AR15.Com Archives
 A newb question: loading .308 and OAL
Avtomat  [Team Member]
8/30/2009 3:07:11 PM
Gun: Savage FP10 in .308

I want to try a load from the Lee 2d ed manual as my first .308 load. I have some experience loading––.223 and 7.5 swiss––but not a whole lot.

I measured the maximum cartridge length––when the bullet touches the lands––using the technique wherein one seats a bullet in a loose neck too long and then chambers it, allowing the bullet to be pushed back in the case and thus resulting in a cartridge at maximum length in the chamber. This results in cartridge with the length of 2.799.

I plan on seating a completed cartridge .020-.030 deeper, let's say .025. Thus, 2.799 minus .025, or 2.774 for my OAL.

Problem: I am using some generic 150gr FMJ bullets I ordered from Graf's. I'm planning on using a load calling for 43gr-45.5gr of H4895. The manual lists the minimum overall length of the cartridge at 2.800 inches, which is longer than my planned load. In fact, at 2.800, the cartridge is too long for the chamber, and the neck doesn't even reach the cannelure.

So is this load not going to do it? I see other loads with this size bullet with shorter minimum OAL lengths, am I going to have to switch to a different powder? Is there something wrong with the techniques I am using? I just want to make sure that I am not missing something...

ma96782  [Team Member]
8/30/2009 3:11:16 PM
The 2.80" COAL (for .308 Win. /7.62 NATO) is usually the accepted norm for ammo used in a magazine fed rifle (i.e. M14, G3, FN-FAL, etc.....).

Chambers vary between manufacturers and where the cannelure is placed also varies between manufacturers of bullets.

You asked what would happen if............

http://www.hornady.com/ballistics/internal.php

Aloha, Mark

PS...........I would be VERY surprised if your rifle couldn't take a COAL of 2.80". But, whatever.
30Caliber  [Member]
8/30/2009 3:16:09 PM
Your measurement sounds incredibly short for a factory rifle. I would expect it to be much much longer.

You can use the cannelure or flat out ignore it.
Avtomat  [Team Member]
8/30/2009 3:23:27 PM
Am I correct in believing that "minimum OAL" in loading data is related to ensuring that one does not create a volume in the cartridge that is too small and thus impacting pressure? I did not think that it was for purposes of ensuring operation in a firearm....
panther308  [Member]
8/30/2009 3:24:10 PM
I believe the number you are looking at is the max OAL my Speer 14 list a 150 FMJ at 2.800" tested and my Sierra list a OAL of 2.750" I am not sure what type of bullet you are using you said you got them from Grafs, are they match quaility ? is you brass prepped and the bullet worth the time to mess with how far off the lands you are running ?
I currently use BH Brass with a SMK 168 with RL-15 in my Savage and run with it about .010" off the lands this has yielded good results but your rifle may be different, some bullets prefer some jump and some prefer to be jammed my suggestion would be to seat them about .010" off the lands to start with and see what results you get
ma96782  [Team Member]
8/30/2009 3:42:30 PM
Originally Posted By Avtomat:
Am I correct in believing that "minimum OAL" in loading data is related to ensuring that one does not create a volume in the cartridge that is too small and thus impacting pressure? I did not think that it was for purposes of ensuring operation in a firearm....


The powder within a case can be all over the place with respect to volume. Some powders are very bulky (or less bulky). Some powders are very fast burning (or slow burning).

Maybe you're confused about "compressed loads" and the "danger" warnings?

For Black Powder..........the powder needs a bit of compression.

But for smokeless powder..........generally you don't want to compress it or to have a large empty volume space within the case.

That being said...........the writers/editors of your reloading manual has done extensive testing to (hopefully) ensure for your safety. Manuals will differ in opinion as to where exactly that level of safety is being crossed. So, besides the COAL.......note the "Max. load data" and "Starting load data."

So, have you noticed that sometimes a manual will say XY gr. of ABC Powder. But, when you try XY gr. the powder will overflow the case?

Some (like me) don't like smokeless compressed loads. So, instead of reaching for a funnel and drop tube...........I just forgetaboutit.

What YOU do is up to YOU.

Aloha, Mark




Avtomat  [Team Member]
8/30/2009 3:43:49 PM
Originally Posted By panther308:
I believe the number you are looking at is the max OAL my Speer 14 list a 150 FMJ at 2.800" tested and my Sierra list a OAL of 2.750" I am not sure what type of bullet you are using you said you got them from Grafs, are they match quaility ? is you brass prepped and the bullet worth the time to mess with how far off the lands you are running ?
I currently use BH Brass with a SMK 168 with RL-15 in my Savage and run with it about .010" off the lands this has yielded good results but your rifle may be different, some bullets prefer some jump and some prefer to be jammed my suggestion would be to seat them about .010" off the lands to start with and see what results you get


Thanks panther––because I have never really measured the lands while reloading I wasn't sure where to start––one website suggested starting at .025 and then working closer to see how accuracy changes.

