out to 500 yards, deer, etc.

.308
6mm Creedmoor
6.5 Creedmoor

.308 would be my pick, but it's not like the others are slouches. 6.5 is a close second.

7mm-08 A.I.

162 ELD-X
165 Tipper Game King
168 Berger Classic Hunter or VLD-H

I carry that every day because it is the most efficient. It delivers the most energy and wind drifts the least. Of any cartridge that will fit in a .473" bolt face, short action.

My .308 is 18" and easily goes out 500+ yards.

For deer-sized game, 6mm Creedmoor is a solid choice in the "efficiency" category.

But, 6.5 mm Creedmoor seems a bit more practical, considering the options for factory hunting ammunition currently available.

Efficient from what perspective? Most of the time when I hear efficient I think most speed for the least amount of powder but you didn't give us anything to be able to go on, like what bullet in each would you shoot? So in short, what are you asking?

All 3 of those will kill deer at 500y.

coin flip sounds like

I just had my Tikka 6.5 CM cut to 18” for a more suppressor-friendly platform. Only shot it a bit at the range and forgot to take my chrono, so not sure about how much velocity I lost over the 24” barrel. The distances I typically shoot deer and pronghorn, I don’t think it will make much difference.

6cm and then 6.5 cm,

But as far as 500 that’s well with in any of those three cartridges

I agree

6.5 CM is carrying 200-300 ft lbs more at 500 than the 6CM.

Yeah, generally you're looking at less overbore cartridges, and heavy for caliber projectiles for short barrel performance.

I wonder how a 175 at 2600 from a .308 compares to a 140 at like 2600 from a 6.5CM at 500yd.

Statistically same as all three are above the randomly selected mostly agreed on min of 1000ft/lb standard. All three meet min impact velocity for most bullet mfg specs also although 308 is bottom of threshold depending on DA for the day.

@ Density Altitude of zero

the 308 175vld/2600@500 1787 ft-s @ 1241 ft lbs
The 6.5 140vld/2600@ 500 1931 ft-s@ 1159 ft lbs
The 6. 105vld/2900@500. 2080 ft-s @ 1009 ft lbs

I think KE is irrelevant, and think impact speed is a better min but not changing most minds

Oh that's a good point, you don't want to neglect velocity on impact for effect on game.

Completely agree. If I was serious about taking a 308 out to 500 yards on game, I think I would go with a 172 Speer Impact. It’s really soft, bonded, tipped, with a high BC. It’s the same construction as the Federal Fusion.


https://www.speer.com/bullets/rifle-bullets/impact-bullet/19-TB308H1.html

Ya I really get hesitant on VLD unless they are Elite Hunter or EOL at 2k or lower. If I was going sub 2k impact I think TMK or ELDM is where I’d go. I’ve haven’t used any speers

The larger the hole in the barrel the less velocity you lose per inch so from that perspective the 308 would be most efficient. Chopping a 6mm off that short might as well get a 6ARC

Buzz I got a 16" Bartlein I took off. You just need an action
Make you a great deal

308

contour and caliber, round count?

Bill Marr, at rifleshooter.com, probably wouldn't agree with this generalization.

He has actually done barrel cut down tests for the 6 CM, the 6.5 CM, and the .308 Win.

In January 2017, for the 6 CM, starting with a barrel length of 30" and cutting it off in 1" increments down to 17", he found that, for a 110 gr Sierra MK, there was a total decrease of 275 fps [for an average velocity loss of 18.3 fps/inch]. For a 107 gr Sierra MK, there was a total decrease of 302 fps [for an average loss of 20.3 fps/inch]. For a 95 gr Sierra Tipped MK, there was a total decrease of 341 fps [averaging 22.7 fps]. He concluded, at that time, "I think a 16 or 17 inch 6 Creedmoor would make a great choice for a compact deer rifle."

Interestingly, he repeated the above 6 CM experiment using a different rifle in May 2019, starting off with a barrel length of 24" and cutting it off again in 1" increments down to 16". In this case, he used 108 gr VLD-M bullets and found a total decrease of 295 fps, for an average drop of a whopping 37.9 fps/inch, leading to a different conclusion: "I'd suggest staying with longer barrel lengths wherever possible with this cartridge."

Similarly, in February 2016, he did a barrel cut down on a 6.5 CM, from 27" down to16". Using 142 gr Sierra MKs, the total velocity loss was 158 fps and the average velocity loss per inch was 14.4 fps. Using 120 gr AMAX bullets, the total loss was 233 fps and average loss per inch was 21.8 fps.

In December 2014, Marr did a cut down on a .308 Win. from a starting barrel length of 28" down to 16.5". Using 168 gr Federal Gold Medal BTHP bullets, average velocity loss was 20.9 fps/inch. With 180 gr Win PP bullets, the average loss was 22.5 fps/inch.

So, FWIW, it sounds like he might be iffy on a shortened 6 CM. But, the 6.5 CM lost less velocity when the barrel was cut down than did the .308 Win.

6.5 with 120 eldms

So essentially he found varied results which is not surprising. Wonder how many rounds he fired every time he shortened the barrel… I would say unless it was at least 10 rounds per inch then not statistically reliable enough to have meaningful conclusions.

He did pretty extensive write-ups on each, detailing rifles, procedures, bullets/loads used, temperatures, elevations, etc. I think he fired only 5 rounds at each barrel length with the .308 Win and 6.5 CM tests, and 4 rounds each with the 6 CM. He did explain his rationale for setting up each aspect of the testing, including "possible sources of error," with "budget restrictions" being a reason for small sample sizes (Plus, in the older .308 Win test, he compared one 30 round sample to his 5 round sample of the same ammunition and found only an average disparity between the two of 0.6 fps/inch).

A closer read would suggest the varied results on the 6 CM tests were more a factor of the starting point. The largest velocity drops were recorded, it seems, once he cut barrel length below about 22". Since his first test started with a 30" barrel, instead of 24", the average velocity drops were skewed because of the results while at the longer barrel lengths.

Circling back to the original question, 6.5 Creedmoor, if you're using an 18" barrel length, could arguably be said to be the strongest contender.

For my 16” 308, I started using 120 Tac-TX which was designed for the 300 Blackout. Supposed to open down to 1400-1500 fps. I’m not even at max charge with Ramshot TAC and I’m getting 3050 fps.