Neck sizing brass for AR15?

[dpaqu]

I was full length sizing some brass I fired in my new AR15. I noticed that it did not take all that much force to get the job done. I took a FL sized case and compared it to an un-sized case and noted that it was just bumping the shoulder, but more than anything it was resizing the neck. I took a un-sized case and chambered it in my AR and noticed no difficulty in doing so.

Can I just neck size my cases until they don’t chamber? I know everything I have read says not to but I am one of those guys that wants to know “why” all the time.


Forgive me if I posted this is the wrong subforum.

[RU shooter]

What I did in my AR was to just partial FL size the case as to not bump the shoulder back ,The gun had a match chamber and I never had a FTF just kept the chamber clean .

Tim

[mike in co]

yup...as long as you pay attention to what you are doing. i have one that i neck size only till any resistance is "felt" in chambering.

mike in co

[Baron von Trollwhack]

Use a means of checking your fired cartridge headspace. If it is OK then partial neck size , but sometimes it takes a full power firing or two to really blow the case out, and you must check as a partially resized , fully blown out case grows in PARTIAL resizing and the shoulder diameter at the case body to neck transition will be too large and cause a jam. Sample enough to be sure. Batch process. You don't want to make 450 beauties , most of which jam. Clearly you must know your fully blown out HS too.

BvT

[shotman]

If your reloading to shoot then you are not looking at max loads. The military case is stronger so it should be fine for neck sizing for several fireings I use neck for a rem 788 and have never had to FLR so far

[NuJudge]

For semi-autos, especially ones such as the AR-15, which do not have primary extraction, just neck sizing is not something I would do.

The cartridge chambering very freely on semi-autos is supposed to considerably cut down the incidence of out-of-battery or slam firing. Out-of-battery firing frequently destroys the rifle and occasionally injures the shooter and bystanders. Fulton Armory's website has some pictures of AR-15 rifles that fired out of battery.

Other things that reduce the incidence of out-of-battery or slam firing include: adding a firing pin retraction spring or lightening the firing pin on semi-autos reduces slam firing from some firearms prone to it. Harder primers reduces slam fire incidence. Loading semi-autos from the magazine, and not inserting a cartridge into the chamber and pushing the bolt release to drop the bolt on the chamber, is supposed to reduce the incidence of out-of-battery firing.

I'm not aware of a AR15 bolt that features a FP retraction spring, but when it's available I'll buy one. The only reason I don't have a Titanium firing pin in my ARs is that when a primer pierces (not infrequent on ARs), the Titanium errodes and then you pierce all primers.

[pbbutz]

+1 totally agree


For semi-autos, especially ones such as the AR-15, which do not have primary extraction, just neck sizing is not something I would do.

The cartridge chambering very freely on semi-autos is supposed to considerably cut down the incidence of out-of-battery or slam firing. Out-of-battery firing frequently destroys the rifle and occasionally injures the shooter and bystanders. Fulton Armory's website has some pictures of AR-15 rifles that fired out of battery.

Other things that reduce the incidence of out-of-battery or slam firing include: adding a firing pin retraction spring or lightening the firing pin on semi-autos reduces slam firing from some firearms prone to it. Harder primers reduces slam fire incidence. Loading semi-autos from the magazine, and not inserting a cartridge into the chamber and pushing the bolt release to drop the bolt on the chamber, is supposed to reduce the incidence of out-of-battery firing.

I'm not aware of a AR15 bolt that features a FP retraction spring, but when it's available I'll buy one. The only reason I don't have a Titanium firing pin in my ARs is that when a primer pierces (not infrequent on ARs), the Titanium errodes and then you pierce all primers.

[Larry Gibson]

NuJudge is basically correct if full powered loads are used. I recommend the use of the regular RCBS X-die for ARs as you also eliminate the need to trim.

The real exception is with cast bullet loads. I found some years back that the LC cases were not expanded enough with my cast bullet loads (225462 over 19 gr of H4895 with a 1/3 gr dacron filler) to require NSing for 8-10 shots. I mostly just NS'd them for 8 firings and then FL sized them. That was pre X-die so I was wanting to get away from trimming. Worked for me in my AR and Mini-14 with 12 and 10" twists.

Larry Gibson

[StarMetal]

I'll have to go along with Larry and NuJudge on this. I also disagree that military brass in this caliber is stronger. I always thing of the older military brass in the 06 and 308 being thicker, but softer.

Another thing that increases when not full length sizing the cases in semi autos is friction....which in turn means heat. I have told the story of my best friend in Tulsa, Ok that had a Remington semi auto in 30-06 and use to load for it with the Lee Loader....which we know only neck sizes. His ejected casing turned blue half way down the case. Once he left a loaded round in the chamber after firing a group and upon ejecting it the bullet and half the case turned blue. An ejected case rolled down the bench one day and melted it's way entirely through the Remington styro foam cartridge box!!! With full length resizing it did none of these things. By the way one of the most accurate hunting rifles I've ever seen...especially for a Remington semi auto.

About the FP retraction spring. Colt tried an unbelievable amount of different firing pin design, including a retraction spring, before settling upon the current design. Maybe they didn't see any benefit to a retraction spring. Again I refer you to, if you want to talk about inertia FP dents and slam fires, to the MAS 49/56.

Joe

[redneckdan]

ARs really need to have the shoulder set back during loading. You need to take a couple cases and load them to max loads and fire form them a couple times to get a true idea of your chamber dimensions. Then set your sizing die to push the shoulder back back between .001-.002" (use .000-.001" for bolt guns). By the time you start to feel resistance its already too late, you would be using the locking lugs to size the case in the chamber. Locking lugs are not designed to do this and the AR lugs are especially prone to galling in these conditions. Best bet is to get either a RCBs case mic or the Hornady case gauging tool and get actual mesurements...if you don't have numbers you are just guessing. By setting the shoulder back .001-.002 you get the best of both worlds; cases chamber easily, but the cartridge also fits the chamber close enough for best accuracy and you are not excessively sizing the cases. No AR-15 has a 'match chamber' (that term means nothing, there is no standard for 'match chambers') that would see any real benefit to neck sizing or neck turning brass, instead of setting the should back a thou or two. Even across the course guns use brass that is set back .001-.002

[Shiloh]

Had mixed results neck sizing. I want it to fire every time. Went back FL sizing. I have "Informal Match" brass as that is as far as I go competitively, and practice or plinking brass. Loaded at mid upper mid-power.

When it gets worn out it goes in the plinking bucket. Fire it till the neck splits, then into the scrap bucket.

Shiloh

[mike in co]

No AR-15 has a 'match chamber' (that term means nothing, there is no standard for 'match chambers')

quite wrong young man.

lots of ar's are shot in nra/cmp/dcm MATCHES.
MOST IF NOT ALL OF THESE RIFLES HAVE "MATCH" CHAMBERS.
and on top of that i have a custom ground/designed reamer for my benchrest ar.
this gun ag's in the sub 2's( as in 5 shot groups under .2 at 100yds). it is shot in benchrest MATCHES.

(there is no such thing as NATIONAL MATCH for an ar, as the government never built them in national match like they did for the m14,garand, and i believe for the 03a3.)


no i do not fl size for this gun...i neck size only.


on the subject of firing pin springs....the ar10 from armalite has a firing pin spring.

you each have to make your own choices for you and your rifle....


mike in co

[waksupi]

There are definitely match chambers. And that is where they should be left, for match shooting. I would not have one in a field rifle. Tolerances are too tight.