INFO: Neck sizing vs FL sizing

So there seems to be a bit of debate on the Internet gasp shock horror someone on the Internet is arguing? Nooo! about Neck Sizing vs Full Length Sizing brass.

Personally, I FL in specific situations, unknown brass; when I am changing brass from one rifles to another; it has grown beyond neck sizing (although I should really start shoulder bumping); or straight wall calibres. Other than that, I batch brass and neck size pretty much 99% of the time. Hunting loads and all. Never had an issue. Personally, I just hate brass prep. Trimming, cleaning lube, etc. Neck sizing seems to do the job well, no mess, no lube, no run out to trim, etc. However, there seems to be one joker I keep seeing on YouTube that (I guess) made it his life’s mission (because, ran out of bacon maybe) to preach in favour of FL and against Neck Sizing.

(@sungazer @Gwion @Supaduke and the rest of the competitive crowd whoever you are)

What do you guys do? Why do you do it and have you tested both to get some defensible data on the subject?


It is as you say, juststarting. Neck size, then bump shoulder when required for easy chambering. Check length each reload and trim as needed, and full length also as needed. This is the usual method for competitive shooters in full bore, and followed by most others with great success. I don’t know what the " YouTuber" is using but will say that most Swiss rifles will benefit from FL sizing every load, as do early Steyr straight-pull rifles, those chambered for the M31 cartridge do not. I found the M14 needed “loose” cases to fire consistantly, as did the Mini14, does this “YouTuber” also use a semi-auto? Perhaps this is why he promotes FL every round? Cheers.

My looking at the topic, I think it’s pro benchrest shooters that eant everything consistent, plus with the current full length size dies that have bushings. They very slightly bump the shoulder and minimal necksize can make brass more consistent and last longer than just full length resize

Most things I neck size only. I FL resize 7.62 X 54r because for whatever reason they don’t offer a neck sizer. You can bodgy it with a .303B neck sizer but I can’t be arsed playing with the settings.
I haven’t done the science but I accept the general consensus that neck sizing only extends brass life. I also believe the theory that fireformed cases offer better gas sealing and consistency.
Having said that. My M39 Finnish Mosin fires FL resized ammo every time and is one of the most accurate rifles I have. My Swedes are both very accurate. Both fire factory and reloaded ammo with excellent results.
I have yet to reload for my Swiss rifles but they shoot factory ammo very well.
My .303’s however , have benefited greatly from fireformed brass.
My conclusion.
A tight chamber , it does not make much difference between neck only and FL resize. It may infact benefit from FL resizing to aid extraction.
Loose chambered rifles like classic military .303s benefit greatly from fireformed brass, in regards to accuracy. Mud and dirt ingress fouling chambers etc obviously no longer an issue.

Bit late to this party but i think it depends on the rifle/chamber and what you are trying to achieve. I have had a few people arguing for the FL sizing in F-class but the way i see it this is probably more a case of having a match grade chamber (very tight tolerances) and dies reemed to spec for that chamber.

Personally i find neck-sizing fine for a pleb shooter like me.

Someone (who may or may not also be on this site- can’t remember but it was pre this forum) gave me a good tip that worked for me. Fire form your brass with the bullet jammed into the lands: this allows the neck to form evenly in the chamber: then only size 2/3 of the neck which makes the shoulder and neck chamber as close to concentric as possible.

May not have explained that very well but it works well enough for me in my rifles.