Chronograph Help

[Tun_x]

Just wondering if there is anybody out there that has a chronograph that would be willing to help a guy out .. I am working on load development for my .308 and I have a load worked up that shoots really well out of my gun I just need to know the velocity so I can make up some dope cards to get me started..


Thanks

Jason

[W.R.Buchanan]

Jason: I have a chrono but I live in Ojai CA about 900 miles from you. I just got it a month ago.

BUT,,,, I read an article on Sunday written by the purveyor of Leverguns.com,, Paco (Frank) Kelly.

His very simple method of calculating a drop profile for a given load is to take a 4x8 sheet of cheap plywood to the range.

Install a bullseye or other suitable aiming point on the plywood.

Sight the rifle dead on at 100 yds.

Drop back to 200 yds, and shoot at the original point of aim. Note drop.

Drop back to 300 yds, and do the same, and in your case drop back in as many 100 yard intervals as you see fit..

This gives you the exact drop for your given load.

Obviously after that you raise the point of impact until you get the distance of "point blank range" you are seeking with your load. IE: 1.5" high at 100= dead on at 200= 4.5" low at 300. All of which will hit within a 6" circle with the same point of aim.

This is the correct definition of "Point Blank Range" Not right off the muzzle as most people think!!! "The range at which the bullet rises and drops the same amount above and below the line of sight. Usually based on a 6" dia kill zone".

Example: the bullet rises 3" above the line of sight and then drops to 3" below the line of sight in 347 yards. Point blank range is 347 yards. Obviously the faster the bullet goes, and the more efficient the bullet is, the longer the point blank range will be

The variables are bullet speed, ballistic coeficient, and bullet weight. Ballistic coeficient, and weight you can look up easily in any loading manual, and there are many bullet drop programs and charts on the internet. But without the bullet speed none of these work. The bullet speed is where you need the chronograph.

Or you can guesstimate based on the published load data for various velocities and extrapolate for your barrel length. This is how I've done it for 30 years, and then you check it at the range.

This is where the sheet of plywood comes in. It is cheaper than the Chrono. And you can see exactly what is happening. A suitable substitute for the plywood is 2ea I x 2 's, 6 feet long held together by 2 sheets of cardboard stapled to the front and back of the 1bys.

Hope this helps a little.

Randy

[Tun_x]

Thanks for the input