Dilema in Caliber Choice..

[gallogiro]

Go with the .308,you won't be sorry.

Yup, I got the 308. Happy with the decision so far. Thanks for all the input. I don't know If I had mentioned it before but the rifle is a .308 Thompson Center Icon w/ 24" barrel, nice trigger (adjustable) and a free floating barrel. What more could I ask for? Really solid, it has a great feel/ balance and the LOP feels much better for my stature. Lighter than my 7mm and will have less recoil. I just need to see how it shoots. I want to put a nice scope on it first.

I read about a lot of people doing barrel break-in on rifles and not sure if it's something I should do on this one. The first new hunting rifle I bought I cleaned it, mounted a scope and shot a box of ammo through it to sight in, then cleaned it again. It shot "ok" for a hunting rifle, about 1" groups consistently w/ the occasional flyer. Anyone have any personal experience on barrel break-in processes and if they are worth the effort?

Thanks for all the help.

 

[tonyspdx]

270 = flattest traj.
308 = Flat traj w/pop

I personaly would go with the 308, best of both worlds and you can get a box for $12-14 easy.

 

[landcbeitner]

270 = flattest traj.
308 = Flat traj w/pop

I don't understand what you mean by this... I agree that the 270 has flat mid-range trajectory but I wouldn't say the 308 is flat or has "pop". Especially not compared with most hunting cartridges.

 

[tonyspdx]

Easy the 308 has more "pop" than a 270, But the 308 has a flatter trajectory than a 30.06. This allows you to sight you rifle in a 200 yrds, but still take a 3-400 yrd shot with minimal compensation. 308 and 30.06 have greater "punch", but the 270 give you less deviation in trajectory. Heavier caliber bullets will "drop" significantly farther at greater distances. All I am saying is that if you are a lazy hunter and only want to make one setting on your scope, then a 270 is the caliber you want.

 

[no time]

Congrats on the 308, you will love it! It's a great all around big game cartridge that has easy to find ammo at about any store in the country.

But if you want to hunt a lot of varmints...the 22-250 might work better...or maybe a 223....you know, less recoil, but easy to find ammo. You probably need a rifle in one of these calibers next....you know, so you have the best rifle for that job....

And we haven't talked about a good lever gun for the brush...

Or a super long range rifle...

Or the dangerous game rifle...just in case that lottery number is good...

You're not finished buying rifles yet! Thank God they make so many different guns for so many different jobs...

Isn't this fun!!!

 

[landcbeitner]

Easy the 308 has more "pop" than a 270, But the 308 has a flatter trajectory than a 30.06. This allows you to sight you rifle in a 200 yrds, but still take a 3-400 yrd shot with minimal compensation. 308 and 30.06 have greater "punch", but the 270 give you less deviation in trajectory. Heavier caliber bullets will "drop" significantly farther at greater distances. All I am saying is that if you are a lazy hunter and only want to make one setting on your scope, then a 270 is the caliber you want.

As stated by another.... the 308 is not as flat as a 30-06... they use the same bullet but the 30-06 has a substantially more case capacity allowing higher velocities with any given bullet weight. You may be thinking that the 308 is a more efficient cartridge than the 30-06 and I would agree with that especially with regard to lighter weight bullets (up to about 175gr).

The 308 and 30-06 use a larger bullet diamater than the 270, but that doesn't translate to greater energy (or "punch"). It's impossible to be dogmatic when discussing energy potential of cartridges using different caliber bullets. The relationship is more complex. Energy is dependant on muzzle velocity, bullet weight, and bullet ballistic coefficient (unless you are only looking at muzzle energy in which case BC is not a factor). A higher BC bullet will allow for greater energy at longer ranges compared with lower BC bullets.

To break down energy potential between the 270 win and 308 win... here's some information based on data from the Sierra Reloading Manual. Both test rifles are listed as having 26" barrels (giving us a good comparison of cartridge potential).
As luck would have it both cartridges have a maximum MV of 2900fps with 150gr bullets this gives them both a muzzle energy of 2,772 ft/lbs. The difference is that the bullet diamater of the 270 is smaller wich generally gives the bullet a higher form factor and always gives a higher sectional density resulting in a higher ballistic coefficient. If we plug in the BC for the 150 gr Berger VLD bullet (.531) energy for the 270 win at 400yds is 1,643 ft/lbs.

The BC for a similar bullet from Berger (I'll use the BC from the 155gr VLD 'cause I can't find any 150gr VLD bullets) is .439. Energy at 400yds for the 308 is 1,459 ft/lbs. The farther out you go the greater the energy advantage of the 270 win.

