Thread: Shorter barrel = less velocity?

Have a browning xbolt in .308 with 18" barrel amd have over barrel suppressor on. Wondering if anyone knows what the fps would be roughly? Shooting factory 150gr Fusion ammo

Less than it would be from a 22" barrel

Maybe 25 fps per inch less. And the velocity quoted on ammo boxes is often very optimistic.

Originally Posted by GWH

Less than it would be from a 22" barrel

Maybe 25 fps per inch less. And the velocity quoted on ammo boxes is often very optimistic.

Yeah i read something similar about x amount fps less per inch. Has anyone done a chronograph on a .308 w/ 18" barrel?

I'd say it'd be about 2750 at a guess, maybe closer to 2700.

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Sweet thanks, wanting to put some info into a ballistic calculator

This is like the proverbial "how many jellybeans in the Jar" thing.
<2751 haha

Nah man I was just checking the MV on a mates howa .308 (1:10 twist rate same as yours) and it had 2950ft/s on the packet of ammo (Winchester super-x) and low and behold that's what it chronied. He doesn't have a suppressor and you do.
I'd say you'll be running 2770ft/s if they were running a 22" barrel for testing. You'd then take off 100 penalty for chopping off perfectly good barrel but then put it back on due to your suppressor (which can add upto the same)

Mine's 18" and was losing 150-170fps from what it said on the back from factory loads, 150 winchesters were getting 2650. wouldn't expect more than 2700 from the fusions.

Don't count on the figure on the back of the box.
These are shot from test barrels and normally longer then hunting rifles

Zero at 100? Shoot a group at say 200 and measure the drop and then work out a pretty close velocity

The only one way to know is to chronograph your rifle with the load you plan on using, no 2 rifles will give the same result even if they came off the production line consecutively,
If not able chronograph shoot at know ranges out to as far as you can and plot the trajectory that will give you the velocity and known sight settings

A timely query- AccurateShooter forum has today an item on that exact topic.

As they say, you're foolish to think the figures are accurate as there are a huge number of variables involved and even batches of the same ammo may vary significantly.

Give me the details and I can run it through Quickload.

Originally Posted by Timmay

Give me the details and I can run it through Quickload.

Nothing to do with .308, but I have a rather tasty load in my 2506, chronied over two different units and in differing light for both units and drops verified in the field, would love to see just what Quickload came up with, waddaya reckon?

Give me OAL of your cartridge, powder, projectile and barrel length. I've found it really accurate with what I get in the field provided I get my numbers right

Originally Posted by Timmay

Give me OAL of your cartridge, powder, projectile and barrel length. I've found it really accurate with what I get in the field provided I get my numbers right

Right here goes!

- Coal :79mm
- Powder: 57gn IMR 7828
- Norma case
- Federal 210 primer
- 117gn Sierra Pro Hunter
- 25" barrel