Best set-up for chrono checks of .308 work-up loads.

Pond, James Pond · April 15, 2014, 04:59 AM

Done my OCW work up for the Amax bullets. Chosen a load and an OAL.

I now want to do some target practice at 100m, but at the same time I'd like those to register on the chrono. A string of ten or so to get a good average velocity. I then want to use it to check trajectory in a BDC program.

What should I look at, look for, set up and account for so that those ten shots are neither inconclusive nor inaccurate?
And is there anything else the range time can tell me (aside from FPS) that I cannot get off the net but still need to make accurate trajectory calculations?

4runnerman · April 15, 2014, 06:23 AM

What the book says and what you get will be your first step. Very seldom is the book right for your rifle. Look for your spread between shots. I assume you have done the box test to prove your scope is good to go. Depending on how far you want to go in the future to reach out and touch targets, I would suggest you ( if you can ) do your testing at 200 yards or farther if you can. A chrony is also very helpful in letting you know about your load consistency. You should fall in to somewhere about 10 to 15 FPS spread, no more than that.

Pond, James Pond · April 15, 2014, 12:00 PM

I mean measurements I need to investigate, record etc that I can't undo or workout later.

For example, muzzle to chrono distance being too close. This would give false readings, large variations etc that cannot be undone later, meaning that distance is something to know and adhere to before hand: can't undo it later.

Any others?

4runnerman · April 15, 2014, 05:54 PM

Muzzle to Chrony distance is a given-- 10 to 15 feet what ever you choose. I did 10 feet. What I did was measure from my bolt ( closed ) to muzzle,Add that length to 10 feet and cut piece of string. Now when I go to the range I hook string on bolt and walk chrony out to end of string. Same distance always. Did same with front and rear rests. It is a little on the anal side ,but I am ok with that

. There is another post going on in here about MV. The thought came about to- Once you are set at a given distance and are shooting tight groups That I want to bring my other chrony with and set that in front of target at 200 or 300 yards and see what it say's compared to what the charts tell you it will be at that distance. I will have MV and Velocity at 200 or 300 yards for each shot.

April 15, 2014, 04:59 AM	#1
Pond, James Pond Senior Member Join Date: July 12, 2011 Location: Top of the Baltic stack Posts: 6,079	Best set-up for chrono checks of .308 work-up loads. Done my OCW work up for the Amax bullets. Chosen a load and an OAL. I now want to do some target practice at 100m, but at the same time I'd like those to register on the chrono. A string of ten or so to get a good average velocity. I then want to use it to check trajectory in a BDC program. What should I look at, look for, set up and account for so that those ten shots are neither inconclusive nor inaccurate? And is there anything else the range time can tell me (aside from FPS) that I cannot get off the net but still need to make accurate trajectory calculations? __________________ When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic. Freedom: Please enjoy responsibly.

April 15, 2014, 06:23 AM	#2
4runnerman Senior Member Join Date: January 16, 2010 Location: Minnesota Posts: 3,577	What the book says and what you get will be your first step. Very seldom is the book right for your rifle. Look for your spread between shots. I assume you have done the box test to prove your scope is good to go. Depending on how far you want to go in the future to reach out and touch targets, I would suggest you ( if you can ) do your testing at 200 yards or farther if you can. A chrony is also very helpful in letting you know about your load consistency. You should fall in to somewhere about 10 to 15 FPS spread, no more than that. __________________ NRA Certified RSO NwCP- Performance Isn't Optional

April 15, 2014, 12:00 PM	#3
Pond, James Pond Senior Member Join Date: July 12, 2011 Location: Top of the Baltic stack Posts: 6,079	I mean measurements I need to investigate, record etc that I can't undo or workout later. For example, muzzle to chrono distance being too close. This would give false readings, large variations etc that cannot be undone later, meaning that distance is something to know and adhere to before hand: can't undo it later. Any others? __________________ When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic. Freedom: Please enjoy responsibly.

April 15, 2014, 05:54 PM	#4
4runnerman Senior Member Join Date: January 16, 2010 Location: Minnesota Posts: 3,577	Muzzle to Chrony distance is a given-- 10 to 15 feet what ever you choose. I did 10 feet. What I did was measure from my bolt ( closed ) to muzzle,Add that length to 10 feet and cut piece of string. Now when I go to the range I hook string on bolt and walk chrony out to end of string. Same distance always. Did same with front and rear rests. It is a little on the anal side ,but I am ok with that. There is another post going on in here about MV. The thought came about to- Once you are set at a given distance and are shooting tight groups That I want to bring my other chrony with and set that in front of target at 200 or 300 yards and see what it say's compared to what the charts tell you it will be at that distance. I will have MV and Velocity at 200 or 300 yards for each shot. __________________ NRA Certified RSO NwCP- Performance Isn't Optional

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