Myth or fact

[Char-Gar]

I have heard about bottle neck cases shortening with cast bullet loads . II have never experienced it. I keep my loads in the 1.5 to 2K fps range.

What say the wise ones... Myth or fact?

[felix]

Fact. Low pressure loads can, but not always, shorten the headspace length. High pressure loads do not. Has nothing to do with what boolit or what velocity as far as I can tell. ... felix

[Buckshot]

.............I've not experienced it either. I heard that the firing pin drives the case forward setting the shoulder back a bit each time. Either the firing pin supports the primer to keep it from backing out, or maybe the case scootches back to reseat it?

Regardless, I still seems to me that I have to do that caseneck trimming job every once in awile. Just don't see any shortening going on. Just a bit initially on first firings when the case expands to fill the chamber. New brass or FL sized only.

Normally I keep my brass in 20 or 50 round batches dedicated to one rifle. A few times with a new aquisition I've taken umpity-bunches of times fired brass, FL sized it to try in the new one and I have to trim them to fit. FL sizing squeezes them back out.

.............Buckshot

[andrew375]

I have heard about bottle neck cases shortening with cast bullet loads . II have never experienced it. I keep my loads in the 1.5 to 2K fps range.

What say the wise ones... Myth or fact?

I've never noticed it and some of my cases have been loaded over fifty times. Then again I've long ceased to worry about case length with bottle necked cases as I use Lee collet dies.

[Bret4207]

32/20 Win does it for me. The weird part is the cases don't ALL do it, just some. Strange.

[Bass Ackward]

The only place I have experienced it is with rimmed cases where firing pin blow has nothing to do with it. Go figure.

[44man]

Normally, cases get shorter only with the first firing of new brass as the case expands to fill the chamber. A very high pressure load for the first firing can flow the brass foreward making it longer but with average loads, they do shorten. If you now full length them, they will grow longer even though they will shorten a little on firing as they fill the chamber again. Eventually, you will need to trim.
If you neck size and shoot light loads, they can stay short for a long time.
It depends on your chamber dimensions, how you size and how hot or cool the loads are. Every single gun is different and can give different results. A gun with tight chambers will not shorten the brass much but sloppy chambers will. It is best to adjust the sizing for each individual gun and load to make brass last longer. Shoulders should not be set back more then it takes to close the bolt with a little resistance. Pump guns, lever guns and autos are a different story though because you want the shells to chamber easier.

[scrapcan]

Guys just to keep it straight there are two types of dimensional changes being talked about in this post.

1) shortening of headspace/shoulder set back. Yes I have experienced this with mild loads in 308 win, 7mm-06 AI, and 8X57. Some where with jacketed bullets and others using cast. the 308 was an instance of using slower than usually 150 gr jacketed to tame the recoil on a savage 99. the 7mm and 8mm are a result of using a mild load that the rifles liked. In my experience the shortening will take place and when loaded to a normal or higher pressure case seperations resulted.

2) shortening of caseneck/overall length. I don't think I have had this happen except when fireforming cases on the first forming. Almost always the 7mm-06 AI and the 8x57 made out of 30-06 cases will tend to shorten after full length size/trim to standard length and then fire formed (as stated above).

[felix]

For example, shooting the 22/40 bench gun (222 ackley), I use full pressure loads all the time, but with a faster powder to keep the velocity at 2400 or slightly less. This ended the headspace problem 100 percent, but increased the donut ring which resulted in my neck turning the cases after a couple of shots. After about three times of cutting out the donut, the cases quit the movement. The cases I use are typically reformed 223 because of the extra brass in those cases. Annealing them is a mistake before about 20 times of being fired. ... felix

[BOOM BOOM]

HI,
Do a thread search there is a lot posted on this subject.
I have found that ALL my cases strech in my 7MM/06, w/ squib loads, with medium loads, & hi pressure loads. THE REFERS TO OVERALL CASE LENGTH.
I did a big experement on it last year.
THIS DOES NOT MEAN THAT HEADSPACE WILL NOT CHANGE.
BUT I HAVE SEEN NO EMPIRICAL DATA THAT IT DOES.
So I keep my cast bullet brass seperate (squib & medium vel. loads) from my hi vel. 3000'/s brass.:Fire:

[Larry Gibson]

Guys just to keep it straight there are two types of dimensional changes being talked about in this post.

1) shortening of headspace/shoulder set back. Yes I have experienced this with mild loads in 308 win, 7mm-06 AI, and 8X57. Some where with jacketed bullets and others using cast. the 308 was an instance of using slower than usually 150 gr jacketed to tame the recoil on a savage 99. the 7mm and 8mm are a result of using a mild load that the rifles liked. In my experience the shortening will take place and when loaded to a normal or higher pressure case seperations resulted.

