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Bolt action rifle


Bob Hostetter

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The advantage of 6.5s are the higher ballistic coefficents and sectional densities for the bullets.  A 140 g. 6.5 mm sierra matchking has a sectional density (sd) of  .287 and a ballistic coefficient (bc) of .545 (when travelling at 2700 fps +).  A 140 g. 7 mm sierra spt has a sd of .248 and a bc of .430 (at 2700 fps plus).  A 150 g. .30 cal sierra fmjbt has a sd of .226 and a bc of .482.  Note the shape of the bullet does effect the bc but not sd.  

6.5s are ballistically better.  For the same weight bullet they will shoot flatter and be less effected by the wind.  In order to keep up with a 140 g. 6.5 bullet, you need to be shooting a 200 g. .30 cal bullet at roughly the same speed.  The .30 will have both higher recoil and less barrel life as you're burning more powder to push a 200 g. bullet that fast.

The high sds of 6.5s also allow for a great deal of penetration (assuming sturdy bullet construction) which is why scandanavian hunters can use them to shoot moose and turn of the century elephant hunters could use them to shoot elephant's brains.

A 6.5 140 g will not have the same energy/power factor as a .30 cal 200 g travelling at the same speed.  The .30 cal will be quite a bit more powerful though.

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Try the Lapua Scenar 139gr HPBT in 6.5 it is long and shapely. Possibly the best 6.5mm projectile I have ever seen. They also do a 144gr but the 139gr is used by a lot of guys in Europe that shoot at 1000M.

The only thing that you must be careful of with the long 6.5mm projectiles. They require quite fast twist barrels and can generate quite high pressures due to bullet friction. I use Moly coated projectiles and this will help heaps. The 260Rem seems to be gaining quite a following in some circles, especially with Silhouette in my area.

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1st of all, thanks for the info but I still have a few questions.

If the 6.5 is better why are the bench rest guys ( at least in my area) using the 6 or 7mm BR instead of a 6.5. These guys will happily spend as much money as needed but don't select the 6.5.

Will the 6.5 buck the wind as well as a 30 cal?

Bottom line is I am getting ready to have a competition bolt gun built for shooting between 100 and 600 yards and am having trouble settling on the cartridge.

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Bench rest guys shoot at 100 and 200 yards.  The big dogs rely on the 6mm PPC not the BR.

In the world of highpower (200 to 600 yd) and 1000 yard shooting, the 6.5s have made their mark.  6mms have also made a showing - particularly the 6mm X - but 6.5s are the hot ticket.  Tubb, the Thompkins clan, and Medesha have all used 6.5s, particularly at longer ranges.  Although the last time I talked to Scott Medesha, he was working on 6mm wildcats and Tubb has been messing with the 6X.  

I can't really answer the question "will a 6.5 buck the wind better than a .30?"  Generally  the answer would be yes due to higher bcs and sds but a .300 Ultra shooting a 200 grain bullet will be more wind resistant than a .260 remington shooting a 107 g. bullet.  So much depends on bullet and case selection.  Either a .260 remington or 6.5-284 will smoke a .308 WCF.

If I were building a rifle to shoot 100 to 600 yards, I would either build a .260 remington to shoot 107 g. Sierras or a 6.5-284 to shoot 139-142 gr. bullets.

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  • 2 years later...

Is this a case of the calibers mentioned above being a LOT better than the .30s, or is it just picking the right tool for the job?

Is it possible to do okay with a .308? I'm inclined to go with a .308 because any rifle I have would be for other uses too.

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I just recently have researching a Manually Operated Rifle setup. If you are doing nothing but punching paper ala Benchrest. There seems to be no question that the 260 and the wonder 6's are the way to go. However if you may be knocking down steel at extended range some have said you are very limited by these calibers due to the bullet weight even though the energy may be the same. The other consideration is barrel life. Some who are shooting the 6's report rebarreling every 1500-2000 rds.

Here's a link to another thread Manually Operated Rifle Setup

Rhino, 308 seems to be just fine for Matt Burkett

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Hi Bob,

I am beginning to come around to the realization that not only is .308 good enough for MOR type competition, but that it is a real good idea for many points the least of which are the ballistic considerations. The accuracy is good enough out to 1000 yards/meters/whatever and the energy is still there for steel response. Another thought I had was ammo compatibility with a lot of others on the line and the cheaper match grade ammo available in that caliber.

I once heard a motivational speaker by the name of Tom Peters say “I reserve the right to change my mind at a moments notice, when given new information”.

--

Regards,

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IMHO scopes like the Horus make the .308 more competitive and reduce the advantages of ballistically superior cartridges.

BUT they do not completely dimish those advantgaes. .308 is nearly a dead duck in Highpower. Why? Superior ballistics do matter particularly in changing enviromental conditions. Likewise, the reduced recoil of the .260 will always be an advantage. The trend in highpower and silhouette is to shoot the least kicking rifle as possible.

If you want to shoot factory ammo .308 may be the way to go but I would stick with a .260.

I think I would avoid the sixes given the lack of bullet weight which may not take steel targets.

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260 is great for paper but has trouble with Larue's at 700+. The big drawback is the lack of match ammo and you're stuck with shit brass or have to form it from .243 or .308 Lapua brass.

The HV scope doesn't make the .308 any better than the rest it will work equally well for all calibers.

