off at the muzzle end and that got me in the ballpark.  Then I started working on the upper lug pads.  Getting those to the point that the barrel would ride over the slide stop pin gives me plenty of engagement.

 

I think the trick was finding the springing point.  Once I did that it was easy going.

 

I still need to check the firing pin hole to make sure it's centered.

 

TBH, next time I think I'm going to use a regular gunsmith fit barrel.  I appreciate the you don't have to cut the lower lugs on the EZ Fit, but it seems to limit your areas of refinements and adjustment.

 - Dave

[ltdmstr]

Firing pin hole doesn't need to be centered.  And if lockup is at the higher end of the range, it's probably not going to be.  As long as it's not way off, you'll be fine.  

[Trader]

On 12/14/2020 at 7:06 AM, Denato1 said:

first I would check to see if a deprimed case primer hole lines up clean with the hammer pin hole.  If it needs to move up then File tiny amounts 3/4in back from the front of the barrel on the top. very small amounts stack up quickly in that area so go slow.

This .

[Bwenning]

One easy way to check the position of the firing pin relative to the case is to use and unprimed case with the primer pocket filled with modeling clay, just put a mark at tdc of the case, chamber the case and manually push the firing pin into the clay.