Fps Downgraded
 

Recently, i've found myself having a LOT of newbie questions. Hopefully, i can be excused since i -am- a newbie.

Alright, moving on...

I have noticed in games descriptions that some have fps maximum depending on the guns. I also seen that it -could- be modified, although it depends on the gun model and so forth.

My question: How can the fps of a gun can be downgraded without any internal modification, and how can i know if it's compatible with one of my rifle.

Thank you in advance for your time and patience with the newbies to the hobby/sport.

You could always get your hands on a TM Velocity Reducer.

http://www.airsoftgi.com/product_inf...roducts_id=302

heavier bbs eg .25 .28 .30 but this means you have to make sure you are allowed to use them where you play. Also IIRC there is a hider attachment that will reduce fps.

How can FPS be lowered without internal modifacation?

TM velocity reducer.
http://www.airsoftparts.ca/store2/in...roducts_id=920

It would help if you could tell us what you have for an AEG.

Noob Question: What do you mean by IIRC?

I got a Tokyo Marui M4A1 New type. Although the question apply also to any gun i would concider purchasing, like for example a springer with high fps that i'd wish to downgrade for other un-conventional guns.

The Speed reducer on that page is an "external" upgrade?.

Yes it is, you unscrew the flash hider and screw the reducer on in the flash hiders place.

Sweet!...thanks a lot ;)

If I Remember Correctly. No worries though, it is the TM velocity reducer that eveyone else is talking about.

IIRC :D heavier BBs make no difference. Its not FPS we worry about its total energy.

Okay, here's yet another Noob question: What's the difference between FPS and Total Energy. When we reduce one, doesn't it reduce the other? Or does that mean that IIRC doesn't actually reduce FPS.

Logically, a "slower" ball has less strength, so i just want to know what you ment by what you said Cheesevillage.

Just my take on things, and really you should clarify with the game host if you are at all unclear of the FPS/power limits for a game/event.

If you're shooting 400fps with 0.20g bbs and then switch to 0.30g bbs, you'll be shooting under 350fps...but that doesn't mean that you can use it in most games that are set at a 350fps maximum.

Most games, to my understanding, are set using 0.20g bbs as a reference and list the max velocity according to that.

Clarify with the game host if in doubt...chrony your rifle to be sure.

One trick for the original question, to reduce your FPS, just reverse the spring, tigher coils into the piston instead of the spring guide. Only works for non linear springs.

AND yes, the FPS is measured with .20's only.

If you have a stock TM M4 you should not be worrying about FPS.
However since your asking Im assuming the M4 is possibily upgraded and if so most likely not by you. Either way the velocity reducer is your best option.

FPS limit is something of a misnomer, it's really a muzzle energy limit.

The AEG itself always outputs a fixed amount of energy, in the form of the piston displacing a certain amount of air at a certain pressure down a certain length of barrel. Unless the internals are changed, that's always the same regardless of the BB weight. That's what determines the amount of energy a shot has, not BB weight.

When you introduce BB into the equation, the BB is working with the amount of energy the gun is providing. A lighter BB will travel relatively faster than a heavier BB out of the same gun precisely because the amount of energy is the same in both cases. However, that doesn't mean a slower, heavier BB has less strength, since it takes more energy to move heavier objects, but the heavier BB also retains momentum much better (takes more to deflect the heavier BB from its path once it starts moving). In the end, lighter and heavier BBs both receive the same amount of energy from the gun, and both will deliver the same amount of energy on impact at point blank distance.

There is no way to safely drop the fps of a gun without changing some parts in it.

The velocity reducer is unsafe in high fps and on full auto. The small lips that slow the BB down can break or bend out of shame and allow the BB to go trough at full speed.

Games host should set their fps limit based on joule output. But since almost no one know what 1 joule is, it's done in fps.

A stock 280fps gun give about 0.70 joules with 0.20g BB.
A 400fps gun will output 1.49 joules with .25g

If I set my field limit at 1.49j, no mater what weight of BB you put in your gun, you still have to be under 1.49j. Heavier BB goes slower, but hit with more energy for a longer time (distance).

Here is an example for snipers.
Normal limit for sniper is 1.88j or 450fps with 0.20g. When using 0.30g, the velocity drop to 367fps. Since the 0.30g BB retain it's energy farter, it require a minimum safe engagement distance of 40 feet to be safe. At 40 feets down range, the BB has slowed anough to carry about 1 joule of energy, wich is a standard energy output that is hard enough to sting but not enough to break skin.

