WE GBB M4 upgrades for non-skirmishing

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Hi. Recently bought a WE M4 that I will be using as a 'tin can/target plinker' for the Summer. Potential oob/stock fps at over 400 on a warmish day on 'Green' is adequate and I don't want to go down the C02 route, as I have enough steel bb guns for that platform.

Using it on full auto, as much as semi is a definite, so I want internals that will hold up for a while. A NPAS kit from what I can see would not be beneficial for my requirements (I wouldn't want to increase recoil for instance or decrease fps). An aluminum nozzle and a steel trigger box and internals would be though I reckon. So this is what I was thinking:

1) Ratech steel trigger set
2) Aluminium nozzle
3) Spare stock WE bolt
4) Hop rubber upgrade (!?!)

I was looking at about £200 worth of upgrades and no more. The more fps (at least up to the legal 1.2 joule) the better(without c02) and the more it will cope with full auto for both bb/non bb firing the better also too.

Edited to add: I am not totally convinced about steel bolts and the amount of work they need for efficient cycling in gbb's - hence having a spare stock bolt. Good maintenance and lube will I'm sure you'll agree keep a stock bolt happy for a while.