Resizing brass with negative headspace measurements

[MVW]

I recently purchased a Savage Varmint rifle and have begun trying to develop precision reloads. To this end, I began by reading the very nice article by Jacob Gottfredson on long-range case prep. I also read several threads on headspace, in particular “Running a case through a body die increases headspace -- why?”

http://forum.accurateshooter.com/index.php/topic,3743017.msg35844568.html#msg35844568

My question pertains to headspace. I have measured new brass and once/twice fired brass (all from the same manufacture) with a Redding Instant Indicator and find that much of it is .002-.003 or more less than the SAAMI minimum headspace indicator (i.e. -.002 to -.003 and some even smaller). I somehow expected the twice fired brass to be fire formed to the chamber and at least be close to the SAAMI minimum, but that does not seem to be the case. I guess that the Savage may have a short chamber, but that is not my question.

Based on what I have read, my premise is that I should start with brass that have consistent headspace dimensions and to get that I need to resize the brass. I have a Redding Body Die, but my experience is that it doesn’t touch the shoulder on the cases with excessive headspace, so even after sizing I still have a bunch of brass with inconsistent headspace measurements.

I notice that Redding makes their competition shell holders, but they seem to take things in the wrong direction from what I need.

In the thread above it talks about grinding down the shell holder or the die to bring the die into better contact with the shoulder. How does one go about grinding down a shell holder? Since I am rather new to this type of reloading, are there other thoughts?

Thanks, M

 

[Yagingaboy]

I'm not sure if this is the exact right answer but I will give it a shot. The only way you can bump the shoulder further back or even get your die to touch the shoulder is to shorten the clearance between the shoulder area of the die and the top of the shell holder. You knew that already. To me it makes more sense to remove material from the shell holder because if you mess it up you are only out a $7 shell holder. If you have an idea of how many thousandths of an inch that you need to come down you can take the shell holder to any machine shop and they can mill that exact amount off for a minimal charge. You can also grind it off with pretty much any grinding tool you may have, even a dremel, but this is a bad idea because you can easily get an uneven grind and the top of your shell holder will no longer be flat. Machine shops, gun smiths, hobby machinists with a small mill, any of these are your best bet for getting a nice flat surface on the top of your shell holder after moving the amount of material you need.

 

[mj2evans]

Are you having trouble chambering sized brass? Just want to make sure you actually have an issue before you spend time and money trying to "fix" something that may be a nonissue. If you really do need to modify a shellholder a couple thou you might try wet/dry sandpaper and some oil on granite tile - cheap and you make whatever size you want.

 

[MVW]

Thanks for the suggestions. I am not having trouble chambering the brass, but I was under the assumption that you wanted the brass to have similar headspace measurements before making other adjustments to the brass. If several thousandth's isn't an issue and I can ignore the variation, I'll not worry about it.

Thanks

Mike

 

[NorCalMikie]

If the brass chambers without excessive force to close the bolt, load, it up and shoot it. If after it's fired you get a stiff bolt, then measure and bump the shoulder maybe .001 or .002. Throw in a body size as needed and you should be good to go. Or full length resize as needed. Don't start worring about a problem if it hasn't shown up yet. KISS.

 

[40X Guy]

Mike, i just went thru this on 2 different calibers that I need to FL size and or bump shoulders back. Was getting very inconsistant headspace reading using my FL die turned down to contact shellholder and then some. I took a RCBS shellholder and ground off a full .015 and tried it ( a little too much on bench grinder) and started to get consistant readings. So I bought 6 of the same RCBS #3 shellholders and took them to my smith and he ground off .002, .004, .006, .008, .010, and .012. And I now have a custom set of shellholders. The Redding comp shellholder kit goes the wrong way as you mentioned and are thicker. Measure your headspace reading on once fired brass and record it, then FL size/ bump shoulder back to that reading not to the new unfired measurement.

Frank

 

[necchi]

Why not just use a Full Size die instead of the Body die?

 

[CatShooter]

Please understand that the SAAMI measurements are not a single "fixed" number - headspace is a range. So you can be "good" over a range of 6 to 8 thou, depending on the chamber... the same applies to the brass.

