308

ive just started reloading 165gr sst what sort of grouping should I be expecting to get at 700m out of a 21inch barrel ? looking to consistently hit a 200mm steel gong. have found 175gr serra hpbt good projectiles . but wanting I little flatter shooting

You are wasting your time trying to get good results with a 165 grain bullet at that range with a 21" barrel. That barrel length cannot develop enough velocity, and you really need 24" at least. You should be looking at bullets in the 140-150 grain area. You may also find that your 21" barrel is fairly lightweight for hunting and will not produce the accuracy you need (better than 25mm groups at 100 metres consistently).

700 metres? even for a target rifle that's getting out there. Assuming the rifle will shoot moa (1 inch at 100 yds=7 inches at 700 yds or in metrics 1/4 mil at 100 m=7 mil @700m) a little wind will shove the bullet up to a metre or more off line over that distance so it's as much about reading the conditions and allowing for them as pulling the trigger.

I ran the 168 amax out of my 21 and 7/8 inch? factory Sako, Would group 3" at 700y when I did my part and it wasn't windy.

If you're only shooting gongs try one of the 155 grain match projectiles they are designed for 1000 yard full bore target shooting, Sierra Hornady Lapua Nosler Berger all make at least one,
AR2206H is a good powder to start load development with and get Lapua cases no fuss minimum case prep, Robert.

thanks.it is a light weight tikka.I get about three shots out of it before the heat sharts affecting acc. so u think lighter projectiles wall be a better choose at 700yrd than heavier?

Im using adi ar2208 as I got bulk powder at half price. it shooting 175gr serra matchkings very wall and agree the lapua cases are very good . but was thinking of going for a lighter projectile. wall there be more wind drift with the lighter 150,155gr than the 165gr?

heavier and higher bc will perform better, ignore the speed

My sons 308 with a 20" barrel shoots sub moa all the time with 165gn Sierrs spitzers moving along at a respectable 2800fps, using 2206H. With the right scope thats perfectly capable of hitting a gong at 700! Shorter barrel try a faster powder, dont get bothered by speed, pick a boolit you like, preferably with a high ballistic coefficient and go shoot some shit - its not rocket science.

I'm no authority, and not saying this stuff is accurate or not but have a read:

The Truth About Barrel Length, Muzzle Velocity and Accuracy - The Truth About Guns
SWAT Article BARREL LENGTH
The Myth of Barrel Length and Velocity Loss - Guns.com

Most of the reading I did before cutting mine back to 20" suggested that there would be either 1 - zero velocity loss, or 2 - fuck all velocity loss. Some articles say none until about 20" and under for 308, others say about 10fps per inch and then it starts dropping a bit more when you go below 18" or so.

I kinda want to cut mine back to 16 or 18 inches :D, but it shoots damn nice at the moment and don't wanna risk any random finicky thing upsetting it. Those short barrells look awesome and would be so easy to offhand shoot. I'm jealous whenever I see those cute little things in threads.