I've worked on lots Of G&P Armalites, but they've all been either the M4A1 or the SPR/A. They are great on the parts and build quality. Nobody does it as well as G&P, except for Systema.
They do have issues of their own. Here are some:
1) Some of the G&P guns in Canada have been upgraded to shoot 450-475 FPS at either the manufacturing or distribution level. This has lead to premature failure on some components like gears and piston/piston head. The piston is a polycarb and that is IMHO one of the weakest parts of a 450 FPS system.
2) Tappet and selector plate failure. This is a problem as G&P uses a clone of a Prometheus hard selector and tappet, which is a poly-amide composite. They are lightweight and strong, but do not allow for any flex. If the tappet flexes, it will break.
3) Nozzle. They use a metal air-seal nozzle with an o-ring inside to give it a very good seal. Keeps air losses from the cylinder system to a minimum. However, this nozzle is too tight for the cylinder head and this has caused many a tappet to fail. Removing the o-ring will solve that potential problem, but at the cost of a flawless air-seal.
4) Motor position. They motor must sit in a very specific position. The wiring must be routed in a precise fashion with bends at exactly the righ spots or the motor will be slightly shifted and bind up. You can not rely on the motor endplate to seat the motor precisely enough. Consequently, a large sudden jarring to the gun can cause the motor to be thrown out of alignment, requiring re-alignment which is not really field-freindly.
Now the good points:
1) 7mm reinforced bearing gear box. Can't go wrong there.
2) Reinforced stanard ratio gears.
3) Beefy metal bearing spring guide.
4) Tapered full capacity cylinder.
5) Steel cylinder head.
6) Low-resistance switch assembly.
7) Metal hop-up chamber.
8) Very good fit and finsh of body components and very solid construction.
Once you get past a few minor issues, they tend to run very well and are very accurate and potentially powerful guns. They only recommendations I have for changes to this gun are:
1) Remove the air-seal o-ring.
2) Replace the tappet with something else, perhaps even a stock Marui.
3) Replace the cylinder head set with a Systema silent head set. If you do this you can keep the o-ring in the nozzle and it is not too tight.
The magic FPS for longevity, range and accuracy seems to be around 390 FPS. Less does not take the gun to it's potential and more just causes stress on some components and may lead to failure.
Age verifier Northern Alberta
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Freedom is the wolves limping away while the sheep reloads.
Never confuse freedom with democracy.