So, with a maximum chamber and a minimum case, there can be ~14 thou of "space" between the bolt face and the cartridge face, and you are still "in spec".

And, in the other direction, you can have a maximum case and a minimum chamber, and wind up with a negative headspace (a "crush fit").

So when you say you have 0.002" headspace, you have nothing to worry about.

If you size with a body die, the shoulder will be moved forwards and the body is compressed... when the die finely comes in contact with the shoulder, it is pushed back in place (to where you want it).

Some folks adjust their dies so the case gives a crush fit on varmint rifles because case life is much longer... but for bench shooting, easy feeding dictates a thou or two of shoulder clearance.

 

[MVW]

My understanding from other threads is that FL sizing is a function of the manufacture and doesn't allow much control over how the case is sized.

In my case, the cases are less than the SAAMI minimum so I don't think FL would even touch the shoulders.

I think I'll shoot more and experiment with the shell holder grinding later after I have a good sense of how the other factors play in the mix.

Thanks, M

 

[ordnancemarine]

I've been reloading for several years now and I have never worried too much about head space uniformity. Head space only becomes a problem after a few re-loadings when the case gets pushed out to meet the chamber dimensions. At this point, a body die or a F/L sizing die comes into play (if you are only neck sizing). I think you would be better served by simply full length sizing each time. If you are just shooting through a varmint rifle then the neck sizing really isn't much of a benefit. Neck sizing, from what I understand, is useful when you have a tight match chamber and your brass doesn't stretch out much. For consistent ammo, you need to focus on neck tension, consistent powder charges, and bullet run-out.

 

[necchi]

Me think's it's something to do with the way your measuring or interpreting the measurement.

Your gauge, only gives you measurements as it pertains to you and your gun. The measurement would be moot for any other purpose, it's just for you.
If you measure a new unfired case it should not be "less than" sammi minimum.
Place the new case in the gauge, then "zero" the dial, that's your beginning measurement, after a case has been fired, measure it again. It will be longer.

If your gun has a chamber that's shorter than Sammi Minimum, an unfired case wouldn't fit??

 

[bsekf]

I have found different reading on fired cases and wondered why. It would seem as though they would all measure the same. I believe it has to do with brass hardness and spring back. Not sure how the Redding Instant Indicator works but I must measure with the primer removed to get consistent measurements. I have decided +/- .0015 is OK when I measure a fired case.*

I do use a Lee collet die and only full length resize when it becomes very hard to close the bolt.

*If you are talking break open guns, it is a completely different ball game.

Bill

 

[eww1350]

It is hard to determine what the issues really are, but if you take your rifle to a gunsmith he can VERY easily reset the headspace to an SAAMI gage..since the Savage rifles have adjustable headspace...if you are getting various readings from fired brass, it is directly related to brass hardness....



Eddie in Texas

 

[MVW]

bsekf and eww1350,

Redding provides a brass gauge that is suppose to be sized to SAAMI Minimum Headspace measurements. When I compare new and once or twice fired brass to their measurement it always ends up anywhere from 0.000 - 0.004 less than the Redding gauge indicating that the cases are less than SAAMI Min. I can't seem to get the body die to size below Min with the current shell holder.

My reason for pursuing this is that I was planning to knock the shoulder back to a constant value prior trimming the cases so that I end up with the same neck length.

I am not as worried about this for the 223, but I'd like to start shooting 1,000 yard shoots with a 308 and want to learn how to give reloading the care it apparently needs for the longer distances.

I may be going overboard on this, but my impression is that the little things matter at 1,000 yards.

M

 

[necchi]

When the needle moves counter clockwise from the original setting, it means the case is longer. The probe or contact area is contacting sooner than zero not beyond zero.
New brass isn't smaller than it should be.

 

[Elkbane]

MVW,
You are measuring the once/twice fired cases with the primer removed aren't you? If the primer is still in place, it can give you a false measurement. Also, you stated above that you can't get the body die to touch the shoulders on excessively long cases. If that is the case, you definitely need to screw the die IN farther. As pointed out in a post above, as the case body is compressed, the volume has to go somewhere so the case gets longer, until the case shoulder hits the shoulder on the die, and then it gets pressed back into its proper position. You need to keep turning the die IN, until you see a reduction in headspace. If your shellholder won't allow any further inward adjustment, then you have two options: facing off the shellholder or facing off the die. Shellholders are cheap - I'd try that first before you start trying to trim length off a die (the are hardened also).