The Lee manual clearly states this is the "min. OAL"––I wish I could find my rcbs manual, which is much better than the Lee manual
ma96782  [Team Member]
8/30/2009 3:50:35 PM
Re-visiting the cannelure issue and how it relates to the COAL (taken from the SPEER site)...........


Q.
The rifle bullet I'm loading has a crimp groove, but the cartridge length recommended puts the groove out of the case. Should I change the seating length to make the crimp groove line up.

A.
No. Not all rifle cartridges require crimping. The groove on the bullet is positioned for those that need the crimp. If the recommended seating length puts the crimp groove above or below the case mouth, we determined that crimping was not needed. Having the crimp groove above or below the case mouth has no adverse effects on accuracy or performance.


HTH.

Aloha, Mark

panther308  [Member]
8/30/2009 7:39:13 PM
Originally Posted By Avtomat:
Originally Posted By panther308:
I believe the number you are looking at is the max OAL my Speer 14 list a 150 FMJ at 2.800" tested and my Sierra list a OAL of 2.750" I am not sure what type of bullet you are using you said you got them from Grafs, are they match quaility ? is you brass prepped and the bullet worth the time to mess with how far off the lands you are running ?
I currently use BH Brass with a SMK 168 with RL-15 in my Savage and run with it about .010" off the lands this has yielded good results but your rifle may be different, some bullets prefer some jump and some prefer to be jammed my suggestion would be to seat them about .010" off the lands to start with and see what results you get


Thanks panther––because I have never really measured the lands while reloading I wasn't sure where to start––one website suggested starting at .025 and then working closer to see how accuracy changes.

The Lee manual clearly states this is the "min. OAL"––I wish I could find my rcbs manual, which is much better than the Lee manual


Alot of handloaders start off right on the lands and then work back, starting off at this point gives you only one direction to go and makes it easier, this is what I did and ended up about .010-.012" off the lands and then you can start using the OCW to develop a load it will boggle the mind
curiomatic  [Member]
8/30/2009 11:37:23 PM
RCBS makes a tool for determining bullet seating depth. It's called the RCBS Precision Mic.
Falar  [Team Member]
8/30/2009 11:55:37 PM
Originally Posted By 30Caliber:
Your measurement sounds incredibly short for a factory rifle. I would expect it to be much much longer.

You can use the cannelure or flat out ignore it.


+1

My Savage 10FCP McMillan needed an OAL of 2.848" to touch the lands with 155gr Scenars. I know one other person with the same gun, he needed an OAL of 2.850" to touch them.
AeroE  [Moderator]
8/31/2009 8:58:02 AM
Originally Posted By Avtomat:
Am I correct in believing that "minimum OAL" in loading data is related to ensuring that one does not create a volume in the cartridge that is too small and thus impacting pressure? I did not think that it was for purposes of ensuring operation in a firearm....


The cartridge length has to be balanced to fit the magazine, the rifle chamber, and bullet seating depth.

Seating depth in bottleneck catridges causes insignificant change in the internal volume of the case. The rule of thumb for seating depth is 1 to 1.5 bullet diameters into the case neck for good neck tension.

Seating depth in straight wall cases should be considered more critically. Small changes in seating depth change the case internal volume in direct proportion and can change pressure quickly.

Since you're having trouble getting a loaded round to chamber at 2.80 COAL, I want to know whether an unloaded case will chamber. I'm skeptical that the gun has short chamber.

I wouldn't obsess over the COAL before I shot a few cartridges to find out whether the bullets you bought are worth the effort.

Falar  [Team Member]
8/31/2009 12:02:43 PM
Originally Posted By AeroE:
Originally Posted By Avtomat:
Am I correct in believing that "minimum OAL" in loading data is related to ensuring that one does not create a volume in the cartridge that is too small and thus impacting pressure? I did not think that it was for purposes of ensuring operation in a firearm....


The cartridge length has to be balanced to fit the magazine, the rifle chamber, and bullet seating depth.

Seating depth in bottleneck catridges causes insignificant change in the internal volume of the case. The rule of thumb for seating depth is 1 to 1.5 bullet diameters into the case neck for good neck tension.

Seating depth in straight wall cases should be considered more critically. Small changes in seating depth change the case internal volume in direct proportion and can change pressure quickly.

Since you're having trouble getting a loaded round to chamber at 2.80 COAL, I want to know whether an unloaded case will chamber. I'm skeptical that the gun has short chamber.

I wouldn't obsess over the COAL before I shot a few cartridges to find out whether the bullets you bought are worth the effort.




Since nearly all factory ammo for .308 loads to ~2.8" I have a hard time believing that a production rifle would have a chamber that short also. Virtually everything would at the lands or into them increasing pressure.