Reduce FPS

di11on

Hi folks,

***Note***
I live in France where the legal limit for a replica is 2J. If I were ever to return to Ireland, all replicas I own would be brought under 1J before importation.
**********

Thanks to my DIY Chrono(<- Check out the link if you're into electronics - it's a nice little project) my new VFC M4 fires at around 380fps. While the legal limit is 2J, the limit on most sites here in France is 350FPS for full auto replicas. How can I reduce the fps by the 30fps required?

I know I can replace the spring... but I'm really reluctant to do that. I've done the job on other replicas, but once I've opened up the gearbox, there's always that lingering doubt and sense of unease after you've put it back together.

What other (non-destructive) ways are there? I've heard of a muzzle brake but haven't come across any. Does anyone have any experience of these?

Lemming

If you have a tightbore barrel, removing it and replacing with a stock barrel (i.e. wider diametre, ergo less air efficient) will bring a drop of some degree, but not a dramatic drop at the FPS levels you've quoted, and will also result in reduced accuracy through reduced stability of BBs in-flight.

The only other thing I can think of - but only from an academic point of view as I am in NO way actually suggesting it - is to perforate (i.e. drill a hole/holes in) the nozzle. But that means you have shearings from the drill holes potentially finding their way into the gearbox and messing things up, and more importantly you end up with a weakened air nozzle and wildly unreliable & inconsistent performance. You would see chrono readings jumping up and down, and such an act renders any other modifications you make absolutely meaningless because you have effectively destroyed your primary means of transferring power from gearbox to BB.

TL;DR: You would be better off changing the spring (which you would have to do anyway to ensure the consistency/result you actually want) and keeping the rest of the gun's internal workings unchanged.

di11on

Thanks Lemming - I'm coming to terms with the fact that I'll have to replace the spring

thermo

Or fit a wide bore barrel (6.20 mm +) you will drop approx 10% of your bb velocity and increase your range and accuracy. Best of all worlds there.

Lemming

thermo wrote: »

Or fit a wide bore barrel (6.20 mm +) you will drop approx 10% of your bb velocity and increase your range and accuracy. Best of all worlds there.

I would have thought that a wide-bore would reduce accuracy (range has very little to do with barrel length; more in-flight stabililty) as the BB has more chance of moving around inside the barrel,thus reducing consistent air pressure across its diametre, and ultimately providing a less stable flight path once leaving the barrel, no?

mack1984

Lemming wrote: »

I would have thought that a wide-bore would reduce accuracy (range has very little to do with barrel length; more in-flight stabililty) as the BB has more chance of moving around inside the barrel,thus reducing consistent air pressure across its diametre, and ultimately providing a less stable flight path once leaving the barrel, no?

Lots of people now choosing wide bores

http://orga-airsoft.com/user_data/about_widebore.php

thermo

Lemming wrote: »

I would have thought that a wide-bore would reduce accuracy (range has very little to do with barrel length; more in-flight stabililty) as the BB has more chance of moving around inside the barrel,thus reducing consistent air pressure across its diametre, and ultimately providing a less stable flight path once leaving the barrel, no?

"the idea behind a wide bore barrel is to have an equal amount of air pressure behind and on the sides of the bb making it more stable in flight but conditions need to be perfect such as a clean smooth barrel, stable hop system and 100% compression of the cylinder."
Taken from another forum.

di11on

thermo wrote: »

Or fit a wide bore barrel (6.20 mm +) you will drop approx 10% of your bb velocity and increase your range and accuracy. Best of all worlds there.

Interesting... I may just have to try this out!!!

Southern Dandy

di11on wrote: »

Interesting... I may just have to try this out!!!

Id still opt for the spring change personally, if your not confident to do it yourself take it to you local retailer. Though if your capeable of making a DIY chrono id say you wont find working on a gearbox overly difficult. Like everything, once you get used to it they are relatively easy to work on.

