Weight of BBs and FPS

[thehumanprimate]

Dear All,

I did a search but couldn't find anything - I was wondering if there was a 'magic' formula of working out the effect of different weight of BBs in reducing/increasing the FPS of a gun?

The reason I ask is that each site has it own limits for FPS and although they are similar, could mean a normal gun at one site being a 'hotgun' at the next site. I not talking about vast differences here, just subtle differences based on a quick trawl of some websites eg 350 fps at one is ok, but hot where the limit is a strict 330.

As I would like to 'try' different sites I was hoping that there could be a very quick fix in using slightly heavier (or lighter, although not less that .2) BBs to
ensure that the gun doesn't become 'hot'.

Or is the FPS for all sites based on the generic .2 bb?

As always any help/advice appreciated

Tony

[bravotwozero]

Re: Weight of BBs and FPS

I understand what you are trying to achieve here, but it doesn't work that way.


All sites measure with 0.2g BB's. because contrary to what you're saying it's the energy which is a factor, not FPS.

[Panoptes]

Re: Weight of BBs and FPS

'FPS limits' are generally based on .20g at most sites. What they're actually doing though is working out the energy in joules so it makes little difference whether you're using .25g, .2.0g or .43g - the energy should (in theory) be the same across the different weights with the same AEG.

[aribos]

Re: Weight of BBs and FPS

You will find most sites will chrono guns with .20gram BB's. Most sites will tell you your gun is too hot or re-test you with .2's if you are found to be using heavier ammo to try and get past the chrono test. Worst case they can ban you from the site for attempting to deceive a chorno reading.

The reason some sites are a strict 330fps is because they are more than likely CQB and it has been found that 330 is the highest fps i think for point blank shots not to seriously hurt a person.

If you want to play at sites at the top end of limits that play 330 and 350fps get two guns or learn how to change your springs.

SIMPLES!

[The Keeper of Secrets]

Re: Weight of BBs and FPS

There was a thread. Someone had a big arguement with me about a .2 going further than a .25, then put up a BIG table proving themselves wrong. It was quite funny. I think it was in one of the tech forums. When I'm that bored I'll see if I can find it for you. It had all the ranges, expected energy and fps at the ranges expected, and during the flight path; someone had done a lot of good research.

[Black Bull]

Re: Weight of BBs and FPS

id also be intrested to read that keeper

[HunterAndy]

Re: Weight of BBs and FPS

If you are found to be using 0.25's for a chrono, people will think you are trying to skirt the rules of the site.

All standard measurements on sites tend to be 0.2g.

If you want to play on a site with the limit as 330fps change the spring in the mechbox, do not change the BB, as this will still mean that on 0.2g BBs it will be over the limit.

I know you probably do not realise what you are suggesting is bad and with good intentions, but some sites are 330fps because they are closer up, the muzzle velocity limits are there to make sure no one is using above a 1j rifle, not to check the speed.

Basically, it is the energy in the BB that hurts people, not the speed of it. don't do it.

[thehumanprimate]

Re: Weight of BBs and FPS

Dear All,

Many thanks for your prompt and informative replies, especially the reminder about energy values rather than just FPS, and for the consensus for sites to use .2s for standard chrono’ing.

I’ve shot air rifles for many years, so I’m aware of the FPS versus energy values on based on the weight of ammunition (the .177 v .22 debate shall forever continue) so
I guess that I sort of knew the answers to my question, but as some one pointed out I guess I was trying to ‘cheat’ the system for the best reasons :+)

Next question(s) where can you purchase a veliable Chrono? As search on a well known auction website and google only gave me millions of hits on tacky watches.

As someone pointed out about 2 guns, my CQB MP5 was 332 when last chromed (site limit 330 + 10%) , but my newest acquisition is longer barrelled but has not been chromed yet but I’m hoping to have it running between the 330-350 mark to use in woodland – and yes learning to change springs would be good, but hopefully unnecessary, except on the sniper rifle :+)

And KOS if you get to dig out that table I’d be very interested in having a look.

Again many thanks

Tony

[The Keeper of Secrets]

Re: Weight of BBs and FPS

The thread is here. It focuses more on range, but is a good read nonetheless:

http://www.zeroin.co.uk/showthread.php?t=15624

[screwdriver]

Re: Weight of BBs and FPS

if your into airgunning then use a combro pocket size chrono for about 35quid most gun shops sell them or order a airsoft chrono from hk or uk

[The Keeper of Secrets]

Re: Weight of BBs and FPS

That's the one I use.

[HunterAndy]

Re: Weight of BBs and FPS

There's alot of chronos on ebay if you look in the right places.

I take it you mean you use it for airsoft ?

[TB-Stalker]

Re: Weight of BBs and FPS

Sounds good, Black Bull you have a PM