Thread: Velocity loss in short barrel 308

Hey guys
Have just purchased a shortened 308 (17inches).
I am keen to make up a rough drop chart for it (very rough indication) and I will try and validate it as and when I can.
I don't reload, and dont have access to a chrono, so take the manufacturers data on the factory ammo boxes. From what I understand, the displayed FPS for 308 is based off a 24 inch barrel, what kind of approximate loss should I expect per inch, to roughly estimate my velocity from a 17inch barrel? I thought the collective forum mind might have a more accurate suggestion then google, as seems quite a range out there. I also know quite a few people have cut down 308s so might have some real world data.
Cheers!

Originally Posted by JoelA

Hey guys
Have just purchased a shortened 308 (17inches).
I am keen to make up a rough drop chart for it (very rough indication) and I will try and validate it as and when I can.
I don't reload, and don't have access to a chrono, so take the manufacturers data on the factory ammo boxes. From what I understand, the displayed FPS for 308 is based off a 24 inch barrel, what kind of approximate loss should I expect per inch, to roughly estimate my velocity from a 17inch barrel? I thought the collective forum mind might have a more accurate suggestion then google, as seems quite a range out there. I also know quite a few people have cut down 308s so might have some real world data.
Cheers!

My best suggestion would be to borrow a chrono from somebody. Or somebody with a Garmin or Labradar et take you to a range. I am sure somebody around the Waikato would be able to help?

https://rifleshooter.com/2014/12/308...ty-28-to-16-5/

looks like about 250 fps which is a bit less than I was thinking.
will vary with ammo faster/lighter ammo may loose more velocity
Z

16inch 1-8 Tikka, 168gn eldm handloads @2450. Not fast but good enough for what I need it to do to 300m
I know I could get more speed if I brought different powder but that means additional cost.
Never used factory ammo in it

Originally Posted by JoelA

I don't reload, and dont have access to a chrono, so take the manufacturers data on the factory ammo boxes. From what I understand, the displayed FPS for 308 is based off a 24 inch barrel, what kind of approximate loss should I expect per inch, to roughly estimate my velocity from a 17inch barrel?

Tried doing exactly that once upon a time and it was so far off, it wasn't funny.

Bergara 16.5 spitting factory Sako gamehead 150gn => 2650fps.

Originally Posted by MB

Tried doing exactly that once upon a time and it was so far off, it wasn't funny.

Good to know - thanks MB

Originally Posted by ZQLewis

https://rifleshooter.com/2014/12/308...ty-28-to-16-5/

looks like about 250 fps which is a bit less than I was thinking.
will vary with ammo faster/lighter ammo may loose more velocity
Z

Thanks for that Z!

Originally Posted by STC

My best suggestion would be to borrow a chrono from somebody. Or somebody with a Garmin or Labradar et take you to a range. I am sure somebody around the Waikato would be able to help?

I may have to try that!

Tika 308 22in barrel,using shop hornady 165gr ssts chronied at 2760ft/sec.Loss of 40ft/s /inch off the factory velocity 2840ft/s using at 24in barrel.Down to a 17in barrel would mean more velocity loss per inch.

@7mmsaum is the North Island Chrony still alive?

@JoelA. I shoot a 16" with supressor but do reload et al. The max range shot I'll take is at 300 metres.

That said; I have used factory ammo in several different brands of shortened .308's. The most consistent in terms of velocity and accuracy was Sako Gamehead. In your shoes I would forget about velocity seeing as you don't have the means to measure it. Assuming you've got access to a range, Zero your rifle @ 100 metres. Then step it out to 200 metres. Group and measure drop, should be roughly 3". That being the case you can safely assume an 8" drop at 300 metres from 100 meter zero.

I figure if I'm taking shots at the two latter extended ranges I've got time to faff about. That has proven to be exactly the case. My scopes a dial up variety. I don't compete but do knock over animals.

Hope this assists. Cheers

Il send you my chrono guessing is just to hard mate

Pick which ammo you think is gonna work, sight it @100, then do a tall target test at 200 and 300. Put your drops in an app - Strelok or Applied Ballistic's etc, and go from there. Should be able to sight it in with 5 or 6 shots, another 3 or 5 to group it, and 3@200, and 3@300. Should still have a few rounds left in the box to go shoot an animal.

I have the SI chrono coming to me next and once I have finished with it can send it south to him @Gibo

Oops just realised he is up north. So ignore above