Large frame accuracy

[MolassesTreeJ]

New here. With plenty to learn. I know nothing about long shot, wanting to start.

Have mega arms maten mkm with extended float tube.

Interested in using this for 600-800yds with a 308win chamber. 6.5CM seems.. more suited for 30" barrels and manually opperated actions.

What type of velocity and accuracy are you guys/gals seeing with 24-26" barrels?

 

[Niles Coyote]

No reason to go longer than 22" on a 308. Speaking of velocity only, the return is minimal on longer barrels. Raw accuracy potential favors shorter barrels as well, provided you are comparing like contours.

My 20" rock creek 308 will launch 175's to the mid to upper 2500's, 168's are low to mid 2600's and 155's will break 2700. It is a M110 profile and were I to change one thing, it would not wear a .750" gas system but a .875 or larger. Every barrel I've had experience with to this point that is larger than a .224 bore has consistently shot tighter groups with thicker than .750 gas and muzzles.

 

[MolassesTreeJ]

I was thinking a heavily fluted 25" barrel. With the +3" extra long rifle gas, 0.9375 gas block and suppressor.

In attempts to muster 2800fps with a stiff charge of 2000mr. Is this beyond possible? With a slow burning powder capable of sustaining high pressure, math is showing 25" barrel being capable of 2900fps. Though, I wonder how much a nitride barrel, moly coated projectiles and suppressor will help.

I have lathe and this is a wild hair. Already have 18" criterion hybrid barrel on it. Shoots fine out to 400yards. Not enough length for 175smk in my opinion though.

Appreciated.

 

[Bradu]

6.5 better suited for 30" barrels? Where did you come up with that at?

 

[Lowlight]

6.5CM rocks with a shorter barrel too, smokes a 308

 

[MolassesTreeJ]

Bradu - the velocity really does not seem to be significantly large enough to merit using it. Plus, the energy retained seems much less than 308.

I am not getting into that can of worms. It is amazing for bench rest. I know it is God's gift to everything and is even better than what pocket bread is.


I have a savage bolt action in 6.5CM. It did not impress me much. It has had the hammer dropped on empty chamber more times than actual live fire. Not stubbing any gurus toes. Not interested in 6.5 unless we are talking a leopard. Not possible on this platform

Thank you.

More about the experience with 308 please.

=D

 

[HoustonB77]

Bradu - the velocity really does not seem to be significantly large enough to merit using it. Plus, the energy retained seems much less than 308.

I am not getting into that can of worms. It is amazing for bench rest. I know it is God's gift to everything and is even better than what pocket bread is.


I have a savage bolt action in 6.5CM. It did not impress me much. It has had the hammer dropped on empty chamber more times than actual live fire. Not stubbing any gurus toes. Not interested in 6.5 unless we are talking a leopard. Not possible on this platform

Thank you.

More about the experience with 308 please.

=D

Build whatever you want but you have no idea what you are talking about. A 6.5 is just as capable in an AR platform.

 

[Bradu]

Bradu - the velocity really does not seem to be significantly large enough to merit using it. Plus, the energy retained seems much less than 308.

I am not getting into that can of worms. It is amazing for bench rest. I know it is God's gift to everything and is even better than what pocket bread is.


I have a savage bolt action in 6.5CM. It did not impress me much. It has had the hammer dropped on empty chamber more times than actual live fire. Not stubbing any gurus toes. Not interested in 6.5 unless we are talking a leopard. Not possible on this platform

Thank you.

More about the experience with 308 please.

=D

It's not just about about velocity, it's a combination of that and higher b.c. bullets. Run the numbers in a ballistic app and you will also see that the 6.5 has more energy past the 300-400 yard range as well. I'm not trying to convince you of anything though, just pointing out the not so obvious for you.

 

[Pusher591]

I was thinking a heavily fluted 25" barrel. With the +3" extra long rifle gas, 0.9375 gas block and suppressor.

In attempts to muster 2800fps with a stiff charge of 2000mr. Is this beyond possible? With a slow burning powder capable of sustaining high pressure, math is showing 25" barrel being capable of 2900fps. Though, I wonder how much a nitride barrel, moly coated projectiles and suppressor will help.

I have lathe and this is a wild hair. Already have 18" criterion hybrid barrel on it. Shoots fine out to 400yards. Not enough length for 175smk in my opinion though.

