i am considering a rebarrel in 7/08
ai. would like to hear some real world performance(velocoties) primarily with 140 to 150 grn. bullets.

thanks

b h

My 708 standard does 140's at 2960 with Varget, in a 21" bbl, if I need more, its a much larger caliber, and possibly case.

I would do a standard case and keep life ez.

If you really want more performance, I'd step up the the .284 win.

To me the advnatage of the ackley case is that it stretches very little on sizing, which is a time saver on a high volume of fire round such as the .223. If you're not burning hundreds or thousands of rounds a month, I see little benefit.

I don't have a 7-08 but I do have a .260ai. I think you can realisticly only get 50-75fps from the AI but why not if you are rebarreling anyway. The round looks great & the cases need little attention after firing, you can use factory ammo in a pinch, not much downside.

Not to disagree with what Fred says, respect his experience, but I do know someone who was disappointed in his AI not getting expected speeds, so he rechambered, and I honestly cannot recall if he went to std 708 or reamed to 284. 284 is a good round, perhaps harder to get brass and ammo, but planning should avoid any real issues.

I personally try keeping things simple, using standard dies (less money usually), and avoid case forming, there is nothing wrong with the AI, but I get all I need from a 7 in the standard version. Varget and 4064 get great speeds in 140 class bullets. 150's are good but after that case capacity using it in a short action limit your 160's and higher.

I believe a top loaded 708 with quality 140 will do to elk up to 400, keeping shots on elk broadside behind shoulder to be sure of penetration, would prefer a 338 bullet, but the elk will die hit with a good bullet through the lungs.

What is your primary game and ranges?

My 7-08AI wears a 22" #2 Shilen Stainless Match, and 3000fps is not difficult with 140gr bullets. With a 1:11 twist barrel, that's the heaviest bullet I shoot. If I need more horsepower than that, I just step up to my 300WinMag. With H414 and Federal 215M primers, I've chronographed 3075fps over the Oehler 35 without stiff bolt lift or flattened primers. Groups were right at 1 MOA, but backing down below 3000fps cut my groups to half that size. My rifle regularly shoots groups that hover around .5 MOA with several other powders, including IMR4350, IMR4831, H380, and RL-19. H380 and IMR4831 are probably the most accurate in my rifle, but they are all worth noting. It's not a finicky round to load.

quote:

Originally posted by bounty hunter:
i am considering a rebarrel in 7/08
ai. would like to hear some real world performance(velocoties) primarily with 140 to 150 grn. bullets.

thanks

b h

It's generally known that AI forms of cartridges built on the 308 case do not yield much if any advantage as the parent rounds are loaded to quite high pressures to begin with and the increase in volume is quite small with the blown out AI cases.

It's your money...have at it.

Exactly my point. The avg. increase in vol. for my .260ai is 2gr, the 7-08 would be prety much identical. I can almost get that by switching brass brands. Still, there is little downside. I fireform new brass everytime I go to the range by shooting 3 fouling shots. When you get your new rifle you'll have to sight in (more fireforming shots), etc.

According to the Sierra book there is not much to be gained by improving the 308 or the 30-06 based cartridges. If you need more than what a standard 7-08 will give you look at the 280 Rem.
Sierra also stated that the 6mm Rem & the 257 Roberts did benefit from this modification, since they are based on the 7x57 I wonder if the same would apply?

thanks sst that's the type of info that i am looking for

b h

bounty hunter,
Kenny Jarrett has been making light weight rifles chambered in 7-08AI for a long time. It's a very popular cartridge for his customers. Kenny also says that he has no problem getting 3000fps out of this chambering, and that's out of his 20" barrel!

2 grs of powder is not going to make a 7-08 into a 7mag. The 7-08 is loaded to 61,000 no telling what people load their 7-08AI too. As to Jarret's claimed 3050fps with a 140 in a 20" barrel I have "no comment".

Re: Kenny Jarrett: My only comment, in 1992, went to his booth, and I do recognize he knows many tricks of the trade, has a good deal of knowledge, and also know he is in business to make money, his employees told me that the 7BR was inadequate on deer and the 'ran off'

such a stark contrast to what Melvin Forbes, owner of ULA told me of his daughter's 7BR on display with 20", "the 120 ballistic tips JELLY the inside of a whitetail and no problems seen using it to the 250 yd limit they have on their shots seen in Virginia.

Interesting, 2 opposite opinions.

Like Fred says, no downside, I admit you might get 100 fps more on average and less case stretch, though I partial size and stretch has been acceptable, but not problematic, now a 243 can be a WHOLE other ballgame!

quote:

Originally posted by 6.5BR:
now a 243 can be a WHOLE other ballgame!

Interested in this - care to elaborate?

Layne Simpson did one up. He called it the SGLC (Simpson's Good Little Cartridge) it's Wildcats Volume II. Impressive little s**t.

ramrod340,
Whoever first stated that you can only increase case capacity by 2 grains is mistaken. What I would consider maximum safe loads with this cartridge in my particular rifle are not the most accurate. Most of my loads for 140gr bullets contain a little over 50gr of powder, and I don't get a stiff bolt lift or enlarged primer pockets. I attain velocities that are higher than factory 7-08 with 24" barrels from only a 22" barrel. Granted, some barrels are simply faster than others, and I'll be glad to admit that I don't know the actual psi of my loaded cartridges. I'm sure it's a little higher than SAAMI specs, but you can safely accomplish that with a properly cut Ackley chamber.

When I had Shilen barrel my 7-08AI, I asked for a SGLC. It came back engraved 7mm-08 Ackley Improved.

quote:

ramrod340,
Whoever first stated that you can only increase case capacity by 2 grains is mistaken

Don't know who stated it. But I have both cases and the difference is just shy of 2 grs of water.

And yes you could see that much by comparing different cases.

Don't get me wrong. The majority of my rifles are blown out improved 280 cases with the shoulders moved forward. I shoot very little factory.

The taper on the 7-08 and 7-08AI is basically the same(per Clymer numbers) you wouldn't gain that extra holding power that many claim from the AI so there is no reason you couldn't load both to the same pressure in a quality cut chamber. At the same pressure you will see almost no gain(in my experience with the 243 & 7-08) with the 308 based cases.

Factory 7-08 is loaded to 61000 at best. Doesn't take much increase in pressure to make a couple inches of barrel. I gave up doubting velocities people claimed years ago. When I started playing with wildcats 25 years ago I used to watch for the same pressure signs you mentioned. I got some fantastic velocities. Then after doing some "real" pressure testing I found many of those signs didn't show up until after 70,000+. Safe?? in moderm rifles probably. Do I care to shoot them any longer NOPE.

Anyone is free to load to what ever pressure they choose. I will not even argue with their claimed velocites. Only thing I will continue to state is from my 25 years of playing with various AI, Gibbs style wildcats loaded to the "same pressure" the gain is roughly 1 for 4. 1% velocity for 4% powder.

quote:

Originally posted by 1894mk2:

quote:

Originally posted by 6.5BR:
now a 243 can be a WHOLE other ballgame!

Interested in this - care to elaborate?

MY experience has had much more case stretch-lengthening of the necks with my 243's and even 260 or 6.5/308's over firings, than the 708. I would expect the 308 and 358 to have even less stretch. Why, don't know, but that seems to be what occured in my ltd. experience......

anyone else care to share their experience?