7mm-08 Ackley Improved..

[Sammy]

Looking for information about the AI version of the 708. Considering some rationalisation in my gun cabinet and wanting to give a bit more ommph to a 708...

I see that Jarrett rifles list the 708 AI as one of their pet calibres with Nosler BT 140g @ 3050fps and 120BT @ 3150, which sounds comparitive with a 280 Rem and not far behind the AI version of that. ,Through a 20' barrel and a short action)

I am considering building a custom hunting rifle on the Barnard SM repeater action and HS mag, and looking for 308 style case options with a bit of kick..because you can't run the 06 length cases through the mag option...

Has anyone got personal experience with the round, has the performance been comparitive with Jarrett's? What were the accuracy results and loads etc, and how about feeding from mags....any issues...

Any help would be appreciated....thanks

 

[sewwhat89]

I guess it depends on what you are wanting to shoot, but my plain 708 shoots 120gr Sierras at 3120fps out of an 18' Model 7. I suspect with heavier bullets, the AI version will help some, but I would not think it would be worth the extra time. If it has to be a SA, I am getting just over 3200fps with my Model 7 7 SAUM shooting 145 gr Sierra Grand Slams.

 

[65BR]

3120 is fast in a carbine, what powder/load if you can?

 

[RonRouse]

Sammy, I have owned 2 7-08AI rifles, one of which was built by Kenny Jarrett, and the other rifle built by Bear Arms of the same town as Jarrett. Both were very accurate but the problem was the fact that both preferred loads that were hot in order to get the accuracy. I would fire-form the brass and then one more firing and the primer pockets were so loose that the brass had to be discarded. The increase in velocity was only 100 FPS over the standard 7-08. In my opinion, it just wasn't worth the extra trouble. Like I said, this is my opinion. Good luck.

 

[Sammy]

I guess that my intention is to shoot a 140 grain Accubond out of the rifle. I have a 7WSM currently running 162 AMAXs at 3050 out of a Nesika Actioned 26 inch barrel and I would be trying to duplicate that sort of speed with the lighter bullet in the 708 AI.

The 7WSM is a big rifle, and carting it up our steep hills is a bit of a chore, and I would use the 708 AI for low country bush hunting as well, being lighter and handier. I realise the long range performance is going to be reduced, but it could be a good compromise.

Thanks for the responses.....but a further question....if I use the custom action Barnard,which is really strong) and good quality brass,necked down Lapua 308) or similar....am I going to get some more reliability in brass longeviety.....?

Also how about mag feeding?

Cheers

 

[Sammy]

Sorry don't know about the loads in those Jarrett rifles...

 

[sewwhat89]

It is either 45 or 45.5gr IMR 4320. It is a hot load, but it shoots this load better than anything else. We went through five or six powders trying to get something to break an inch with the 120s. The rifle really seemed to like the 139 gr Hornady, but my dad did not want to shoot that weight bullet.

 

[Sammy]

Do you know what brass he is using and what sort of action....??

Thanks

 

[65BR]

Thanks for the 4320 rec.

 

[Grand]

Sammy: I've got 2 with one more on the way. Velocity gains with the AI in this caliber are marginal 50-100 fps. Personally, I don't like running max pressure. So, with the AI, I can shoot the 120BT at 3150, and 140's at close to 3,000 without excessive pressure. Some will argue that those velocities can be achieved with the parent cartridge, and they can, but usually at a cost, such as short brass life. If your going AI purely for velocity gain, you may be disappointed. Some times you just get a slow barrel, or a barrel that shoots best below max. Also, if your a volume shooter, probably best to stay away from this AI,.223 AI is different). Choose an AI because you like to Wildcat and shoot somthing not so plain vanilla and you'll be happy, and maybe pick up some speed to boot.

 

[Sammy]

Thanks Grand....are familiar with some AI cartridges and had a 25-06 Improved at one time. Probably have decided to go with a straight 284 Win which should deliver similar or slightly faster performance for the 120s and 140s...

