So... buckle in. Looking for advice.

I'm looking to pick up my first "big game" cartridge bolt gun to practice learning ballistics, long gun shooting fundamentals, and go hunting with (up to and possibly including elk).
I've pretty much been between 6.5CM and .308. For as passionate as I am about firearms, I don't have much trigger time or experience. With them being about the same cost that isn't much of a deciding factor. I like that the 6.5CM will recoil less just for practice, not to say that I'm recoil sensitive but it just makes sense.

Keeping in consideration the ole 1000ft. lbs. energy for deer and 1500ft. lbs. energy for elk, Hornady HITS formula recommendations, plus 1900fps speed threshold for reliable bullet performance, the 6.5CM is a ~250-300yrd elk and 500yrd deer cartridge and the .308 is a ~400yrd cartridge for both. At this point, I'd never take a shot on an animal at that distance anyway, my current self-limit is ~250yrds but I like the capability for as I gain experience and confidence. I know this all depends on load. I plan on shooting the 143 ELD-X in 6.5CM or something in the 165-180gr. range for .308.

I was really set on getting the new Tikka T3x Roughtech Ember in 6.5CM when they finally get imported into the US but that comes with a 24.3" barrel. I will be putting on my Dead Air Nomad 30 most of the time which will extend it another 6-8 inches depending on how I configure it. 30" of barrel length just seems ridiculous. Doesn't seem the most practical hiking around in the woods or mountains with.

I started doing research on shorter barrels for both calibers and how it would effect their down range performance. It seems like even at 16.5" barrel, the 6.5CM would still be a ~250yrd elk gun and a ~400yrd deer gun. I'd be saving 8" of barrel length and weight for pretty much the same practical field performance for me. Similarly with the .308 losing about an average 25fps per barrel inch, going from a 20" gun I was looking at down to a 16" gun would only lose ~100fps at the muzzle. So I'm still getting a ~350yrd elk and deer cartridge plus saving the length and weight.

For all practical purposes, it seems straight forward to just chop the barrel down, yeah? Am I forgetting or not considering anything important?

Reminder: I'll be primarily plinking/target shooting for the secondary purpose of hunting. No "PRS"/competition, don't care about dime sized groups at 300yards blah blah blah. I'm talking bare-bones practicality.

What's your take?

First of all, all the crap in red is nonsense. Forget about bullet energy because it tells you nothing about how a bullet will perform in a game animal. The Hornady speed threshold tells you all you need to know for how far the bullet will perform to. The rest is up to you putting the bullet where it needs to go. Between your two options the 6.5 creedmoor will be better, primarily because of the lower recoil. Recoil develops bad shooting habits that leads to misses and wounded game.

If we factor ammo availability into it, 308 will probably edge out on top currently.

If you want something actually practical for learning how to shoot at long range AND capable of killing, pick up a Tikka in 223 and get after it.

Saw your response in the Precision Rifles section. Thanks! I have a .223 gas gun and .22-250 bolt gun both for coyotes. Looking for a "big game" cartridge. So you think as long as I have speed energy doesn't matter? What's your threshold, is it the 1900fps? That would, in theory, extend the usable range for elk with the 6.5CM big time.

@KO21outdoors
Long answer:
The bullet construction is the primary driver for effectiveness on game. Saying energy doesn't matter tends to ruffle feathers, but essentially the bullet construction will determine how that energy is expended in the target. The velocity threshold should tell you where that bullet continues to perform/expand at reliably based off of its construction. With that being established, soft heavy for caliber bullets(such as sierra TMK, Hornady ELD and ELDx, and many berger designs), will penetrate adequately in game and cause major damage in the chest cavity, leading to rapidly expired game.

What people tend to do is choose toughly designed bullets and believe they need magnum cartridges of larger caliber to produce adequate wounds.

To answer your specific question 1800-1900 fps is the commonly accepted threshold (actually I think it's as low as 1600fps) of ELDm and ELDx bullets and I would be confident using them to that threshold. Which means if you're achieving 2600fps with the 140 ELD the bullet will perform out to 600 yards at sea level using 1800fps as your threshold.

I would highly recommend you check out the forum Rokslide where you can find a lot of this information and pictures of successful kills using said bullets at distance. One thread I highly recommend is the  223-for-bear-deer-elk-and-moose where you'll see the 223 being used out to 450 yards with the 77gr TMK combo very effectively, and yes dead moose. It might make you a believer in 223

Awesome, thank you for the education. It's pretty much sealed the deal on me wanting to go with a shorter barrel now.

do you have an update for this?

I’ve shot moose and butchered elk. I wouldn’t want to shoot them with a 6.5 if I could help it, but if that’s what I had I would use it and not worry. If that makes sense. Barrel might as well be short, if the barrel length is the problem, the barrel length is not the problem.

18” .308 … Not personally a fan of the 6.5 ManBun.

Shoot the two at or past a thousand and get back to me. 6.5CM has distinct advantages after ~400m. It's a great cartridge, and I say that as someone with eight .308 rifles in the safe with another half dozen chambered in comparable cartridges.

OP: For your uses, .308's almost certainly the way to go. I don't think 6.5 is going to offer you anything given those parameters, and .308 is way easier to source.

Yes! I went with a Tikka T3X in 6.5 with a 24" barrel that I got chopped locally to 16.1" and threaded 1/2x28. So I'll likely directly thread my suppressor on or get a thread adapter and a QD muzzle device. More than likely direct thread. I'll try to come back and post pics if I can figure out how to do that. I DIY cerakoted the barreled action and rattle canned the stock. Upgraded to a limbsaver recoil pad and got the OEM straight grip. I think it turned out great. Still testing various ammo manufacturers and loads with it.

Tikka Project

OP, sweet setup you are going to love that rifle.  I went that way with a budget off the shelf setup a couple years ago and it's one of my favorite all around rifles out of the dozens I own. I like the 129grn bullets for that barrel length to get velocity back up to around 2700fps. Currently using hndy interlocks because I have a ton of them and the load stays moa out to 400.  I limit the whitetail range to 300 for it and it worked perfectly on a broadside doe at that range. I think the nosler long range accubond 129 would be perfect for this velocity/game/distance envelope.

Awesome! That's great information. I'll keep my eyes peeled!

I prefer the 6.5 over the .308 I’ve killed with both and if I said just the opposite it wouldn’t matter they both work .
That said the 6.5 143 ELDX is a killing machine

Go 18in