Ballistic calculator need help please.

[MCLE]

HI all I'm just wondering if someone might have a ballistic program that they can run my 308 load through so l might be able to check it against my old chrony. I am using 155.5 Berger's lap brass with 46.5 gr of AR 2208 out of a 28 inch barrel 1 in 13 twist .My chrony is saying 2980 fps.Thanks

[Pom]

All ballistics calculators I know of work around you entering your bullet weight, BC and velocity to calculator all the other factors.

You would use a chrono (like you did obviously) to get the muzzle velocity first, then use that to work out trajectory and energy and everything else.

I don't know of anything that lets you enter load details to estimate the velocity.

[Pom]

Sorry forgot to say though,

Data according to ADI website says 155gr bullet with 47gr of 2208 should have a muzzle velocity of 2910.

Seems you're a little fast?

[Monty]

I don't know of any calculators to estimate velocity either. Is there a reason you don't trust your chronograph?

In any event, you can confirm it in other ways...

Using a trajectory calculator, enter your bullet details - weight, BC and your chronograph velocity reading - and it will give you the trajectory and drop of your bullet based on your information.

When you're at the range do a few shots at 100m, 150m and 200m and compare the amount of drop to the trajectory table from your calculator.

If your bullets are not dropping as much as your table says, your load is faster.

If they're matching the rate of drop, it's accurate.

if they're dropping more than your table says, your load is slower.

Not quite what you were after I know, but it will get you a more accurate answer than a velocity estimator.

[Norton]

Overlooking an obvious answer here...

Borrow some guys chrono at the range for 5 minutes and confirm that way?

[MCLE]

Thanks for the feedback .I had a look at the ADI book and there figures they have come from a 24inch barrel and from what l have herd one inch in barrel length can give you somewhere from 30 to 50 FPS so maybe that might be about right ??. As for my chrony I don't know howe accurate they are and was just trying to check.Thanks

[VICHunter]

As for my chrony I don't know how accurate they are and was just trying to check.

A chronograph is a pretty standard bit of kit these days. Pretty safe to assume that it's accurate.

As mentioned above, if it's critical you get it right you can always borrow someone else's one, or do some trajectory testing like Monty said.

Good shooting.

[RDobber]

On the subject of trajectory calculators, the JBM ballistics one is very good IMO.

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

[Vati]

Yep, JBM ballistics is a winner.

I did my ballistics cheat sheets with JBM and they're just about spot on.

[MCLE]

Well I was lucky enought to be at the one of the clubs that I shoot Fclass at and one of the top shooters had his chrony there a top end one better than my old one.And the good news is my chrony isn't as far off as I thought my chrony was giving me 2980 .As l was saying I'm loading 46.5 of 2208 with 155.5 Bergers.l put 12 shots through the better chrony and they ranged around 3010 FPS to 3018 FPS .So I will be backing them off a little so they are under 3000FPS.

[Old Fart]

Well I was lucky enought to be at the one of the clubs that I shoot Fclass at and one of the top shooters had his chrony there a top end one better than my old one.

There's always someone willing to help at your local range