Do necks thicken?

[Joe R]

Ok guys,
As a newbie I have to defer to experience, so I apologize if I was leading someone astray. It may also be possible that there is more than one way to solve the problem depending on your method.

It could be because SS pins remove all carbon, whereas traditional media leaves some residual carbon in the necks. I spoke to one of the techs at Federal and he told me that all their brass gets annealed and then polished. The only exception is the 7.62x51 that are made for the military. I failed to ask why. But if I know DOD I would guess there is a reg somewhere dealing with that. Just a guess.

Kindest regards,

Joe

 

[CatShooter]

Ok guys,
As a newbie I have to defer to experience, so I apologize if I was leading someone astray. It may also be possible that there is more than one way to solve the problem depending on your method.

It could be because SS pins remove all carbon, whereas traditional media leaves some residual carbon in the necks. I spoke to one of the techs at Federal and he told me that all their brass gets annealed and then polished. The only exception is the 7.62x51 that are made for the military. I failed to ask why. But if I know DOD I would guess there is a reg somewhere dealing with that. Just a guess.

Kindest regards,

Joe

The 7.52x51 that are made for the military ARE annealed, but are NOT polished. They look like Lapua cases.

 

[Joe R]

The 7.52x51 that are made for the military ARE annealed, but are NOT polished. They look like Lapua cases.

That's what I meant to say.

 

[bigedp51]

Started getting signs of overpressure with my primers flattening and cratering. Rifle is a Rock River AR. 7th loading on my .223 Lapua brass. Annealed them after 3 loadings and again after the 6th. Minimum loads of 25.5 gr. Varget pushing a 65 grain Sierrra. Was curious so I checked the neck thickness of my reload against a quality Winchester round. Winchester measures .246 and my hand laods measure .248. Is my brass thickening in the neck and causing the neck to be tight in the chamber and causing slight overpressure. Also had a loss of accuracy with my last loading and when I used the factory round I'm back to nice little 3/4 inch groups. Hate it when my handloads aren't up to factory loads. Thanks

timvv50

If you full length resize your necks can thicken because the brass can only move upward into the neck when FL sizing. And this can be even more pronounced if small base dies are used, and the people here who told you otherwise are neck sizing only.

Your Rock River either has a Wylde chamber or a standard military 5.56 chamber, and as you can see below the necks of both these chambers give you ample neck clearance.

Below is the milspec requirements for Lake City and commercial contract 5.56 cases and the neck thickness is .0125-.00020. This will give you a comparison for your Lapua neck thickness.

I would give your chamber and bore a good scrubbing, check your scales for calibration and double check everything else. My guess is carbon buildup and on a over gassed AR a lot of powder residue can be blown to the rear so make sure you scrub the chamber well.

CatShooter, sorry but you asked where the brass comes from and when you full length resize if flows forward.

 

[CatShooter]

CatShooter, sorry but you asked where the brass comes from and when you full length resize if flows forward.

That is what I said... Wassamattaforyou???

"Necks do not "thicken"... if you have a headspace problem, and are constantly pushing the shoulder back, then the base of the neck, just at the shoulder junction can get a little thick, but by that time, your cases are ready for the trash bin."

But that is not neck thickening - if a 1/2" long neck "thickens", it means that 1/2" of neck gets thick. If you size a 30 cal neck to 243, the neck gets thick(er)...

Growing cases from oversizing or headspace problems, thicken the base of the neck at the shoulder - by the time the problem shows itself in "The neck", the case has stretched so much that you have spent a week trimming it.

 

[dkhunt14]

I do not neck size and my brass gets thinner with multiple loadings. I have measured this with my neck mikes and measured to one ten thousandths. It is hard for brass to flow around a corner. That's what I believe causes a donut. I believe it is why Ackley cartridges doesn't need trimmed as much. I keep track of how thick my brass is so I can run the same tension. Maybe in a fairly straight walled case it can. If it would flow forward you would think it gets thinner. Some of my cases only get one ten thousandth thinner after 10 to 15 sizings. Now this is on custom chambers with 3 thousandths total clearance and I only bump .002. Matt

 

[bigedp51]

dkhunt14

A AR15 doesn't have a custom tight chamber, in fact the chamber is .002 larger in diameter than a standard SAAMI chamber.

I just neck turned the cases fired in my AR15 A2 HBAR for the second time after being fired four times and the necks were tapered. Meaning when I turned the necks the second time I removed more brass as I got closer to the shoulder.

So just remember the more the case expands when fired the MORE forward movement of the brass you will have when the brass is "compressed" when full length resized. "AND" if small base dies are used you will have even more brass flow toward the neck.

Bottom line if you do not reload for a AR15 with its "large" chamber you should not be commenting about brass flow and neck thickening.

When full length resizing Newton was correct........ For every action, there is an equal and opposite reaction.

I just switched several of my RCBS dies to Forster decapping spindles and have been monitoring the neck thickness and runout.

Below a RCBS .223/5.56 small base die with a Forster decapping spindle installed.

