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Ballistics data help needed

 
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  #1  
Old 04-16-2013, 08:49 AM
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Join Date: Mar 2013
Posts: 8
Ballistics data help needed

I just got a New Savage 308 rifle for my long range target work and I'm using factory Hornady Match 168Gr BTHP ammo. It shoots great for factory stuff but when I got out to the farther ranges, 4-500 yards I could not hit crap with it. I'm using a Leupold Mark 4 LRT 6.5-20 scope and I'm dialing for my ranges. My question is how much difference does barrel length make on the speed of the bullet exiting the muzzle? Hornady shows a velocity of 2700 FPS for this round but my gun has a 26 inch barrel and I was wondering if it is faster or slower exiting the barrel if it would throw off my range dialing for those longer distance shots? I don't own a chronograph so I was wondering if there is a basic way to calculate this or if the speed difference would be very small that it would not matter that much for dialing in at those ranges. Any help would be appreciated. BTW here is a pic of my new rig..

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Old 04-20-2013, 09:38 PM
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Join Date: Mar 2013
Posts: 5
Re: Ballistics data help needed

Odds are that cartridge was tested in a universal chamber and a 24" barrel. Your velocity may be higher. If it is then it will probably only be 50-60fps higher. But, other factors can determine velocity. I would shoot it over a chronograph if one is available. Your other option is to put up a large target and shoot at it until you have dialed your rifle in for that particular load at all distances that you will shoot. You can write down your dope and use it for future engagements. Just make sure b4 you go to the trouble that your zero is set for that round and you don't change it afterwards. A 1" difference in zero at 100yds can make a huge difference at 700,800,900, etc.
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Old 01-01-2014, 10:44 AM
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Join Date: Sep 2009
Location: South Dakota
Posts: 400
Re: Ballistics data help needed

Quote:
Originally Posted by melloyello View Post
...Your other option is to put up a large target and shoot at it until you have dialed your rifle in for that particular load at all distances that you will shoot. You can write down your dope and use it for future engagements.
That.
A chrono is rarely better at giving your velocity than the guide on the side of the box or a reloading manual.
I don't even use it anymore...ever.


As stated. Put up a target that is big enough that you can print a group at 400 or 500 yards. Use a 4'x4' or bigger target if you need to.

Make sure you have a good aiming reference point and dial to an elevation that will at least get you on target.

Judging by where your group impacts, in relation to where your aiming point is...you can calculate your TRUE velocity, based on the BC of your factory ammo and current atmospheric conditions.
It's best to use a good ballistic program for this, so you don't have to worry about keeping a data book, but a data book is a good thing to learn anyway.

If the ammo shoots well at 100, then the only reason it won't shoot at 4-500 is shooter or equipment error. As said, it's pretty likely that the 26" barrel is giving you a little velocity boost, but it's not going to be an insane amount.
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