I've just bought a RCBS Precision Mic to help accurately size my cases and have come across a problem. I measured a bunch of cases with the mic and determined that they are an average of +.002 over the minimum size. So now, if I'm not mistaken, I'm suppose to size them -.002 to allow for expansion using the full length die, right? Now when I size using the FL die no matter what I do the cases come out +.006 over the minimum size, I just can't get them any smaller.

I'm using RCBS dies
Calibre is .243

Any thoughts or advice would be greatly appreciated.

Lazo G

Well..yes and no...

Assuming you are loading for a bolt action hunting rifle...

You should resize so your cases will easily chamber in your rifle.

Forget abotu the specs for a moment- each rifle is slightly individual.

Resize a little at a time, until your cases will easily chamber. Remember that you must take into account OAL and trim accordingly.

Many reccomend FL resizing for all hunting ammo, and neck or partial sizing for accuracy, but I think it is best to find what works for your rifle the best.

maximum accuracy is often attained by using cases that are sized only a little, but if you want no problems in the field, you must resize enough so that there is no little resistance when chambering your ammo.

SO- resize a little at a time, checking the case for chambering. When you have it so that it will nicely fit your chamber, you are done.

So, no matter what your mic tells you, your gun will tell you what is proper..

Then you get to play around with seating depth of bullet- a whole new ball game.

All of the above assuming the brass has been fired in the rifle for which you are reloading.

OK, I'm still confused as to why the case are coming out longer after they have been resized, and is that OK for the cases to be longer than my fired brass. It just seems wierd.

I should have mentioned that I was measuring once fired brass and that I was shooting a bolt action.

As Gene said if, you'r measuring the overall length of the case,it will lengthen somewhat with each full length sizing operation. Its normal and nothing to be concerned about as long as you trim the cases when or before they reach the maximum case length.Fired cases usually are shorter before they are resized. You can't control the overall length of the case with the sizing operation. Heres a link to Stan Watsons site,has some good info for beginners and pros both. http://www.reloadingpro.com/
Jeff

Just want to mention that I'm using the Precision Mic to measure the cases and it measures them from the base to the datum line on the shoulder it's not an overall case length. I believe it's the head space length.

Just making sure because that doesn't make sense to me It seems like they would have chambered hard to begin with .

could you be dragging the expander back thru the neck, thereby stretching it back out? did you lube inside the necks? mica is good for inside neck lube.

Sometimes the neck expander will drag brass ( and sometimes the shoulder) forward.
Take a Q-Tip and wipe a little case lube on the inside of the case where the neck
meets the shoulder befire full length sizing.
Good Luck!

Every time you FL size any cases they will stretch. Only neck sizing only will reduce case stretch to a minimum. Over working your brass is not condusive to long brass life. The standard 243 SAMMI spec chamber can stretch a good bit when you FL size them every time. If your shooting a bolt action 243 you will get longer brass life by neck sizing only. Neck sizing only demands you use that brass in the same rifle it was fired in as it will not work in another rifle.

You must have limited experience in reloading if you think FL sizing your brass should not stretch your cases between firings. Only neck sizing brass will limit how much it will stretch form one loading to another. Trim your brass per your reloading books instructions. Brass length is critical in order to not jam a case that is to long in the chamber. Pressure spikes can occur and may damage the rifle by not letting the bullet release properly when the rifle is fired.

Any time you FL size any case it will stretch and trim length must be checked and adjusted as needed. The AI version of the 243 case will stretech less when FL resized. Neck sizing cases improves accuracy and keeps the case chamber size for the least amount of brass workage.

Thanks for the great info.I just want to get this straight, if I have a tight chamber and want to size my brass to suit there is a possibility that the dies I'm using may not allow the brass to be sized that much. Are there dies that will give me a greater range of adjustment or is that not possible, necessary or relevant? Sorry if my question sounds a bit dumb, I'm still a bit of a newbie.

I should also add that the die is adjusted down to the shell holder and I use mica to lube the inside of the necks.

Thanks again.

If indeed you are measuring the shoulder length right is questionable. You are calling that dimension the minimum. What exact number are you calling the minimum? Do you mean the chamber or cartridge dimension? Do you have the cartridge and chamber drawings? What are the actual readings before and after sizing? How does a sized case chamber?



In general one does not need to measure anything but the case overall length and trim that if necessary. One just sets the FL die to size the fired case just right.

You have great expanations of how cases stretch.

You still haven't mentioned whether or not the cases chamber in your rifle.

You've also stated the brass is longer than "minimum". What is the "minimum" to which you refer and where did you obtain that.

