Loading for semi-auto .308


July 7, 2010, 12:45 PM
I posted this question under a different thread that may have confused some people as I've had very few responses. :banghead:

I just bought an FNAR 7.62x51 (.308 winchester) which is a semi-auto. I've reloaded for bolt action hunting rifle 308s before but never for a semi-auto. I've read that you should always use a taper crimp whether or not your bullet has a cannelure (sp?) when loading semi-auto. Can anyone confirm? Should I stick with bullets that have a cannelure? I would appreciate any input on what I might/should do differently when loading for a semi-auto. Thanks in advance.

If you enjoyed reading about "Loading for semi-auto .308" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
July 7, 2010, 01:50 PM
Assuming the gun and magazine feed correctly without battering the bullet tips, crimp should not be necessary.
But, only if you have proper neck-tension on the bullet.
That is the most critical factor in keeping a bullet from moving in the case.

As for a taper crimp?
No, if you crimp rifle loads, you use what the seating die provides, and it is not a taper crimp.
It actually folds or bends the case mouth into the bullet cannelure.

As for crimping bullets that do not have a cannelure?
I have tested accuracy with a very accurate CZ-527 .223 using a Lee FCD crimp die to crimp non-cannelure bullets.
I could tell no difference in accuracy, or at least not enough to be statistically valid.

It seems to work with the Lee FCD collet die.
But I wouldn't try it with the seating die crimp as I think you would see some crumpled shoulders show up.


July 7, 2010, 04:26 PM
i don't really think crimping is a bolt-vs-semi issue, though i agree with rcmodel's post

the issues i've seen loading 308 for semis is that you get lower velocity, you have to seat the bullets to magazine length (which is often annoying), and you REALLY need to double check that your primers are seated properly, and you need to full-length size instead of neck sizing, and with some rifles you'll want to do something so you don't have to catch a bus to go pick up your brass.

July 7, 2010, 04:34 PM
Most sizing dies squish the neck a'plenty that you don't need a crimp.
Some expander balls expand the neck too much - but that's rare.

The most common mistake for rookie reloaders, when loading bottleneck ammo for semi-autos seems to be not getting the shoulder set to the proper spot.
A case gage will confirm whether you got it right.
Use a case gage if you aren't using one already.



July 7, 2010, 05:18 PM
Most sizing dies squish the neck a'plenty that you don't need a crimp.

Have to agree with W.E.G., although rather than use the highly technical term of "squish", I'll just call it neck tension.;)


July 7, 2010, 07:33 PM
+1 on the case gauge. It's absolutely necessary when loading for a semi. Dillon also makes a good case gauge. Cheap and really, really necessary.

I load 7.62 x 51 for a FAL and M14 and shoot both a lot. I also load for a Browning 1919A4. I prefer to use a Lee FCD to get a good crimp but that's not a requirement just my perference as sometimes my ammo gets banged up a bit before it's fired.

July 8, 2010, 01:03 PM
Thanks all. The taper crimp idea was put in my head by one of those pamphlet type books that are published for each of the calibers (can't recall the name). It states that when reloading for semi-auto in 308, you should use a taper crimp. Also saw it online a few places. However, my RCBS seat/crimp die gives a roll crimp, which lead me to my post on here. I've reloaded non-semi 308s a lot with no crimp and always get a good tight neck around the bullet so I'm not too concerned about neck/bullet fit.

As for setting the shoulder, how do you do that? I just full length size my cartridges and then measure the cartridge length to make sure I'm in spec. If not, I'll trim a bit before I load. I'll get a case gauge but I'm just not sure what to do additionally if it doesn't fit/measure properly per the gauge.

July 8, 2010, 01:23 PM
Sizing die adjustment will allow you to push the shoulder back any amount necessay to make the case fit the case guage.

You will see when you get going and try it.


GW Staar
July 8, 2010, 03:45 PM
I think you've already got a lot of great answers. A good primer for loading gas operated autoloaders...especially military ones is found in Sierra's handbook. Or you can download it and print it here (http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm). It covers everything you need to know.

Head spacing, setting the cases shoulder back properly and case sizing are mentioned in the replies above...and in Sierra's article.

The reason for all those concerns, including primer setback, is that gas guns sometimes can slamfire (firing as the bolt closes, before you pull the trigger) and worse, out-of-battery firing, where the round goes off before the bolt closes! You don't have those problems with a bolt gun.

The main point of every reply you got, is that the round has to chamber smoothly, and far enough in to go easily into battery, and with primers not out enough to be hit harder than normal (floating firing pins do dimple slightly even properly set primers).

They can be reloaded safely only if you pay close attention to all the details. I will join the "Do get a head space gauge and learn how to use it" replies.:)

July 9, 2010, 08:45 AM
Thanks all. Ordering a gauges now....

If you enjoyed reading about "Loading for semi-auto .308" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!