Which cartridge(s)?

[BurnOut]

I am in the planning stages of my next build, and while I have goals in mind, I could use some input regarding which cartridges I should choose. My criteria are this:

* This will be a 6.5mm/7mm switch-barrel setup, so the two cartridges chosen must share the same bolt face
* This will be a long action (leaning towards Big Horn TL3 at the moment), and be magazine-fed
* Max barrel length will be 26" at the crown... I'd like to go down to 24", but don't know that I'll be able to hit the speed goals below with the shorter barrel(s)
* I'd like to be able to shoot the 147 gr 6.5mm ELD-Ms at 3000 FPS at the muzzle
* I'd like to be able to shoot 16x gr 7mm projectiles at 3000 FPS at the muzzle
* Barrel life of 1500+
* Would prefer for the cases to be different enough such that they're not easily confused (i.e., 6.5-284 and .284 Win; I don't want to be inadvertently necking cases up and down if the brass gets mixed)

I know that my goals are easily attainable if I go with Billy Bignutz cartridges like a 6.5/7mm Rem Mag, but I don't want to go that big if I can help it. I was originally planning on going with the 6.5 Addiction and .284 Shehane, but I don't know if that will get me where I want to go on the 6.5 side... so I started looking at stepping up to a Magnum bolt face, and going with the new Hornady 6.5 PRC and the 7 SAUM. I s'pose that I could go with a standard bolt face, and a 6.5-06/.284 Shehane combo, but I have doubts that the 6.5 barrel would make 1500 rounds...

 

[OH58DViper]

If you're going long action why not go with a magnum bolt face. If it were me I would go 6.5 4S and 7 rem Mag.

I don't understand the billy big nuts comment. If a 162 leaves the barrel at 3000 it feels the same regardless of the bolt face diameter or cartridge....for the most part anyway.

 

[BurnOut]

I don't understand the billy big nuts comment.

It seems that when larger cartridges are loaded down, they lose a lot of efficiency, meaning that they burn a lot of extra powder (for a given result) vs. a more appropriately sized case. Obviously, the downsides there are fewer loaded rounds from a given amount of powder, and possibly more barrel wear since you're burning more powder.

That's my thinking, anyhow... I could easily be full of shit.

 

[NovaHunter]

280 Ackley is a great cartridge as well

Sent from my SM-N920V using Tapatalk

 

[Conrad]

Why pick 2 calibers that are so close in diameter? Why not do a 6.5-06 and a 300 Win Mag? If you can get a SAUM or WSM to feed from the long action then even better for the 6.5.

Shoot 14#'s and 215s and cover a lot of ground. Especially for hunting and ELR. 300 WM is very easy to shoot with a good brake.

 

[BurnOut]

Why pick 2 calibers that are so close in diameter?

That's a fair question. At this point, I am kind of filling in the gaps in my collection... I have the small 6.5 covered (Grendel AR), and medium 6.5 covered (.260 Rem and 6.5 CM), but feel that I'm leaving some performance on the table without the ability to drive the heavy-for-caliber bullets at respectable velocity. The deal with the 7mm is that I plan on doing a big 7 (7LRM or 28 Nosler) in my Desert Tech, but also want something that will allow me to get some of that sweet, sweet 7mm BC without beating me up too bad (or being so heavy to haul around).

Regarding the 300WM, I have a barrel for my Desert Tech, but again, want something that doesn't thump quite as much.

 

[spife7980]

If you're leaning towards building it on a TL3 then you can just swap the bolt faces for 125 bucks and run whatever you want in whichever configuration.

 

[davisj3537]

With this much money wrapped up in a build I'd just buy an extra bolt in a magnum bolt face...that's what I did actually. I don't know about bighorn specifically, but most custom actions can be ordered with a second bolt for around $350-400.

 

[BurnOut]

As spife mentioned, extra bolt faces for the TL3 are actually pretty inexpensive, so I may end up doing that. On a side note, I may have come to a decision, with y'all's help; NovaHunter mentioned the 280AI, so I started doing some research, and comparing it to the .284 Shehane that I was originally wanting to use for my 7mm cartridge.

It looks like in my original research on the .284 Shehane, I overlooked the barrel lengths that people were using to obtain their stated velocities... it seems that 30-32" barrels were the ticket. Hmmm. That won't work for me, given my intended use of this rifle (target shooting/banging steel out to maybe 1200 or so, and hunting white tail, feral hogs, and perhaps mule deer or antelope).

