Looking for a New 7mm to Shoot

[7mm Man]

7 SAUM or 280 AI

 

[Mag_7s]

7 SAUM or 280 AI

7 Saum for me, but you're splitting hairs between the two.I would suggest whatever you can source a barrel life of components for.

 

[LostWapiti]

Take a look at the 284 Winchester while you're at it.

.284 win is so sexy I have no reason to get one but want one so bad even though I already have 280AI.

 

[LostWapiti]

When you get a 7PRC. Since that is the logical choice, make sure to get ADG brass and you will see much better performance. Lots of people are seeing disappointing performance with Hornady brass.

 

[BLCT]

I ended up going with the 6.5-7 PRC, with a custom free-bore to accommodate 180gr Berger VLDs. I have a COAL of 3.03", shoots well with h1000 and CCI 34.

I am looking to build a 7 Saum, I've been collecting whatever I can find brass wise. After 8 months ended up with 400 pieces of AGD brass w/ different lots sadly.

However after many months, that 7 PRC is looking very interesting.... Seems like 7 PRC offers everything a high-end custom 7 Rem Mag rifle would offer to us. 7 PRC has the twist rate to accommodate the heavier hornady ELD-M, and was designed up on those heavier bullets. So tolerances are tighter, snice they designed the cartridge for a specific bullet.

 

[7mm Man]

I ended up going with the 6.5-7 PRC, with a custom free-bore to accommodate 180gr Berger VLDs. I have a COAL of 3.03", shoots well with h1000 and CCI 34.

I am looking to build a 7 Saum, I've been collecting whatever I can find brass wise. After 8 months ended up with 400 pieces of AGD brass w/ different lots sadly.

However after many months, that 7 PRC is looking very interesting.... Seems like 7 PRC offers everything a high-end custom 7 Rem Mag rifle would offer to us. 7 PRC has the twist rate to accommodate the heavier hornady ELD-M, and was designed up on those heavier bullets. So tolerances are tighter, snice they designed the cartridge for a specific bullet.

What FPS you getting with 180s in your 7-6.6 PRC? I love my SAUM. I can get close to 2900 fps with a 175 ABLR and retumbo in a 24" barrel.

 

[BLCT]

What FPS you getting with 180s in your 7-6.6 PRC? I love my SAUM. I can get close to 2900 fps with a 175 ABLR and retumbo in a 24" barrel.

With my custom free bore, and COAL of 3.03” I’m getting 2888 with a 10-shot group (SD of 1fps ES of 2 fps). It does show mild pressure signs however I am not done experimenting with seating depts. I am using 180gr Berger Hybrid Target, also 29” Brux MTU profile barrel.

 

[back_at_it]

I have a Remington 700 in 280 AI, Lilja 26" barrel. It shoots Berger 180-grain VLD-H at 3,035 fps with RL-26 powder. Very efficient cartridge IMHO.

 

[LostWapiti]

I have a Remington 700 in 280 AI, Lilja 26" barrel. It shoots Berger 180-grain VLD-H at 3,035 fps with RL-26 powder. Very efficient cartridge IMHO.

That’s amazing. Beating a 7PRC with a case that holds 15 grains less. I gotta get myself a long barrel 280ai.

But also I still haven’t figured out how to break in to the black market so I can sell my extra organs for RL powders.

 

[Vern400]

Ballistically speaking there are already too many 7mm cartridges. They're so close each other, the steps in performance are way too small to make a difference.
It's a plus not running a belted Magnum for me.
I don't see a need to burn more than 55 to 59 grains of powder in one shot. So to a degree efficiency matters to me at 50 bucks a pound.

The 280 AI does a great job with heavies as long as you use enough barrel to let it do its job. At this point it's largely a handloaders cartridge unless you want to buy expensive ammo.

The 7PRC might be a better choice if you want a shorter barrel, but the performance will come at the expense of efficiency. And maybe barrel life if you shoot it a bit. Most folks don't.

If you pick something obscure better go ahead and figure in the cost of buying enough brass to burn the barrel out. Of course that's from a handloader's perspective. I can put my hands on a 5 gallon bucket of 30- 06 RP brass so the 280AI isn't looking bad.

