Another .308 question

45auto45 · May 23, 2007, 11:19 AM

The shoulder spec for the case is .454, with no _ or + are given. What is tolerable and still functional????

**Unclenick** · May 23, 2007, 02:16 PM

Drawings in loading manuals are usually the SAMMI maximum for any cartridge. These numbers will be plus zero minus something. Probably two or three thousandths. The SAMMI .308 chamber is about 0.011" wider than the case and is minus zero plus a couple of thousandths if I recall correctly? I cant find where I put the copy of the SAMMI drawing for .308 that I have.

The bigger question is, why do you care? The SAMMI spec should only matter to you if you are loading ammunition for sale and have no idea what gun it will shoot it? The only purpose of the numbers is to guarantee compatibility with unknown guns. When the round fires in your own gun's chamber, it expands to fill that chamber, becoming "fireformed". This new volume is the one that determines load pressure in your particular gun with the powder charge and bullet in the case. When you resisize, if you are loading singly, just size the neck for best accuracy and leave the rest of the case custom fit to your chamber. If you need the ammunition to load from a magazine, then you need to full-length resisize, but usually only enough to push the shoulder back about .002" or so from its fireformed position. This is especially useful to know if you fire the .308 in a gun with a 7.62x51 NATO chamber, which is about 0.004" longer at the headspace. No point in working the brass all the way back to SAMMI for that bigger chamber. Some self-loaders are more picky about getting the case to feed, and may require you to use a small base sizing die to narrow the case more than a standard sizing die does, especially if you are not pushing the shoulder back to original position.

45auto45 · May 23, 2007, 04:09 PM

Thank you for your information! Useful!!

I ask, because at times, I develop issues with bullet seat and crimp. On occasion, I get a hard to seat bullet that I have to use excessive force to get it started. I know this isn't right and something is going on. I haven't been able to figure this one out yet. What happens is, when I get this hard round to seat and crimp, it rolls the shoulder or puts a slight bulge at the shoulder and that .454 spec, is then out of spec. I am going to start seating separately and use a Lee crimp die for the last step. Funny thing is, all the brass is sized to the same length but every once in a while I get one that becomes wasted in the die. All the brass is LC head stamp. This one has me puzzled

My concern with the shoulder spec at .454 is for chambering, will it or will it not.. Obviously to much bulge or roll and it will not. This is why I am curious about how much over the .454 is OK. Thanks for your input.

T. O'Heir · May 23, 2007, 04:23 PM

"...have to use excessive force to get it started..." Have you chamfered the inside of the case mouth?

45auto45 · May 23, 2007, 05:57 PM

Yes.

The only time this happens is to a load that will be wasted, if I continue. It's like a warnning, if if starts out hard, that round will be no good, so now I don't continue with that round. I almost have to laugh because I'm still trying to figure out what's happening.. My main concern is the shoulder spec.

azredhawk44 · May 23, 2007, 06:01 PM

45auto45:

Pull the case mouth expander ball out of your die and measure it. IIRC, you had another thread running a while back where you were having similar problems with the case mouth not accepting bullets.

Sounds like the expander ball is too small, or just on the cusp of being too small.

45auto45 · May 25, 2007, 02:48 AM

Well, I think I know what is happening, the case length is a little to long! When the brass goes up in the die, it compresses at the top of the cone making the shoulder bulge a little. Guess I have a bunch of extra work ahead of me salvaging everything but the brass! I hate wasting brass!

May 23, 2007, 11:19 AM	#1
45auto45 Member Join Date: April 1, 2007 Location: Girly Man!!!! Posts: 38	Another .308 question The shoulder spec for the case is .454, with no _ or + are given. What is tolerable and still functional???? __________________ The road to hell is paved with Democraps!

May 23, 2007, 02:16 PM	#2
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Drawings in loading manuals are usually the SAMMI maximum for any cartridge. These numbers will be plus zero minus something. Probably two or three thousandths. The SAMMI .308 chamber is about 0.011" wider than the case and is minus zero plus a couple of thousandths if I recall correctly? I cant find where I put the copy of the SAMMI drawing for .308 that I have. The bigger question is, why do you care? The SAMMI spec should only matter to you if you are loading ammunition for sale and have no idea what gun it will shoot it? The only purpose of the numbers is to guarantee compatibility with unknown guns. When the round fires in your own gun's chamber, it expands to fill that chamber, becoming "fireformed". This new volume is the one that determines load pressure in your particular gun with the powder charge and bullet in the case. When you resisize, if you are loading singly, just size the neck for best accuracy and leave the rest of the case custom fit to your chamber. If you need the ammunition to load from a magazine, then you need to full-length resisize, but usually only enough to push the shoulder back about .002" or so from its fireformed position. This is especially useful to know if you fire the .308 in a gun with a 7.62x51 NATO chamber, which is about 0.004" longer at the headspace. No point in working the brass all the way back to SAMMI for that bigger chamber. Some self-loaders are more picky about getting the case to feed, and may require you to use a small base sizing die to narrow the case more than a standard sizing die does, especially if you are not pushing the shoulder back to original position. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

May 23, 2007, 04:09 PM	#3
45auto45 Member Join Date: April 1, 2007 Location: Girly Man!!!! Posts: 38	Thank you for your information! Useful!! I ask, because at times, I develop issues with bullet seat and crimp. On occasion, I get a hard to seat bullet that I have to use excessive force to get it started. I know this isn't right and something is going on. I haven't been able to figure this one out yet. What happens is, when I get this hard round to seat and crimp, it rolls the shoulder or puts a slight bulge at the shoulder and that .454 spec, is then out of spec. I am going to start seating separately and use a Lee crimp die for the last step. Funny thing is, all the brass is sized to the same length but every once in a while I get one that becomes wasted in the die. All the brass is LC head stamp. This one has me puzzled My concern with the shoulder spec at .454 is for chambering, will it or will it not.. Obviously to much bulge or roll and it will not. This is why I am curious about how much over the .454 is OK. Thanks for your input. __________________ The road to hell is paved with Democraps!

May 23, 2007, 05:57 PM	#5
45auto45 Member Join Date: April 1, 2007 Location: Girly Man!!!! Posts: 38	Yes. The only time this happens is to a load that will be wasted, if I continue. It's like a warnning, if if starts out hard, that round will be no good, so now I don't continue with that round. I almost have to laugh because I'm still trying to figure out what's happening.. My main concern is the shoulder spec. __________________ The road to hell is paved with Democraps!

May 25, 2007, 02:48 AM	#7
45auto45 Member Join Date: April 1, 2007 Location: Girly Man!!!! Posts: 38	Well, I think I know what is happening, the case length is a little to long! When the brass goes up in the die, it compresses at the top of the cone making the shoulder bulge a little. Guess I have a bunch of extra work ahead of me salvaging everything but the brass! I hate wasting brass! __________________ The road to hell is paved with Democraps!

May 23, 2007, 04:23 PM	#4
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	"...have to use excessive force to get it started..." Have you chamfered the inside of the case mouth?

May 23, 2007, 06:01 PM	#6
azredhawk44 Junior member Join Date: September 28, 2005 Location: Mesa, AZ Posts: 6,465	45auto45: Pull the case mouth expander ball out of your die and measure it. IIRC, you had another thread running a while back where you were having similar problems with the case mouth not accepting bullets. Sounds like the expander ball is too small, or just on the cusp of being too small.