Orga magnus barrels are expensive and with the dollar being what it is to import from an asian retailer plus shipping and VAT, a 10-15euro spring with a little bit o work I know what I'd be choosing.

thermo

I'm using Prometheus delta strike barrels with Prometheus purple flat hops. Much cheaper than orga Magnus barrels

di11on

thermo wrote: »

I'm using Prometheus delta strike barrels with Prometheus purple flat hops. Much cheaper than orga Magnus barrels

What's your experience of this? Did you test vs. a tightbore setup? Do you see improved range/accuracy?

Edit: I've read some people having difficulty with too much hop with flat hop setup - what weight BBs do you use?

Southern Dandy wrote: »

Id still opt for the spring change personally... Orga magnus barrels are expensive... a little bit o work... I know what I'd be choosing.

If the Prometheus delta strike works well, I might favour that over a spring change, but I can't see myself shelling out 100 knicker for an Orga. Given that your compression needs to be 100%, I'd say there's a fair bit of uncertainty regarding the impact of a widebore vis-a-vis accuracy.

Anyone done any testing?

LeeHarvey

Wide bore barrel, and a spring change will bring FPS down. A muzzle brake doesn't reduce velocity, it vents gasses on firing a weapon in directions that either pull the weapon forward thereby reducing felt recoil (.50/.408/.416 etc), or push the barrel downwards to resist muzzle rise on fully automatic or rapid firing.
A suppressor reduces muzzle velocity somewhat.... but seeing as were talking airsoft guns here..... I don't think any of this relates, so as I said - spring and barrel are your best bet.

mack1984

LeeHarvey wrote: »

Wide bore barrel, and a spring change will bring FPS down. A muzzle brake doesn't reduce velocity, it vents gasses on firing a weapon in directions that either pull the weapon forward thereby reducing felt recoil (.50/.408/.416 etc), or push the barrel downwards to resist muzzle rise on fully automatic or rapid firing.
A suppressor reduces muzzle velocity somewhat.... but seeing as were talking airsoft guns here..... I don't think any of this relates, so as I said - spring and barrel are your best bet.

He's probably talking about the muzzle FPS reducer, not a muzzle break

http://www.fire-support.co.uk/product/marui-power-down-muzzle-adaptor-velocity-reducer-new

thermo

di11on wrote: »

What's your experience of this? Did you test vs. a tightbore setup? Do you see improved range/accuracy?

Edit: I've read some people having difficulty with too much hop with flat hop setup - what weight BBs do you use?

I have tested the delta strike barrels vs mad bull 6.03 and 6.01 barrels and despite the drop in fps I'm getting more usable range. So much so I have actually left the wide bore in and given the tight bores away to team mates who wanted them.
Next step is to re-up the fps and see if there is much more improvement with the extra 30 fps.
Using the wide bore and flat hops I'm using .2, .25 & .28 g bb's it's not that picky

di11on

thermo wrote: »

I have tested the delta strike barrels vs mad bull 6.03 and 6.01 barrels and despite the drop in fps I'm getting more usable range. So much so I have actually left the wide bore in and given the tight bores away to team mates who wanted them.
Next step is to re-up the fps and see if there is much more improvement with the extra 30 fps.
Using the wide bore and flat hops I'm using .2, .25 & .28 g bb's it's not that picky

Thanks Thermo - Definitely going to give this a shot. How is it accuracy wise compared to the tight bores?

thermo

It's a good bit better, hard to give exact figures with field testing. But had the wide bore in today and with .2's and a decent breeze I was placing 90% of shots in torso sized targets at 70 M +. Will try it with .25's the next day. By the way I have upgraded the power back to 320 fps with .2's.

mack1984

I hate to be that guy but 70plus meters with a sub 328fps aeg is an astounding claim.

thermo

mack1984 wrote: »

I hate to be that guy but 70plus meters with a sub 328fps aeg is an astounding claim.

Well your welcome to try the rifle out........

mack1984

Bit far away mate but unless it's a physics defying rifle im calling BS. Video or it didn't happen.

thermo

mack1984 wrote: »

Bit far away mate but unless it's a physics defying rifle im calling BS. Video or it didn't happen.

If you look on line you will see they are rated to 60-70m. So the claim of 70 + meters for a rifle fitted with one of these barrels paired with a flat hop (which you may be aware are very efficient at slinging a bb) is not as outlandish a claim as it may appear.
But you are of course free to believe what you like.