 

[7mm Man]

Ballistically speaking there are already too many 7mm cartridges. They're so close each other, the steps in performance are way too small to make a difference.
It's a plus not running a belted Magnum for me.
I don't see a need to burn more than 55 to 59 grains of powder in one shot. So to a degree efficiency matters to me at 50 bucks a pound.

The 280 AI does a great job with heavies as long as you use enough barrel to let it do its job. At this point it's largely a handloaders cartridge unless you want to buy expensive ammo.

The 7PRC might be a better choice if you want a shorter barrel, but the performance will come at the expense of efficiency. And maybe barrel life if you shoot it a bit. Most folks don't.

If you pick something obscure better go ahead and figure in the cost of buying enough brass to burn the barrel out. Of course that's from a handloader's perspective. I can put my hands on a 5 gallon bucket of 30- 06 RP brass so the 280AI isn't looking bad.

There's never too many cartridges. Especially 7mm cartridges........

 

[back_at_it]

A recent post doubted the possibility of getting a 280 AI to push a Berger 180-grain VLD-H at 3,035 fps. I developed my load at 35 degrees F, for hunting in the Rockies in Oct.-Dec. Using RL-26 with that bullet in a 27" barrel, COAL = 3.579" (just a few thousandths off the lands), QuickLOAD says I can get there with 1.5kpsi excess pressure and 99.6% fill ratio (100% propellant burn). Ballistic efficiency 29.7%. (My actual powder load was substantially lower. I chronographed with a MagnetoSpeed, which may have been a bit high.) Compare the numbers for a similarly high-fill, max-pressure, 100% propellant-burn 7mm Rem. Mag. load at the same temperature and speed (within 5 fps), with a ballistic efficiency of 27.9%. So yes it's possible, and yes the 280 AI is pretty efficient. (And no, I wouldn't run the load illustrated here on a much warmer day!)

 

[back_at_it]

A recent post doubted the possibility of getting a 280 AI to push a Berger 180-grain VLD-H at 3,035 fps. I developed my load at 35 degrees F, for hunting in the Rockies in Oct.-Dec. Using RL-26 with that bullet in a 27" barrel, COAL = 3.579" (just a few thousandths off the lands), QuickLOAD says I can get there with 1.5kpsi excess pressure and 99.6% fill ratio (100% propellant burn). Ballistic efficiency 29.7%. (My actual powder load was substantially lower. I chronographed with a MagnetoSpeed, which may have been a bit high.) Compare the numbers for a similarly high-fill, max-pressure, 100% propellant-burn 7mm Rem. Mag. load at the same temperature and speed (within 5 fps), with a ballistic efficiency of 27.9%. So yes it's possible, and yes the 280 AI is pretty efficient. (And no, I wouldn't run the load illustrated here on a much warmer day!)

View attachment 709444
View attachment 709446

Sorry, I neglected to re-set the temp. for the 7mm Rem. Mag. load. Here's the right QuickLoad image. At 35 degree the load becomes compressed, the propellant burn is just short of 100%, and the ballistic efficiency is 27.5%. Switch to 6.92 grains of IMR 7828 at the same temp and muzzle velocity, and the ballistic efficiency improves to 28.9%, still not as efficient as the 280 AI.

 

[back_at_it]

If you're chasing ballistic efficiency (ratio of the kinetic energy of the projectile to the total energy released by the propellant), you can bump that number by playing with energy density. For example, IMR 4831 has a volumetric energy density of 3,245 J/cm^3, and 55.4 grains of that powder behind the Berger 180 in a 280 Ackley at 70 degrees yields a muzzle velocity of 2,837 fps at a ballistic efficiency of 32.7%, which is substantially better than the numbers I cite above, even though the muzzle velocity is lower. Other powders I use have energy densities of up to 4,000 j/cm^3. They may not yield the same ballistic efficiency, but they produce higher muzzle velocities. Ballistic efficiency is a function of powder properties such as energy density, as well as a function of the rest of a cartridge's design (brass dimensions, bullet choice, etc.). Having said all of that, my impression is, the 280 AI is quite "efficient."