Rebarrel a 308win to what cartridge?

[tdot]

I have a Kimber Montana 308win, that I'm considering rebarreling. This will be for mountain hunts out to say 500 yards on goat/sheep and Grizzly protection at 50 yards and below. My original plan was to try and find a used 280ai Mountain Acsent, but they are rare in Canada.

What high performance cartridges will fit in a Short Action and a 308 bolt face? I've ruled out any 6.5 as I already have a 260Rem and a 6.5SS.
I've considered the 7-08ai and that probably makes ths most sense to me, though I keep seeing varying data on the actual velocity gains. This will be an 18"-20" barrel. I'd considered the 338 Federal and 358win, but I don't think either will work for me. Will likely be shooting solid coppers, so bullet weights will be on the average to light side of any caliber.

Any suggestions?

 

[EastMT]

I just went through this as well. After comparing and mapping the trajectories to 500, which is past my personal game shot limit, I decided to build a uberlight 308. Just ordered the pencil barrel, chopping it off at legal limit.

Out to avg game distances there almost zero difference, and I like 180 PT in squatch land, and every time I get up with the goats or sheep, the bears are there with me. So I figure pack for a bear.

I have an extra new 308 laying around, I’ve almost talked myself into a JES rebore into 375 Raptor(375-308 basically). If you are bored, look that website up. Pretty neat.


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[tdot]

I forgot about the 375 Raptor, I'll have to research that cartridge again. I'd decided on that direction once before for a dangerous game gun. But maybe I need to look at it for a Mountain gun too.
Thanks.

 

[Wapiti1]

.284 Win or one of the .284 wildcats. Now, getting it to feed well is a trick, but doable.

When you add bear, I would really look at the .358 harder. It will push a 180 TTSX 2750fps without trying real hard. A 200grain Partition will get to 2600+.

Jeremy

 

[Trogon]

308, 7-08ai, or 7saw otherwise I think you’re headed to a mag BF. I played this game in my mind for a long time and just went for a long action (280ai).

 

[wildwilderness]

I would cut your 308 first to your desired length and run some 124 Hammer hunters through it and see what velocity you get.

With short barrels larger bore will gain velocity back, then throw a light copper bullet and you are back in the game.

After you get a baseline with what your 308 will do you can decide if you need to step up.

 

[Rob5589]

7/08 SAW looks awesome on paper.

 

[wildwilderness]

I think a 30-284 would be easy. Or even better the 338-284 would be neat. You could shoot the 160 ttsx maybe 3000 fps or 185 TTSX and get a lot of energy

 

[TauPhi111]

I wouldn't rule out the 338 federal or 358 Win just yet. You'll have the best short barrel performance with those 2 sticking with the 308 base case. I have an 18" barreled 358 win that I love. With a 200 grain TTSX and 52 gr. TAC, i get 2562 FPS and can get out to 450 yards at Rocky Mountain elevations before I reach the min expansion velocity for that bullet. I'd bet with the higher BC 338 bullets out there, you'd get out to 500 easy with the right load.

Otherwise, if you're looking to get as much powder capacity you can get in a short action and 308 bolt face, I'd look to the 284 Win or a wildcat based on such.

 

[Spoonbill]

I think a 30-284 would be easy. Or even better the 338-284 would be neat. You could shoot the 160 ttsx maybe 3000 fps or 185 TTSX and get a lot of energy

I think shooting times had an article on 284 win wild cats, pretty interesting read. I included a link to it below. with the new 270 bullets coming out a 270-284 could be interesting. Don’t see a practical difference when compared to the 284 win, but practical isn’t the point.

Wildcatting the .284 Winchester

Long-range shooters and wildcatters have kept the .284 alive.

www.rifleshootermag.com

 

[CApighunter]

338 fed or 7 SAW would be my picks.

 

[BjornF16]

284 Shehane pushing 145 LRX 2800+ FPS.

Barnes reloading manual shows 284 Win pushing 145 LRX at ~ 2800 FPS from 24” barrel.

 

[eoperator]

I have an 18" 308 pushing 152 hammers over 2900fps

 

[Trogon]

I think a 30-284 would be easy. Or even better the 338-284 would be neat. You could shoot the 160 ttsx maybe 3000 fps or 185 TTSX and get a lot of energy

Can you fit a 284 based cartridge in an 84M action, with enough space to make it worthwhile? I don't know the box length on those, but it seems across the board the 284 is better suited to an XM or LA box.

 

[tdot]

I would cut your 308 first to your desired length and run some 124 Hammer hunters through it and see what velocity you get.

With short barrels larger bore will gain velocity back, then throw a light copper bullet and you are back in the game.

After you get a baseline with what your 308 will do you can decide if you need to step up.

I'm actually in load development with the 124's right now. If I'm happy with them, then I'm more likely to keep the gun as is.

May have to try the 151 Absolute Hammers too. That might make all the difference. But I was never able to get the 152HH to shoot well or anywhere near some other reported loads.

 

[EastMT]

I put this spreadsheet together awhile back, I pretty much use partitions exclusively as BC doesn’t really mean much if you don’t shoot far. You can see up until the 338 Fed, you could use the same setting on your scope for hold over it’s so close. 338 Fed seems to be the best of the fatties for up to 400 and is 6” lower at 400 for a much bigger bullet, not bad IMO.

I added 7mm08AI with 160 PT as well, same bullet so can compare Apples. Interesting that the AI with 160’s is exactly with the CM, heavier bullet same path essentially. I didn’t track past 500 yards because I could care less about past 500 performance.


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[tdot]

308, 7-08ai, or 7saw otherwise I think you’re headed to a mag BF. I played this game in my mind for a long time and just went for a long action (280ai).

What am I missing about the 7Saw? Just looking at it quickly it seems like the shoulder is pushed back and powder capacity decreased. Main benefit is that can be done on a press, with a die, vs. Pushing the shoulder forward via fire forming with the AI. Is there a performance increase that I'm not seeing?

 

[tdot]

I have an 18" 308 pushing 152 hammers over 2900fpsView attachment 230279

Whats your load?

 

[eoperator]

Whats your load?

lapua brass
win std primer
152 hammer
50.5gr cfe223 (from my memory not sure, at work)

I'm done chasing wildcats for 2% more performance

 

[Trogon]

What am I missing about the 7Saw? Just looking at it quickly it seems like the shoulder is pushed back and powder capacity decreased. Main benefit is that can be done on a press, with a die, vs. Pushing the shoulder forward via fire forming with the AI. Is there a performance increase that I'm not seeing?

Been a while since I looked at it, but yeah I think you're assessment is about right.