Gas shotgun performance

[Mad dog 49]

I've recently picked up a tri shot gas STF12. I'm wondering, is it normal for only 1 barrel to produce any power and the other 2 barrels just seem to flop out the thing for range around 10-15ft?

 

In relation to this though, it was only about 3⁰C all day but, even with orange or red gas, it was the same. 1 barrel goes to the horizon and barrel 2 and 3 are weak.

 

Does anyone know how to get a gas shotgun apart so I see the fixed hop and feed routes?