Low fps in my kwa sr12

by **Toan** » Sun Mar 06, 2011 10:45 pm

So I chrono'd my sr12 today and saw that it shot a whopping 200fps....wtf? Anyways, its in a stock setup with nothing changed. I opened up the gearbox to see if there was anything wrong with the internals but saw that everything was where it was suppose to be and that nothing was caught up on anything. I checked the seal of the piston/cylinder with the air nozzle in the palm method and it was very hard to push the piston into the cylinder unless i pulled the air nozzle off my palm. Also the hopup unit seems to be intact and operational, the bucking is not riped, the barrel doesn't seem to have any bends. I honestly don't know whats wrong, maybe I'm missing something, but as far as I can see its not shooting where it needs to be.

Any assistance would be greatly appreciated.

by **Icepick** » Sun Mar 06, 2011 10:50 pm

Shoot an undented pop can from 1-2 inches away and see what the gun can do in terms of puncturing the can. (Don't hold the can while testing. Use .20g)

by **dom186** » Sun Mar 06, 2011 10:59 pm

My KWA, when I chrono'd it for a game a few months ago, was shooting at 300FPS, and it's an SR10. Maybe our guns shoot sooooo fast they the chronograph misreads it

keep us updated with how you solved the problem.

by **pappyjump** » Sun Mar 06, 2011 11:26 pm

Did you leave your gun sitting half cycled? That can decrease your fps considerably.

by **Minerva** » Sun Mar 06, 2011 11:41 pm

dom186 wrote: Maybe our guns shoot sooooo fast they the chronograph misreads it

Uhh what?

by **Beran** » Sun Mar 06, 2011 11:47 pm

pappyjump wrote:Did you leave your gun sitting half cycled? That can decrease your fps considerably.

only if you leave it for a loooooong time. leaving a gun half cycled for six months on a test someone here did a while ago only dropped the velocity by like 10fps.

its probably a compression issue, if it still has the stock spring. it should be shooting at around 400fps.

by **Toan** » Mon Mar 07, 2011 12:16 am

pappyjump wrote:Did you leave your gun sitting half cycled? That can decrease your fps considerably.

No, cause the thing is, I chrono'd it a few days ago and it was at ~380 consistantly and this is on the SAME chrono (xcortech). Now I chrono it today (Sunday) and it shoots at a meesly 200 fps. Some weird sh!t if you ask me. All my other guns chrono fine except for the sr12, so I know its not the chrono.

by **Toan** » Mon Mar 07, 2011 12:21 am

Beran wrote:
pappyjump wrote:Did you leave your gun sitting half cycled? That can decrease your fps considerably.

only if you leave it for a loooooong time. leaving a gun half cycled for six months on a test someone here did a while ago only dropped the velocity by like 10fps.

its probably a compression issue, if it still has the stock spring. it should be shooting at around 400fps.

Its definitely not a compression issue, the compression in the piston/piston head/cylinder/cylinder head is good. Unless the method I used "testing" the compression isn't a valid method, then I honestly don't know. Cause I tried to force the piston setup into the cylinder setup and it would not budge in at all, the only way the piston would go in, is if I took my palm off the air nozzle. It also got to the point if I pushed the piston in hard enough the cylinder head would pop out of the cylinder, if thats not good compression then I don't know what is. Its not possible to have too much air compression is there?

by **Keeper** » Mon Mar 07, 2011 8:28 am

Would a bad BB jam tweak up the air nozzle? Removing it with a unjamming road too hard or something like that.

I often wondered about that.

by **Beran** » Mon Mar 07, 2011 9:49 am

compression isn't just in the gearbox, it can be between the box and the hopup or in the hopup itself as well. i had a friend who had an M14 that was shooting 350 on an M140 spring until we took the hopup apart and put it back together. something wasn't right with it, and after that it chronoed in the high 400s.

what kind of magazines are you using? ive actually seen that affect velocity on some occasions because of the mag holding the hopup in the wrong place and causing a pressure leak between the nozzle and the chamber. shouldn't be happening on the KWA since it has the two piece hopup, but you never know.

by **xKingSizex** » Mon Mar 07, 2011 11:25 am

Is your barrel and hop up unit totally clean? Check your barrel also to make sure it is straight, if it somehow bent it could cause a decrease in your velocity.

by **Toan** » Mon Mar 07, 2011 5:44 pm

Yea the barrel is clean and the hop up is put together correctly and still the same results.

by **Knewbie Knight** » Mon Mar 07, 2011 6:07 pm

bucking... time for a new one.

by **Toan** » Mon Mar 07, 2011 6:13 pm

Knewbie Knight wrote:bucking... time for a new one.

The bucking shows no signs of rips or anything. So maybe. I have an extra brand new hop up ill toss it in and test and ill post back with results

by **Icepick** » Mon Mar 07, 2011 8:29 pm

Have you range tested? And are the velocity changes actually noticable when you fire? It might be the chrono itself... Gotta think about every factor.

Low fps in my kwa sr12

Low fps in my kwa sr12

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