223 Full Length Resizing

I asked that question some time ago. So neck sizing is fine when used in the same Bolt gun as it forms to that chamber.

Why is it not just as fine if used in the same semi auto gun? Isn't it fire formed to the chamber of that semi auto as it is to the bolt gun??

It comes up from the mag and is slammed forward into the chamber same as bolt only it does it automatically and with more force.

So I still do not get it, I follow the procedure, but still confused.

That is the million dollar question.

The brass is still expanding when it is yanked out of the chamber.

FLR is recommended when you need reliable feeding, e.g. hunting. This is because neck sizing only can result in tight fits that may result in a jam.

So if you don't mind having your semi auto jam, then neck sizing only may be for you and hopefully give you increased accuracy.

Case clearance is something that is carefully studied in military actions. This clearance is 100% critical for reliable function and safety.
This chart came from AMCP 706-247 “ Ammunition Series, Section 4, Design for Projection”, I highly recommend reading starting section 4-76 Cartridge case and Chamber Design”


Many bolt gunners are able to get away with reloading techniques that will positively jam a semi automatic mechanism. Some think as long as they can beat the bolt closed and knock it open with a block of wood, they have demonstrated expertise in reloading. Neck sizing, partial neck sizing, etc, these reloading techniques will work with manual mechanisms for a time but in time even beating down the handle won’t close the bolt and the case will be so stuck in the chamber that a cleaning rod is required to knock the case out.

Factory case dimensions will provide the highest degree of function in a semi automatic mechanism. Cases that are larger than factory are more likely to drag in the chamber causing a failure to extract. Full length sizing in a standard die will not reduce the case to factory dimensions, a small base die gets it closer.

Anyone actually try partial necsize in a semi auto? I bet iit's fine with harder/older brass.

I full length size 223.

I small base size 308 win. (THAT, is a positively good workout, by the way. Takes a lot of effort.)

edfardos said:

Anyone actually try partial necsize in a semi auto? I bet iit's fine with harder/older brass.

Click to expand...

Personally, I would not try partial neck resize in an AR. I have had enough cases stuck in one of my ARs that a full length sizing die did not size them enough.

It is no fun getting the stuck cases out.

But have at it if you want to try it.

In a semi-auto rifle, case ejection is often starting before the brass has contracted and is fully released from the chamber walls. This means your brass is usually stretched more than it would be in a bolt rifle, and won't usually fit easily back into the same chamber it was fired from. The body is usually fatter and longer to the shoulder datum than the chamber itself, and can cause cases to stick on loading, preventing the bolt from closing completely and can occasionally even cause a slam fire.

Ifishsum said:

In a semi-auto rifle, case ejection is often starting before the brass has contracted and is fully released from the chamber walls. This means your brass is usually stretched more than it would be in a bolt rifle, and won't usually fit easily back into the same chamber it was fired from. The body is usually fatter and longer to the shoulder datum than the chamber itself, and can cause cases to stick on loading, preventing the bolt from closing completely and can occasionally even cause a slam fire.

Click to expand...

Thank you.
This is the closest to an actual explanation or answer yet.

Try it, or I wouldn't do it, really is no answer. Both the OP and myself were trying to understand why. No one is beating on a bolt or trying to get a case to fit. or take anyones word for it, simply explaining it is nice. As mentioned I do FL size for semi autos, why ? Because we always do it that way.

The answer is pretty darn obvious, if you have done enough neck sizing for a bolt rifle. Eventually, you have to FLR, right? When do you do this? When it becomes difficult to close the bolt. That's fine on a bolt action, cuz all you have to do is press harder.

Well, you could wait for your AR to start jamming, but by then you might have a round light off OOB. Apparently, the design of the AR can allow a round to fire (or slam-fire, maybe? I'm not sure of the specifics.) even before the locking lugs have engaged.

Even if it were completely safe, who wants the increased risk of a jam? Now add the way that AR's spit out brass, how could you even be sure that every piece of brass you reloaded was fired out of the correct gun? Even if you kept track of number of firings to be able to bump the shoulders back before problems arose, you'd have to figure out how to keep stray pickups from infecting your brass.

"This means your brass is usually stretched more than it would be in a bolt rifle, and won't usually fit easily back into the same chamber it was fired from."

