Isn't brass supposed to stretch after firing
- Thread starter Wendyj
- Start date
603Country
New member
If any of you didn't carefully read Unclenick's post on belted cases and headspacing on the belt or the shoulder, I suggest you read it again. That's information you won't find just anywhere, and it is certainly worth knowing.
About 15 years ago, or maybe it was 20, my SiL had a 7 MM Rem Mag, and I set up his dies to be sure they would cause the cases to headspace on the shoulder. We got quite a long case life out of that brass.
About 15 years ago, or maybe it was 20, my SiL had a 7 MM Rem Mag, and I set up his dies to be sure they would cause the cases to headspace on the shoulder. We got quite a long case life out of that brass.
condor bravo
New member
Re: OP's post 21--having to trim .308s after every firing.
It has been my impression from day 1 of the OP's initial postings that she has been setting the shoulders back after each .308 firing in order to conform with case length gage dimensions (who needs such a thing?) and this will cause the case to stretch some upon each firing. I have tried to suggest that this practice might eventually lead to case head separation. In short, whether rimless or belted, it's primarily a matter of the correct sizing die setting matched to chamber (fired case) dimension. I load for over a dozen belted mag cartridges and along with rimless, my "trimming" amounts to no more than squaring off the case mouths occasionally. No the brass isn't necessarily supposed to stretch after each firing but guaranteed if you set the shoulder back too much.
It has been my impression from day 1 of the OP's initial postings that she has been setting the shoulders back after each .308 firing in order to conform with case length gage dimensions (who needs such a thing?) and this will cause the case to stretch some upon each firing. I have tried to suggest that this practice might eventually lead to case head separation. In short, whether rimless or belted, it's primarily a matter of the correct sizing die setting matched to chamber (fired case) dimension. I load for over a dozen belted mag cartridges and along with rimless, my "trimming" amounts to no more than squaring off the case mouths occasionally. No the brass isn't necessarily supposed to stretch after each firing but guaranteed if you set the shoulder back too much.
I will tell you who needs such a thing. I do. Or rather did when I started. My shoulders on 308 are barely bumped back and I may or may not have to trim. I just do. I'm not in front of manual but I think 2.005. I just loaded 50 this afternoon and may e half needed to be trimmed. I thinks it's because of the near max loads I was running. Low end and mid range loads were consistent. No trimming necessary. And I did read the post. All of them. I try to learn everything I can via loading books or Internet or other reloaders. And as for that thing as you call it I still reference a few cases here and there with it. You may be an expert but I'm far from it. I'm trying to do this safest way a beginner can. If I don't trust brass I trash it. I inspect after fired. After cleaning. After resizing. After trimming. After seating bullet. I have inserted sizing die and gave 1/8 turn extra. If I don't give it extra 1/8 it feels sticky in chamber. Extra bump lets bolt fit snug but easy to close.
T.Oheir, overworking brass shortens life, even if its a mild loading, improper sizing or oversizing brass can shorten life.
7Mm rem brass sized by standard dies tends to bulge in front of the belt. I use a Forster Bonanza Benchrest Full length resizing die to resize my 7mm rem mag brass, so far I have test cases that have been fire 5-7 times with only normal trimming required, no signs of giving up yet. Larry Willis makes a die that will take this bulge out, I bought it, and never have to use the damn thing it sets up there on a shelf looking on...
7Mm rem brass sized by standard dies tends to bulge in front of the belt. I use a Forster Bonanza Benchrest Full length resizing die to resize my 7mm rem mag brass, so far I have test cases that have been fire 5-7 times with only normal trimming required, no signs of giving up yet. Larry Willis makes a die that will take this bulge out, I bought it, and never have to use the damn thing it sets up there on a shelf looking on...
I have fired cases that shortened .400"+, I have fired cases that shortened .240"+. The cases did not show case head separation, the cases did not split.
I have fired old cases that had never been fired, some were accused of having splits. I did not agree, the gap was too wide to be a split, the cases I fired had a gap up the side of the case body that was caused by gas cutting. I thought the answer was simple, those I disagreed with are still arguing.
Hooligan1,
I am the fan of cutting down on all that case travel. I am the only one that has control over the stretch of the first firing. It is just something I do, I want to know the length of the chamber from the shoulder to the bolt face. When I have a case that is too short from the shoulder to the case head for a long chamber I use a 'case stretcher' (new word or group of words or phrase) or I use long cases from the shoulder to the to the case head. Again, my favorite case is a case that is too long for the chamber from the shoulder of the case to the case head.
