Chronograph

hermie

CGN Regular
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I have been handloading for years and have always accepted the Loading Manual's velocities as correct. This year I bought an Alpha Chrony, and am finding quite a variation in these velocities. My 8mm Mag is right where the Nosler manual says lit should be, my buddies .300 wm is 150 fps slow, my .338wm is right on with the 225 gr, but 250 fps slow with the 250 gr., my .223 right on. Can anybody explain this to me. Thanks-Karl
 
Different components, either type or lot numbers, different temperature and shooting conditions.

Your chrono could be calibrated wrong, or theirs.

To name a few.
 
yep, this is normal. Quite a wake up call, really. Rimfire ammo is generally bang-on factory specs, but pretty much all other factory ammo is optomistic I've found
 
I love it when I let guys shoot over my chrony at the range :D the look on their face when they realize their magnums arent so magnum...priceless! :redface:

7mm Mag especially :(
 
There are several variables that will cause the differences that you see. Test barrel length is most likely. If you're barrel is shorter, you'll drop about 100 fps per inch of barrel. Elevation, humidity and temperature also affect it. Try shooting on a very hot day, you'll gain substantial velocity. Some powders are more prone to it that others.
 
With some powders the velocities climb as you shot a group,chamber heat.With other powders as the barrel warms, it gets looser,velocity drops.Some barrels are tight and high friction,slow, others are too loose and slow, too.
 
If you're barrel is shorter, you'll drop about 100 fps per inch of barrel.

More like 25fps to 50fps depending on the cartridge.A smaller chamber will also result in more velocity than a larger chamber.Differences in lot#s of powder can also cause significant differences in velocity.
 
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