The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

I bought some Hornady "American Gunner" ammunition in 308.

They claim 2700 fps from a 24" test barrel.

On my rifle, when tested with a MagnetoSpeed chronograph, I only saw 2520 fps (give or take 15 over a number of shots).

I have a 1 in 10 twist, 24" barrel - so was expecting to be near factory figures...

Is this just manufacturers claims or am I likely to see much difference on a hot day etc?

Calibration on your chrono?

IainWR wrote:Calibration on your chrono?

Ha ha - I only chrono'd to calibrate my calculations...

Now I have to chrono a chrono?

Altitude, ambient temperature, barometric pressure and the fact you are not using the same test barrel, will all have an effect on muzzle velocity.

Factor in any variance in your chrono and you would be very fortunate to replicate the test load velocity.

Hold a few rounds back from your batch and test fire them on a warm sunny day and see the difference!

How many people actually get the published MPG out of a gallon of fuel as advertised by vehicle manufacturers?
ukrifleman