Appreciated.

Just seems like a 24”-26” semi-auto (especially with suppressor) defeats the semi-auto purpose. Semis were suppose to support the bolt gun (at least in combat operations) and had shorter barrels, 20” and shorter. They were suppose to be more maneuverable and were most of the time expected to engage targets from a shorter distance.

When you start adding suppressors and stiff charges into the mix as well, your asking for issues. Suppressors create more back pressure which you want to reduce on semi’s especially suppressed.

If you want to shoot long distance suppressed with a semi-auto my recommendation is a 6/6.5 variant (18”-22” barrel) and run pointed 123/130 grain projectile.

 

[Steelhead]

You might even look at 6mm Creedmoor, especially for the ranges you listed. Even better than 6.5 Creedmoor. Mine has a 23" barrel and is awesome out to 1200 yards.

Run the numbers in your ballistics calculator. 105 gr. Berger Hybrid at 3075 fps.

 

[MolassesTreeJ]

I used the hornady 4D calculator with a sourced g7 coefficient for various 6.5mm and 7.62mm projectiles versus posted velocities I found while lurking this forum for the last month.

All i saw was after 800yards, the 308 has a greater plunging effect. The 6.5mm was typically lower in energy beyond 600yards. Unless someone else is seeing 3400fps with those 123's..

The 6.5mm has a more flat flight path. The 308 seemed to have more energy to 800yards. After they evened back out. The 6.5 and 308 were down to sub 300lbs around 1000yards.

That knockout rating which most hunters apply.. says anything under 900lbs is unacceptable.

Unless the 6.5CM outlies traditional calculators, it trends to require longer barrels for the energy to match heavier 308 projectiles.

A standard 45acp weighs 230gr and goes 850fps. Making more energy than the 9x19 115gr going 1300fps. The same seems to trend. Now, I have spent quite a long time looking at the 6.5mm however it seems I missed something. My appologies.

When cutting a barrel blank, I had intended to run specific powders and start with a .06" gas port then slowly enlarge.

I have 25-06, 7mm rem, a few 7-08, 6.5CM, 300winmag all in bolt rifles. The 6.5CM is the last one I ever grab. Bought it during the hype a few years ago. I highly dislike the fad round. Perhaps that is a shortcoming on my end. Rifle has seen less than 100 rounds and sat five years. It does nothing golden when compared to the 25-06 or the 300winmag. It seems to me like a procharged stroked out honda drag car. You gotta pull the bumper and put giant slicks for it to even do anything. Still only makes 400 horsepower.

Yes, it is 'soft and flat'. It replicates a 260rem but functions in the short action autoloaders with 140gr projectiles. Yupyup, great BC.

I see that.

I really was looking for some information about what people are getting out of the highpower style rifles.

I agree, it does in a way defeat the purpose. However, that additional weight tames recoil. Bolt and barrel extension from nitrided 17-4 should handle everything just fine.

I appologise for poking a sleeping bear. It was a mistake and there will be no more aggrevating done.

 

[Spblademaker]

45 v 9
6.5 v 308
G7
All in one post.

 

[DavidAR10]

I used the hornady 4D calculator with a sourced g7 coefficient for various 6.5mm and 7.62mm projectiles versus posted velocities I found while lurking this forum for the last month.

All i saw was after 800yards, the 308 has a greater plunging effect. The 6.5mm was typically lower in energy beyond 600yards. Unless someone else is seeing 3400fps with those 123's..

The 6.5mm has a more flat flight path. The 308 seemed to have more energy to 800yards. After they evened back out. The 6.5 and 308 were down to sub 300lbs around 1000yards.

That knockout rating which most hunters apply.. says anything under 900lbs is unacceptable.

Unless the 6.5CM outlies traditional calculators, it trends to require longer barrels for the energy to match heavier 308 projectiles.

A standard 45acp weighs 230gr and goes 850fps. Making more energy than the 9x19 115gr going 1300fps. The same seems to trend. Now, I have spent quite a long time looking at the 6.5mm however it seems I missed something. My appologies.

When cutting a barrel blank, I had intended to run specific powders and start with a .06" gas port then slowly enlarge.

