Need help to understand performance potential with a custom chambering... 7RM v 280ai

cooperjd

Senior Member
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Dec 30, 2016
Messages
379
Location
castle pines, co
OK...

I am about to go and place an order for my first custom rifle.
It will be based on a Rem 700 long action with an extended wyatt's mag box. It will have a 24" lilja #2 barrel, 1:8" 7mm.

Now, I am wavering between the boring old 7mm rem mag, or the 280 ackley.

I am having the chamber throated for long, heavy 7mm bullets, also hence the fast twist and extended box. I am looking also at the 172gr "absolute hammer" from hammer bullets, a 1.62" projectile.

Now, I want to understand if there will be a significant performance gain with the 7 rem mag over the 280ai when going custom.

I understand that in factory length chambers, there isn't much performance difference between the two. I have a 7RM currently and just sold my 280ai.

However, to my pea brain, if i can get either cartridge OAL to somewhere around 3.6", I will not take up as much room in either case with the longer bullets, and as a % gain I should gain more case capacity for powder in the 7RM... and since it comes with more capacity in the first place, would I gain a larger % increase in capability with the 7RM over the 280?

I've never had a custom chamber/throat done like this, so I'm trying to understand what I may or may not gain by doing this.

Bottom line, with the custom chamber will the 7RM really shine over the ackley? Or will they still be pretty similar in performance, and go for the ackley to take less ass-whoopin at the back end?

Purpose of the rifle: 6.5 - 6.75 lb mountain deer/elk rifle. Looking at a mcmillan game hunter, mesa altitude, or manners eh2 stock to hold everything together.

Thank you
 

wind gypsy

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Joined
Dec 30, 2014
Messages
4,472
I haven’t messed with 7RM at all but with 10+ grains more case capacity it will definitely have more juice than a 280ai.

Shooting from the hip here but I’d guess you’re looking at 100+ FPS higher velocity with heavies from the RM at similar pressures.
 
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Shooter71

Member
Joined
Apr 15, 2013
Messages
58
How many rounds do you want in the magazine?
I’d pass on the extended box in a Rem long action.
 

762Gunner

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Joined
Oct 6, 2020
Messages
389
Location
northwest
OK...

I am about to go and place an order for my first custom rifle.
It will be based on a Rem 700 long action with an extended wyatt's mag box. It will have a 24" lilja #2 barrel, 1:8" 7mm.

Now, I am wavering between the boring old 7mm rem mag, or the 280 ackley.

I am having the chamber throated for long, heavy 7mm bullets, also hence the fast twist and extended box. I am looking also at the 172gr "absolute hammer" from hammer bullets, a 1.62" projectile.

Now, I want to understand if there will be a significant performance gain with the 7 rem mag over the 280ai when going custom.

I understand that in factory length chambers, there isn't much performance difference between the two. I have a 7RM currently and just sold my 280ai.

However, to my pea brain, if i can get either cartridge OAL to somewhere around 3.6", I will not take up as much room in either case with the longer bullets, and as a % gain I should gain more case capacity for powder in the 7RM... and since it comes with more capacity in the first place, would I gain a larger % increase in capability with the 7RM over the 280?

I've never had a custom chamber/throat done like this, so I'm trying to understand what I may or may not gain by doing this.

Bottom line, with the custom chamber will the 7RM really shine over the ackley? Or will they still be pretty similar in performance, and go for the ackley to take less ass-whoopin at the back end?

Purpose of the rifle: 6.5 - 6.75 lb mountain deer/elk rifle. Looking at a mcmillan game hunter, mesa altitude, or manners eh2 stock to hold everything together.

Thank you
The 7 RM has the same capacity (83 grains depending on brass) as a 7wsm.
I can tell you that my 22" 7wsm built on a LA and throated for 195's is getting 3000 fps with 180s, and up to 2900 with 195's
 

Slugz

Senior Member
Joined
Dec 31, 2020
Messages
211
Not really answering your questions but I wanted to give you my methodology/thinking when I built my Weaver custom rifle. I had it down to 28 Nosler and 280AI. I wanted a very lightweight, no brake 400 yard shooter that was easily packable.

I think with all the .284 calibers using the distance you wanna shoot is the determining factor in caliber choice.
 

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204guy

Senior Member
Joined
Mar 4, 2013
Messages
1,113
Location
WY
Do you already have a donor? Bolt faces are different between the 2. Givin the times current components on hand, assuming you reload? No way the 280ai can outrun the 7rem givin like pressure.
 

eoperator

Senior Member
Joined
Apr 4, 2018
Messages
365
Location
wisconsin
My .02,

280ai for a more moderate build, less recoil, better with lighter class bullets (155hammer,168berger)

7rm for longer range and heavier bullets with longer barrel

If your sights are set on absolute's I don't believe you will need a longer throat due to short bearing surface.
 
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