The RCBS expander button on the left is .0015 smaller in diameter after reducing its stock diameter, I did this because I did not want to crimp the bullets and have more neck tension. The expander button on the Forster unit is the standard .223 in diameter and I'm getting far less runout with my finished rounds. I have two 100 round boxes of Lake City brass that I have been testing in my HBAR and checking each case after being fired and I can assure you the necks do get thicker. And my neck turning tool doesn't lie when it removes brass.

 

[bigedp51]

Case necks can thicken.

Where does the metal come from to make it thicken?

I shoot several rifles with turned necks - si I know thwir exact thickness to 0.0001"... I have never seen a neck get thicker.

So where does the metal come from to make a neck thicker??

CatShooter, sorry but you asked where the brass comes from and when you full length resize if flows forward.

That is what I said... Wassamattaforyou???

CatShooter above are your exact words and you said they do not thicken.

Your words above are exactly what a person who neck sizes only would say and you have already told us you neck size only.

And when you full length resize far more of the brass flows upward in the die as you resize. The 200 5.56 Lake city case necks became .001 thicker starting at the shoulder and tapered off to the .011 at the case mouth, and the necks were turned to .011 the first time and after being fired four times.

 

[BoydAllen]

There are a couple of reasons that the military wants the annealing visible. One is that so that it can be visually verified.

Way back (sometime in the 1920s I think), there was some nickel plated (30-06) match brass made that did not get annealed after the final forming. The result was much higher neck tension and neck welding of the cupronickel jacketed bullets in the case necks, to the extent that bullet pulling forces ended up being so high that rifles were blown up. There may have been fatalities. At the time it was put off to the then common practice of greasing bullets as they were being shot.

Another reason is that studies showed that anything that was done to the brass in the way of polishing it tended to reduce the life of the loaded ammo. This may have been because it has been common for polishes to contain some ammonia, or because the oxide that was removed in the process gave some protection from further corrosion.

 

[DBailey]

I've had it happen with a tight chambered 6.5-284. I didn't ask the brass where it came from, I just trimmed it off.
If I had to guess I'd say it comes from the same place as the brass that makes trimming the case neck length necessary.

I'm not here to have an internet expert debate. The OP asked if it was possible and it is, although it's very unlikely that it is his problem with a factory chambered AR.

If he'll just stick that bullet in the fired case he'll know for sure.

Sticking a bullet in a case doesn't prove anything. You can take a properly turned case with the right clearance and fire it and a bullet won't fit after fired. Brass springs back at different rates. Matt

It proves plenty, and it's reloading 101.
If you have a factory rifle (which the OP apparently does) you have a problem if a bullet will not slip into a fired case from that rifle.

On the brass spring back thing. I don't shoot point blank bench rest so I can't comment on their calibers. But I do have experience with a few tight neck long range calibers, and regardless of the brass spring back rate I can tell you without a doubt that if you have more than a very slight resistance when inserting a bullet in your fired case you are running to tight. Not only are you flirting with disaster, you'll shoot better and much more consistent if you open the neck clearance up a little.

 

[artbosco]

Read this on the properties of brass: http://www.kenlightmfg.com/cartridgecaseannealer.htm Forget the annealing portion.

 

[Frankr]

All I can say is case necks can and do get thicker. I do not think it's normal but it does happen. a long time ago
I had a 22ppc very accurate. sub 1/4 moa. but on the third firing it would go from shooting .200 to .550 what we found was the neck's had grew in diameter .003 they were turned but could never get them to shoot. we shot sako,norma,Lapua's ect . we could never figure out what caused it. maybe high pressure in that chamber. but we re barreled it to 22ppc with another chamber and never happened again. a 6 dasher would thicken up it's neck about half way up the neck I had re turn them several times. hun it has a 40 deg shoulder. all I really know is if you run into necks that thicken up and you can, best to rechamber. Now that I know a lot more I think it could be a die matching problem but with the 22ppc we neck sized only. so who knows... I move on and don't dwell on it. I do know that most of my rifles do not do it. if I do run into it. it's gone.

 

[timvv50]

wow I am anxious to see what a headspace gauge tells me and dully noted about carbon buildup. It also is worth noting unit shot great with factory rounds. Thanks

 

[rogn]

Every rifle and every situation is individual in nature. As far as tight neck and bullet pull goes, a long time ago I shot "Hunter Class" quite successfully, and in several years of competition I never neck sized. The fired cases would not accept a bullet without some force. The force required to seat was easily monitored with a hand seating die. The consistency of these loads was very impressive, as at 265 yes groups for as many shots you wanted stayed under a number I won't list due to not wanting to start another diversion. These necks never thickened, but over time and multiple reloads would get a tad thinner due to simple wear.
Now Im messing with ARs, mostly the 10 form, here the brass does all kinds of things. I believe this is due to the generous clearances/tolerances, specifications dictated by autoloading function. As mentioned cases go frequently every firing, sometimes a tad when fired, but almost always when FLSed. As I understand all case brass is drawn and by design is tapered from the web to the mouth. When as has been described the brass from the "swollen" base and body is forced back to its original shape the walls are forced forward, hence case lengthening. Push that taper forward and the neck gets some extra unwanted material.