Thread: chrony on factory loads

Originally Posted by deer243

Well box factory ammo is nearly always tested with 24 inch proof barrels , sometimes 26 inch. Most seem to test less than stated but will by some point
anyway if using a shorter barrel. Couple i tried in factory over a chrony were only 50-90 less and that was with a 24 inch barrel.
Also, as im not sure(someone will know) arent factory box speed from straight from the muzzle? (other than a few feet with a chrony) Just thought i read that somewhere.
Plus a top end chrony will be more accrurate than some cheaper models and different rifles barrels will affect the speed also.
they never going to be perfect

Factory ballistics are "corrected to the muzzle". This means that the velocity is raised a little from what you would read on a chronograph. Generally the difference is small. 10 or 20 fps.
GPM

Originally Posted by stuart165

Hi All, i havent shot factory ammo for 15yrs but got asked to sight in a friends rifle for him, i thought while i was at it id run the loads over my labradar, its a remington 783 in 243 shooting winchester super x 80gr projectiles. the box says 3300 ish and my radar says 2740.... it wouldnt surprise me to be 100 or so out but 600fps almost??...

could i suspect its old degraded ammo or a slow short barrel? my labradar reads what i expect on all my handloads so i dont think it would be that.

Interested to hear what others have experienced.

Are you shooting from a tikka or sako? They have a bit of a reputation for slow barrels

its coming out of a remington 783

Originally Posted by stuart165

its coming out of a remington 783

Could just be a massive chamber and freebore.....tho 600fps is a hell of a lot.

Been a while since I crohnyed any factory ammo but I remember doing 308 fed blue box threw my standard Sako and being surprised it was within 50-60 fps of what the box said.
I was surprised at the time because of the wildly held beleif that the box fps is very optimistic....in that case it was pretty bloody close I thought considering the 22ish inch barrel of the Sako