Chrono how many?
- Thread starter heyrosco
- Start date
I like 15 feet from the muzzle.
For some very powerful rifles, that may be a bit close, muzzle blast can give erroneous readings.
I like to run 10 rounds through the chronograph to get a decent average, but will use just 5 occasionally.
During load development, I am mostly interested in the change each step in the charge makes.
If, during 'graphing steps going up, you run into a situation where little gain is seen, it often means you are close to max working pressure.
Regards, Eagleye
For some very powerful rifles, that may be a bit close, muzzle blast can give erroneous readings.
I like to run 10 rounds through the chronograph to get a decent average, but will use just 5 occasionally.
During load development, I am mostly interested in the change each step in the charge makes.
If, during 'graphing steps going up, you run into a situation where little gain is seen, it often means you are close to max working pressure.
Regards, Eagleye
I like to do 5, it allows you to conserve material so you aren't building to many rounds that dont work and allows for a good average for velocities. It also means you don't spend alot of time waiting for barrels to cool. I know alot of guys who load 3 but the course I took we were taught 5 for those reason
I have a Custom 308 Norma Mag load with the 180 TTSX that read as follows:
3122, 3127, 3127, 3128, 3125. Almost unbelieveable!
The more consistent a load is, the better it is for drop at long range.
And this load really shoots! Not unusual for 3 shots in a single ragged hole at 100M, and I have shot 300M groups that were just under 1¼".
My other Norma Mag, A PH M81 Classic is almost as good with the 200 Accubond, averaging just a tad over 3000 fps for 5. extreme spread in this one is 14 fps.
Regards, Eagleye.
3122, 3127, 3127, 3128, 3125. Almost unbelieveable!
The more consistent a load is, the better it is for drop at long range.
And this load really shoots! Not unusual for 3 shots in a single ragged hole at 100M, and I have shot 300M groups that were just under 1¼".
My other Norma Mag, A PH M81 Classic is almost as good with the 200 Accubond, averaging just a tad over 3000 fps for 5. extreme spread in this one is 14 fps.
Regards, Eagleye.
I typically use 5 shot strings for velocity measures. Be aware that a low spread does not mean that the load will group well. I have shot more than one group out of more than one custom gun that had less than 10 fps spreads but fired less than acceptable groups. Be sure to take the data for face value!
Norm
Norm
Seriously erroneous readings .... I was shooting a 22, switched to the 45-70 and forgot to move the Chrony away. Well even at 3 feet away from the muzzle and no bullet impacting any part of the chrony or stand, the muzzle blast blew the whole thing over! That's one tough Chrony!
I now use about 10' for most everything, and 15' for the 45-70. Usually 5 rounds.
I use 5 rounds for 2 reasons:
1. I do my load test with 5 shot groups
2. My CED calculates SD on 5+ readings
Once I have what I think is THEE load, then I put 15 or 20 through to get a better idea of ES and SD over the number of shots I will actually be using.
My laser 6BR (which is no more) was 15fps ES over 15 rounds which equated to an SD of 1.
1. I do my load test with 5 shot groups
2. My CED calculates SD on 5+ readings
Once I have what I think is THEE load, then I put 15 or 20 through to get a better idea of ES and SD over the number of shots I will actually be using.
My laser 6BR (which is no more) was 15fps ES over 15 rounds which equated to an SD of 1.
