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.308 cartridge lenghts

3K views 9 replies 7 participants last post by  Rascals 
#1 ·
Hello all, I have a quick question about .308 cartridge lengths. I recently acquired a new ptr91, and yesterday I went to pick up some rounds. Unfortunately I did not have much time, and as it's a new rifle, I wanted several different brands of ammo, to make sure I didn't get tons of rounds my rifle won't eat. So in my haste, I picked up a box of soft point, and a box of SPCE(soft point cut edge I believe?). Now when I got home, I realized on the box that I had accidentally picked up more specialized rounds than the usual FMJ I buy for my other rifles, and as I am completely new to .308, I was somewhat concerned, that these cartridges are different overall lengths (Everything IS marked .308win or Winchester, and this is what my rifle is stamped as), and wanted to ask to make sure that these are safe to cycle through my rifle. Thanks in advance for any help!
 
#2 ·
overall length isn't as much an issue as length to the shoulder. It's almost 1.6 inches from the base to the shoulder, and the length of the case is 2.18".

As long as it says .308 Winchester, you'll be fine.

here's a picture of all the various measurements of a .308 shell:
 
#3 ·
I load 308's in different lengths, one is standard for all 308s and then some for individual rifles. The first ones so they can go into any gun that is 308. The others are custom lengths for individual guns. Some are as much as .145 longer then max overall. Why because we shoot long distance and it makes a difference to have your ammo set up for a gun when you are shooting out at 1500+ yards. But if you took those rounds they would not even fit into the magazines for a PTR, a FAL or a M1a, oh and the AR10. If its commercial its fine for your gun.
 
#4 ·
Ok thanks everyone! I figured they were ok, but wanted to get the knowledge from more experienced people in this round before I risked having a catastrophic malfunction from being hasty haha. Better to admit lack of knowledge than to turn it into stupidity and hurting yourself.
 
#7 ·
FYI, one of the reasons for differences in overall cartridge length is to improve the accuracy of your specific rifle. Rifles chambered in 308(or any other) will have different length throats. One theory is that you want the fat part of the bullet(ogive) to be right next to but not touching the rifling of the barrel. They will measure the distance required to be just before the rifling and load their cartridges to that length.

Some long range shooters believe the theory and some don't.
 
#9 ·
Truth of the matter is that it's different with each rifle, bullet and load

It's a fact and not a theory. A person just needs to try each particular loading with varying lengths to find where the most accurate load will be at.

Light for caliber bullets generally won't get close to the rifling, medium and heavy for caliber bullets can be seated further out.

Some loads can benefit with a good amount of freebore travel and some are more accurate getting closer to the rifling.

Unless you try all combinations, you just won't know. Most folks won't take the time either. Those who do, know!

I seat 115gr Nosler BT's at .002 off of the rifling in my 25-06. Sierra 120gr SP at .005. This doesn't work for every 25-06 just my rifle and the particular bullet/load combination I'm using.

It's called interior ballistics, the other part of the equation is exterior ballistics, then you have the terminal ballistics.......all 3 are different but combine to get you to your objective.
 
#10 ·
There is a reason some of us spend so many hours working up loads for each of our Toys. So we can enjoy our sport and also be as good as we can to show respect for our prey that we harvest to feed our family year in and year out. We have not bought meat from the grocery store now for something like 12 years. But then again I still wonder how so many people go hunting every year and not get there animals. Maybe they don't practice enough or figure out the most accurate loads for there weapons? They don't understand why they cant hit anything beyond 500 yards and don't even think 1000, or 1300 yards is even in the scope of reality. But some of us think of it as a practice session of fun times.
 
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