F. Guffey
I have fired old cases that had never been fired, some were accused of having splits. I did not agree, the gap was too wide to be a split, the cases I fired had a gap up the side of the case body that was caused by gas cutting. I thought the answer was simple, those I disagreed with are still arguing.
Hooligan1,
I am the fan of cutting down on all that case travel. I am the only one that has control over the stretch of the first firing. It is just something I do, I want to know the length of the chamber from the shoulder to the bolt face. When I have a case that is too short from the shoulder to the case head for a long chamber I use a 'case stretcher' (new word or group of words or phrase) or I use long cases from the shoulder to the to the case head. Again, my favorite case is a case that is too long for the chamber from the shoulder of the case to the case head.
F. Guffey
Back to the 7mm Remington mag: No one measures case diameter, I have gone through 600+ 257 Weatherby magnum and 7mm Remington Mag cases in the last month. I have sorted cases, some of the cases had expanded .020" ahead of the belt, the extractor groove had expanded .009", I know, that means nothing to most but the same cases with the large diameter case bodies and expanded extractor groove had loose primer pockets.
The original question was about case stretch. The original poster wanted to understand what all the Internet reloaderns were talking about when they insist on using the term 'case stretch' when the case actually shortened. Then there was the Wilson case gage, a most accurate gage, problem, those that do not understand the gage use it as a 'drop in gage'. I use a straight edge and feeler gage or a dial caliper or a height gage.
The OPs case did stretch/form, the OP did not measure the case before firing. Measuring the case before firing would allow the shooter/reloader to determine the effect the chamber had on the case when fired.
Then there is the
Well hang on there little buddies, there is more to it. There is a primer, there is a firing pin, always omitted in the story of the case, bullet and powder outrunning the firing pin is the primer. We all know the primer unseats it self and launches itself back against the bolt face. To complicate things there are different receivers and bolt designs, cases have been fired in chambers without shoulders or the shoulder was so far forward the shoulder of the case never made it to the chamber shoulder, no stretch, no case head separation, only artifacts of the old neck, shoulder and shoulder/case body junctures and shoulder/neck junctures. Again, when the case was fired the shoulder of the case became part of the case body. MEANING! The case did not stretch between the case head and case body.
I am the fan of cutting down on all that case travel.
For about the 10 time, a friend built a magnificent rifle, he had 5 case head separations out of the first 10 cases fired. I told him I could have determined if that would happen before leaving the ship, I told him I could have 'fixed it' long enough to allow for fire forming cases and I could have met him at the range and fixed it long enough to allow for forming cases.
F. Guffey
The original question was about case stretch. The original poster wanted to understand what all the Internet reloaderns were talking about when they insist on using the term 'case stretch' when the case actually shortened. Then there was the Wilson case gage, a most accurate gage, problem, those that do not understand the gage use it as a 'drop in gage'. I use a straight edge and feeler gage or a dial caliper or a height gage.
The OPs case did stretch/form, the OP did not measure the case before firing. Measuring the case before firing would allow the shooter/reloader to determine the effect the chamber had on the case when fired.
Then there is the
, problem, too much to keep up with and it seems reloaders max out with "the firing pin strikes the primer and then everything takes off for the front of the chamber until the shoulder of the case contacts the shoulder of the chamber, and then? Everything gets busy".
Well hang on there little buddies, there is more to it. There is a primer, there is a firing pin, always omitted in the story of the case, bullet and powder outrunning the firing pin is the primer. We all know the primer unseats it self and launches itself back against the bolt face. To complicate things there are different receivers and bolt designs, cases have been fired in chambers without shoulders or the shoulder was so far forward the shoulder of the case never made it to the chamber shoulder, no stretch, no case head separation, only artifacts of the old neck, shoulder and shoulder/case body junctures and shoulder/neck junctures. Again, when the case was fired the shoulder of the case became part of the case body. MEANING! The case did not stretch between the case head and case body.
I am the fan of cutting down on all that case travel.
For about the 10 time, a friend built a magnificent rifle, he had 5 case head separations out of the first 10 cases fired. I told him I could have determined if that would happen before leaving the ship, I told him I could have 'fixed it' long enough to allow for fire forming cases and I could have met him at the range and fixed it long enough to allow for forming cases.