One could make the argument that for the 270 one rarely finds bullets of over 150gr and for the 308 one could easily use bullets over 200gr for greater energy potential. Unfortunately shooting heavy bullets will require slover MV's and in turn lower muzzle energy. For example the maximum MV for the 308 with a 200gr bullet is 2450 fps giving a Muzzle energy of 2,633 ft/lbs the good news is bullets of this weight will have higher BC's for the reasons stated earlier. I'll use the BC of Berger's 210gr VLD (since they don't make a 200gr VLD) of .631 giving us 400yd energy of 1,635 ft/lbs... very close to what we got from the 270 win and a 150gr bullet. If you go farther out the 308 would eventually have more energy. The problem is extra bullet drop at such low velocites and the ability of bullets to expand when hitting game at these lower velocities (some bullets are much better than others in this regard). For the 270 win/150gr load used earlier we'd hit at 2,221fps and have 20" of drop to 400yds from a 200yd zero... for the 308 win/200gr load we'd hit at 1,919fps and have 29" of drop to 400yds from a 200yd zero. I compensate for range with scope corrections anyway but for your average hunter the energy break down generally favors the 270 win over the 308 win.

Although I quoted you I'm not directing this at you Tony...I'm not trying to get on anyones case... I just think it's important to give information that is accurate... as these small and sometimes unimportant discussions are used by the less experienced to make decisions on cartridge and caliber selection for hunting. None of this is as critical as shot placement, but I've seen the results of poor cartridge and caliber selection before. Even selecting which bullet (in both weight and construction) to use for your application can be very important. I didn't mean to get so lengthy and I hope I don't come across as arrogant... if the moderators feel this is off topic or in poor taste feel free to move or remove this post.

 

[Riot]

22-250 is a GREAT calliber...I'm actually suprised that is hasn't gotten any more popularity than it has. You basically get match-grade performance out of factory ammo. Those rounds shoot out FAST!

 

[landcbeitner]

As far as I can tell....The "efficiency" of the 308 has allot to do with the powders used (with respect to bullet weights). The case can be filled to a higher percentage with the burn rates that work well with the relitavely light 30 cal. bullets (up to about 175gr). You'll notice that these lighter bullets get relitavely excellent MV's with with faster burn rates like Varget and RL-15. If you were to try and load the 30-06 with to the same percentage with such a fast powder and you run into pressure issues. So the 30-06 uses a much lower charge by percentage (actual powder charge is higher) and is less efficient even though it will infact run slightly higher MV's.

For example with 175gr bullets the 308's max load (according to Sierra Reloading Manual) is 41.7gr of Varget giving 2600fps. The 30-06 with 175gr bullets maxes out at 45.7gr (only 4gr more) also giving 2600fps (30-06 can get more MV with this bullet using slower powders).

So the obvious solution is just to use slower powders in the 30-06 and this does work, but it's not a perfect solution. The slower burn rate builds pressure slower (so the bullet accellerates slower at the begining), and since the lighter weight bullets spend less time in the barrel (due to higher MV's) much of the powder may not be completely burned by the time the bullet exits the muzzle and can no longer be effected by the remainder of powder that burns (usually in the form of muzzle flash ) So the 30-06 does achieve higher MV's even with light bullets but again, isn't as efficient as the 308 with the lighter bullets.

The relationship between these cartridges changes quickly as the bullet weight goes up. With the heavier bullets, fast burn rates can create a pressure spike early and must be run at very low charge weights (comparitavely). Heavier bullets do well with slower burning powders since they remain in the barrel longer and the slower buring powders don't spike as much early allowing much higher charge weights that keep pressures up all the way. The 308 doesn't have enough capacity to take full advantage of the slow powders and MV's suffer. The 30-06 works well in comparison with the heavier bullets and slower burning powders, the extra capacity is no longer a handicap. With the heavy bullets I would say the efficency of the two cartridges is very close and the 30-06 shows what the extra capacity is capable of.

With more advanced powders becoming available all the time, the older and "less efficient" cartridges will likely look better and better. I believe I commented on this in another thread on WSM's vs. standard belted magnums.

Technically the 308 has a higher opperating pressure (60,175 psi) compared with the 30-06 (58,725 psi). This difference is also reflected in the data above. Many believe this is to protect reloaders from over pressuring their older military rifles, and they load to higher pressure levels in their modern bolt rifles (I won't comment on this).

 

[orygun]

But the 308 has a flatter trajectory than a 30.06.

Excuse me? The exact same bullet at the same, or less, velocity does not a flatter trajectory make!
The .308 is the equal of an 06 in lighter bullets with factory loads, but falls short of 06 when the weights hit 180, or when going to handloads.

Same bullet at slower speed means more of a rainbow, not less. Granted with factory loads of 165 or less grains the difference is nothing that matters, but you got it backwards Dude.

