Gg Cm16 Srl Firing at 250fps

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AJ_WORSELL

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Hello all,

I was wondering if anyone had any advice on the fps from a stock cm16 SRL. Mine is currently shooting at 250 fps and wasnt sure if it needed any adjustment to get higher fps or if it just needs upgrades to get higher fps.

Thank you in advance

 
Low fps can be one of 2 main suspects.

First is it's a weak spring, can be pretty common on guns lazily downgraded to uk limits.

Second is poor air seal, this can be caused by a number of factors but the symptom is less energy than the spring should push and poor consistency (ie the shot-shot fps variance is large)

Generally i'd suggest looking at the air seal first, this isnt expensive in terms of parts, but will require cracking open the gearbox which can be daunting the first few times.

Only once you know the air seal is good will you know if the spring is weak or not.

 
AJ_WORSELL said:
Hello all,

I was wondering if anyone had any advice on the fps from a stock cm16 SRL. Mine is currently shooting at 250 fps and wasnt sure if it needed any adjustment to get higher fps or if it just needs upgrades to get higher fps.

Thank you in advance
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What weight BB were you using and was the hop turned on or off?

 
Hi

Was using 0.2g bbs

Not sure on hop i did adjust last time i was on field to ensure my bbs were flying correctly.

 
Adolf Hamster said:
Low fps can be one of 2 main suspects.

First is it's a weak spring, can be pretty common on guns lazily downgraded to uk limits.

Second is poor air seal, this can be caused by a number of factors but the symptom is less energy than the spring should push and poor consistency (ie the shot-shot fps variance is large)

Generally i'd suggest looking at the air seal first, this isnt expensive in terms of parts, but will require cracking open the gearbox which can be daunting the first few times.

Only once you know the air seal is good will you know if the spring is weak or not.
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Cheers will try and look into this. Or take to a shop when i can

 
Adolf Hamster said:
Low fps can be one of 2 main suspects.

First is it's a weak spring, can be pretty common on guns lazily downgraded to uk limits.

Second is poor air seal, this can be caused by a number of factors but the symptom is less energy than the spring should push and poor consistency (ie the shot-shot fps variance is large)

Generally i'd suggest looking at the air seal first, this isnt expensive in terms of parts, but will require cracking open the gearbox which can be daunting the first few times.

Only once you know the air seal is good will you know if the spring is weak or not.
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Hi

I have made sure the air seal is good in the gun and fitted a m100 spring which apparently should have given me around 320fps.

However i currently get around 270 fps which is an improvement.

I have charged my batteries in a while but not sure how much that will effect fps

Any help please

 
Skara said:
Are you sure?

Wrapping ptfe around the cylinder head o-rings doesn't mean fixing the air seal.

It's a bit more complex.
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Based on information for checking air seal it appears good.

I got a new cylinder head, piston head and air nozzle. My old air nozzle appeared to have no o rings inside it.

Applied silicone grease. And after testing got good airseal.

 
What about the nozzle to hop rubber and the hop rubber to barrel seals?

Have you checked the hop rubber integrity?

Batteries don't affect fps (others state otherwise though).

 
Have not checked hop rubber or the seals that end.

What should i be looking for and how can i check the air seal?

Thank you

 
Nozzle to hop involves 2 parts.

At first look through the hop feed tube while shining a light down the barrel (make sure the nozzle is fully pressed forward).

If light comes through the nozzle (or the rubber lips) is too short.

2nd part, turn the gun upside down place a small piece of tissue over the feed tube hole, fire a shot. If the paper moves you have an air leak between the nozzle and the rubber.

For the rubber to barrel it's easy, 2 wraps of ptfe where the rubber ends.

 
Skara said:
Nozzle to hop involves 2 parts.

At first look through the hop feed tube while shining a light down the barrel (make sure the nozzle is fully pressed forward).

If light comes through the nozzle (or the rubber lips) is too short.

2nd part, turn the gun upside down place a small piece of tissue over the feed tube hole, fire a shot. If the paper moves you have an air leak between the nozzle and the rubber.

For the rubber to barrel it's easy, 2 wraps of ptfe where the rubber ends.
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Have shone light down barrel and there is light coming through the feed tube.

Is there an easy fix for this or new air nozzle.

Have not checked the rest yet

 
IF the nozzle was completely forward I'm afraid you'll have to buy a new, longer nozzle.

Unless someone knows of another way to fix it. Nozzles are cheap anyway so you may as well pick a couple and test.

Just don't get one that is too long or you'll have feeding issues.

 
Skara said:
IF the nozzle was completely forward I'm afraid you'll have to buy a new, longer nozzle.

Unless someone knows of another way to fix it. Nozzles are cheap anyway so you may as well pick a couple and test.

Just don't get one that is too long or you'll have feeding issues.
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Hi

Was having another look today

When i reattach the upper receiver there is no light coming from the hop feed tube. However after firing on single the light gap appears and when firing on full auto there is a bigger gap.

Dont know if you still feel the longer nozzle is the way to go.

 
The definite test is chrono variance, if you're confident the rest of the air seal is good then any variance should be mostly nozzle->hop

A good system can be as low as +/- 1fps, but if your seeing a big shot-shot change then you still have a leak.

The other test as skara says is to use tissue paper, lightly block the barrel and use the paper to see if theres any air getting blown out the feed tube.

If this is the problem then either the nozzle is too short (unlikely if its stock, entirely possible if it's been changed) or the feed lips on the hop are too short/damaged.

Maple leaf hop rubbers for example can sometimes have the opposite problem, their feed lips are slightly long which can interrupt feeding.

 
After looking at a few different things online.

I decided to see if my spring was in the right way round.(didnt know there was a "right way")

Turned out it was in wrong way round, so i flipped it and now get relatively consistently 295 fps. Which i am much happier with. I may get a m110 spring soon to improve the fps further but will leave it for now.

Thank you for all the help

 
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