.308 chrony questions and I snipe question

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mooger31

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So I finally got to go out and use my chrony for the first time. I've worked up a load that I'm really happy with. Very accurate shooting sub moa out of a tikka tac with a 24" barrel. So take some shots to make sure my rifle is on. And I take ten shots of my load. I get a average of 2549 ft/sec. All numbers look good. But when I check the nosler reloading manual ( by the way I'm shooting 168 gr silver ballistic tips and 44.7 gr or rl 15) it says at 44.0 grains of rl 15 I should be getting 2820 ft/sec.

Just curious what could be effecting my speeds by almost 300 ft/sec. Is my chrony off or something else going on?


Question 2. About I snipe app. When entering the the scope height. Do you measure from receiver to middle of scope or from receiver to bottom of scope?
 
Congrats on getting a chrony and welcome to the unrealistic world of reloading manuals. I quite often find most loads come in under what the manual states and never over.
You`ll probably find that you will have to lower the published B.C. of your bullet as well because most of those are over estimated too. Berger bullets seem to be accurate and so do the barnes lrx -175 grain .308 anyway.
Bryan litz has a book - applied ballistics which has lots of bullets tested for accurate B.C`s
I believe the scope height you want to input is from the center of your bore to the center of your scope.
For comparison I get about 2720 fps with varget and 168 hornadys out of my 26 inch tubed 308.
Have Fun
 
When you are obtaining scope height for your software you want centre of bore to centre of objective to be the most accurate.

For the most accuracy you will want to confirm the input data in the program. I find the best way to do that is spend a but of time shooting at distance. For a .308 try and stretch it out to 800. Find out what you dope is for the day and record all the atmospheric conditions and enter it into the software. Then back calculate the rest. I have found chronographs, especially the cheaper ones can be out a bit. Doing it the way I described above I have had more accurate results.
 
This is a dumb question but does elevation play a part in the variance of fps? I shoot at 1500' and seem to get pretty good velocity according to my chrony.
 
There would be less atmospheric pressure the higher your elevation. I`m not sure how much that would affect fps but it does affect bullet drop
 
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