TB barrel with less FPS???

[BIG]

Hi guys!

I'm a bit confused...

I have a CA M6A2 LWRC blowback.

My barrel is very short (around 200mm) and the gun shoot 340FPS bone stock.

I ordered a madbull black python V2 6.03 TB barrel (the one for AK at 455mm) and had to cut it down to 390mm because it was too long even with a silencer on.

i did a very clean cutting job and regrind the interior of the tib of the barrel.

I chronied it and now I have around 280 - 310 FPS.

My hop-up is used (i have one being hostaged by canadapost at the moment) and not perfectly round at the tip (facing toward gearbox) but very slightly out of roundness. The lip is in good shape. not just perfectly round.

So. Why the decrease in performance? Anybody have an idea?

Thanks!

[coach]

did you change your cylinder?

[Szevin]

Could be that the rubber sleeve isn't seated properly on the barrel/hopup chamber. Maybe it's not making a good enough seal with the nozzle? That happened to me and I lost almost 80 fps.

[BIG]

Originally Posted by coachster

did you change your cylinder?

nope

didn't changed anything else beside barrel

[Amos]

If you didn't change the cylinder your gun isn't going to be pushing enough air to expel the BB out of the barrel before friction takes effect.

[BIG]

Originally Posted by Szevin

Could be that the rubber sleeve isn't seated properly on the barrel/hopup chamber. Maybe it's not making a good enough seal with the nozzle? That happened to me and I lost almost 80 fps.

the sleeve was very easy to slide inside the hop-up housing...

Maybe it's that? I'll see with my new rubber sleeve.

[BIG]

Originally Posted by Amos

If you didn't change the cylinder your gun isn't going to be pushing enough air to expel the BB out of the barrel before friction takes effect.

you mean with a ported cylinder?

Mine is not ported.

[Hectic]

according to this the length shouldnt be an issue

maybe bad nub placement?

[Styrak]

Originally Posted by BIG

My hop-up is used (i have one being hostaged by canadapost at the moment) and not perfectly round at the tip (facing toward gearbox) but very slightly out of roundness. The lip is in good shape. not just perfectly round.

So. Why the decrease in performance? Anybody have an idea?

Thanks!

If the end of your hopup rubber (barrel/nozzle interface) is even slightly damaged it can cause airseal issues.

[BIG]

ok. thanks guys. I'll wait untill my new rubber arived and I,ll let you know how it goes.

Thanks again!

[battleXtar]

hop up sleeve definitely leaking air... replace 1 that is slightly tight & hard to get in the barrel & teflon tape it when assembling into the hop up chamber.

[BIG]

do you put the teflon tape between the barrel and the sleeve our between the sleeve and the chamber?

Never saw that before but sound like a good idea!

[Reckless]

teflon tape rubber to barrel, at the end of the rubber where the clip indents are...


when you reinsert the barrel into the housing... make sure the end with the lips of the rubber (where the nozzle meets) isn't hung up and not exactly round... sometimes twisting and moving the barrel a little till the lips are nice and round and matching all around.

also make sure the nozzle itself is sealing to the barrel... easy way to do this is make sure the nozzle is at full extention forward into the hop chamber... take a flashlight and shine it into the bb loading "hole"... look down the barrel (muzzle end) and if you see light, that means the nozzle and rubber lips aren't sealing.

[BIG]

I'll try that tonight!

Thanks.

[BIG]

Problem resolved!

I removed the rubber sleeve and carefully replaced it inside the hop-up chamber. Making sure by twisting the barrel that the tip (lips) are perfectly round.

Now I'm at 360 FPS!

Thanks guys.