Posted 05 July 2012 - 11:17 AM
Just performed some upgrades and wanted to share my results.
The Shredder Concave Spacer (SCS) hop-up nub fits the stock KWA hop-up unit like a charm. Additionally, the System packing fits, albeit very tightly with a KM TBB. The only modification to the packing is cutting just a bit off the end to ensure the inner barrel can fit with the hop-up unit, which others have found to be the case as well.
I recently purchased a replacement hop-up unit and KM 6.02mm TBB from the KWA Pro Shops, and along with an SCS nub and Systema packing have seen improvements in shot grouping and range. But I have to say the stock parts work extremely well and you’ll do swell without upgrades.
For external upgrades I found the Troy Industries MRF line of rails fit nice and tight without having to tool with anything. The MRF-MX 10” was placed on a KM4A1 upper (which is used on an SR7 lower so the battery is in the stock). You will have to remove the stock delta ring and retention spring (as you would on real steel) in order to fit the MRF rails. The KM4A1 barrel nut should fit fine, but because I’m lazy I replaced the entire barrel nut with a “plain” Kings Arms barrel nut. The KA barrel nut fit without issue and no wobble on the outer barrel.
If you are going from a KM4A1 or KM4 RIS, you may need to replace the front sight/gas block, depending on the MRF rail length. I found that a Kings Arms low-profile gas block and tube fit well, which is a replica of the Troy Industries low-profile gas block.
I’ve also found that the Knights Arms Co. RAS rail fits well on a stock KM4A1 upper. The only thing you may have to do is move the front sight/gas block forward 1/16”. If you experience issues fitting the rail, consider taking the rear clamp off the RAS unit, as it may be flush with the gas tube. Even after removing the clamp the rail fit very tight with no wobble.
One word of warning I found with one of my KM4A1 uppers is that one of the receiver’s threading was cut so that the barrel nut grooves, when fully tightened, were a little off center. Because the KAC RAS has alignment pins that fit into the barrel nut grooves at 10 and 2 o’clock. Because of this the RAS canted my front sight a little. You could probably fix this through modifying the RAS or loosening the barrel nut just a smidge and tightening the barrel using nylon tape.
I only had the offset barrel nut on one of my KM4A1 uppers, another upper, which was purchased from the same place at the same time, was just fine.
The final thing to report is that the Mako/FAB Defense rail attachment for the stock KM4A1 hand guards fit. You may have to make a small incision on the rails (or handguard) in order to have all the screw holes line up. Once that’s done you’ll be good to go.
Hope this helps with some upgrade ideas.