F. Guffey
F Guffey, thanks for replying again. Maybe a misunderstanding. I had measured cases after firing. I measured again after full length sizing. Not just using Wilson case guage. Using digital and analog calipers to measure. Don't really prefer the digital calipers since I figured out the analog. Zero is more tolerant. I did however just measure case length. Have never measured neck length. After firing my first factory round according to Wilson guage directions and a few you tube videos I inserted fired brass. Guage has set screw so I set it to the dimensions of my first fired cartridge from this rifle. I only use it to check if I'm over or under the 2 lines on neck side of guage. But I measure length with calipers first. Full length size. Trim if needed. Debur. Load powder and seat bullet. I'm watching this brass very closely as I'm told somewhere on this forum that maximum loads for a belted magnum are 5-6 reloads. No signs of stress yet. Primers look good after firing. Primers seat good and firm when reloading. Don't see any breaks or cracks or oddball lines or grooves in the brass. Inspect after shooting. After vibratory cleaning. After sizing. After loading. If I've left anything out I should be doing I'm open to advice or criticism. A great Memorial Day to all and for our fallen troops and those living. God bless you and your families for your sacrifice to this country.
Wendyj,
Are you measuring case length to the shoulder when you resize? Or to the mouth?
One way to set up your dies to "bump back" the shoulder for less sizing is to use a spend 9mm case over the neck of fired brass and mark down the total measurement you get. Then lower your die a quarter turn at a time until you get a reduction of 0.001 to 0.003. Then lock down your die and do a partial resize that way. Works the brass less on sizing and firing.
Works the same way on belted and non-belted cases.
Jimro
Are you measuring case length to the shoulder when you resize? Or to the mouth?
One way to set up your dies to "bump back" the shoulder for less sizing is to use a spend 9mm case over the neck of fired brass and mark down the total measurement you get. Then lower your die a quarter turn at a time until you get a reduction of 0.001 to 0.003. Then lock down your die and do a partial resize that way. Works the brass less on sizing and firing.
Works the same way on belted and non-belted cases.
Jimro
T. O'Heir said:
If a piece of brass fits a chamber perfectly, even if it is brand new, then it has no place to stretch too. So it doesn't stretch. This is why neck-sized-only cases generally don't stretch or need trimming if load pressures are normal.
Most new brass, however, is made shorter than minimum chamber headspace for reliable feeding, and that's why it stretches on first firing, even in a minimum chamber. If the chamber is larger than minimum, it stretches even more. This is why, when you get mixed brass from a match where issued ammo is used, they don't all measure exactly the same size from head to shoulder datum. The difference in headspace in the rifles has controlled how much stretching there is.
For example, a .308 Winchester SAAMI minimum chamber is 1.630" from breech face to shoulder datum. Most new commercial and U.S. military bulk brass measures about 1.628" from head to shoulder datum. This means it will have at least 0.002" of front-to-back room to stretch into. Most chambers are not minimum, though. Most new .308 chambers are in the 1.632" range, half way between the standard GO and NO-GO gauges, so 0.004" of longitudinal stretching room is what most new brass sees.
In the end, the difference in chamber and brass size determines how much stretching there is because that difference is how much room there is for the brass to stretch into. Headspace and shoulder position (setback from the as-fired position, when it's reloaded), relative to one another, do affect how much brass stretches when fired.
Last edited:
Jimro. Total length of case is what I'm measuring. Just bought 50 rounds of new Hornady 7 mag brass and sized a few. According to measurements they will all have to be trimmed. They appear to be thinner as they drop below back of case in Wilson guage but I'm sure that will change when pressure expands the case after firing. These are not pre fired cases. According to measurements I'm bumping back o.0021
But they probably didn't have to be trimmed before you resized them. There is always an argument about the need to size new brass (and I mean truly new; not reconditioned once-fired brass). Some swear it's essential and some never bother. I generally fall into the latter camp. New brass comes from the same lots of brass the factory uses in their commercially loaded ammunition, so if you don't have to use a body die to resize factory new loaded cartridges before you can fire them, you shouldn't need to do it to their empty new brass, either. The exception is when case mouths have been bent by the extra handling they get. A mandrel die or Lyman M die will normally fix that without additional brass working.
