New category on the site "Services" listing base hourly rates for work on SEG's etc
Perhaps Tune up packages can be offered that include install price.
maybe also even service packages
G36 tightbore barrel + install = ?
AK47 tightbore barrel + install = ?
Gearbox check and service inc shimming = ?
SEG warrant of fitness even, check over = ?
admittedly some work will always need a quote but considering this is just make up some parts and service bundles and putting them on site its pretty easy, and might allow you to tap into a new revenue stream.
Another recommendation, Find some mofsets (marmosets!! wth Firefox spellchecker) and fit/sell them, wouldn't require high stock level and if people want to buy a bigger battery for their gun its something you can offer them on top of it.
something i noticed while i was there last time, people shooting into the box by the counter seemed to make the lady that was there with her sons a little uncomfortable. perhaps it can be shifted a little. Its not going to bother players and personally i feel it adds to the atmosphere but its not exactly a safe look if your trying to promote the sport as safety focused and you have people blasting away with no goggles/glasses in the middle of the shop.
You could also use that to your advantage to demo some of the safety goggles you stock.