AOSC Forum Archive

I have a CA M15A4 CQB Seal.  It is has a tightbore and silencer, but other than that it is stock.  It is currently shooting around 300 fps.  Would installing the next higher spring keep the fps below 340 fps?  I couldn't tell you what the current spring is.

This is a great opportunity for a quick lesson on the relative "strength" of AEG springs. For an example lets look at some of the most widely used springs today: Systema Springs.

Below is a picture of a Systema M100 spring:
[img width=600 height=450]http://www.airsoftadvantage.com/images/m100.gif[/img]

I know it is a little hard to see but, notice on the front of the package there is a sticker that says: "M100". Now, a few people I have talked to seem to think that this is just an arbitrary number that represents the relative strength of the spring. This is not true, there is nothing arbitrary about that number. The designation "M100" stands for "Meters 100" or in other words "100 Meters Per Second." The "M" designation is actually telling you how fast your gun should shoot with this particular spring using .20 bb's, assuming your gun is in good working order (Please see note below).  

So if you were to buy a Systema M100 spring you could safely assume that you will be chronoing right around 100 meters per second or 328 fps using .20's. You can use a "Meters to Feet Converter" to quickly find out what your gun should be shooting with a particular spring. Please remember however that not every gun is alike so the fps on your particular gun can vary, and from my own experience, the estimated fps is usually within plus or minus 10-15 fps.


Now, one quick note: Systema, like most other manufacturers use .20's when calibrating their springs. Some companies, like MadBull, use .25's to calibrate their springs. At this moment MadBull is the only one I know of that does this, but I have heard there are 1 or 2 other companies that do as well, I just can't remember which ones ATM.

I know from experience that Airsoft GI Masamune Series, G&G, Guarder, Prometheus, and Systema Springs are all calibrated with .20's.

I hope this helps out guys!

I'm shooting around 300, so using the calculations, the stock spring in my CA would be an M90.  Does that sound correct, or does someone know exactly what spring is in my gun?

More than likely your stock spring was an M100 and was probably originally shooting around 330fps (This is about average for CA). Since you have had it, the spring has probably compressed a little bit, hence the 300fps. An M100 should keep you below 340fps.

Remember to decompress the spring after playing to minimize FPS loss due to compression, as well as avoid other unnecessary wear. Systema variable pitch stainless steal springs have been the most consistent and highest quality springs I've used.

Dominum wrote: Remember to decompress the spring after playing to minimize FPS loss due to compression, as well as avoid other unnecessary wear. Systema variable pitch stainless steal springs have been the most consistent and highest quality springs I've used.

How do you decompress a spring?

http://www.southcarolinaairsoft.com/forums/http://www.southcarolinaairsoft.com/newforums/viewtopic.php?t=1

Refer to section 2.

Dominum wrote: http://www.southcarolinaairsoft.com/forums/http://www.southcarolinaairsoft.com/newforums/viewtopic.php?t=1

Refer to section 2.

Ok, I do that pretty much every time I finish using my gun.  But, my gun has always shot around 300, that's why I was wondering if it actually has a stock M100, which from the information presented, should shoot around 330.

Might not be the spring, might be the piston o-ring isn't sealing as well as it could in the cylinder.  Nozzle might be worn and it's not sealing 100% to the hop up or cylinder head.  How many rounds have you put through that gun?

There's a lot more to FPS than just a spring and losing 30fps is not hard to do if you have a small airleak.

severed wrote: Might not be the spring, might be the piston o-ring isn't sealing as well as it could in the cylinder.  Nozzle might be worn and it's not sealing 100% to the hop up or cylinder head.  How many rounds have you put through that gun?

There's a lot more to FPS than just a spring and losing 30fps is not hard to do if you have a small airleak.

How many rounds, well, maybe around 9 - 10k.

Have someone disassemble the gearbox and test the compression, and definitely get a new Oring (number 14 at a hardware store). At this point in it's life, it needs to be cleaned and lubed, and If it's never been done it will need to be shimmed as well.

I had a same problem. It is nothing serious, really. It is just your AEG starting to get old after putting a good number of rounds through it.

Some cheap O-rings contract a lot during the winter time due to the temperature.

This problem can be easily solved by replacing the O-ring to a better one, or you could try to put a brand new M100 in it.
If you really want to, and if you have the resource, you can try out multiple different cylinder assembly items to find out which ones fit the best to give you the best compression.

Systema aluminum double O ring cylinder heads provide an excellent seal, as do their air nozzles that have a built in O ring (unlike most). Also, their aluminum and polycarb piston heads provide a great seal, especially with a #14 O ring.

*Other companies make comparable upgrade parts with similar features, I just prefer Systema to other upgrade manufacturers. Guarder, Prometheus, JBU, PDI and Laylax are also good parts manufacturers. Stay away from cheaper ones like Deepfire.