Reloading observation

[godscountry]

I am reloading some .308 bullets for my M1A and got curious. I'm using 150 grain boat tail ballistic tip bullets, the powder is IMR 3031. My manual shows to get 2800 FPS to use 43.8 grains of powder. Out of curiosity I looked up specs for the 30.06, it shows to use 47.8 grains of 3031 to get the same bullet to 2800 FPS. I was wondering why the 30.06 needs more powder to get the same bullet to fly the same speed as the .308? Any ideas?

[Derrill Fox]

Case size is the reason. More powder is required to achive the same velocity because of the size of the larger case.

[eford]

I agree with PFox on this. An underloaded case is in the zone of having detonation and I have no idea how low a 30/06 case would have to be to get a detonation.
For my M-1 Garand the same amount of Varget can be used in the service grade load with the Hornady 150gn and 168gn bullets.

[Derrill Fox]

Think of it like this the larger case/chamber needs more powder (larger case) to get the same pressure a (smaller case) does.

[truck driver + 2]

The .308 win case is slightly more efficient then the 30-06 with lighter for caliber bullets.
If you want to see something even stranger look at the 338-06 and the 35Whelen both designed off the standard 30-06 case with just a larger caliber bullet. 35 Whelen will launch a 200gr Bullet slightly over 3000fps, try to do that with a 200gr 30cal bullet in a 30-06.

[Huntnmachine]

Think of it like this the larger case/chamber needs more powder (larger case) to get the same pressure a (smaller case) does.

Great explanation purplefox.
I am not a reloader so when you folks get into a discussion about reloading I find myself scratching my head.....lol
I plan to get into reloading when I retire in a few years so maybe by then I will be able to chime in...…
Until then I will continue to enjoy your threads and learn


Terry

[badsection]

Load that same bullet in a 300 Wby mag!   

[.257]

Think of it like this the larger case/chamber needs more powder (larger case) to get the same pressure a (smaller case) does.

+1

[godscountry]

Load that same bullet in a 300 Wby mag!   

     I just checked against the 300 Win. mag. It takes 54.3 grains of IMR 3031 to reach 2800 fps. with the same bullet. Looks to me like the .308 is the superior cartridge when it comes to powder charge. It takes less powder than both the 30.06 & 300 win mag to throw a 150 grain bullet 2800 fps. Interesting observations here.

[oldchet]

Load that same bullet in a 300 Wby mag!   

     I just checked against the 300 Win. mag. It takes 54.3 grains of IMR 3031 to reach 2800 fps. with the same bullet. Looks to me like the .308 is the superior cartridge when it comes to powder charge. It takes less powder than both the 30.06 & 300 win mag to throw a 150 grain bullet 2800 fps. Interesting observations here.

Welcome to the world of reloading and ratios. Let me add something that makes my sister in law shake her head. If all you are trying to do is accomplish a particular velocity for the exact same projectile, caliber, weight, ballistic coefficient, then all you NEED is the one rifle. But as you get into it you will discover that by looking at ballistic charts and different bullets that a particular .308 bullet at 2800 FPS with a BC of 0.41 (Nosler 165 grain partition)would reach out just a little bit further and hit a little bit harder with a .308 bullet at 2800 FPS with a BC of 0.507 (Nosler 180 grain Accubond) the 308 Win. will be way past it's limit, but a 30-06 with the right powder can do it. That is when you will NEED a new rifle in the caliber that will do that. You can usually slow down the next caliber larger to the same velocity as the smaller one. It will cost a little more powder, sometimes a little more for brass, but you can not make the smaller (308 Win) safely reach the higher velocities of the larger (30-06 Rem). That is the true joy of reloading when you can make your own custom ammo work exactly as you want. It will sometimes try your patience, but with the help of forums like this one it is well worth the time and energy spent.

[Blackbear3]

The only problem I have with that comparison is the type of powder used, you may find the opposite is true if you used a different burning rate of powder!!!

