Tyrell Frazier, on 27 November 2013 - 10:22 AM, said:
First, Hello and Thanks to all who read and respond. Im new to airsoft and I've been reading all I can find about sr7 upgrades but I seem to hear alot of mixed opinions and ideas. So far what research that I have found that I have questions about is The CQR MOD 2 and the KM4 SR7 both have the same length barrel which proshop states is 273mm. But the fps on the MOD 2 is 315-325. The fps on the KM4 SR7 is 330-350. Barrel same length so what causes the fps to be different? What I have read on different topics about sr7 is that its the spring, the cylinder, and the barrel. Which one or all? My main focus is I just want to know, I have a KM4 SR7 devgru and even though it is designed for cqr I want to convert it to get better fps and better accuracy long range. If I have to change barrels for longer length I dont care. I just want the truth from someone who knows and or has tried it and has gotten facts. Can anyone help me? I would greatly appreciate anyones help.
I think I can help. One or the things to remember is that KWA has a tendency to tweak their designs for any number of reasons that can range from cosmetic and economics to performance. Case in point, the SR7. Early SR7s had a type 1 ported cylinder and a KWA m100 spring. This produced around 350 FPS. It also lead to some over spin and pre-engagement issues with some LiPo batteries due to a high ROF 22 RPS and a soft spring. This caused double shots in semi (on occasion) and ate pistons when out of spec batteries were used.
The later SR7s (current production) have employed an m120 spring which helps to eliminate the pre-engaggment of the sector gear on the piston body but would also boost the FPS. So, to bring the FPS back down, KWA is now using the CQR cylinder found in the MODs 1 and 2. This leads closer to 330 FPS give or take.
To increase accuracy, I recommend a longer, tight bore barrel like the KM Head 6,02 found in the Pro Shop: http://store.kwausa....arrel395mm.aspx
I have this barrel and love it. Now, if you have the old SR7, simply add the barrel and you are up to about 380 FPS. If you have the new SR7, the FPS will drop to around 310-315 because the cylinder is too small for the barrel. Therefore, you add a Typ1 or Type 0.5 (KWA brand) and you will be at about 390-400 assuming a good airseal and non-compressed spring.
The question is, what SR7 do you have? If you post a picture of the cylinder showing the port on the right side I can tell you.
Hope this helps.