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  Leaking down the barrel

Well it's been a very busy month to say the least. The Pittsburgh Open was a lot of fun as was playing in a local tournament and the practice in between.

This month I will be covering the dreaded air leaking down the barrel. This is the most common problem on the Automag with velocity consistency being next. The parts that can cause the leaks are the power tube spring, power tube o-ring, power tube, main spring, bolt, sear, main body, rail and if you are still using it, CO2 in liquid form.

Power tube spring & o-ring - This is an easy one to fix--just replace the o-ring after cleaning the power tube. If you still have a little leaking you might want to try replacing the power tube spring. This can be a little more of a problem because of the difference in the springs that are available. A way around having a lot of extra springs around is to use the new power tube spacer kits that AGD is now selling and putting in the current guns. When using the spacers you have to pay a little more attention to the main spring...more on that a little later. Don't forget that if you are using CO2 you can freeze the o-rings if you get liquid into the system.

Main Spring - Another easy one here if your main spring is below the level of the bolt face (see diagram) then you need to replace the spring. A weak main spring will allow the bolt to sit too far forward on the power tube o-ring, allowing a leak.

Bolt - This one is a little harder to find unless you have a good quality dial or digital calipers. If you've tried to replace the power tube o-ring and power tube spring and are still getting a leak, try swapping out the bolt just to see if that might clear up the problem. Some bolts wear a lot on the sear engagement area and that will allow a leak. Also the power piston inside the bolt can in some cases start to push out. If you can manage to measure the piston depth, the foamie bolt should be .190 +/- .005 and the foamie-less bolts will be .205 +/- .005.

Power Tube - This one is a real pain because it is a very hard leak to find. Some of the ways you can narrow this down is using a good photo loop that magnifies 10X or more. Remove the bumper and clean the area well and start looking for a crack around the base of the power tube. Most of these cracks will go around the base - a few will crack vertically. If you can't find the crack with the loop then gas up the gun and stick you finger down the front of the gun and press on the bolt and see if you get a change in the pitch of the leak. This would be a good indicator of the leak being a crack in the power tube. At this point you should be sending the gun in to AGD for servicing.

One other thing with the power tube is it can sometimes loosen from the rest of the air valve. On some of the early guns, red Loctite was used and this can break free. Most of the newer valves are soldered in place and are much more secure. If your power tube comes loose, send it to AGD for servicing DON'T try to fix it your self.

Main body & rail - Okay, again this is a hard one to find. The best way to check for this is to just swap out your valve into another gun that is working and see if your problem goes away. If it does then you could have a main body or rail problem. If you have a front bottle adapter or a front grip, you will be more likely to bend the rail when you fall or drop your gun. Some main bodies somehow just get bent or warped and you just have to send the gun into AGD to be serviced. Some of the other things to look for when you have a bent rail or main body are shoot-down and just odd leaks or ball breakage. One note on main bodies - there is a washer that is soldered into the main body and this holds the main spring, and can sometime come loose. This can also be a source of leaks down the barrel.

Sear - This one generally is only a problem if someone has been playing around with a file while doing "trigger jobs" on the engagement surface of the sear. When filing, people take too much material from the surface. This will allow a leak and will in the long term, wear the bolt much faster than normal. Another place that people will file is the top the sear, smoothing this out isn't going to cause problems, but some people go a little too far and remove so much material that the sear will no longer catch the bolt correctly.

That's all for me, I'll see you in Chicago.

(Rob Hoover, is a certified Airgun Designs technician and can be found at most major Paintball events working the AGD booth.)