[oldchet]

The only problem I have with that comparison is the type of powder used, you may find the opposite is true if you used a different burning rate of powder!!!

You could be right.. I just have not been able to get any of my 308 Winchesters, even with maximum safe loads from a 24" barrel using the exact same projectile, to match what my 30-06 will do with the same length barrel using the maximum  safe load for the 30-06. The 308 Win will however be as accurate, if not more accurate with the loads it likes best, than the 30-06, but the conversation was about velocity using the same diameter and weight bullet.

[godscountry]

You're spot-on Oldchet, with the heavier bullets the '06 can be loaded above the .308's capabilities, it just has more room for more powder. I used the 150 grain because that's what I'm currently loading for my Springfield M1A.

[oldchet]

I have been shooting centerfire since 1962 and reloading since 1964. I am by no means an expert in either. That being said I did not even shoot a 30-06 until 2016, my wife and I own a few 308 Winchesters. My wife kept asking why I did not get a 30-06 as it could do more than a 308. I agreed, but the 308 Win can be had in a lighter rifle, is just as good on deer, black bear, and feral hogs at the distance she limits herself to as a 30-06 and will do so with less recoil and better accuracy from the less recoil. Well in 2015 two of her uncles died and both were hunters and both had daughters only. Their son in laws did not shoot so they sold all the firearms and gave me the rifle reloading dies and log sheets. For my birthday in January 2016 she bought me a Ruger American with the copper stock. I worked up some loads keeping the velocity down to 308 levels and it works really well. My wife says that because of the slight weight increase it does not kick any harder than her 308 so she can now hunt with the same caliber as her uncles.

[zonie]

www.zediker.com/downloads/14_loading.pdf   read it completely and carefully.  M14's and M1a's are a breed to themselves to reload.  7.62 x 51 and commercial 308's are loaded to different pressures along with different primers and commercial vs military brass cases which are built differently.  Factory commercial 308 ammo is built to higher pressures, and anyone that tells you differently are wrong.   My personal load is Varget which is probably too slow of a powder , but  I'm not loading very hot actually a pretty mild load,  velocity is 2550 fps.  win lg rifle primer,  oal 2.800, Hornady 168 gr bthp match,  Lake City Military brass,  accuracy @ 100 yds using  Nikon 4x12 scope is one ragged hole as long as I'm holding steady  which is hard for me to do anymore.   I love shooting my M1a  It's a rifle I grew up with in the Navy.    Be very careful of primer height and possible slam fires,  your military brass the primer is set deeper eliminating most of the problems along with the military using a less sensitive primers designed for a more powerful hammer/firing pin  drop,  you will notice the indention in the primer  the first time you let the bolt go foreward into battery and then open the bolt and look at the primer a very small dent.   This is one reason you probably should use  military cases,  generally I get 4 firings out of military brass cases,  carefully inspect the case rim !  M14's are very hard on brass and it's safer to just toss the brass when in doubt.   Loading the M1 Garand is about the same.   As far as the original question  The guy's are correct the 308's in general is a very efficient case design plus newer powders vs older powders make differences,  but there is more to it e.g. case capacities vs bore diameters,  bearing surface of the bullets,   etc.  You can take a look at 5 different loading books and they all are going to give you  difference and the only way to tell for your gun and your self is to run it on a chronograph and see what the actual differences are.  Reloading manuals are for lack of a better way to put it are good information for safe handloading so long as you follow the recipe to a T including backing off powder charges by their recommended percent and using the same brass, primers,  same bullet,  oal,  and under the same test conditions.    A side note :  I have shot factory  308 loads 150 gr PP velocity was 2820 fps and I  can tell the cycle rate on the op rod and bolt are different,  accuracy wasn't too bad.  If I wasn't getting such good accuracy and mild recoil with my lite load of varget I'd most likely use one of the 4895's  or even 3031 .   Really It would depend upon what the guns likes and your load combo.