Factory 123 SST Velocity 20" Barrel?

[Adam Lilja]

Anyone know the average velocity of a factory SST from a Lilja AR740 off-hand? I am sure I could find it posted in here but busy busy busy! Thanks!

[LRRPF52]

When I chrono'd one of your 20" AR740's, it was 2602fps with factory Hornady 123gr SST. I put the chrono 15ft away from the muzzle like the distractions say, not right up to or even 10ft from the muzzle. Not sure what others are getting.

It's in the mid-2400's from my 16" barrel.

[Jakal]

[cory]

Hope this helps Adam.



Jakal the AR740 is actually a 19" barrel and the 16" barrel is more of a 17".

[Drifter]

~2520 at 100' above sea level

[Heywood]

I get an average of 2490 with my older than dirt pact one chrono at 4000' elevation.

[Adam Lilja]

Thanks guys! Paul why is yours so much higher than everyones ? Cory, I see around 100 fps difference in six of your shots at 77 degrees, is that from your barrel heating up? All of your others seem pretty consistent.

[cst]

i dont have the 20" but my 319 contour(FWIW) shoots the 123SST factory stuff at 2440fps at sea level 80deg....magnetospeed

[LRRPF52]

Altitude and external pressure isn't going to matter for muzzle velocity. The cartridge and barrel would produce the same speeds on the moon at the muzzle. It's a contained pressure vessel, with only temperature affecting mv to a degree.

[cory]

Thanks guys! Paul why is yours so much higher than everyones ? Cory, I see around 100 fps difference in six of your shots at 77 degrees, is that from your barrel heating up? All of your others seem pretty consistent.

Possibly, but I doubt it. I was using a cheap pro chrono. A change in light would change that chrono.

I want that damn Doppler Chrono!!!

[NugginFutz]

Soon, they're saying at LabRadar. Soon...

[Lonehill]

Been getting very consistent 2505 fps + or - 10 fps with 20" Shilen