I have 25-06, 7mm rem, a few 7-08, 6.5CM, 300winmag all in bolt rifles. The 6.5CM is the last one I ever grab. Bought it during the hype a few years ago. I highly dislike the fad round. Perhaps that is a shortcoming on my end. Rifle has seen less than 100 rounds and sat five years. It does nothing golden when compared to the 25-06 or the 300winmag. It seems to me like a procharged stroked out honda drag car. You gotta pull the bumper and put giant slicks for it to even do anything. Still only makes 400 horsepower.

Yes, it is 'soft and flat'. It replicates a 260rem but functions in the short action autoloaders with 140gr projectiles. Yupyup, great BC.

I see that.

I really was looking for some information about what people are getting out of the highpower style rifles.

I agree, it does in a way defeat the purpose. However, that additional weight tames recoil. Bolt and barrel extension from nitrided 17-4 should handle everything just fine.

I appologise for poking a sleeping bear. It was a mistake and there will be no more aggrevating done.

You're doing it wrong.

All wrong.

And it doesn't take the integral of f(x) by separation of parts to figure this out.

 

[DP425]

I get 2680fps out of my suppressed 20" OBR running 168 Hybrids and Varget.

In my mind, that's likely the best I can get out of my 20". I could run 155's faster, but keeping them under 2800fps, I don't think they will beat out the 168 hybrids.




I highly doubt long barrel .308 will net you much of anything when loading to mag length in an autoloader. JP only offers up to 22" in .308. Prob a reason.

 

[Bradu]

I used the hornady 4D calculator with a sourced g7 coefficient for various 6.5mm and 7.62mm projectiles versus posted velocities I found while lurking this forum for the last month.

All i saw was after 800yards, the 308 has a greater plunging effect. The 6.5mm was typically lower in energy beyond 600yards. Unless someone else is seeing 3400fps with those 123's..

The 6.5mm has a more flat flight path. The 308 seemed to have more energy to 800yards. After they evened back out. The 6.5 and 308 were down to sub 300lbs around 1000yards.

That knockout rating which most hunters apply.. says anything under 900lbs is unacceptable.

Unless the 6.5CM outlies traditional calculators, it trends to require longer barrels for the energy to match heavier 308 projectiles.

A standard 45acp weighs 230gr and goes 850fps. Making more energy than the 9x19 115gr going 1300fps. The same seems to trend. Now, I have spent quite a long time looking at the 6.5mm however it seems I missed something. My appologies.

When cutting a barrel blank, I had intended to run specific powders and start with a .06" gas port then slowly enlarge.

I have 25-06, 7mm rem, a few 7-08, 6.5CM, 300winmag all in bolt rifles. The 6.5CM is the last one I ever grab. Bought it during the hype a few years ago. I highly dislike the fad round. Perhaps that is a shortcoming on my end. Rifle has seen less than 100 rounds and sat five years. It does nothing golden when compared to the 25-06 or the 300winmag. It seems to me like a procharged stroked out honda drag car. You gotta pull the bumper and put giant slicks for it to even do anything. Still only makes 400 horsepower.

Yes, it is 'soft and flat'. It replicates a 260rem but functions in the short action autoloaders with 140gr projectiles. Yupyup, great BC.

I see that.

I really was looking for some information about what people are getting out of the highpower style rifles.

I agree, it does in a way defeat the purpose. However, that additional weight tames recoil. Bolt and barrel extension from nitrided 17-4 should handle everything just fine.

I appologise for poking a sleeping bear. It was a mistake and there will be no more aggrevating done.

Let's hear what bullets and velocities you used. You do realize you can run the 140 class bullets right? These posts are comical

 

[mensajd]

"Das ist nicht nur nicht richtig; es ist nicht einmal falsch!" --Wolfgang Pauli

 

[padom]

When you think you've heard it all...

 

[flyright]

Love the interweb expertise... I learn sommuch.

 

[cleric]

If you want a 308 because you like the round, then by all means go 308.

But at any barrel length comparing appropriate bullets the 6.5 will do better at distance because of the higher bc. The 308 bullet will be heavier and carry more energy within a limited distance. But as you go further the 6.5 makes more sense.

Also energy is not the best measurement for a hunting bullet. You will want to look at what velocities the bullet expands.

In terms of accuracy I have seen accurate 16in barrels and accurate 30in barrel. It’s more of a function of chambering, build, and trigger quality.

 

[Bradu]

When you think you've heard it all...