 

[flatlander]

I guess a 284 with 120 & 140gr bullets could be loaded to feed through the magazine of a short action, but doubt you'd be able to feed anything much heavier. That's one reason the straight 284 has become so popular over the past few years among LR prone & F-class shooters - when built on a long action, 168-180gr VLDs will fit easily in AI 300 Win Mag magazines. I've got a couple of them - one on a M700LA, the other on a BAT 3LL - and they're good rifles for 1000yd any/any prone matches.

I built myself a 7mm-08 Improved 30* a year or so ago, on a bare M700 w/PTG custom bolt with .061" fp hole and mini-16 extractor. I left a 1-9tw Krieger Rem varmint at 26", and have been fairly pleased with it, using S168MKs & H100V to fire form WW7mm-08 brass that's had necks expanded to .308, then partially sized to leave a false shoulder. IIRC, I'm getting around 2660fps with Hornady 162 AMax in the fire form loads. Not unhappy with it at all, but haven't taken the time to work up a better load for use in formed cases. Recoil is considerably milder than it is with either of my 15.5lbs 284s. I'm looking to try RL16 & 23 in this rifle when I get the time, but really don't expect to safely reach in excess of 2700fps with 162-168gr bullets. Accuracy is king - what good does it do to ruin brass by running hot loads?

 

[bsekf]

Start with 308 Palma cases from Lapua, small primer pocket, they will stand the extra pressure if you are pushing them fast. PO Ackley really liked the 7x57AI. My 7-08AI is on an Encore and I start with 307 brass, my loads are standard Max loads. You don't gain much when you AI the 308 family, usually <10%.

Bill

 

[alf]

Hopefully Sammy got it figured out, since the thread is 10 years old, & he hasn't logged on for 6 years.

 

[XTR]

I shoot a 7-08 as my favorite hunting rifle. I get ~2900FPS with 140s from 25" barrel, and could get more but don't see the need to push it, it shoots well there. Nothing that gets shot with hit would be any deader if the bullet had another 100FPS.

Getting the improved shoulder angle is great and all, but in a 308 based case the increase in capacity when you AI it is only a few %. I know I've seen some pretty great claims on the interwebs for velocity, but think about it, a 30-06 only gains about 150FPS over a 308? I agree with the post above that the 7-08AI probably isn't worth the effort.

If you want a faster 7 in a short action I'd suggest a 284, it will show gains over anything you can do with the 308 based case in any form. It will work great in a short action with middle to light weight 7mm bullets. The only problem will be in your head when you start thinking that it could launch the big 7mm pills and trying to make it do both.

 

[ShootDots]

Start with 308 Palma cases from Lapua, small primer pocket, they will stand the extra pressure if you are pushing them fast. PO Ackley really liked the 7x57AI. My 7-08AI is on an Encore and I start with 307 brass, my loads are standard Max loads. You don't gain much when you AI the 308 family, usually <10%.

Bill

You are exactly right Bill! Palma brass is THEE ONLY way to go>>>>whether 7mm-08, .260, 243 or the A.I. versions of each! T-Rust me, that brass is almost indestructible!

 

[bbarber25]

@Mulligan

 

[65BR]

Palma brass- is it all small primer? I wonder if there are potential ignition reliability issues in cold temps? Read test results showing mixed data on the pros/cons of Palma brass in the smaller calibers.

 

[DocDoc]

Great information on the 7-08 AI from our Aussie brothers down under.
https://www.ozfclass.com/phpbb/viewtopic.php?f=5&t=7100

 

[NortexDM]

Palma brass- is it all small primer? I wonder if there are potential ignition reliability issues in cold temps? Read test results showing mixed data on the pros/cons of Palma brass in the smaller calibers.

I've ran palma in 7mm-08ai in sub freezing temps with no ignition problems running varget or 4451.