Case Length Resizing

[AussieShooter]

I am trying to achieve a uniform 308 case length of 2.005.

My brass is 2nd hand once fired lapua.

My questions are;

1. Can you use / should I use the body die included in the Redding Competion Neck Sizing Die set to resize the brass so the headspace is to the SAMMI spec then focus on the neck length or should I use a FL die and try to achieve this resizing to SAMMI spec in one go?

2. Is this reasonable given that I read you can not resize brass longitudinally?

Thanks.

 

[Shynloco]

Aussie,
I'm not sure there exists a fool proof method that will guarantee that your brass is "exactly" @ 2.005 each time you fire and then prep your brass for another round. I've used both methods that you've mentioned, but each time I make sure and re-measure every piece of brass after having fired it, FL resized, or even just neck sized it (neck sizing alone is something I quite do after the Benchrest crowd taught me -"what you do to one, you do to all"). The caliber is irrelevant (as far as measuring) to my statement because I've found that one piece may remain at 2.005 in a tight chamber and another might be 2.006 or even 2.007. Bottom line, I retrim the brass if needed. Bottom line - rather than guess, I just re-measure every piece after running it through either an FL, Bushing or even Body Die, having used Competition Shells holder to manage the shoulder bump. Just my take on your question.

Alex

 

[AussieShooter]

Hi Alex,

I got most of what you say and understand what you said apart from the competion shell holder.

Is their a difference from a normal shell holder and a competion shell holder (is their a competion shell holder?)

I am also using an RCBS Rockchucker.

Thanks,

Aussie

 

[Shynloco]

Hi Aussie,
Yes there is a difference between the two types of shell holders. Competition Shell Holders come in a pack of 5 that are .02 apart. In other words, they allow you set you die to a specific setting and then by merely changing the shellholder, that will provide you a .002 bump of the shoulders of the casings. The Comp Shell Holders come in .002, .004, .006, .008 and .010 sizing. Each caliber family has it's own set of shell holders.

And yes I too use a Rockchucker as well as a Redding Big boss. Redding and RCBS Shell Holders are interchangeable, but also have different numbers assigned to identify them. The competition Shell Holder set is a Redding so I can't really say what the RCBS numbers would be, but I believe it provides the same bump regardless of the press or the designation assigned it.

Alex

 

[Joe Maisto]

I am trying to achieve a uniform 308 case length of 2.005.

My brass is 2nd hand once fired lapua.

My questions are;

1. Can you use / should I use the body die included in the Redding Competion Neck Sizing Die set to resize the brass so the headspace is to the SAMMI spec then focus on the neck length or should I use a FL die and try to achieve this resizing to SAMMI spec in one go?

2. Is this reasonable given that I read you can not resize brass longitudinally?

Thanks.

Hello "over there",

I shoot with some of your people here in the U.S. during the month of May at the famous SUPER SHOOT.
Here is what we do . We find the length of our chamber, and trim our brass back to perhaps .015. We shoot PPC, but I cannot imagine it makes any differance what cal., as long as you remain short of that dimension. We clan and load after every heat. After a few loadings, we check our brass for growth.
Example;
If my chamber measures 1.525, many of us trim to 1.500. ( some trim to 1.495) Most if not all of us BR shooters have a device in our box which will trim during an event......if need be. I am not sure why you would need to be at that exact dimension you stated, as long as your cases are all the same short of your chamber. It is easy to find out what that measurement is. Either through your "smith" or by using a small device which you insert into an empty ( shortened by .100) case, and pushed into your chamber by hand or with your bolt. This device will get pushed into your empty round and will stop going forward when it reaches your chamber length, at which time you gingerly remove it and measure from the base of your cartridge to the end of the device which you slipped into your case mouth.
Hope this has been helpful.

Does the name Stuart Elliot mean anything to you ? He comes here with his wife each year to participate. He in fact is the sole distributor of March scopes in Australia.

One year he was at my loading table and I noticed he was wearing a pair of "jeans" with the label.....RM Williams.
I took off one of my boots and showed him the same label.
We had a good laugh over that !

 

[BoydAllen]

Why would you want to size you brass to SAAMI spec. instead of putting its shoulders where the need to be for proper clearance with you chamber? Perhaps if you told us what you are using the brass for we could give you better answers. If I want cases of a particular length, after sizing, I trim them to that length. I feel like I am missing something here.

 

[bigedp51]

I know this is slightly off topic, but my son went to college with a New Zealander and he said the Australians always cheat at Rugby. Your comments please, I saw the movie Breaker Morant and always thought about what the New Zealander said.

 

[K22]

A fire case in your chamber should be used as the baseline of measurement from which you adjust your full length sizing die to bump the shoulder back; usually .002 is recommended for bolt rifles.

This will give you a precise fit for your chamber and assure proper functioning of the cases in that specific rifle.