But I'm with NorCalMIkie - you may want to re-read his post above. It's sound advice. Once the cases max out in length (and this may take several firings unless it's one of the WSM's), then you can see if your die can address the problem, and apply the appropriate fix. Also, changing shellholders may provide some relief. They have quite a bit of variability in size between manufactures, and even between two from the same manufacturer........we're talking about a few thousandths of an inch.....
Elkbane

 

[holstil]

I think you need to reevaluate your readings as necchie says. Sounds like something is backwards.

If you think that the comp bushings would take you in the opposite direction from getting the shoulders bumped to the same (shorter) length, something is wrong.

Forget sammi specs for a minute, your brass=your chamber.

Jim

 

[6BRinNZ]

I use the redding instant indicator with the redding FLS kit and the redding adjustable shell holders. The brass SAAMI spec case that comes with the die is used to zero the dial gauge. When a fired case is measured, the dial will do 1 of 3 things. Move counter clockwise, indicating the case (base to datum) is slightly shorter, go back to zero or move clockwise, indicating the case is slightly longer.

Redding do state that the brass case is set to minimum SAAMI spec and therefore cases should come out longer (dial moves clockwise), as one purpose of the RIID is to indicate where your chamber spec is against SAAMI minimum...to what benefit I don't know. Redding do go on to say that cases should only be used to measure that have been fired 2-3 times and only neck sized in between, with the longest length being the best indicator of base to datum.

My experience with the tool has been similar to the OP in that typically cases will be zero or maybe .001" under...no matter who has chambered the rifle. However I have had the odd case measure .002" over. Those cases get put aside. The implication is that the chamber is slightly larger but the majority of cases are retaining some of their original dimensions.

I then use my redding shell holders to bump the shoulder back ~.001" - .002" from the longest length recorded, in this case from the zero point as the odd cases longer than that are put aside. Spring back means that a .002" change in shell holder still leaves you within .001 - .002 bump. The beauty of this system is it is fast and easy to measure, so I can measure bump on every case in the same manner I can measure seating depth for every loaded round.

I have never measured the SAAMI spec case to check if it is a minimum spec as I simply want to know how much to bump my fired case back (as others have stated the fired case bump dimension is actually the only one to care about), so I just use the brass case as a reference point to create a zero.

OP - I had the exact same concerns as it was "woh my case is .001" under minimum spec" but as I measured and played around more I stopped worrying about the minimum thing and just started sizing.

If you can't use any of this to get the correct bump then I would be looking at the sizing die, shell holder setup in the first instance.

Good luck

 

[ordnancemarine]

MVW... You do not need to worry about the minor differences in head space. Just trim all of your cases to the same length. I have been shooting 1K for a few years now and it is not necessary. As long as the head space is under spec, you will be fine.

 

[lynn]

MVW
Lets cut through the chase here a bit.
Until your bolt is a little bit snug on closing your brass doesn't truly fit your chamber.Once you notice it snugging up you screw down your body die while you have a case in the shellholder and the ram is all the way up.You now lower the ram and measure a case.
You then start screwing your body die down in 1/4 turn increments and measure that same piece of brass each time.Nothing will happen at first then it will start to get longer.When it starts getting longer you screw the body die down in smaller increments until you see the brass stop growing longer.
Now screw the body die down in very small increments until you see the shoulder get setback 0.001 in length.
In case your curious your necks will now be getting longer.
Lock down the ring on the body die and put a stripe down the front of it with some bright colored paint or magic marker and you'll never need to adjust the die again until you re-barrel the gun.
All your brass will now drop in effortlessly as well.
If your body die makes firm contact with the ram and your not yet pushing the shoulder back take 80 grit sandpaper and run your shellholder over it in a figure eight pattern.The figure eight pattern allows you too evenly remove material from your shellholder and it works quite well.
Remember you don't need to bump your shoulders back until it is necessary.
Lynn