Will brass "grow" after resizing?

[riflewoman]

There MIGHT be an advantage to hold the case in the die for a second or two. Depending on the spring of the press, the viscosity of the lube etc, it might take a second for all that to work itself to an equilibrium.

 

[Lefty Trigger]

Well you guys are all correct, seems like the problem was/is that I ruined a bunch of that brass by getting it too hot. The brass went soft I guess and was collapsing at the neck because of the die bushing. With the shoulder deformed the brass would not go into my Sinclair shoulder gauge properly for an accurate length measurement. I got those 20 cases back that my friend hot salt annealed and tried to resize them, worked perfectly and went right to size and stayed at that size. Currently looking into purchasing my own kit to salt bath anneal.

 

[Uncle Ed]

If you make a workup load with new brass starting at the suggested starting load and work up to max, the fired cases will have different shoulder locations. Meaning the chamber pressure will effect the shoulder location in relation to the chamber.

On the flip side of this I buy bulk once fired 5.56 and 7.62 Lake City cases that were fired in a variety of different chambers. And when sizing these cases if I didn't pause for several seconds and use Redding competition shell holders there will be several thousandths variation in shoulder location.

Below Dillon and JP Enterprise .308 case gauges showing variations in gauge diameter. And the same case is pictured in both gauges. The once fired Lake City case pictured was resized in a standard Forster full length die. And brass spring back after sizing is keeping the case from dropping all the way into the gauges. "BUT" when these cases are full length resized in a small base die they fit in my gauges and Savage .308 chamber.

Pausing does help minimize brass spring back and having more uniform shoulder location and body diameter. And there are YouTube videos showing the benefit of pausing at the top of the ram stroke. When you full length resize the case you are reforming the case to a smaller size than when it was fired and the brass wants to spring back to its fired size. Just like why a fired case springs back from the chamber walls when fired. And a case fired in a semi-auto should be .003 to .005 smaller in diameter than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably.

Bottom line, brass spring back after sizing and firing does happen, and how much spring back is governed by brass hardness, and by chamber and die size.

Some competitive pistol shooters that pick up range brass have to use smaller diameter dies to compensate for brass spring back and the chambers the cases were fired in.

Lee U Carbide Undersized Sizing Die
https://www.midwayusa.com/product/1012827841/lee-u-carbide-undersized-sizing-die

Lee U Carbide Undersized Sizing Dies are great for reloaders looking for ultimate feeding reliability in their handgun. These dies undersize brass between .002" and .003" smaller than other Lee Carbide Sizing dies. Ammunition with undersized brass cases will chamber each and every time it is loaded out of a magazine giving reliable chambering each time a round is stripped out of the magazine or loaded into a cylinder. Competition shooters rely on having ammunition that will feed and chamber each round of ammunition as it is stripped out of the magazine. One of the other benefits reloaders have reported when using Lee U dies is increased consistency and accuracy in loaded rounds because these dies help increase and provide more consistent neck tension on loaded bullets.

And at the Whidden website they sell expander kits from bullet diameter to .004 under bullet diameter. And this is to control bullet grip from sizing and expanding the case neck and brass spring back.

 

[3GRacing]

I have purchased once fired LC .308 MilSurp brass which is usually 10thou plus over for my chamber. If I don't pause at the top of my stroke I'll get erratic measurements using Imp sizing wax on a Redding UltraMag and a Dillon Die.

 

[Clancy]

Well you guys are all correct, seems like the problem was/is that I ruined a bunch of that brass by getting it too hot. The brass went soft I guess and was collapsing at the neck because of the die bushing. With the shoulder deformed the brass would not go into my Sinclair shoulder gauge properly for an accurate length measurement. I got those 20 cases back that my friend hot salt annealed and tried to resize them, worked perfectly and went right to size and stayed at that size. Currently looking into purchasing my own kit to salt bath anneal.

I hate being that guy that says told ya so................ so I won’t.

You’re lucky all that came of it was ruined brass.

 

[chop house]

Yeah Here is a snapshot of some creep data published here way back in the 1960s. https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph101.pdf

There are couple of samples that might be of interest. There is one at 84%cold drawn at 400F and one at 37% at 300F. The way to read this is that it takes the applied stress of “Y” to give the creep strain of “X” . 50000 psi applied stress give about 1 millionth of an inch per inch per hour. So .004 inches of creep on a 1.5 inch basic dimension at this stress and temperature would need about 111 days to complete.

So there’s something else going on here.

i have a question. so, creep is cumulative, as is anneal as regards to time over temp. BUT let's say in my attempts to anneal i don't quite reach desired temp/time. have I done anything to soften the brass, or nothing at all. or, more likely, would the mouths be properly annealed but not down on the shoulder (due to concentration of heat)? AND, if one does an improper job say, 3 times, would the desired effect eventually be obtained? OR, put another way, is anneal time/temp dependent on the hardness of the brass at the start? thx

 

[chop house]

and another question. if, on firing, you have marginal starting force due to well annealed case mouths, 0.0015 neck 'tension', and very little bullet seating depth in the neck can this lead to necks not sealing. At first, it would seem the soft necks would help the seal, however the bullets may be released too soon, at too low of start pressure? btw loads are with mid-burn rate powder for the bullet/cartridge combo and very near book max.

 

[riflewoman]

i have a question. so, creep is cumulative, as is anneal as regards to time over temp. BUT let's say in my attempts to anneal i don't quite reach desired temp/time. have I done anything to soften the brass, or nothing at all. or, more likely, would the mouths be properly annealed but not down on the shoulder (due to concentration of heat)? AND, if one does an improper job say, 3 times, would the desired effect eventually be obtained? OR, put another way, is anneal time/temp dependent on the hardness of the brass at the start? thx

The anneal “critical temperature” (the temperature where recrystallization occurs) is dependent on the amount of cold work and residual energy left in the brass. If the brass is heated below this temperature a significant amount of this residual energy gets relieved but the dislocations and “slip planes” remain as the metal has not recrystallized. The softening is incomplete. Since the residual energy is gone, repeating the process doesn’t do much.

and another question. if, on firing, you have marginal starting force due to well annealed case mouths, 0.0015 neck 'tension', and very little bullet seating depth in the neck can this lead to necks not sealing. At first, it would seem the soft necks would help the seal, however the bullets may be released too soon, at too low of start pressure? btw loads are with mid-burn rate powder for the bullet/cartridge combo and very near book max.

In a rifle the bullet starts to move during the ignition phase when pressures are low. To give an idea a 400 pound bullet pull in a 223 only requires 10000 psi acting on the base of the bullet. The military specifies only that the bullet pull is not less than 45 pounds in the specification for M855 5.56 mm ammo. For 7.62mm M118 it is 20 pounds. Then the bullet stops while it engraves from the rifling. There the pressure builds enough to seal the chamber by expanding the case neck. Depending on seating depth and relation of the bullet to the lands, the bullet may still be partly in the neck while it expands.

 

[Richard Coody]

this experience is why i cringe every time i read about do-it-yourself annealing ideas on this forum. better not to do it at all then do it wrong. we see here he obviously overheated his brass. well we all know consistency is the key to all things reloading. what do you think the odds are using this method that all the brass is being annealed consistently. experiences like this are why so many have a bad opinion of annealing.

 

[cw308]

Agree , sometimes less is better . I full size no heat or neck turning . My work better if your shooting with the rifle laying in the rest an your only contact is pinching off on the trigger . Once you settle in behind your rifle , let the games begin . Can't only blame the round . Keep it simple not sloppy and see if it makes a difference. Haven't had the problem of my brass changing after sizing .