G&G Knock Arm & Plunger Set
For those unfamiliar to the M700 internals, the magazine consists of multiple components. Personally, I find the system unnecessarily complex, but it seems to work okay...
An explanation of the system:
1. Trigger is pulled
2. Valve knocker (hammer) is released
3. Valve knocker strikes the striking plate on the back of the magazine
4. Striking plate in turn strikes the plunger inside the magazine
5. The plunger than hits the knock arm. (The knock arm is supported by an internal structure in the magazine that it can rotate against)
6. The knock arm's 90 degree extension sits inside a groove on the release valve. When the knock arm's upright arm is knocked by the plunger from behind, the other arm forces the valve down, and thus, releasing gas into the gas route connection
7. The gas route connection has an integrated spring tensioned release outlet. This is what the G&G gas route connector spring upgrades. It puts tension against the bolt's intake port for the gas.
So... given that fairly complex explanation of the inner workings of the magazine, you immediately notice a downfall of the design: TOO MANY MOVING PARTS!
Particularly, the striking plate itself is a redundant part. It touches the plunger... and all it does is acts as an interface between the valve knocker and the plunger. But at the same time, due to the design of the knocker, and of the plunger, the valve knocker would quickly get damaged, and so would the plunger over time.
In steps the G&G Knock Arm & Plunger Set.
The KM Custom magazine parts is similar... but not the same. The KM set consists of:
- Plunger
- Knock Arm
- Gas valve opening
- Gas route connector port
It has two more parts. Are they necessary? Does one set perform better than the other? That was what I was about to find out.
The first thing I noticed about the G&G set, was that the design of the plunger eliminated the need for the striker plate! Very nice. The end of the plunger is now replaced with a protrusion that ends in a larger striking surface. One less moving part is always good in my books! The KM set just goes as far as 1:1 replacement of the stock arm. An impact plate is still required to interface the plunger with the valve knocker. The G&G setup is simple, yet effective.
So installation proceeded. Taking the magazine apart isn't too difficult, if you're familiar with how gas chambers work and such. These Tanaka magazines have a TON of parts. No wonder they're so insanely expensive. And heavy.
Once completely disassembled, two c-clips are removed to extract the plunger arm and the knock arm. The G&G versions went right in without much hassle. Just the reverse of removal, except the plunger arm needs the striking end to be screwed in from the other side. G&G was kind enough to drill a small detent so that a small allen key or something can be inserted on one end to hold it still, while you screwed the other end in.
While I had this all apart, I replaced the gas route connector spring with the G&G version. I like the spring. It seems to tighten up initial velocities a bit and improves the air seal.
Magazine all assembled. Time to fill gas.
*PSSSSSSHSHHHHHH*
"WTF?!??"
Cold propane all over my hand again, from the release valve. Something's holding the valve open again. Either the valve knocker's release arm is a bit too big and pushing the valve down... or the plunger is a bit too long and pushing the valve knocker down.
So I removed the G&G knock arm and replaced it with the stock Tanaka one. Once reassembled, first gas fill was a success. So it seems like the dimensions of the knock arm are incorrect.
I didn't test the materials of the G&G part versus the Tanaka part, so I can't really say which one is better. But the Tanaka part seemed sturdy enough, so I decided to stick with it. I may revisit it in several months to see if any wear has made an appearance. I pretty much just stuck with the Tanaka part out of laziness in not wanting to modify the G&G part to fit. Some elbow grease and a file should be able to take down enough material to make it work.
Time to fill up the magazine and test it out.
Results:
485fps
461fps
457fps
457fps
454fps
455fps
451fps
453fps
453fps
450fps
446fps
446fps
453fps
451fps
Avg: 455fps
WOW!!!! :shock: I LIKE THIS SETUP! Now THIS is the kind of performance I've been looking for, that I expect, and that I'm used to! Very consistent, and for gas setups, you WANT it to start high and ramp down. Not the other way around! It gives you a better chance of that "one shot, one kill", because hop up will not be affected negatively.
But KEEP THESE RESULTS IN MIND for safety reasons!! Remember your engagement distances, and if it's been a while since you've last fired a shot from your mag, the first following shot will be higher than the magazine average!! Keep it safe.