chrono broken (how to figure speed)

[dragman]

I got the load for my newest gun 300 win mag 24" barrel with 168 berger hunting VLD's. Funny enough it shot the best with bergers max load for the powder I chose. 70.5 grains H4350 with a CCI 250 primer. shooting just under .5 MOA @ 100 yards, but I have a little problem my chrono seems to have crapped out. Over 5 shots I got readings from 3503-3679! and since the batterys are new and I didn't get any pressure I am sure it is broken. I am guessing this load should be in the 3000-3025fps range.

 

[wvuredneck09]

Use JBM online calculator with a known BC, known drop from say 100 to 200 you should be able to determine speed. within reason obviously as BC is always changing due to speed.

 

[dragman]

Use JBM online calculator with a known BC, known drop from say 100 to 200 you should be able to determine speed. within reason obviously as BC is always changing due to speed.

Great idea! I didn't even think to try that. I will get out tomorrow and do this just so I can get close til I buy a new chrono.

 

[bheadboy]

your crono may not be broken, muzzle blast can cause early trigger of the system. move it back further, it could be that the different powder burnrates gave a different blast effect.

besure to be at least 15ft away and try again.

Bob

 

[dragman]

It was at least 10 ft back. this would be the first time I had an issue, but I will try 15 feet.