It IS possible that the dies aren't sizing enough. Mistakes can be made. However, merely touching the dies to the shellholder doesn't insure proper full sizing. Did you adjust the die to butting agains the shellholder and then turn the die down another � turn so that the press cams over?

Measure a case fired in your chamber with the Precision Mic. Whatever that measurement is, is the headspace length of your chamber. All you need to do is size a case so that the measurement is either the same as the fired case or about .001" under that size. If it will chamber and you get the -.001" measurement in a fired case, you're there.

Make sure your die is adjusted as above. If you don't get this measurement then send the die back for adjustment by the manufacturer.

I use the Mics all the time.I even set my belted magnums to the shoulder rather than belt. I measure the fired brass to get the headspace and set the dies to size 2 thousands smaller. Problems I have run into. Ammo may not fit other guns as factory is -.02 on gauge. I had a set of RCBS 22-250 dies I had to file the bottom to get desired sizing( would only go down to +.06 and gun was +.02) . Used brass will work harden and I have had to run some brass thru die twice. Some still would not resize enough without adjusting the die some more. I have had the expander ball stretch the neck back out and now polish the expander ball in a drill with 600 grit polish.

Forget all this tech crap, trim your cases properly (thats 10 thous.) and then resize them...Every time you resize a case it lengthens..Cases need to be trimmed about every 4 loadings or more, depending on how maxed out your loads are....Necks stretch when the expander ball is pulle out of them...

When you size your case, does it take a lot of effort to pull it clear of the resizing die? If so you're having
trouble clearing your expander ball. A little resizing lube inside the case neck will make the expander ball
work a little smoother, reducing the pull and thus the amount of stretch you're experiencing. This is just
another curse of the damn expander ball. It's the reason I use Wilson knock out dies. Don't forget to
take a Q-tip and wipe the sizing lube back out of the neck when finished. Best wishes.

Cal - Montreal

OK guys, he's not talking overall case length,but headspace. The problem is that his die is not bumping the shoulder back if I understand correctly? You said that you have your die adjusted so its touching the shell holder? You need to go further.As Ol'Joe said
"Screw the die down until it touches the shell holder with the ram in the top of its travel, then add about 1/4 turn. You should feel the ram cam over when you size. Brass has to go some where when you squeeze it and its path of least resistance is along its lenght. The RCBS tool will allow you to find the best die setting by adjusting and mic`ing then lock your die at this setting and leave it. The optimal setting will have your head space at ~.002 max below the fired measurment to the datum."
I adjust the die down in 1/8 increments,myself,but whichever you want to do. When you get the reading on your mic where you want it lock your die and make sure the case will chamber.
Jeff

Somebody else posted that they had to modify theirs. What dies do you have?Have you used them before? It doesn't seem that the resized cases would even chamber at least without considerable resistance. I'd contact the manufactor monday,as it sounds as if you'v tried all else.
Jeff

Lazo,

Does a sized case chamber in your rifle?

Whoah!!!

Don't file your dies just yet!

Put the mic away for a second.

Do what Atkinson suggested.

1. Trim a case to the length described in a loading manual. For a .243, it's 2.035 according to the Speer manual. This will give you a bit of room to manouver.

2. Put a shellholder in your press, and raise the ram.

3. Screw down the die until it touches the shellholder, then back it off about one turn.

4. Lube and resize a case.

5. Check it in the chamber of your rifle. If it won't chamber, or it requires force to chamber, screw down the die a 1/4 turn at a time until it chambers with no resistence.

6. Measure THAT case,a nd write it down. Lock the ring on the die so that it doesn't move.

7. Place a bullet in your (uncharged) case and load it with your seating die. Make sure that it chambers properly.

Now you can play around with bullet seating depth.

Reloader66; If as you say Fl sizing lengthens the case, why then dosen't the case return to the
properl length upon firing?. It has been my experience that the neck sizer has a lot to do with growth.
Size your cases with/ and without the neck sizer and see.
Take Care?

Lazo,

What is the overall length of the cases after sizing?

Is there any mark or reduction in diameter on the end of a neck after chambering?

What brand of shell holder are you using?

Yes you can reduce the size of a die or shell holder, buy shell holders that are smaller or larger in height or send the dies and fired cases back to RCBS. The dies are quite hard and a stone will work better.

Remove the firing pin from your bolt. That will improve the feel.

