7mm-08 velocity for 18" barrel

[KHNC]

Anyone have any velocities for 120gr factory ammo or 140gr factory for a 7-08? I have read to reduce 50fps per inch. Getting my 20" cut down to 18" now. But i have not shot thru a chrono. Are most charts based off 22" bbl or 20" ?

 

[zion zig zag]

I’d say you’re looking more at 25fps per inch. And I bet most factory charts are based on 24 or 26 inch barrels. I just recently cut a stock Tikka barrel down to 18” but I haven’t had a chance to chrono yet.

 

[hereinaz]

50 fps per inch, that seems really high. My experience is between 20 and 35 fps is more likely based on rifles I have cut down and what I've discussed and read.

Hornady lists a 24" test barrel length on their ammo with velocity. Not sure what other manufacturers would. You can go to reloading manuals, and pick a bullet and they will give you velocities and tell you what length their test barrel is.

https://www.hornady.com/ammunition/rifle/7mm-08-rem-139-gr-interlock-sp-american-whitetail#!/

 

[260madman]

It’s going to be 25 fps. Chrono my loads from 24” to 20” in a 260Rem is a 100 fps difference. I chrono’d 6 different loads and none exceeded 110 fps that I can remember.

 

[KHNC]

50 fps per inch, that seems really high. My experience is between 20 and 35 fps is more likely based on rifles I have cut down and what I've discussed and read.

Hornady lists a 24" test barrel length on their ammo with velocity. Not sure what other manufacturers would. You can go to reloading manuals, and pick a bullet and they will give you velocities and tell you what length their test barrel is.

https://www.hornady.com/ammunition/rifle/7mm-08-rem-139-gr-interlock-sp-american-whitetail#!/

This chart should work pretty well. I was thinking of using this bullet anyway. As of now, i have some Federal 140gr and Remington 120gr factory loads.

 

[KHNC]

Just found some Barnes 120gr TTSX-BT ammo.. Ordered 3 boxes. Hornady is sold out everywhere. I like Barnes ammo and have shot it for years in my 308 and 300WSM. Looks like 3005 with 24" barrel. I may end up going down to 16" barrel now that ive thought about it a little more.

 

[hereinaz]

It’s going to be 25 fps. Chrono my loads from 24” to 20” in a 260Rem is a 100 fps difference. I chrono’d 6 different loads and none exceeded 110 fps that I can remember.

Yup, my rule of thumb is 25 fps for the typical barrel lengths. Adding an inch past 26" has diminishing returns, adding less and less velocity per inch to where 30 to 32 inches doesn't give much benefit at all. On the other side, once going under 20" the loss per inch increases the shorter it gets. For example, you will lose more going from 18-17 than you will going from 26 to 25 because there is still significant gas expansion between 18 and 26 inches. You have most of the powder burn before 18 inches, but as I understand the gasses are still expanding and combustible gases are still burning. That is why you get brighter flash and louder blast the shorter a barrel gets. Uncorking while the pressure is higher from the gases--bigger pop.

 

[Doc Holliday]

Are most charts based off 22" bbl or 20" ?

My Barnes and Swift reloading manuals are based on a 24". Nosler manual is based on a 26"

 

[brushape]

I don’t know what speed they we’re going but my buddy and I stacked up some pigs with his 16” Ruger m77 7mm08 with the factory Barnes 120 grain loads recently and they killed very well the largest pig was the furthest shot at 240 yards

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[zion zig zag]

I like the "Bear Hunting is not a Crime" bumper sticker!

 

[brushape]

I like the "Bear Hunting is not a Crime" bumper sticker!

Thanks! One of my customers made me those because I always get fired up on the politics of bear hunting and all the property damage I get from them in the summer


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[LaRoche3]

I’d say you’re looking more at 25fps per inch. And I bet most factory charts are based on 24 or 26 inch barrels. I just recently cut a stock Tikka barrel down to 18” but I haven’t had a chance to chrono yet.

Any chance you've checked those 18inch speeds yet ?