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Old March 13, 2012, 09:26 AM   #1
Senior Member
Join Date: September 6, 2011
Location: Wyoming
Posts: 1,309
Is my chronograph wrong?

I just finished chronographing some .223 loads and the results are dissapointing. I used 25.3 gr H335 under a 55 gr Hornady SP with a CCI 400 primer. Hodgdon's manual said that the load produces 3203 fps.

Well, I didn't even come close to that velocity! The five shot average was 2875 fps, with and ES of 71 and an SD of 27!

I use a Lyman beam scale and weighed each powder charge.

My rifle is a Ruger SR556E with a 16.12", 1:9 twist barrel. I was expecting a bit slower speeds than the manual, but not 300 fps? What is going on here?
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