This belongs in the stupidest things you've heard thread lol

 

[VegasHKShooter]

I going to stick with just facts, and leave my opinion out. A 16”-18” .308 gasser is absolutely 100% doable and capable to 850-1000 yds. Seen it, personally have done it. You do not need a ton of barrel on a .308 to get jobs done. Once you get full burn and use of the gasses, any gain after that will be minimal, and not worth the trade off of length of barrel and weight. Most professional shooters will tell you that by 18” you’ve gotten what you’re going to get out off the .308.

The 6.5CM has a much higher BC. It carries itself better at distance. My own GAP-10 in 6.5CM has gotten hits at 1600 yds. Repeatedly, with other people around. Not “one time, out by myself.”
I’m not sure what numbers you ran in your calculator, but the 6.5 in a Hornady 147 ELD-M in my GAP-10 22” barrel is still carrying about 800 ft lbs of energy at 1000yds. That round stays supersonic until well past 1300yds. That’s a 22” has gun. My 26” A.I. does better still. Every single thing I am typing has been checked, done, and proven MULTIPLE times. None is guess work. I think you may have gotten your numbers mixed up on your ballistic app.

The .308 is still a great round. Very capable, and not likely to go away soon. I still shoot it and enjoy it. But I understand it’s limitations. The 6.5CM is not the be all end all, with a cure for cancer in its pocket. What it is is a neat .264 bullet with a very high B.C. that allows my wind calls to be less than perfect at 1K and still make hits.

 

[Rick7353]

Just seems like a 24”-26” semi-auto (especially with suppressor) defeats the semi-auto purpose. Semis were suppose to support the bolt gun (at least in combat operations) and had shorter barrels, 20” and shorter. They were suppose to be more maneuverable and were most of the time expected to engage targets from a shorter distance.

When you start adding suppressors and stiff charges into the mix as well, your asking for issues. Suppressors create more back pressure which you want to reduce on semi’s especially suppressed.

If you want to shoot long distance suppressed with a semi-auto my recommendation is a 6/6.5 variant (18”-22” barrel) and run pointed 123/130 grain projectile.

HI
I was wondering if you could answer why the m24 has a shorter 2.0 length on the barrel vs a light varmint. Usually the "B" on the barrel contour guide. I want to put on a 6.5CM bbl on my REM 700 and I can only bench shoot due to disability. I was looking at the Krueger chart. The bbl mfgs all have different bbl #''s

 

[Rick7353]

HI
I was wondering if you could answer why the m24 has a shorter 2.0 length on the barrel vs a light varmint. Usually the "B" on the barrel contour guide. I want to put on a 6.5CM bbl on my REM 700 and I can only bench shoot due to disability. I was looking at the Krieger chart. The bbl mfgs all have different bbl #''s

 

[TheGerman]

I have a real KAC M110K1 and have no issues getting to 1k. Is the 7.62 better than a 6.5; thats really up to you. The nice thing is, looks like KAC made a 6.5CM upper for the M110/SR25 so I'll have both.

7.62 semi auto gets diminishing returns on velocity with more barrel length after a certain length (forget what it was) and a 16 inch is more than capable and will benefit from a better bullet like the Berger Juggernaut which was made for SR25 length mags.

Velocity alone won't be the factor to determine what's 'better' as bullet design and BC come into play here too.

On a side note, I hit 28/30 rounds at 640 yards on a 8 inch plate with a 16 inch Mk12 ModH earlier today. That's 77g 5.56; you should have no issue with a 7.62 or 6.5

 

[Birddog6424]

My 308 gas gun versus my 6.5 Creedmoor gas gun..

The second figure from the right is foot pounds of energy. 682ftlbs at 1000 yards for the 308 175gr Tipped SMK. 760ftlbs at 1000 yards for the 6.5gr 140gr Nosler RDF

308

6.5 Creedmoor

 

[roamin]

When you're heavily invested into 308 and realize you've spent alot of money on dies, brass, projectiles, & rifle's for the wrong caliber. The only solution is taking a deep breath to prepare the vocal cords aaaaand NOT MY PRESIDENT, NOT MY PRESIDENT.........Sums this tread up OP was well aware of the differences between 6.5cm and 308 before arriving here.

Hope the OP enjoys his 26" barreled 308 AR. ?