 

[Martin52]

Hi Aussie,
If you're referring to SAAMI just to ensure the once fired brass will fit your chamber, there is a better way. K22 makes a good point. If you have some Lapua brass that has been fired in your own chamber then measure the base to shoulder dimension. Do this after depriming the case to avoid the used primer affecting the measurement. Then measure the once fired brass (again deprimed) that you have picked up and compare the 2.
Assuming you are already full length sizing your cases and that these cases do fit your chamber, your current die setting should be OK for the once fired brass but your measurements will confirm this.
Now regarding the trim length you seek, 2.005, you will find full length sizing will usually cause your cases to lengthen and the lengths may vary so you will generally have to trim back to get to 2.005. Then chamfer and deburr the case neck mouth.
If you do not have a gauge to measure cartridge base to shoulder Davies Triggers here in Aus. make a good one, they also make a seating depth checker if you need one.

http://daviestriggers.com.au

You can certainly use your body die to set back the shoulder, then trim the case necks to 2.005, then neck size. You can also do the resizing in one go using a FLS die. Either way, you will still need to measure. Hope this helps.

Martin

 

[BoydAllen]

While we are at it, it typically takes more than one firing for a case to reach the maximum shoulder to head dimension attainable in a particular rifle/barrel combination. For that reason I recommend that as a first step, that you measure a case that has been sized and fired once, with a fairly hot load, in your rifle. I think that you may find that if you set your FL or body die so that it gives the same shoulder to head dimension as the once fired case, that it will chamber just fine. Another thing that you should know that the amount of shoulder bump that you get, using a given die setting will vary within a range. It will not be the same for all cases sized.

 

[AussieShooter]

Hey Joe,

Annie and Stuart are very knowledgable.

I get most of my reloading gear from them. Always friendly and always willing to give free advice.

The reason I wanted to trim to that length is that is the suggested length from one of my reloading books.

Using these as a benchmark starting point I would use my Chrony for load development. Once I get the velocity right I would measure the brass expansion.

 

[AussieShooter]

Hi Aussie,
Yes there is a difference between the two types of shell holders. Competition Shell Holders come in a pack of 5 that are .02 apart. In other words, they allow you set you die to a specific setting and then by merely changing the shellholder, that will provide you a .002 bump of the shoulders of the casings. The Comp Shell Holders come in .002, .004, .006, .008 and .010 sizing. Each caliber family has it's own set of shell holders.

And yes I too use a Rockchucker as well as a Redding Big boss. Redding and RCBS Shell Holders are interchangeable, but also have different numbers assigned to identify them. The competition Shell Holder set is a Redding so I can't really say what the RCBS numbers would be, but I believe it provides the same bump regardless of the press or the designation assigned it.

Alex

Thanks for that Alex.

I'll order shell holders Monday.

 

[AussieShooter]

Joe,

Is the gauge you were talking about something like the Hornady OAL gauge?

 

[AussieShooter]

I know this is slightly off topic, but my son went to college with a New Zealander and he said the Australians always cheat at Rugby. Your comments please, I saw the movie Breaker Morant and always thought about what the New Zealander said.

The Kiwis would say that!
They usually beat us in the rugby. But hey it's their national game.

 

[AussieShooter]

Hi Aussie,
If you're referring to SAAMI just to ensure the once fired brass will fit your chamber, there is a better way. K22 makes a good point. If you have some Lapua brass that has been fired in your own chamber then measure the base to shoulder dimension. Do this after depriming the case to avoid the used primer affecting the measurement. Then measure the once fired brass (again deprimed) that you have picked up and compare the 2.
Assuming you are already full length sizing your cases and that these cases do fit your chamber, your current die setting should be OK for the once fired brass but your measurements will confirm this.
Now regarding the trim length you seek, 2.005, you will find full length sizing will usually cause your cases to lengthen and the lengths may vary so you will generally have to trim back to get to 2.005. Then chamfer and deburr the case neck mouth.
If you do not have a gauge to measure cartridge base to shoulder Davies Triggers here in Aus. make a good one, they also make a seating depth checker if you need one.

http://daviestriggers.com.au

You can certainly use your body die to set back the shoulder, then trim the case necks to 2.005, then neck size. You can also do the resizing in one go using a FLS die. Either way, you will still need to measure. Hope this helps.

Martin

Hi Martin,

I was previously using a 550b and so with the implementation of the Rockchucker to eliminate the flexing of the base plate hope to have more uniform loads.
I have changed reloading presses and dies to suit a more precise reloading practice.
If I was using previously fired cases in my rifle would these dimensions be adequate or would the cases need to be fired multiple times? In other words would the case closely mould the chamber or would the case only closely mould the chamber after multiple firings?
I use the Wilson case gauge for tolerances.
I don't know if I have already stated this but if reload to the SAMMI min then I can use the stretched cases as a stencil of sorts if you will.
Is this a backwards approach or is there a better way I need to understand?

