Removing metal tube from inside plastic barrel

[Jib]

Anyone have any ideas on how to remove this metal tube from inside this plastic barrel? This is the detailed M1 Abrams gun from Specials Ops Models off of eBay. It looks great, but I want to use it for airsoft, and it comes in three pieces you have to assemble. Each piece has a brass tube in it, and to connect the three pieces you have to use a smaller diameter brass tube to act as a connector to join them together. So the Airsoft pellet would exit the unit into an area with a larger diameter, then a smaller diameter, then big, then small, then big again, then exit. I imagine this would play hell with the FPS of the BB.

I had thought to use a new tube where the OD of the tube matches the ID of the plastic part of the barrel (8mm), and the ID matches the OD of the Airsoft tube (7.6mm). This way I would have one long solid tube throughout the barrel, and then that tube would fit directly over the tube of the airsoft unit.

However, first I would have to get the old barrel out. This was easy to do for two of the three barrel sections by pushing the metal tube out with another 8mm tube, but this is not working for the tube in the final part of the barrel. I’ve tried whacking the tube in the final part of the barrel out pretty hard by essentially aligning my sacrificial 8mm tube up with the tube in the gun barrel by using the slight smaller connector tube to join them, and then trying to push that tube out by slamming it on concrete (I did try to be gentle at first), but the tube won’t budge. I also messed up the outside part of the barrel by putting it in a vise and trying to hammer it out, didn’t budge. So now I’m going to have to fix that.

I’m afraid that for whatever reason the other metal tubes weren’t glued to the plastic, but this one is. I have thought maybe using an adjustable hand reamer to drill the metal out by widening it?

Any ideas?

[tankme]

I have one of those barrels. It's not glued...the brass tube is used in the casting process so the resin is cast around the tube. Good luck getting that out without destroying the barrel. I would also assume that the brass tube gives the resin some rigidity so that it don't break. You could drill it out, but once again...you are weakening the barrel and that process may destroy it.

[Jib]

Yeah I’m hoping to ream it out and replace it with a tube of the same diameter, but the muzzle gets pretty thin at the end. Maybe the reaming process will loosen it? Maybe it will be easy to grind out because it’s brass?

It sucks the other two were hard to remove, but it could be done. This one is not happening.

I also have an idea to get a longer barrel that will fit inside that first third of the barrel and then use the another barrel of the same size as the one in the front of the barrel. So I’ll have two pipes that fit over one another, but still have the ID to be able to fire airsoft. I’ll have to wait until early august for them to arrive though

[Jofaur86]

Good morning,
I would say ? heat (gently without burning) the exterior or interior part with a heat gun, which should? can it make it easier to remove the brass tube? there is also maybe? mill around the brass tube, the resin and while holding the tube vertical for a while, insert acetone (solvent) perhaps it will be able to go down around the brass and dissolve the resin? there might be? also, leave the tube in the freezer (the metal shrinks) overnight, and then see, this technique is used to unblock pistons by mechanics of thermal bikes. It's just ideas like that, with no guarantee on my part ,just possibly help

[Pavel]

This tube is the basis for the outer barrel.
It is not possible to eradicate it..... unfortunately.
The only solution is to use a tube of suitable diameter.
The airsoft barrel has a 6 mm inside, I think you can find a suitable tube in stores.
You don’t need special accuracy, like with an airsoft weapon, I have a 5.98 mm barrel on my gun, I calibrate the balls, otherwise they might get stuck....

[Jib]

The only airsoft barrels I’ve been able to find have had an OD of 8mm or greater, which won’t with with that metal tube still inside it. And I only found that out because almost nowhere lists the OD of their airsoft barrel, only the ID.

I think im going to wait for the 8mm and the interlocking 7.6mm barrels to come in in August before I try anything more invasive.

Thank you all for the suggestions! Hopefully I can make the interlocking tubes idea work.

If the owner of the company that makes these barrels is anywhere on this forum and sees this, it would be really awesome if you could make this with one long barrel with and ID of 7.6mm instead of three separate sections of interlocking barrels. That way you can just slip over the HL airsoft mechanism barrel. I know Airsoft is kind of the red headed step child of the RC tank industry, but it would be nice if its possible to make this change.

[Jofaur86]

I think it would be possible to do it from the inside with a lathe!!!!

[Jib]

Well if I have to I got this here hand reamer. That’s about as close to a lathe as I’m going to be able to get to. Hopefully I’ll be able to figure out a way around it. Should know by this Friday which direction I’m going to go.

[Jib]

So, after this post I’m going to create a build log in the next day or two as this is just one of several things I am doing to my Abrams all at once.

So I finally had some success today, so I’ll leave what I did here as this would be an actual tip/trick instead of me just asking questions (I just noticed the giant red text today said says this sub form is for posting tips, not asking questions, sorry).

So let me drop some numbers. The ID of the plastic part of the gun barrel is 7.9mm. The OD of the brass tube inside of the plastic part of the gun barrel is also 7.9mm. The ID of that brass tube is 7.2mm. The OD of the smaller brass tubes that are used to connect the three parts of the gun barrel are also 7.2mm. The OD of the metal tube on the Airsoft unit is slightly under 7.6mm and the ID is around 6.5mm. As a comparison, the ID for an airsoft gun barrel on a airsoft gun that shoots 6mm pellets ranges from 6.02mm to 6.04mm.

To replace the brass tube, I bought a stainless steel tube that has an OD of 8.0mm and an ID of 7.6mm. Although the fit of this tube onto the airsoft unit tube doesn’t have a lot of give in it (especially compared to the stock HL barrel that has an ID of around 7.85mm, so it wiggles a lot) it slides back and forth easily on the Airsoft unit barrel, making it perfect for this application.

I bought a series of 117mm long drill bits ranging in 0.1mm increments from 7.2mm all the way to 8.0mm in diameter. While the 7.2mm drill bit went completely inside the brass tube I was trying to remove, the 7.3mm bit went in a little bit and then caught on the tube. Instead of reaming it out, it began to push the tube out of the other end of the barrel piece. So I worked it out slowly until the drill bit was all the way inside that piece of the gun barrel.

At this point although the drill bit was all the way in, the brass tube was not all the way out. I grabbed the tube with some curved pliers and reversed the drill to get it out. I then slowly rotated the plastic barrel by hand, holding onto the brass tube with the curved pliers, and slowly worked it out.

Unfortunately the end of the barrel ripped off, but it doesn’t seem so bad that I can’t fix it.

Now, I took the 8.0mm drill bit and drilled into one of the more sacrificial sections of the gun barrel to see if it would fit. It did, about as tight at the original 7.9mm brass barrel, which was VERY tight. I decided to order a 8.1mm drill to see if it will make it a little easier to push the tube in without making it slide too easily. Should come tomorrow some time.

So if anyone cares enough about airsoft and gun barrel detail to do the same thing as me with the exact same product, this is a tip on how to accomplish this. I’ll be putting this and other things in my build log once I get that started.