Barrel needs to be upgraded. I had a J&Jceramic 12" with an attached APEX I replaced it with. replaced the trigger assembly with the upgrade. All the internals are stock. I replaced the Hammer spring about a month ago, which seemed to increase velocity a little. Also reccomend an electric hopper. something not too expensive that is capable of keeping up with 12-15 balls per second. I selected a VL 300 hopper, I have never chopped a ball, Only a few barrel breaks now and then. But then again its expected with an APEX at the end of the barrel. Not all paint is created equal.
Right out of the box I had a fully electric marker for a lessor price.
None that comes to mind.
I have to say I also like the A5 but refused to spend that much on a marker considering I would play paintball once a month, or even less in some instances. If you have kids wanting to get into the sport, I don't see why this would not be an excellent maker. Provided its maintained. I have friends that have A5s, MR3s, Pilots, and BTs, and I think it holds it on on the field.
I personnaly think the US 5 is very reliable. I had it for two years with no breaks either on the field or off. I had problems with my CO2, but that was due to issues with my remote line o-rings. Some external items for the A5 (stock, G36 rail& stock) will fit the US 5. I used the G36 stock and Rail system that fit nicely on the US 5 with no modding. Its been a great maker thus far.
I did replace the hammer spring with a new stock one from a kit that I picked up and switching between the old one and the new one chrono readings were significantly higher.
If your not wanting to spend alot of money on a marker I think in my opinion this is a great starter marker.