Question about 8mm bb's

Buckmark

I know its probably been asked a hundred times but.........How do I chrono an 8mm .34g marushin bb ? I seen loads of different views on this saying the size is irrelevant, its the density that counts, cause an 8mm bb slows down much quicker cause of surface area (around double) so anybody a chrono that can chrono an 8mm .34g bb, or know how many fps a chrono set for 6mm .20g would read in fps for a one joule .34g 8mm bb ?


Minimum Engagement Distances in Feet
Mass of Projectile Used in Match / Event
Muzzle Energy / Class
Muzzle Velocity (relative to 0.20g / 0.30g BB's)*
0.12g - 0.30g
0.31g - 0.43g


6 mm



< 1.2 Joules
<360 / 295 fps
15
20
1.2 - 1.5 J
< 400 / 325 fps
30
40
1.5 - 1.9 J
<450 / 365 fps
45
60
1.9 - 2.3 J
<500 / 410 fps
60
80
2.3 - 3.4 J
<600 / 490 fps
80
120
3.4 - 4.6 J
<700 / 575 fps
100
145


8 mm

Muzzle Energy / Class
Muzzle Velocity (listed as 0.34g / 0.45g max)**
0.34g
0.45g< 1.5 Joules
<310 / 270 fps
20
251.5 - 2.3 J
<385 / 335 fps
35
502.3 - 3.4 J
<460 / 400 fps
55
703.4 - 4.6 J<540 / 470 fps65854.6 - 5.3 J
<580 / 505 fps
75
100

Leftyflip

You can imput different weights and diameters with the Xcoretech models.

mafiaboy

hope you dont mind this but where do you get your 8mm from ???

Gatling

here's a link worth checking

http://www.boards.ie/vbulletin/showthread.php?t=2055353665

Buckmark

Leftyflip wrote: »

You can imput different weights and diameters with the Xcoretech models.

Thanks fella

Buckmark

mafiaboy wrote: »

hope you dont mind this but where do you get your 8mm from ???

Usually If I buy something from uncompany I get packet of marushin's 8mm bb's, they're around 8.50 dollars for 500, but as you know uncompany is get for coupons and to de-value for customs so I reckon I'm paying more a less nothing shipping on em, I use them with a marushin 6 shot revolver so I don't use a lot anyway. Where do you get em ?

Eoin3k

A bit off the point but what bbs would be the best for mid to long range sharpshooting?

sliabh

Buckmark wrote: »

I know its probably been asked a hundred times but.........How do I chrono an 8mm .34g marushin bb ? I seen loads of different views on this saying the size is irrelevant, its the density that counts, cause an 8mm bb slows down much quicker cause of surface area (around double) so anybody a chrono that can chrono an 8mm .34g bb, or know how many fps a chrono set for 6mm .20g would read in fps for a one joule .34g 8mm bb ?

The law is just based on 1J allowed energy. Kinetic energy is calculated from the formula:

Kinetic energy = (0.5) x (mass) x (velocity squared)

Which means the only things you need to worry about are the mass of the bb, and the speed leaving the barrel.

In your case energy is 1J, which is 1000 kg m2/s2, and mass is 0.34. So if we call the maximum velocity Vmax:

1000 = (0.5)(0.34)(Vmax)Vmax)

which works out to

Vmax = 76m/s or 251 fps is you are old school.

The diameter isn't a factor in the initial energy calculation for the gun being legal or not. It will change performance though. A bigger diameter bb will generate more drag and so will slow down faster.

mafiaboy

Buckmark wrote: »

Usually If I buy something from uncompany I get packet of marushin's 8mm bb's, they're around 8.50 dollars for 500, but as you know uncompany is get for coupons and to de-value for customs so I reckon I'm paying more a less nothing shipping on em, I use them with a marushin 6 shot revolver so I don't use a lot anyway. Where do you get em ?

never ordered any,, i got my hands on a 3shot full stock pump and a bag of 8mm and used nearly all of the in berget... im down to about 20bb :eek::eek:
thanks for the link...

Eoin3k

Eoin3k wrote: »

A bit off the point but what bbs would be the best for mid to long range sharpshooting?

Also what bbs are best for cqb

Witcher

Eoin3k wrote: »

Also what bbs are best for cqb

You should use various weights and choose what ones work best for you.

Eoin3k

Thanks again blay