2) shortening of caseneck/overall length. I don't think I have had this happen except when fireforming cases on the first forming. Almost always the 7mm-06 AI and the 8x57 made out of 30-06 cases will tend to shorten after full length size/trim to standard length and then fire formed (as stated above).

As manley describes it #1 is what happens. This NOT caused by the firing pin drivingf the case forward but by the primer explosion driving the case forward and setting the shoulder back. Usually takes 3-5 firings before it is really noticeable. This has been proven time and again by simple experimentation. I have only found it to be the case with LR primered cases. I've not encountered the problem at all with .222/223 cases (has anyone ?).

In some rifles this will lead to miss fires. In rifles (mostly CF types) where the extractor is a good fit and holds the cases securely the cartridge headspace will diminish only the the length the extractor allows. With light cast and jacketed bullet loads of 1500 fps or less I usually dedicate and clearly mark a lot of perhaps 50 cases that are well fire formed. I then drill the flash hole out with a #28 drill. This stops the primer from blowing the case forward andit also improves ignition with the small amounts of fast burning powder (most often Bullseye) used in these loads.

I also have found that cases with the drilled flash holes work best with medium powders and bullets of medium weight in the 1500-2000 fps range. To illustrate I recently completed experiments with the 30-06 using light charges of 4895 under an M2 bullet in an '03. I found 34 gr to be a nice comfortable and accurate load at 2060 fps. However, as these were in FL sized cases the primers were really backing out on the third firing. I fire formed them with a service load on the 4th firing and then drilled the flash holes. The primers do not back out now and headspace of the cartridge has not diminished after 2 additional firings. The shot to shot fps variation has also decreased so ignition is more uniform. Again, I mark these cases (and usually use an odd headstamp lot) and am carefull not to put a regular load in them.

I use such flash hole drilled cases in the 6.5x308, 6.5x55, 7x57, .308, 30-06, 7.65x53, 8x57 and .35 Rem. I have also used them with numerous other cartridges over the years. I use rimmed cases with the flash hole drilled not for the headspace problem but to increase the efficiency of ignition with the reduced loads. Works for me.

Larry Gibson

[trooperdan]

Larry, what size to you open the flash holes up to? I have an '03A3 I'm getting ready to laod for and this seems like a handly solution to a potential problem.

[NVcurmudgeon]

I have had headspace shortening occur with (I guess) low pressure loads in .35 Whelen. Cases formed from .270 or .30/06 may start to misfire at ten firings, when partial full-length sized. At this point, the Wilson case gauge shows less than normal head to shoulder length. When sized in a true neck sizing die, cases have gone a few firings farther. When full power loads with jacketed bullets were used, and the cases were neck sized, there was no headsace trouble. Being a timid soul, I retire cases after ten full loads, so don't know if pushing the brass life envelope with factory equivalent loads would cause misfires.

[joeb33050]

I have twice done this: oiled new primers, put one in the case and measured headspace with various pieces of paper. Then fired the gun-oiled primers = no bang-replaced the primer, fired, replaced and so on for 20 firing pin hits on new primers. No increase in headspace = the firing pin isn't driving the case forward.
I can't understand how the primer backing out will drive the case forward. If you drill the flash hole out and put a long rod in the bore through the flash hole to the primer, and whack the rod, the case won't move forward.
What makes the case go forward?
If there was gas between the bolt face and the case, maybe. But there isn't.
I don't see what makes the case go forward when the primer goes backward.
joe b.




As manley describes it #1 is what happens. This NOT caused by the firing pin drivingf the case forward but by the primer explosion driving the case forward and setting the shoulder back. Usually takes 3-5 firings before it is really noticeable. This has been proven time and again by simple experimentation. I have only found it to be the case with LR primered cases. I've not encountered the problem at all with .222/223 cases (has anyone ?).

Larry Gibson

[13Echo]

What makes the case go forward when the primer fires is the sudden, large increase in pressure in the primer pocket. It doesn't all escape through the flash hole instantaneously so the primer and pocket acts like a piston and cylinder. The primer presses hard against the bolt or block face and the case moves forward against the shoulder.

Jerry Liles

[felix]

Yep, that's why opening up the primer hole is ideal for low pressure loads. ... felix

[Larry Gibson]

Larry, what size to you open the flash holes up to? I have an '03A3 I'm getting ready to laod for and this seems like a handly solution to a potential problem.

I use a #28 drill, will have to measure it when I'm home tonight and report (unless someone has that measurement handy?). I've found that is about the max you want to open them up for reliable support to the primer anvils legs.