This totally makes sense to me. I've only been hand loading for six months and the cases fired from our two AR-15's require quite a bit more trimming than cases from my 6.5x55 and .270.

Ifishsum said:

In a semi-auto rifle, case ejection is often starting before the brass has contracted and is fully released from the chamber walls. This means your brass is usually stretched more than it would be in a bolt rifle, and won't usually fit easily back into the same chamber it was fired from. The body is usually fatter and longer to the shoulder datum than the chamber itself, and can cause cases to stick on loading, preventing the bolt from closing completely and can occasionally even cause a slam fire.

Click to expand...

This is the main reason.

You can find reference to this in this article.

http://www.zediker.com/downloads/14_loading.pdf



the bolt can unlock before the case has fully
retracted from its expanded dimensions. We’re
talking about milliseconds, but that’s all we have
devoted to the entire process. The net result is that
some amount of additional expansion frequently
occurs in a case fired through an M14.

Best to full length size for an M16A1

Tried neck sizing for a M16A1. One magazine didnt like the fat bodies, slow feeding causing jams. IMR 4198 at maximum does not expand the brass as much as Nato ammo or high pressue loadings. You would need to FL size every other loading. With maximum full pressure loading, your going to have to FL size every time. Case life is the same when using a expander ball, FL or neck sizing dont matter. The necks go first.

223 Full Length Resizing

The brass is still expanding when it is yanked out of the chamber.

Click to expand...

Not in an M16. The question is not about M14 rifles.

It does in my AR-15's, my Mini-30. my Browning BAR's and my Mini-14. YMMV.

...and the slower the powder the more the increased expansion.

There's significant more lag time in the unlocking action of an AR-15, than there is a Mini-14, BAR, or M14 rifle. Unless you're doing something wrong (with powder), the bullet will be out of the muzzle before the round begins extraction. That isn't strictly true for the browning actions, the action is much more direct. (Ar15 bolt has to move quite a lot to unlock, that takes time; by the time it happens, that bullet is GONE and the gas pressure is vented)

EDIT: Pistol length gas systems with high port pressure, 16" barrel, and fast burning powder, might make my above statement false, but they're the exception to the rule.

If you want 100% evidence, firsthand experience is your best teacher in this instance. I've been neck sizing my .308's for my one and only .308 bolt gun and had several occasions where a seemingly proper round chambers fine and expands just enough to cause a sticky or stuck bolt that requires more than "gentle persuasion" to open. This would probably cause a FTE in a semi auto or a missed follow up in a hunting situation.
In this case, there is no harm in trying it out yourself so long as you know how to extract a stuck case from your gun. With this experience, I FLR all the rounds I intend to use in semi's and for hunting in the bolt gun.

thanks SlamFire1
I'll take you up on your recommendation of reading AMCP 706-247 “ Ammunition Series, Section 4, Design for Projection”

I'm always interested in this kind of reference.

if anyone else is interested in this book, I found a downloadable pdf file here at this link:
http://www.dtic.mil/dtic/tr/fulltext/u2/830296.pdf

I'm stubborn, I tried necking for the AR and ended up learning the hard way. It's pointless first of all, as there is little, if anything to be gained with regard to accuracy, it's not a bolt gun. I had the now and then minor sticky extraction issue at first, it took getting a case stuck really good for me to go back to FL sizing. In fact I started using a SB die for my Rock Island because I had a sticky extraction with the standard FL die. Since going to a SB die, I have had zero cycling issues over the last 5 years.

So, full length size at the least, and using a SB die is not at all extreme when it concerns reliable cycling for an AL rifle, or MG.

GS

I have seen it tried.
There was a shooter with some sort of AR-10 hereabouts. He got tired of paying for factory loads and set up to reload. He asked an experienced handloader how to go about it. Unfortunately, he did not know the novice was shooting an auto instead of a bolt action like his, and recommended neck sizing.

He wasn't a shooter at the next match because his rifle would not handle neck sized cases. He sat that one out and ordered a full length die.

I reloaded ONE time with out a FLR. Stuck the heck out my bolt twice in one mag. For an AR, you better use a FLR or find yourself down at the range with a inoperable gun. I did it.