Im looking at building a lightweight, short action, 18" barrel rifle, and Im having a little trouble picking a caliber. Trying to decide between 308 and 6.5cm. I have a couple of longer bolt guns, this one is primarily being built to be as handy as possible. So assuming the 18 inch part is non-negotiable, which of these two calibers is likely to offer me more fp of energy at 500 yards with common factory ammo? Looking at Hornady ELD-x 178s vs 143s, 308 has the edge out of whatever test barrel Hornady used, but its a pretty narrow gap. Would a shorter barrel widen that gap with the increase in bore-size on the 308? Is there another readily available caliber I should be considering?
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Shorty rifle build-help picking a caliber
- Thread starter kmontang
- Start date
Go 6.5 creed and run the 130s. Velocity is gonna be better measurement than energy. I'd rather hit a critter with velocity in a match bullet than "energy" in a traditional bullet. When a Berger dumps its complete energy, its a giant mess of lung soup.
Inside 500, both are gonna pound steel.
Inside 500, both are gonna pound steel.
I have a 18” 6.5 CM that shoots 140 hybrid Berger’s at 2660 FPS with a SD of 7. Used that last week for a match at GTI. It was solid out to 800 and drop was only 6.0 mils. My partner shot a 16.5” 308 and it was a drastic difference in wind and drop that the extra 1.5 “ would not have changed.
You'd probably be fine with a 6.5 creed with an 18" barrel. Aftermarket/custom barrels typically have higher velocities than factory barrels in my experience. Deer and similar sized game won't know the difference between 308 and 6.5
I know it wasn't listed as an option, but have you thought about 7mm-08? In a short barrel, the 7mm-08 can do everything that a .308 can do, but with those oh-so-slippery 7mm BCs.
IMO, the 6.5 CM really leans on velocity for its effectiveness on target, and to get there you either need to run lighter projectiles (thereby giving up the best of the 6.5 projectiles) or a "full length" barrel. The .308, obviously, has a WIDE variety of projectiles available, but in the sub-180 gr range (which are most appropriate in a short barrel) the BCs, while not terrible, are short of what is offered by the 7mm projectiles in the same weight range.
Just my $.02.
IMO, the 6.5 CM really leans on velocity for its effectiveness on target, and to get there you either need to run lighter projectiles (thereby giving up the best of the 6.5 projectiles) or a "full length" barrel. The .308, obviously, has a WIDE variety of projectiles available, but in the sub-180 gr range (which are most appropriate in a short barrel) the BCs, while not terrible, are short of what is offered by the 7mm projectiles in the same weight range.
Just my $.02.
Consider what you may already reload for or plan on being able to aquire for ammo.
I'd go 6.5 because that is primarily what I load for.
I'd go 6.5 because that is primarily what I load for.
Did somebody say 7mm-08?
18” and shoots the 150 ELD-X’s very well. Not as sexy as new stuff but an old timey classic. Worth considering, but then again I’m clearly biased.
I think it's both a great and often overlooked round for this sort of application. I wouldn't mind seeing a modern short action/.473 bolt face cartridge, but I feel like the Creedmoor case doesn't have the capacity to really drive the 150+ gr projectiles (IMO, part of the reason why the 30 TC never took off). Maybe a slightly shortened .284 Win? I dunno.
I mean. I had 175’s running 2580 in a 16.5” barrel with varget and lapua brass. Add a couple inches and I don’t see why an 18” 308 wouldn’t drop your game at 500yds and in.
I suspect that on average the 308 will have more energy with a short barrel inside 500yrds, but it'll be so close I'm not sure it will matter. The 6.5 will be less impacted by wind. FWIW my shortest 308 is 18" and my shortest 6.5 is 20".
I have an 18” .308 that was hitting at 1018 yds.....
will be more consistent with better load development and a better shooter.
wind was normal for CO, but a 175 going 2550 isnt so good in wonky winds (which is everyday on the CO plains).
am working up a load with Lapua brass, Varget, and a 155 TMK. If the published BC is close, getting that moving should be a Good combo.
will be more consistent with better load development and a better shooter.
wind was normal for CO, but a 175 going 2550 isnt so good in wonky winds (which is everyday on the CO plains).
am working up a load with Lapua brass, Varget, and a 155 TMK. If the published BC is close, getting that moving should be a Good combo.
Think thats what the 7mm saw was going for.
There’s no free lunch as they say. Going short barrel I gave up on any notion on matching velocity of full length barrel. The nice thing i like about this 7mm-08 is that with the 150/162gr bullets they don’t seem to need to be pushed blazing fast to be effective and therefore I don’t feel like i need to torch a barrel out by firewalling hand loads. I know barrels are made every day but if I can get good results without then why do so.
Same as @Sprayed99, I have built 2-16.5" 6mm Creed's one on a Criterion, which my brother has commandeered and I am now running a Proof barrel at 2780 fps- 41.5 gr H4350, 105gr Berger Hybrid. Has worked great on Axis, Whitetails, Hogs, Yotes and Jackrabbits. Shoots 1/2 MOA fairly consistantly , steel out to 600, have never had a range longer. With a suppressor they are conventional rifle length.
I’ll add a vote for the 7-08. Split the difference of the two original choices and drives the 150 class stuff very well.