 

[landcbeitner]

The same argument could be made about the .308 being more efficient than the .270 since the .308 cartridge will create higher pressure easier than the .270 at say equal weights of 150 gr. Am I correct?

The relationship between the 308 and 270 are complicated in this regard also. I think I understand what you're getting at. As far as pushing a 150gr bullet to a given speed yes the 308 does it with much less powder. The 308 will use a powder with a faster burn rate and gets up to pressure quicker. The 270 is able to match the velocity because it has a higher capacity and can successfully use a slower powder to get the same results.

The way I look at efficiency is a little different. I only compare straight across if the same caliber of bullet is used (like the 308 and 30-06). I compare cartridge of different caliber by comparing how fast the cartridge can push a bullet of a given ballistic coefficient (in its respective caliber). Of course this is most fair when bullets from a given manufacturer and design are used (but some cartridges have poor selection of high BC bullets) So the way I look at it, they brake down more like this...

308 win
155gr VLD bullet: .439 BC
Max. MV: 2900fps

270 win
130gr VLD bullet .452 BC
Max MV: 3100fps

So in my mind the 308 is not significantly better in terms of effiency. I don't know if there is a correct or incorrect way of looking at it. I guess it depends on your use for the cartridge. Here's a link to my broad view of cartridge/caliber selection and comparison if you're interested...
http://www.shoot-farther.com/My_Homepage_Files/Page1.html
...you'll have to excuse the site... it's not professional.

 

[landcbeitner]

Many hunters don't shoot game beyond 200yds (I read somewhere most game is taken within 100yds) in which case the I think your comparison of bullet weight and MV would be most appropriate.

 

[landcbeitner]

Yes sir....

By the way... I LOVE the 243 for long range (not particularly for taking game as energy is not especially high).... when the barrel is of a propper twist rate for the higher BC 6mm bullets... the results are low recoil and good ballistics!

http://www.youtube.com/watch?v=9yTucXChRDY

 

[SquatchWorks]

Just go 308 and dont look back... There is always ammo at walmart in 308, Tons of Online Info on the 308.

the 308 is what the 30-06 was 30 years ago

 

[2506]

Yes sir....

By the way... I LOVE the 243 for long range (not particularly for taking game as energy is not especially high).... when the barrel is of a propper twist rate for the higher BC 6mm bullets... the results are low recoil and good ballistics!

http://www.youtube.com/watch?v=9yTucXChRDY

You bring up a good example of cartridge comparison. The 243 Winchester can be DIRECTLY compared to the 244 Remington. In this case (pun intended) the 244 wins due to case capacity.


Further, defining efficiency varies from one source to another; Art Pejsa defined it as a ratio of energy delivered at the muzzle as compared to the energy wasted in recoil. No mention was made in the examination of energy loss due to heat, etc. and the honors are always pointed toward the heaviest firearm. Another popular theory for efficiency is the ratio of velocity gained per grain of powder used. The major problem with this method is that the scale is tipped toward the smallest cartridge and bullet. In other words, the old .22 Rimfire Short will usually come out on top. Others have shown that efficiency can be based on the most effective use of the energy contained in the gunpowder. And in this light, the .300 Hawk really shines.

http://www.pejsa.com/

 

[landcbeitner]

Thanks for the link... interesting. I've never paid much head to those types of effeciency calculations. If I were designing cartridges it would be good to know exactly how one can influence efficency in the technical aspect to get the most from your available powder charge. For my personal use I first decide what kind of energy I require out to a given distance of intended use (not applicable for target shooting), then determine what bullet weights and ballistic coefficents would be required to meet my goals. Next I find the cartridges that allow the MV's required, from these I'll look at relitave effiency between them. If I were looking to use 155gr .308" bullets I would most likely choose the 308 over a 30-06 (this wouldn't actually happen to me since I'd look at .277" and .284" bullets in the 150-160gr bullet range).

It's funny that you mention the .244/6mm Rem vs. 243 win. a buddy of mine built a 6mm Rem expecting to beat up on my 243 in long range performance. Both rifles were 26", 1:8 twist barrels for the 105-115gr bullets. The 6mm Rem definately had the ability to push bullets faster. Unfortunately for my buddy, both rifles were most accurate arround 2950fps and he simply used more powder without any performance benefits. He could run better ballistics if that was the primary goal, but of course he wanted the accuracy as well.

 

[Hondo]

.308 baby, hands down. Tons of different grains and styles. It will kill anything in North America. Just learn how to shoot it and put that bullet perfect everytime. Use HPBT on varmints. Reak havoc on all living creatures. Maybe someday some Zombies will show up at your front door and you could shoot them too. Yahoo! God was gracious enough to put all living things on this earth for us to blow up.. Thank You Jesus God Bless America!