I'm with Atkinson. Forget that die you have. Fire the case, trim it to OAL, and load and fire again. I've gotten to liking the Lee collet dies real well. Haven't had a bit of trouble with headspace or chambering. For cartridges that I do not have a Lee die for I use Redding neck sizers and always lube inside neck with a qtip to reduce drag. No problems. It seems like after an initial trimming after first or second, third, whenever, firing, trimming is no longer an issue - but length is still watched. In fact most cases seem to shrink some. Belted mags included. Seems to me the only way to control headspace with a die would be to custom cut the die to you chamber. sundog

I've tried that Q-tip method only once, never again! Talk about labor intensive! I use the excellent RCBS nylon case neck brushes. Simply roll the brush lightly on the lube pad, pass it in and out of the neck, then size as usual. It leaves a light film on lube on the inside of the neck, just ebough to ease the expander button through. Mica is not the answer either. I tried it once also, not much difference from using nothing!

This sounds like a die that is on the max tolerance for length. OR an undersized chamber. Dies ARE quite hard. A normal file should not cut them. Also getting the bottom square would be nearly impossible. A lathe with a carbide cutter would be needed. Best bet would be to send several cases fired in your rifle to RCBS, along with the die. They will determine if the dies is over long or if not then take a cut off the bottom to allow it to size to your chamber.

LazoG,
I had RCBS dies for a 222Rem. that had to be altered to get the cases short enough after FL sizing to fit the rifle. So You may have to alter the dies, but this needs to be done with extreme caution. This was the only way I was able to get the FL die to size down to were the case would fit the rifle. I had to remove .010 off the OAL of the die to get it to work properly and so far everthing seems to work fine.
Gravel

On rare ocassions a die may need alteration but before I did that I woul alter the shell holder if I was looking for a very small amount, then you won't ruin a set of dies...but from what you have said I believe all you need to do is perhaps take 3 thousands off the return button and trim your cases.

Went out and bought myself a set of Redding Competion Shell holders today, these things are great. I put the +.008 shell holder in the press adjusted the die a bit and presto cases come out the exact size I needed. Problem solved and I didn't have to grind my die down. Lets see if accuracy improves now.

Thanks for all the great replies.

I'm not sure I understand you question.



You should measure the length of your cases only AFTER resizing them. Then trim them if they need trimming.



The length of the case before you resize it is irrelevant. All cases change in length during resizing, and the amount of the change is not easily predictable, nor does it matter.



Also, don't be concerned whether your fired and/or resized cases conform to new factory brass. It is almost certain not to conform exactly. What matters is whether your resized cases go into your rifle without undue pressure on the bolt.



If these cases do go into your rifle readily, then there's no problem. If they do not, it could be because: (a) the chamber of your rifle is unusually tight (undersize) and/or (b) your sizing die is unusually large (oversize) or (c) your cases are too long to fit your rifle's chamber. If (a) is true (this is highly unlikely if you have a factory bolt action rifle), then you MAY need a special die, made undersize, and known as a Small Base Sizing Die; these are made by RCBS.



The act of firing a cartridge causes its brass to expand to fit the particular chamber of the rifle it is fired in. For this reason, it is frequently true that fired brass from a given rifle will produce somewhat more accurate loads for that rifle than will new brass.



Summary: Size your fired brass. Then measure it for overall length, measured from the outside base of the cartridge to the cartridge mouth. If it is too long, then trim it. Do both of these steps only AFTER sizing the brass.

LazoG: I am confused by all these posts and would like to back it up a little. My first question is what kind of bolt action are you using? Is it factory or custom? My second question is have you made a chamber casting?

I do not want to insult you, but the case length for a 243 Winchester is 2.045. If you are loading hot and exceed that length, the excess case length will curl in on the bullet and this will raise the chamber pressure very quickly and can be very dangerous. This is why one must trim the case length any time it exceeds the book standard.

Let me try to explain why the case stretches. Brass is soft and made to expand and contract upon firing and cooling. Because it is soft, brass will flow from the web to the neck as it becomes displaced. Your dies can have the same affect if not properly lubed. Have you noticed a bright ring on the case just ahead of the web? That ring indicated the thinning of the case wall. Where did it go? The brass went to the neck and should be trimmed off to 2.045 or less. Please don�t use a case that exceeds 2.045 in a custom chamber that may be real tight. You may not like the experience. You won�t have any trouble cranking such a round because of the bolt will act like a press and simply crush the case neck into the bullet. Thus, chamber pressure will rise dramatically. Just trying to help.

LE 270,
I agree with your posts however I would bring to your attention that many of the trimmers out there today have the caliber guide that is sized to fit only unsized brass, so it will work either way, before or after, your going to get a little stretch in every thing you do and trimings needs doing at least every 4 reloadings or perhaps more, so before or after probably wouldn't make a lot of difference.