Larry Gibson

[Larry Gibson]

I have twice done this: oiled new primers, put one in the case and measured headspace with various pieces of paper. Then fired the gun-oiled primers = no bang-replaced the primer, fired, replaced and so on for 20 firing pin hits on new primers. No increase in headspace = the firing pin isn't driving the case forward.
I can't understand how the primer backing out will drive the case forward. If you drill the flash hole out and put a long rod in the bore through the flash hole to the primer, and whack the rod, the case won't move forward.
What makes the case go forward?
If there was gas between the bolt face and the case, maybe. But there isn't.
I don't see what makes the case go forward when the primer goes backward.
joe b.

13echo and Felix already answered your question. Additionally I have run the test numerous times with live primers. How many firings it takes for cartridge headspace to increase depends on many factors. To name a few; how much shoulder (and angle) the case has, how hard the brass is in the shoulder, the force of the actual primer, how well fire formed the case is, how much taper the case has, etc. With well fireformed WRA 63 7.62 cases it took about 5 primers to get any measureable increase in cartridge headspace. With once fired Peters .35 Remington cases (minimal shoulder) I got misfires after firing 3 primers.

Larry Gibson

[joeb33050]

I'm trying to understand this. If the primer gas is pushing the primer back/case forward, then the increasing-headspace phenomenon will be found when firing a series of cases with JUST PRIMERS. Is this true?
I have read that leaving sizing lube on bottleneck cases/low velocity loads eliminates the increasing-headspace problem, but this doesn't have anything to do with primer gas and a cylinder/piston operation.
JUST PRIMERS?
joe b.


What makes the case go forward when the primer fires is the sudden, large increase in pressure in the primer pocket. It doesn't all escape through the flash hole instantaneously so the primer and pocket acts like a piston and cylinder. The primer presses hard against the bolt or block face and the case moves forward against the shoulder.

Jerry Liles

[joeb33050]

Is this a lead bullet bench gun?
joe b.



For example, shooting the 22/40 bench gun (222 ackley), I use full pressure loads all the time, but with a faster powder to keep the velocity at 2400 or slightly less. This ended the headspace problem 100 percent, but increased the donut ring which resulted in my neck turning the cases after a couple of shots. After about three times of cutting out the donut, the cases quit the movement. The cases I use are typically reformed 223 because of the extra brass in those cases. Annealing them is a mistake before about 20 times of being fired. ... felix

[felix]

It is now. ... felix

[Char-Gar]

OK guys.. I am convinced. I am going to dedicate a lot of 100 LC-54 cases for my new Feaux NRA Sporter. They will be fired the first time with a full snort service load and thereafter necksized only. I will open up the flash holes with a 28 drill. I will keep the loads in the 1,500 to 2,000 fps range.

I would like to use 2400 and/or 4759 as powders with no fillers. How does this sound?

[felix]

Perfect application! Paint the case head backs red with fingernail polish. ... felix

[Larry Gibson]

OK guys.. I am convinced. I am going to dedicate a lot of 100 LC-54 cases for my new Feaux NRA Sporter. They will be fired the first time with a full snort service load and thereafter necksized only. I will open up the flash holes with a 28 drill. I will keep the loads in the 1,500 to 2,000 fps range.

I would like to use 2400 and/or 4759 as powders with no fillers. How does this sound?

Sounds good to me...

Larry Gibson

[Bob S]

I have several lots of cases that have been loaded with nothing but low-pressure cast loads since the late 60's, and fired only in Springfields. A "lot" is 50 cases in an old MTM box, back when the labels had 30 or 40 check boxes to keep track of how many times you loaded them. The cases are several lots each of FA 37, Den 42, and EW 43; all the check boxes were "X"ed out years and years ago, so I think conservatively they have all been loaded and fired over 40 times. The Den 42 cases have been used with 40 grains of WW II surplus 4831 and 311284; the other cases have been used with 15 grains of 2400 and 311291 or the Lee equivalent, both very low pressure loads. The cases are unmodified (no drilling of flash holes, &tc.); the boxes are clearly labeled "For lite loads only". Primers back out from .005 to .010" after every firing, and the edges are well-rounded. They are reloaded with an Ideal 310 tool (neck sized only), and I have not had to discard a single case yet. Even with neck sizing, the cases will interchange in my modest collection of Springfields (and Rock Islands, Remingtons and S-C's ... currently 15 rifles), as long as the bullet seating is done for the shortest throat.

I never measured the headspace dimensions of the cases with a Sinclair or Wilson tool, but it would seem that the cases have been shortened. The claw extractor would seem to both restrict continued shortening, and hold the case for reliable ignition. Even the "generically loaded" cartridges (bullets seated for the shortest throat) will group reliably under 2 MOA in the as-issued rifles; if the bullets are seated for the individual rifle, they will do better than that. I have posted here before the sub-minute groups from my heavy match 03A3, so the case shortening has not been an accuracy or reliability issue. And the cases will most likely out-live me.

Resp'y,
Bob S.