Cartridge for 18" barrel?

[brocksw]

I think if you putz around with powders, you'd be able to get 3000 with the 140 7mm AI in an 18" tube. I'm easily getting 3050 with a 22" bbl and I've got room to go, pressurewise. The 7mm seems to be in the sweet spot for AI chamberings, along with the 257 Roberts AI.

what powder are you using in the 18"?

 

[Fire_9]

I have bounced around 7mm08AI.

check out the 7 saw if you’re looking at the ai

 

[Ben Lamb]

what powder are you using in the 18"?

I'm using RL-17 in an 18" 8mmJ with a light load & 200 grain pills to hit 2300 fps, but that's my only carbine. My 7mm AI is a 22" bbl. That gets RL_17 as well.

 

[VikingsGuy]

Plus there is the whole hammer angle. When I switched from TTSX to 134 hammer hunters in my 22" 7mm08 it added 150fps almost immediately (leaving my final load at 2975 fps with zero pressure signs). I would expect (but certainly don't know) that an 18" 7mm08AI shooting 143 hammer hunters would easily be in the 2800 range and the 140 absolute hammer hunters might get close to 3000.

 

[VikingsGuy]

check out the 7 saw if you’re looking at the ai

Not familiar with SAW, what's the advantage?

 

[brocksw]

I'm using RL-17 in an 18" 8mmJ with a light load & 200 grain pills to hit 2300 fps, but that's my only carbine. My 7mm AI is a 22" bbl. That gets RL_17 as well.

have you fiddled with RL 16 or 23?

 

[Ben Lamb]

have you fiddled with RL 16 or 23?

I have not. I'm in the middle of lots of powder, and I'm pretty happy with where everything is at, so I've not been in load development mode for a while now.

 

[brocksw]

I have not. I'm in the middle of lots of powder, and I'm pretty happy with where everything is at, so I've not been in load development mode for a while now.

I hear ya. I've hopped on the new alliant powder train and am in the same boat. Big kegs of each sitting in my reloading room. No need to experiment much. Though, I could use some H1000.

I'd doubt 16 would recreate the velocity that 17 is getting for you.

 

[ImBillT]

I have bounced around 7mm08AI.

Although .308Win based cases don’t gain an awful lot from being AI’d, they do gain a little, and you’re so close to meeting your criteria with a standard 7-08(and probably could with the right powder, brass, and seating depth), that I would suspect you’re comfortably there with a 7-08AI.

The Mauser cases are longer than a .308Win and have substantially more body taper, thus they gain considerable performance from being AI’d. When you AI a 7x57, you go from being practically equal to a 7-08, to being closer to a 280Rem than to a 7-08. If you’re gonna run a medium or long action, a 7x57AI would be quite wonderful.

 

[Ben Lamb]

RL 17 has been a winner for me in 8mm, 7mm, 35 whelen & 9.3x74R.

 

[brocksw]

RL 17 has been a winner for me in 8mm, 7mm, 35 whelen & 9.3x74R.

 

[ImBillT]

have you fiddled with RL 16 or 23?

My guess would be that RL-23 is a little slow for max velocity from a 7x57AI unless he’s going with 180-195gr bullets. I’m using it in a 6.5x257AI behind 156EOLs, and can’t stuff enough in the case to reach pressure signs. RL-23 should work well in a 280/280AI. For a 7x57AI I would think max velocity would come from something in the realm of RL-16/17/19. I haven’t used RL-16. Might be too fast.

 

[brocksw]

My guess would be that RL-23 is a little slow for max velocity from a 7x57AI unless he’s going with 180-195gr bullets. I’m using it in a 6.5x257AI behind 156EOLs, and can’t stuff enough in the case to reach pressure signs. RL-23 should work well in a 280/280AI. For a 7x57AI I would think max velocity would come from something in the realm of RL-16/17/19. I haven’t used RL-16. Might be too fast.

23 is bulky for sure. For my 7 Max, RL 23 pressures up to quickly, had to go to a slower powder for the 140 class.

 

[ImBillT]

@VikingsGuy if you’re willing to AI, go with the 7-08AI.

 

[ImBillT]

23 is bulky for sure. For my 7 Max, RL 23 pressures up to quickly, had to go to a slower powder for the 140 class.

That’s a far bigger case than a 7-08AI.

Approximate case capacity in gr H2O

7-30TC 53
7-08 54.5
7x57. 55.6
7-08AI 57.5
7x57AI. 63
280Rem. 67
280AI. 73
7mag. 83

 

[RaiderRich]

The old school in me is saying .308 but 7mm SAUM sounds very interesting. I am a 7mm-08 fan but not sure if it has the nads for everything you are looking for in the build.

 

[VikingsGuy]

I like AI, and I like 7mm, so I am now down to 7mm08AI, 7x57AI or 280AI. For the brass I have 280AI and have extra 7mm08 to fire form up to 7mm08AI, 7x57AI would require new brass purchase. For dies I have 280AI but would need 7mm08AI or 7x75AI. So, seems like 7mm08AI might struggle to hit my specs (but hammer bullets may solve that) and the 280AI would be the cheapest option up front but would guess I am just blowing the extra 10-16 grains of powder into the suppressor and that the 7x57AI might be the best balance (of course, leave it to me the choose the most expensive option on the list - i'm looking at you @Ben Lamb).

Any reasons (other than my up front cost) I shouldn't go 7x57AI?

I am going to shoot 140-160 grain monometal hunting bullets (almost certainly barnes ttsx, barnes lrx, hammer hunter or absolute hammer) I am assuming 1:8 twist is optimal?

 

[Fire_9]

Not familiar with SAW, what's the advantage?

Similar to the AI but you can buy brass for it and don’t have to form it

 

[Ben Lamb]

You'll be dancing on 280 AI velocities with that 57 mm case blown out to the 40 degree shoulder. And use can use the seating die for the 280. Just get a neck sizer and use that for all 7mm's. You'll only be spending for brass (get the Norma, it case forms really well) and a sizing die.

It's going to be less than $200 for this. Like, literally 1/10 the cost of your suppressor & ATF stamp. Don't be a punk.

 

[Deleted member 16014]

With 7x57ai on tikka, M+ or LA mags will give you lots of options for long bullets and chasing the lands if desired.