I'm sure all of you know that joining and sanding two part plastic barrels is like a mission impossible :-)
That is the main reason I like metal barrels, but sometimes you have to use kit barrel.
Do you guys have any tips or ideas on how to deal with that seam without making the barrel flat?

Thank you for your time

When I have a seam like this facing me, I like to use a plastic welding cement like Tenax-7R or Ambroid Pro-Weld.

These are a little stronger than your typicaly liquid cement in that they melt the plastic more. I just hold the part together, but leave a very slight seam, then apply the liquid cement with a microbrush so that it gets pulled into the seam. Squeeze together for 10-15 seconds, and you'll see a thin bead of melted plastic pop up between the halves. Let it dry well (I usually wait until next day), then gently scrape away the bead with the edge of your hobby knife. Works quite well for me.

This is a popular technique amongst aircraft builders as it makes those fuselage halves easier to blend in.

Hope that helps!

Primoz
I use Franks technique also. Here is a little more added to his technique. Use a "Flex - I - File." I'm pretty sure you have seen one, but in case you havn't, it is a square shaped bar with one side of the square missing. Between the corners of the missing side, a thin band of sanpaper is placed. When you sand it "flexes" with the curve of the barrel. Hence, no flat spots.

Just be gentle srapping the seam until it is almost flush. Next I use a piece of emery cloth(fine) and wrap it around the barrel. By twisting the barrel back and forth and using finer sandpaper the barrel comes out round. Constantly check your progress otherwise your main gun barrel may only be good for a co-axial MG :-) :-)
Hope this helps.

What I've done for the barrels I've worked on so far was to put a little extra glue on the halves, join them together and let it set. Scrape it away and if you're still having problems you can always try a mixture of putty thinned with glue and painted down the seam with a small (old) brush, let it set and sand away.

I'm sure I have some flat spots on my barrels, I just don't worry much as long as it's not very obvious. If you see a flat spot you can always try to build it up a bit using some white out, put extra on as it will shrink. Once it's set, sand away nice and easy with some fine sandpaper, smooth it out with some fine steel wool.

I have a simple technique I glue the barrel together with a good amount of glue ..I let it dry over night and then I put it in my good old electric drill chuck (protecting the sided of course) and slowly sand the turning barrel ..Never had a flat spot on a barrel here!

Rick

Another too which helps is a No. 104 Xacto blade, It is curved and allows the removal of the bead and still maintain the curve. Still have to be careful.

After gluing the halves together and letting them dry I hold the wet'n'dry paper in my fingers and rotate the barrel inside the paper - prevents flat spots. By moving the barrel up and down at the same time the sanding is kept constant over the length of the barrel as well. When the whole barrel shows that it's been sanded and there's no seam then it's done.

I agree with Rick, Dave, and India11A's method. I use graded sandpapers so the finished product looks like it was never touched and completely seamless. I also use dollar-store mini clothes pins to clamp the two halfs of the gun barrel together while it dries overnight. (These mini-clothes pins are great for clamping all sorts of stuff, and they are cheap!)

All of the above suggestions have worked for me.

What I have since started doing after any/all of the above;

from the breech end of the barrel, dip in Future and suspend muzzle-end down over the sink.
The Future runs uniformly runs down the barrel, drips away, and finally down dries clear and "polishes" all of the sanding/scraping marks into a nice smooth finish.

JM2cents

Richard,

Dang! I thought I "patented" that idea!! :-) That method works fantastic!! I've only used that method on, what, 3 barrels...way back when; but I used that method to polish metal (various types) rod.
Heck, I even used a VSR drill, with a "special" bit, to polish my collar brass before the introduction of that hi-tech "no polish" stuff young Troops are using these days. Those nice tight, even circles looked much better than that new stuff. I will admit tho before I retired from the Army, I did buy a set. heheheh

Mike