1 joule output is equivalent of a hit from a 0.25g BB comming from a 350fps gun at 10 feets.

You now have a good idea on how things work.

Thanks a lot to have enlightened me on the subject. I'd advise perhaps creating a document on the topic for the newbie area as it's not really covered, and i think it's a rather essential part of choosing a gun, since it would be sad to have someone purchase a gun that he can't use in some games.

Neat FYI, I remember CND_Stalker posting up his fps results using different weights and I was bored so I converted them all to energy on excel. There was only maybe 10 readings per weight but the trend was clear - the enegy increased slightly as you increased the weight of the BB used. So to be a stickler at games you should really chrono using all .20's, energy, or an velocity conversion from the limits set at .20's.:banghead:

Now that I think of it that would make sense. because since the BB is travelling slower it spends more time being effected by the pressure build-up in the barrel.

Thanks for a very interesting post... Despite my ignorance I've tried to follow along, so can I recap?

BB weight can reduce FPS but increase energy?

Therefore a site should specify BB weight in it's limits, and also check energy?

Hope I understood that correctly.

bb weight can reduce fps but the energy remains the same.
If u shoot say a 400fps 0.20gram bb
and switch over to .30gram bb your fps will drop to 300
but the energy of the bb in both cases will be the same

Thats why when you chrono at a game u use .20 grams

Food for thought
.36g BB @ 800FPS would carry alot of energy

J=[M(V*2)]/2000

so if my math is correct it's 10.72J that would hurt thats for sure.


The max FPS is usualy determined with .2g bb's

EDIT never mind I'm too slow

To expand on this;

The bb's energy on exiting the barrel will be the same, but at 100 feet, a heavier bb will have lost less energy than a lighter bb.

So heavier bb's travel slower, but with less wasted energy, coupled with hop up: a longer, and straighter flight path.

People feel heavier bbs at extended ranges more distinctly than they feel lighter bbs at the same range.

0.25/0.28/0.30 will result in a much more predictable flight path compared to 0.20 bbs.

Any maximum range that you give up by using heavier bbs you gain in increased effective range. You might be able to shoot a little further with lighter bbs...but, % wise, you won't hit what you're aiming at out at your maximum range with light bbs. This may not be completely accurate, but it should convey the idea. Spread your arms out as far as possible...that's the shot pattern at max range with light bbs. Now imaging moving 15ft closer to the shooter and put your hand shoulder width apart...that's the shot pattern with heavier bbs. If you were the shooter...which would you want?

At a couple of the games this year, the field organizers asked each player to bring their rifle and an empty magazine to the chrono when they registered for the game. They were given a couple of 0.20g bbs and their FPS and rifle type was noted on their sign up sheet. This may not happen at every skirmish and paintball-field game...but it's very effective for ensuring that everyone knows what they're shooting at.

Well here's some useless stats I just cooked up which are hard to make sense of but seem to follow a trend. There are 4 sets of chrono data found in this thread: http://www.airsoftcanada.com/showthread.php?t=51752 on pages 1 (middle), 3 and two on 5 compliments of Stalker and m102404 all using .2/.25/.25/.3 Bastards. I calculated all the energies from each individual fps reading, took averages of those energy values in for each weight (in each of the 4 sets of data) then calculated the percentage increase/decrease in energy (compared to .2 as a standard). Here's what it looks like:

Page...... 0.25....... 0.28....... 0.30
1........... 5.910%... -1.752%... 5.266%
3........... 3.388%... -2.792%... 2.433%
5.1........ 9.008%... 2.629%.... 8.815%
5.2........ 2.448%... -8.259%... 1.421%

Avg:...... 5.189%... -2.543%... 4.484%

Note for m102404's results I ignored the outliers (used the 10 middle values).

The trend is for .25's and .30's to actually increase in enegy and for .28's to actually decrease for some reason.

Thanks for the number crunching. I would have switched the chrono to Joules readings and recorded those values as well...but it would have taken forever and I don't recall if there is a 0.28g setting on the chrony.

NOTE: I initially had some very odd FPS readings from my single bag of 0.28's. It may have been a bad bag...not sure. I didn't have any others to test with. Also...I think that I used Madbull IPSC precision 0.20g bbs where as Stalker may have used 0.20g BBbastards.

Math is confusing...all I know for sure is that heavier bbs cut through leaves better and are felt more by the people being hit at extended ranges...LOL!

I just remember the momentum formula from physics and know that P remains the same.

P=MV

P=momentum (oomph)
M=Mass in kg
V=velocity in m/s

I know it's not really useful but It's just how I think of it all.