If you're building a gun just for paper or 600 yds and in the .260 with 123 Lapua scenar's is the way to go. If you need to drop long steel stick to a .308.

The highpower crowd is just poking paper so it doesn't need the extra knockdown.

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Thanks, guys!

My decision will be influenced by the fact that 1) I will be shooting factory ammo (unless my personality changes!), and 2) as with my other firearms, it will be intended for more "practical" purposes, with shooting games a fun bonus and a training tool.

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Is there Minor/Major in MOR? Does it even matter because it's mostly a steel target game?

No major/minor in USPSA MOR, but that isn’t the only game you can come across. I figured a 6 sumthin’ would be better too, but recently realized that not all steel will always be a well greased MGM swinger.

The knockdowns you can run into in more sniper oriented matches will not respond to less than a good 30 or similar. After recently watching ‘Tater‘ Moots clean several difficult MOR style stages incredibly fast with a .308 using factory match grade ammo, I am re-considering my thoughts on anything but .308 for this type game. It also really spanks heavy hanging steel nicely at longer ranges, makes it easy to see it happen in the scope really fast.

Being a NATO standard round and not being a barrel eater are not small things either.

The .260 is not really known as a barrel eater, but it is also not known as the king of loaded ammo and cheap component availability either.

--

Regards,

Edited by George
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Chris I beg to differ about the .260s ability to take steel compared to a .308. I compared a 142 SMK .260 load at 2700 fps versus a .308 175 SMK load at 2600 fps on Sierra's Infinity program.

.260 Rem:

Energy at 500 y 1228 ftlbs

600 y 1066 ftlbs

700 y 922 ftlbs

800 y 796 ftlbs

.308 Rem:

Energy at 500 y 1246 ftlbs

at 600 y 1055 ftlbs

at 700 y 893 ftlbs

at 800 y 756 ftlbs

As you can see they have quite a similar energies but the higher BC of the .260 starts to factor in once the distances get farther. I fail to see how the .260 will not take steel as well as the .308 when it is hitting the target with equivalent and even higher amounts of energy. The larger frontal area of the .308 bullet may help but I doubt that that would make much of a difference.

My comment about the Horus scope is not that it makes .308 any better than the rest. Using that reticle evens the field between cartridges since you simply plug in the data and hold wherever HAL tells you to. So with a 6.5-284 you may have to hold 2 hashmarks less than a .308.

It is true that .260 match ammo is not nearly as commonly available as .308.

Will a .260 beat Tater on it's own? No way (at least not until I finish mine :P )

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.260 is what I am getting my AW rebarrelled in and will be using the Berger 140 bullets with a .637 BC.

Run the ballistics at just 2900 with the above BC and see what happens on drop/drift at 1K yards.

Flatter is better but the wind is what you want to beat the most. The .308 is like throwing fancy shiny rocks downrange.

Take care,

Matt

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Kelly,

What determines the ability of a bullet to take steel is not the kinetic energy, but momentum. Knocking down a target is an inelastic collision and for that you must use the conservation of momentum.

If you can recalculate your data using simple PF calcs, it will be better representative of steel-cleaning performance.

[/Physics Nerd Mode OFF]

E

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Well here it is. The Berger .264 140gr VLD at 2900 fps vs. the Berger .308 168gr VLD at 2700 fps.

I ran these in RSI Shooting Labs and converted the astronomically high mfgr G1 BC’s to a G5 boat tail drag model which halves the BC in the calculation but delivers spot on results in the real world.

The 140 in .260 definitely whomps the .308 in terminal energy and drag resistance at 1000 yards for sure, but not by 50%, more like 20-25%. But note that the final G5 corrected BC is very close for both. I am thinking the higher SD of the smaller diameter 140 is what makes the LD ballistic difference so much greater than the BC difference. **

Editors Note: Just noticed I ran these off with a 7 degree inclination set in the parameters. Just checked it with zero inclination and the difference is just under 3 inches less drop at 1000 yards for the .308 and just over 2 inches less drop for the .260. There is no difference in wind drift. Being inherently lazy, I will not redo them for this insignificant of an error margin (less than 1%).

berger260.gif

berger308.gif

--

Regards,

Edited by George
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What determines the ability of a bullet to take steel is not the kinetic energy, but momentum. Knocking down a target is an inelastic collision and for that you must use the conservation of momentum

That mirrors my real world experience of heavier projectiles at the same PF (130) as lighter ones being noticeably more authoritative on poppers all of the time.

--

Regards,

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Kelly,

Give Terry Cross a call and ask him about the .260 on long range Larue's. He had some issues with them at one of the Sniper matches. Computer programs are nice and energy looks comparable but as Eric stated it is Momentum that knocks things down and breaks them. Same reason that you don't hunt Cape Buff with a 22-250. Energy puts a premium on velocity. If it is a gun strictly for IPSC MOR and the ranges are 600 or less the .260 is the choice. If it is dual purpose then the .308 is the better choice. Hell if you really want to buck the wind moved up to a .338 LM. ;)

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Thanks for the info Chris. Were they 139 + bullets? Or 107 -129s?

You don't hunt buff with a .22-250? You gotta use a Barnes solid. :D

Redmercury, 6.5-08 and .260 rem are essentially the same thing performance wise but 6.5-08 reamers may have some differences and chambers might not be identical.

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