Gamo Urban Customized: Full length Shroud Conversion

[LeE]

I have been asked by numerous people how I convert the Gamo Urban (this will work on similar models) from the hideous looking LDC that comes with each rifle to the to the classic full length shroud that takes the bark out.
I start by separating the barrel from the action (if you do this, be mindful of all the little pins, springs and other small parts that will fall out as you separate the two halves) and chucking the barrel in the lathe. I use a groove tool to cut the LCD off about an inch from the taper. Once I get through the outside wall, it is weak enough to snap off by hand. I then turn that section of the barrel where the LDC was down to a precise diameter so that I can later press fit on the newly designed air stripper.  Since no length of barrel is cut off, this method preserves the choke and the performance.


My old air strippers used (6) 1/8x1” slots to redirect the air. While it did work, it was nowhere efficient enough to do the job I demanded. With later experimentation I did with my Kral 22 last year, I found that using fewer but larger porting makes all the difference! With the addition of having a CNC mill this year that I didn’t have then, I designed the new air stripper to be twice as long over the old but the slots at .273. The slots are also 3D milled at an angle to increase the port size without losing strength. My theory is that because the internal geometry is thinner as it comes together at a sharp corner over a flat wall from the previous, it aids in stripping off more air and causes more disruption. 
Here is the air stripper on the mill, ready to be slotted.



After the milling is completed, I deburred and degreased the part to get it read to mount on the barrel. The other side was reamed out a half though under the size of the barrel and heated up in the oven and put the barrel in the freezer. After the barrel and stripper are seized together, I chucked the barrel back into the 4 jaw so I could dial in the bore and machine off the remaining stock left on the air stripper.
What is left to do for the full length shroud is to machine the tube, the barrel mount and end cap. The rear barrel support is among the tightest tolerance parts out of the whole build (in addition to the air stripper bore for mounting). I machine the bore so that it is within a couple thou of the barrel OD. This part sets the alignment of the rest of the shroud so it is crucial to get this part correct. I finish the part on the mill to match the angle of the breech and drill/tap for setscrews.
 I use the Mrod style cones and a spring forward of the air stripper for more air disruption. I finished all black parts with a matte black powder coat. The pictures don’t do it justice but that black really matched the rest of the gun well!


My buddy requested new barrel band be made to fit his newly shrouded Urban as the cheaply made plastic one clearly isn’t going to fit and this one machined from aluminum allows the barrel to free float. I used three evenly place setscrews to hold the barrel band in place (My BSA did not have a barrel band from when I did a full length shroud for so I made two ).

[Rob M]

very nice work ! I'm trying to figure out how you did the spiral vents without a 4th axis.. Ill have to think on that one before checking back

[LeE]

very nice work ! I'm trying to figure out how you did the spiral vents without a 4th axis.. Ill have to think on that one before checking back

I used a 5c collet block and indexed the block 4 times to have 4 slots.

[Rob M]

gotcha , I now see theyre straight cuts, just angled on the x axis slightly ..

[Bob Pratl]

Lee, very nice work and design.

[LeE]

Lee, very nice work and design.

Thank you very much I really enjoy designing and machining.

[screwwork]

Nice work done on the ole lathe & mill!

[LeE]

Nice work done on the ole lathe & mill!

Nothing like having the freedom that machine tools gives to enable your ideas!

[screwwork]

I worked in a machine shop for 15yrs, I miss having a machine shop so bad, especially since I have got in to AG's..   

[LeE]

I worked in a machine shop for 15yrs, I miss having a machine shop so bad, especially since I have got in to AG's..

I could not imagine being without after having them.Especially in this ever addicting AG hobby! So many ideas and so many things I want to build!!

[Rob M]

I worked in a machine shop for 15yrs, I miss having a machine shop so bad, especially since I have got in to AG's..

I could not imagine being without after having them.Especially in this ever addicting AG hobby! So many ideas and so many things I want to build!!

agreed.. Airgunning and machining go hand in hand.. I really could not see being into airguns anymore if my home shop disappeared.

[LeE]

I worked in a machine shop for 15yrs, I miss having a machine shop so bad, especially since I have got in to AG's..

I could not imagine being without after having them.Especially in this ever addicting AG hobby! So many ideas and so many things I want to build!!

agreed.. Airgunning and machining go hand in hand.. I really could not see being into airguns anymore if my home shop disappeared.

That would be like take an instrument out of a musician's hands!!