Best BB weight for 450 fps gun (with .2's)
 

Hey guys, I play alot of airsoft on private fields where there isn't a large emphasis on fps limits, as long as everyone abides by a 50 foot engagement rule.

My main reason for this thread (and it may possibly be in the wrong category) is to get some information on BB weights. I am trying to achieve maximum accuracy, and hoping to reach out about 150 feet with my gun. All the internals are upgraded to achieve this, but the last issue I'm having is finding the best BB, without having to spend loads of money on every kind of BB trying them all out, and having to sight in my gun every time.

As stated, my gun shoots 450-470 with .2's on average, so I am curious which BB weight would suit the gun best, to accede greater accuracy.

Any input is much appreciated. Thank you!

Deven.

0.36g Bastards

Will give them a try. Thanks alot man, do you know of any calculators that will tell me what my gun will be shooting with .36's? Let me know, Thanks!

Rule of thumb is 0.36g will shoot roughly 100fps below what 0.20g BBs do. Don't focus so much on velocity though, the last few years of my playing I ran my M24 at 395fps w/0.20g, and used only 0.36g Bastards, never before did I have such range and accuracy when shooting at higher velocities. So yes, I was flinging the 0.36g Bastards out at about 300fps.

Its very true, my friends all tend to think that FPS>everything else.... But its funny how a TM VSR10 that shoots 320 FPS out ranges a big l96 that fires 500 fps!

Back to the subject tho, I have used nothing but .36's in my guns, I find that anything lighter doenst do a good job for a B/A

When I had my aeg's set for the 395-400fps mark they really liked shooting 0.30 bb's. I was very consistent 300 with them. The .36 should do you good for 450. I tried my one aeg at that speed and the 0.36 was good. I liked the madbull flavour of the .36's (and most bb's in general)

In my experience .40's perform better than .36's in most situations.


Fox.

+1 to .36g
You might want to think about going down to 420fps so you can use .30s though, you'll find .36g's are pretty pricey.

Once you have the right BB weight, upgrade your hopup rubber. The single most important part of your gun for achieving maximum range and accuracy is that $10 rubber sleeve.

Like the others, I find that heavier BBs mean lower FPS, but higher accuracy in general.

I use .20s because I can find a steady source but I'd take a bag of .3s over that anyday.

Heavier BB's don't technically affect "FPS" as an airsofter sees it.

FPS in airsoft means more hitting power, Using a heavier BB will make the actual speed that the BB is traveling slower, but the impact energy remains the same.

Wait a minute...I thought FPS meant feet per second...and that defines speed, not hitting power as far as I know...
Isn't the energy measured in joules?

Exactly. And, in fact, heavier BB's will actually mean more energy on GBBs.


Fox.

Yes, it's measured in joules, just look at it the other way, as Amos explained it, we look for energy retention to get longer ranges and be less affected by wind and air currents, so we focus more on that than the velocity. And the faster the velocity, the higher the spin put on the BB, the greater chance it'll veer off course due to the overhop. Is a balance we try to achieve, which is what sets us apart from the AEG guys, they want the BB to hit as soon as possible so they can get the kill.

I'm talking about in context, not literally.

The gearbox and all airseal components are only ever capable of delivering a maximum force limited by the spring. All parts other than the spring help determine the efficiency of how that spring power is coverted to air pushing power, but the limiting factor is always the spring. So with a force delivered to a bb, the BB's weight will determine how much momentum is imparted to the bb from the air (momentum = velocity x mass). You increase the mass, the velocity (speed/fps) by law must decrease. Therefore you will always drop FPS with a heavier BB, however a BB with a greater mass can better resist the force of wind and will have different flight characteristics under the same hop up conditions you had with a differently weighted bb. This is why hop up must be adjusted to different bb weight.

Don't get wrapped up in joules or FPS.. joules are a measurement of force through a distance, FPS is speed. Joules will never change regardless of BB weight, again thanks to the law of conservation of momentum. FPS will change depending on bb mass. FPS is actually an inferior measurement for this context since in airsoft, we are worried about energy delivered. Needless to say, a .40g bb at 400FPS is going to do a helluva lot more damage than a .20 at 400FPS. If we measured in joules, you would always be able to determine an accurate safety limit regardless of BB used (as long as you knew which one was used).

To clarify lets say you have a gun that shoots a .20g bb at 400fps. If you put .40g bbs in it, you would shoot 283FPS. Your system always delivers 1.48J if this is your setup.

Also, as for distance traveled... air resistance increases exponentially with speed. A higher FPS bb will meet more air resistance. This is why, with hopup, it is possible to shoot a heavier BB farther than a lighter BB despite a lower FPS. OP: You definitely want to use a heavier BB, unless you can find a physics major to help you out, I would recommend just hitting the range and experimenting with a few different weights of BB to see what you can shoot the farthest (just remember the key to success is your hop up setting). Too bad BB bastard doesn't offer a sampler.

As said before, it will change considerably on a GBB; hence why I've always thought FPS measurements are obsolete and force people to chrono with .20's (giving the wrong energy read for someone gaming a GBB with .40s). Guns should be chronoed in Joules, and with the BB weight they are going to be using in game.


Fox.

Don't forget that if the gun uses a spring loaded magazine (all AEGs) and the spring is insufficiently strong, and you're firing fully automatic, you may encounter jams as the BB is halfway into the hopup chamber when the nozzle comes forward. You will need stiffer magazine springs (Read; better magazines in most cases) to fire heavy weight BB's in full auto.

It's a problem a lot of people never consider.

You are absolutely right sir.
But He was talking about AEG's. Anything spring powered will maintain it's joule rating over any BB weight.
However anything GAS powered will change it's joule rating depending on the weight of ammo used.
And so chronoing with .20s is standard and very accurate for AEGs, but you're correct in saying that GBBRs need to be chrono'd with the BB weight they will be using in game, and a conversion to joules must be done.

Here in Mb, we write out the max FPS for each BB weight. So there's different FPS limits for each BB weight, but they all come out to the same force (1.48j for auto, 2.04j for bolt)

And +1 to everything McKee said. Through field trials I've found that all BB's generally have an optimal relative velocity of 330-360fps.
For example, at 2.04j (470fps on .20s), a .30g BB will have LESS accuracy than it does at 1.7j (430fps on .20s)
This was compared side by side with 2 marui VSR-10s of the same internals, and again on one marui VSR-10 with a 470 then 430fps spring.

I thought this data had been lost but through the power of magnets I found it again..

http://mackila.com/airsoft/atp/

Literally all the physics data you could ever hope for in airsoft. Check out section VII in particular. If you're shooting 450FPS (1.88J) you can see what effect various bb weights would have http://mackila.com/airsoft/atp/07-b-09.htm

Basically to answer your question outright: .30g bbs. They have the flattest trajectory with hop-up and the difference between .36 and .30 is that while .36 goes very slightly farther (like 3 feet), the flatter trajectory of .30s will make for more accurate shots and not to mention they are cheaper!

http://mackila.com/airsoft/atp/images/07-b-082.gif

0.30g will get blown off course easier, where the 0.36g will power on through. Add in elevation, your range will increase by a lot, and 0.36g will blast through brush better. I've used every weight and brand (including a few boxes of 0.29g SGM, 500rds at $40 per box), and settled on the Bastard 0.36g as being the best bang for the buck.

Well physics and math is one thing. What actually happens in the field can sometimes be completely different.
.36g is the way to go