 

[Martin52]

[/quote]


1) If I was using previously fired cases in my rifle would these dimensions be adequate or would the cases need to be fired multiple times? In other words would the case closely mould the chamber or would the case only closely mould the chamber after multiple firings?

2) I don't know if I have already stated this but if reload to the SAMMI min then I can use the stretched cases as a stencil of sorts if you will.

3) Is this a backwards approach or is there a better way I need to understand?
[/quote]

Hi Aussie,

Just numbered your questions to try and answer them.

1) Cases that have been previously fired in your rifle will be a guide but unless these have been fired multiple time (3-4 times ) and without being full length sized then they may not have stretched to the limit of your chamber. In my chamber, new Lapua 0.308 cases that start their lives measuring 1.629 inches (using Davies comparator) can stretch to 1.634 (max). Your fired cases, depending on how many times they have been fired and neck sized are likely to sit in a range that could be 5-6 thou depending on your chamber. (I usually FLS to 1.632).

2) Any cases that have been fired multiple times (3-4) and have fully stretched within your chamber will give you the upper end of the range eg 1.634. If you resize these to minimum spec's eg 1.629 then you will be overworking the brass and risk case head separations.

3) Resizing to minimum spec's is probably a backwards step and will overwork the brass. Fired cases need only have their shoulders bumped back 2 thou when fully stretched.

Take a fired deprimed cleaned case and chamber it in your rifle, preferably with the firing pin removed as this will increase the feel - there should be little resistance when you close the bolt handle. Cross reference this against the measurements you have taken.

As you probably know, the bolt will be harder to close on a loaded round once your brass has stretched to max chamber size.

One thing to compare is the outside neck diameter of cases fired in your rifle v the once fired brass you have acquired.

Hope this assists.
Martin

 

[Joe Maisto]

Joe,

Is the gauge you were talking about something like the Hornady OAL gauge?

Yes. However, I find it much easier to ask your smith about your chamber dimensions, and go from there. Using that little device which slips into a "shortened case" to measure your chamber LENGTH, ( in conjuction with a drilled & tapped case ) was ( for me at least) inaccurate.
Your smith knows the reamer he used. Simply ask him about the OAL of your chamber. I see no reason you cannot trim your cases .015-.020 less than that measurement.
The important thing is they are not too long.

 

[BoydAllen]

Lacking the piece that Joe described, the Hornady headspace gauge (an attachment for calipers, dial or digital) is what I prefer, rather than a Wilson gauge, because I think that the Hornady gauge lends itself to more precise work, and is more versatile and when a number of calibers are reloaded, economical. For setting up a sizing die, the important thing is not the absolute number, but rather the difference in readings comparing a fired to a sized case. With this gauge, if you start out with a new, or even a once fired case, neck sizing a case, with relatively stout loads, you will readily observe how the case shoulder dimension reaches its maximum.

When a round is fired both it and the chamber expand together under the peak pressure, and while the chamber snaps back to its original dimensions, the case will retain a small amount of its expanded size, and over several firings growing a little in its dimensions with each, come to a point where when it snaps back from the pressure of firing, that it is in a slight interference fit with the chamber, causing resistance to be felt as the bolt is closed. The closing cams in the front of a typical front lug bolt action combined with the length of the bold handle, provide the mechanical advantage and mechanism to force the case into a chamber that it is ever so slightly larger than. The main locations of this resistance are at the shoulder to head dimension, and the diameter of the case body near the head of the case. By paying close attention to how much we "bump" (push back) the shoulder when we FL size, brass life is enhanced over what it would be if that clearance was increased to that of an unfired case. I believe that there is also an accuracy advantage to cases more closely fitting the chamber that they are fired in. As I mentioned in my previous post, just because one case that is sized in a die that has been set to bump its shoulder for minimal clearance fits the chamber properly, does not mean that all the cases will respond to the die setting in an identical manner, this is due to the differences in hardness and spring back of even new high quality brass, so some experimentation may be needed to find the setting that gives the minimum bump to the springiest cases in the set. This is another application for the aforementioned gauge. Also, as cases harden with subsequent firings, a die that was set for minimal shoulder bump will have to be reset, because of the progressive work hardening of the brass from repeated firings and FL sizings. More advanced reloaders may anneal cases to, among other things, reduce the variance in bump within a given set of cases, at a given die setting.
Finally a word about SAAMI specifications...Rifles vary in the sizes of their chambers due to manufacturing tolerances and reamer wear, so the specifications for new ammunition assure that it is small enough to fit in the smallest chamber that falls within a specified range. This results in ammunition that does not fit most chambers as closely as would be desired for best accuracy. My point being that you have the advantage of knowing the size of the chamber that you are loading for, and so have no reason to recreate the clearances that new ammunition manufacturers must, and if fact have good reasons not to.