So, as I looked more into the 280AI, I started thinking about a 6.5mm solution, and am currently leaning towards the 6.5-06AI. Bigger than I originally intended, but not so large as a WinMag case, and it looks like I may be able to hit my velocity goal with a 24" barrel without pushing it too hard. My biggest concern with this is the barrel life criterion stated in my original post, but it could be one of those situations where a tradeoff must be made (from what I can tell, the consensus is that 800-1000 rounds is a reasonable expectation). Aside from that, if the barrel degrades to the point where the best it can hold is 1/2 MOA, that's about the limit of my skill as a shooter, anyhow. Beside that*, with two barrels, it's likely to be awhile before I run enough rounds through one tube or the other to wear it out...


*I recognize that I've gone into self-justification mode, here... by the time it's all said and done, I may end up convincing myself that I *need* one of those Anzio 20mm rigs...

 

[lancetkenyon]

6.5-06AI & .280AI

I know a 6.5-06AI will push a 142 SMK at 3150 from a 26" barrel, so a 147 should easily net 3100.

A .280AI can push a 160-168 @ 2950-3000 as well.

The .280AI should last 1500+.
The 6.5-06AI will be close as well.

Buy different head stamped brass, and clean/reload them at different times to keep the brass sorted.

 

[hollowoutadime]

Old man here. I'm moving towards thinning the # of calibers I load for in an attempt to be more proficient at those that remain. (So I sold off my redundant 6.5CM as I'm capable with my .260). Just a .02 cent opinion here. I do think you ought to get the 20mm Anzio, it's not redundant, and I'd like to see it used on some feral hogs.

 

[Greg Langelius *]

Very easy choice for me. .260 Rem and .280 Rem. Now, then; running down through your reasoning:

* This will be a 6.5mm/7mm switch-barrel setup, so the two cartridges chosen must share the same bolt face

They do.

* This will be a long action (leaning towards Big Horn TL3 at the moment), and be magazine-fed

They will.

* Max barrel length will be 26" at the crown... I'd like to go down to 24", but don't know that I'll be able to hit the speed goals below with the shorter barrel(s)

You won't hit those speeds with the chamberings I mentioned, even using a 28" with the .260 as I do.

Something has to go, and I think it's your goals. Realistic peak velocity goals for the .260 are 2850fps, and 2900fps for the .280. A 28" barrel and a 16" LOP produces a 52" rifle. That's the realistic max length to fit the rifle into a case. Honestly, when doing a long range rifle, length is really only a factor for gun cases, the rest of the 'usual' concerns are just daydreaming. The rifle doesn't conform to your expectations, you conform to its realities.

...And before you turn away from the chamberings, my recommendation are predicated on being able to keep a barrel on the rifle long enough to actually get something out of it that's like what you paid for the whole shebang. Unless you're shooting a Savage or a Remage setup and doing your own barrel replacements, your rifle will spend roughly half of its time languishing in a gunsmith's work queue.

* I'd like to be able to shoot the 147 gr 6.5mm ELD-Ms at 3000 FPS at the muzzle.

OK, but I prefer the 142 ELD-X. Great BC, and the added capability of doing something besides punching paper or going ping when it finally gets all the way out there,

* Max barrel length will be 26" at the crown... I'd like to go down to 24", but don't know that I'll be able to hit the speed goals below with the shorter barrel(s)

See my comments above.

* I'd like to be able to shoot 16x gr 7mm projectiles at 3000 FPS at the muzzle
* Barrel life of 1500+

See my comments above.

* Would prefer for the cases to be different enough such that they're not easily confused (i.e., 6.5-284 and .284 Win; I don't want to be inadvertently necking cases up and down if the brass gets mixed)

Should not be an issue. If you can mix up the.260 and the .280, well...

I know it's not what you wanted to hear, but my comments are about experience and the associated realities. Better you grasp those realities now than you be disappointed later.

Greg

 

[TheGerman]

Just get an MRAD.

You eventually will. I'm just saving you time and money.

You're welcome.

 

[bogeybrown]

Just get an MRAD.

You eventually will. I'm just saving you time and money.

You're welcome.

Says the happy new owner of a "Cash me Ouside" MRAD. Trust The German, I'm his spirit animal and he knows how to spend money.