7mm/08 AI velocity confirmation

[wapitiaddict]

I've been doing a lot of research on this cartridge, including on this form. Most say the (lack of) velocity gains in the AI version isn't worth it over the standard. With one exception...

I found a website, Jarret Rifles, that says "Most of our 7mm-08 Imp. rifles have a fairly short barrel, usually no longer than 20", yet we get an honest 3050 f.p.s. with a 140 gr. bullet."

Thats about 200 fps faster than the standard 708, which is quite a bit higher than other reports I've read. Most people report less than 100fps in velocity gains with the AI.

But maybe I've mixed up my research....any thoughts?

If I could get 3000+ ft/s with a 708 in a 20" barrel I'll probably do one.

 

[manitou]

Me too! I am only getting 3040 fps in my 26" barreled .280 Rems loaded over max with 140 grainers.
If I could get 3050 with a 24" tube it would peak my interest.
(Loaded with a temp sable powder, of course).

 

[jimbires]

I load a 140 berger VLD-H , 49.0 gr RL17 powder , norma brass , CCI200 primer . in my 24" bbl I get 3080 FPS . this is not an Ackley Improved chamber .

 

[wapitiaddict]

I load a 140 berger VLD-H , 49.0 gr RL17 powder , norma brass , CCI200 primer . in my 24" bbl I get 3080 FPS . this is not an Ackley Improved chamber .

Wow, that seems smoking compared to other velocities people seem to report. What is your coal? Saami spec?? That would be an awesome hunting round at those speeds.

 

[jimbires]

Wow, that seems smoking compared to other velocities people seem to report. What is your coal? Saami spec?? That would be an awesome hunting round at those speeds.

2.844 COAL measured off the tip

 

[willyqbc]

I run a 139 lrx @ 2940 in a standard 7-08 24" barrel using rl17. Its throated long to make the most of case capacity. I see no reason a similarly throated AI version wouldn't hit in the 3000+ range.

 

[wapitiaddict]

I run a 139 lrx @ 2940 in a standard 7-08 24" barrel using rl17. Its throated long to make the most of case capacity. I see no reason a similarly throated AI version wouldn't hit in the 3000+ range.

Yeah, that's more of what I see posted. But by the time you adjust for a 20" barrel, do you think you could still pull 3000+ with an AI version like Jarret Rifles claim? https://www.jarrettrifles.com/pet-calibers.html

Jimbires velocity numbers would seem to match up with a short barreled improved cartridge.

 

[willyqbc]

I also have a 20" barreled 7-08, that I can push the same 139 up to about 2850 fps. Even throating long, I suspect 3000+ in a 20" AI is probably pretty pressured up. That's the thing about the AI's though...they tend to "hide" the pressure well.

 

[nmbarta]

I also have a 20" barreled 7-08, that I can push the same 139 up to about 2850 fps. Even throating long, I suspect 3000+ in a 20" AI is probably pretty pressured up. That's the thing about the AI's though...they tend to "hide" the pressure well.

That's exactly why people with 280ai's think they can run with a 7 rem mag. Good point of caution there, any cartridge with very little taper won't give you the classic pressure signs. When your primer pockets lossen in a couple rounds, it's time to back her off a bit!!

 

[J E Custom]

I've been doing a lot of research on this cartridge, including on this form. Most say the (lack of) velocity gains in the AI version isn't worth it over the standard. With one exception...

I found a website, Jarret Rifles, that says "Most of our 7mm-08 Imp. rifles have a fairly short barrel, usually no longer than 20", yet we get an honest 3050 f.p.s. with a 140 gr. bullet."

Thats about 200 fps faster than the standard 708, which is quite a bit higher than other reports I've read. Most people report less than 100fps in velocity gains with the AI.

But maybe I've mixed up my research....any thoughts?

If I could get 3000+ ft/s with a 708 in a 20" barrel I'll probably do one.

3000 ft/sec with a 140 grain bullet is very possible in a 7/08 AI. 150 to 200 ft/sec gain is normal and possible if the proper powder is used.

Varget seams to be the fastest powder in the 7/08 and the most accurate I have found was with H414 but it gives up about 100 to 150 ft/sec in a standard 7/08.
My most accurate load is 49.5 grains of H 414 .054 5 shots @ 100 yards with a 120 grain ballistic tip at 3010 ft/sec the Varget load ups the velocity to 3133 ft/sec with a group size of .071. My 7/08 AI ups all of these loads by 150 to 200 ft/sec depending on the bullet used and allows the 140 to meet or exceed 120 grain velocities without pressure.

Unlike the 7/08, The 20 " barrel will be marginal for the AI to exceed 3000 with a 140 but add 2" to 22" and it will work. My 7/08 AI has a 23" barrel and it doesn't have any problems reaching 3000 ft/sec with a 140 ((The reason I added 2+inches to the AI). The AI can utilize a longer barrel and can use anything from 22' to 26' and beyond to get the maximum velocity with the added powder charge.

The AI version of the 7/08 not only adds powder capacity, it adds efficiency to the powder burn and this is where/why it can boost the velocity as much as it does.

J E CUSTOM

 

[jimbires]

does Jarret rifles say what 140 grain bullet they are using ? I'm guessing the Berger 140 vld-H used with RL17 , same as I'm using in this 7-08 .

JE , I've never used varget so I can't speak from experience , but from what I see varget gives up about 150 - 200 FPS compared to RL17 in the standard 7mm-08's all things being equal .

 

[hunter67wa]

You know P.O. Ackley really liked the 7x57 improved for a large gain also. Could be that area of case size and bore diameter.

 

[laker]

You know P.O. Ackley really liked the 7x57 improved for a large gain also. Could be that area of case size and bore diameter.

7x57 has a lot more case taper to blow out compared to the 7mm-08.

 

[laker]

I must not have leaned on the couple 7mm-08 ackleys I had hard enough as 2900-2925 with a 140 seem to be about all I could get out of them before short brass life. That was with 22-24" barrels. This was before rl17 though which seems to get the most out of the 7mm-08