The idea behind bumping back 0.002" is to bump the shoulder back 0.002" from whatever size the case expands to in the chamber during firing. New brass will already be shorter than a SAAMI minimum chamber, so if you push a new shoulder back and additional 0.002" without first firing it, you are just setting the shoulder back below spec and making it blow out that much further during firing, thereby shortening case life.
The idea behind bumping back 0.002" is to bump the shoulder back 0.002" from whatever size the case expands to in the chamber during firing. New brass will already be shorter than a SAAMI minimum chamber, so if you push a new shoulder back and additional 0.002" without first firing it, you are just setting the shoulder back below spec and making it blow out that much further during firing, thereby shortening case life.
Last edited:
I haven't trimmed them yet. I don't trim before resizing. I trim after if needed. Not sure of the new brass. Nowhere does it say once fired. Hornady 308 brass I bought at bass pro stated once fired. Seems to be a good lot. Length and weight is pretty consistent. The 308 once fired varied a lot with each case. I measure everything but most important to me is final oal so they will fit in blind box magazine of adl. These are my husbands hunting bullets. I'm sure he doesn't want to feed one at a time. It's grouping under a dime with 3 shots at 100. IMR 4831 62 grains and 140 nosler bt. That mostly Federal brass. Don't know what Hornady might change. Right now having issues finding Remington 9.5 magnum primers unless bass pro got some in this week.
603Country
New member
If you are shooting 3 rounds under a dime at 100 yards, you need to be giving reloading advice and not asking for it.
Wendyj, you are welcome, no misunderstanding. It is an illusion, 'stretch' is it, there is nothing else except
In the beginning Holland and another Holland designed the belt, it was something the British did. They pinned the case to the rear of the chamber and then pulled the trigger. They did not have a plan on what happened to the case in front of the belt, the British did not have a plan of rimmed cases with rims, they pulled the trigger, the rim held the case to the rear and the case body filled the chamber and that sealed the chamber. They had a lot of case tapper with no sharp shoulders.
The misunderstanding is about a case that gets shorter when fired and stretches at the same time. And as always there are different designs.
Case travel, I am the fan of cutting down on all that case travel. I am the fan of the 'LEAVER POLICY', When the case fits the chamber I leaver that way. Difference in designs, some designs allow me to fire a case without forming, other designs allow for case stretch between the case head and case body.
Again, I have fired cases in chambers with .127" clearance between the case shoulder and chamber shoulder. Had the case stretched it would have experienced case head separation/insipient case head separation. Instead, the original shoulder never moved, it became part of the case body, meaning the case did not move. It got shorter, so short the neck became part of the shoulder.
F. Guffey
Here's what caused my confusion:
So maybe what you meant by "not pre fired" is that you haven't shot them in your gun yet. I took it to mean they were factory new cases. Hence my last post.
If the cases were never fired in your gun, are you then setting the shoulders back -0.002" from where other case shoulders are when they have been fired in your husband's gun? That would be good number, and -0.002" is going to be short enough to feed completely freely even with very rapid bolt work. Even -0.001" is usually enough, and is often preferred by target shooters bor best accuracy.
If you are resizing cases fired in a number of other guns without adjusting the die position, the case lengths you wind up with are going to vary. You will find the die in one position sets some shoulders back more than others until they all have been fired once in your husband's gun. That variability is caused by the mix in starting shoulder lengths from the head. Also, differences in the diameters of the cases from different chambers will affect overall spring-back of the brass when it comes out of the die, as well as different length. You may even have to anneal necks and shoulders to get the most consistent setback.
Wendyj said:
So maybe what you meant by "not pre fired" is that you haven't shot them in your gun yet. I took it to mean they were factory new cases. Hence my last post.
If the cases were never fired in your gun, are you then setting the shoulders back -0.002" from where other case shoulders are when they have been fired in your husband's gun? That would be good number, and -0.002" is going to be short enough to feed completely freely even with very rapid bolt work. Even -0.001" is usually enough, and is often preferred by target shooters bor best accuracy.
If you are resizing cases fired in a number of other guns without adjusting the die position, the case lengths you wind up with are going to vary. You will find the die in one position sets some shoulders back more than others until they all have been fired once in your husband's gun. That variability is caused by the mix in starting shoulder lengths from the head. Also, differences in the diameters of the cases from different chambers will affect overall spring-back of the brass when it comes out of the die, as well as different length. You may even have to anneal necks and shoulders to get the most consistent setback.