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If fired cases fit back in the chamber, why are you resizing anything but about .100 of neck? If you want precision, you have it in a case that IS the same as your chamber, less a smidge of spring-back. All you need now for the case to be perfectly concentric with the bore is to shrink a bit of the neck to hold the bullet.

The taper of the body fits the taper of the case and most of the neck is a slurp fit to the neck portion of the chamber and the bore diameter portion of the bullet is a slup fit in the throat.
STRAIGHT, SOLID and SQUARE equals ACCURACY.

THIS is where dimensions come into play. I'll use a good shooting 6mm as an example because I just ordered 'dies' an hour ago. It's a custom barreled Ruger #1 with a 'standard' chamber, neck and throat.

Factory unfired cartridge (old W-W) .270 neck OD.
Resized, new 257 Robts necks with bullet seated is .273 This is what I'll be shooting.
Fired neck OD .278

I just ordered a Wilson neck bushing .270 in diameter. The .257 brass is a better fit (.005 instead of .008). The neck expands to .278 but only the last .100 is resized. The re-sized portion of the neck is about .0025 smaller than the bullet.

You can do the same with Lee collet die or any number of neck bushing dies now available. No expander plug and no need for one. Size ONLY what needs it. That's where the accuracy comes from. Tolerances are for dirt, dust and other field conditions. Reliability goes WAY down when you start trying for zero-zero tolerances, but at least fitting factory chambers is not as 'dangerous' as BR necks and only .001 neck clearance.
Using this method, you'll never have to anneal brass and brass last many, many reloads before the primer pocket gets too loose to hold a primer. They'll always be more accurate than a case that rattles' in the chamber.
 

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Discussion Starter #42
If fired cases fit back in the chamber, why are you resizing anything but about .100 of neck? If you want precision, you have it in a case that IS the same as your chamber, less a smidge of spring-back. All you need now for the case to be perfectly concentric with the bore is to shrink a bit of the neck to hold the bullet.

The taper of the body fits the taper of the case and most of the neck is a slurp fit to the neck portion of the chamber and the bore diameter portion of the bullet is a slup fit in the throat.
STRAIGHT, SOLID and SQUARE equals ACCURACY.

THIS is where dimensions come into play. I'll use a good shooting 6mm as an example because I just ordered 'dies' an hour ago. It's a custom barreled Ruger #1 with a 'standard' chamber, neck and throat.

Factory unfired cartridge (old W-W) .270 neck OD.
Resized, new 257 Robts necks with bullet seated is .273 This is what I'll be shooting.
Fired neck OD .278

I just ordered a Wilson neck bushing .270 in diameter. The .257 brass is a better fit (.005 instead of .008). The neck expands to .278 but only the last .100 is resized. The re-sized portion of the neck is about .0025 smaller than the bullet.

You can do the same with Lee collet die or any number of neck bushing dies now available. No expander plug and no need for one. Size ONLY what needs it. That's where the accuracy comes from. Tolerances are for dirt, dust and other field conditions. Reliability goes WAY down when you start trying for zero-zero tolerances, but at least fitting factory chambers is not as 'dangerous' as BR necks and only .001 neck clearance.
Using this method, you'll never have to anneal brass and brass last many, many reloads before the primer pocket gets too loose to hold a primer. They'll always be more accurate than a case that rattles' in the chamber.
I think you are probably looking at a whole different level of precision than I am. I do want reliability in field conditions, as I intend to do some hunting with my rifles too, and I often shoot in less than perfect conditions. I'm looking for sub-moa (because I know from previous experience it is capable of it) and obviously to make the case head separation issue stop.

Your neck sizing advice makes sense, I'm resizing with an FL die because it's what I have available. I've only ever neck sized for my 22-250, and only because the Hornady FL dies available at the LGS were out of specs, so I returned them and got RCBS neck size dies. I've been left under the impression that the neck sized brass will continue to grow until it will need to be FL sized anyway(I've never personally experienced this yet), so I've been buying full length dies at the advice of a lot of people who are better shooters, with a lot more experience than me. With the hope that they know something I don't.

I may just buy another rifle and start over with load development if this one gives me too much trouble.
 

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OK--- Now we're getting somewhere. You want tolerances but not too much to effect good accuracy.

Think of a machine taper again---(You can do this experiment without getting fired) Stick a piece of tape on the shank of the taper shank tools. Does it still fit the socket? It'll stick out nearly a quarter inch! From just one piece of .003 tape!

If you back off on the FL die by ONE FULL TURN, you'll only resize the neck because it's parralel. the TAPERED sides won't touch unless your chamber is very large or die very small. In that case corrections would have to be made.

Your chamber is bigger than the case and the case is bigger than the die. Where is it bigger and by how much? You can cast the chamber and the die and measure directly, except those #^@^ TAPERS defy measuring without ring gauges, sine table and gauge blocks. All we can do is eyeball micrometer positions and try to see how much bigger the shoulder is in the chamber compared with how big the shoulder is inside the die. You'd really like to see only a .004 difference between chamber and the die and have the cartridge dead in the middle. This would be cutting SAAMI tolerances by a factor of about 4 (!!!) (SAAMI specs are nothing to be proud of.)

Cut the neck off a fire-formed case and see where it hits the die. That'll give you an idea of the 'fit' between chamber and die and so also, the fit between chamber and re-sized cases.

Dies can be diamond lapped to a specific size if you care to do it.
 

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JBelk,
Your advice is top notch and doesn't require the cartridge length comparator. I use the comparator to measure my new cases, fired case and then start with the die set high and gradually lower the die while sizing until the length is reduced by .001". I record that length and then I check it again after firing to check for growth in the length to the shoulder. Now, I always start with new unprimed cases and run them through the sizing die to make sure the neck is round and at the right diameter and then run them all through the trimmer to check for long cases. (sizing 7x57 cases to 257 cases they do come out a bit long but when I am not forming cases they rarely trim.

I believe that your student has the die adjusted the way the instructions say with screwing it down until it hits the shell holder and then 1/2 to a full turn down. That would cause the case head separation. As long as he continues to size that way he will continue to get head separations.
I hope he listens to you... ;)
 

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Discussion Starter #45
JBelk, I'm planning on doing some shooting this coming weekend, so I'll cut the neck off of a fire formed case then, and report my findings. I'll try only sizing the neck too.

shooterPaul, I was previously reloading as you suggested, with the die all the way down, plus a bit more. I'm pretty sure that you are right, and this is the cause of my issue. So I am not doing that anymore. That is why I have been asking about "bumping the shoulder back". I'm hoping to avoid buying new dies at the moment. In the future I'll buy a nicer set, but at the moment I'm in kind of a weird spot financially. In the past month I paid off all of my debt, to include my house and all but one car, and bumped my retirement contributions up to 15%, so money is going to be good soon, but I'm being really cautious about my spending right now until I get a good grip on exactly where I am at. When everything kind of levels off, I'll be more likely to buy better equipment, but for now I'm just trying to work with what I have.
 

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JBelk, I'm planning on doing some shooting this coming weekend, so I'll cut the neck off of a fire formed case then, and report my findings. I'll try only sizing the neck too.

shooterPaul, I was previously reloading as you suggested, with the die all the way down, plus a bit more. I'm pretty sure that you are right, and this is the cause of my issue. So I am not doing that anymore. That is why I have been asking about "bumping the shoulder back". I'm hoping to avoid buying new dies at the moment. In the future I'll buy a nicer set, but at the moment I'm in kind of a weird spot financially. In the past month I paid off all of my debt, to include my house and all but one car, and bumped my retirement contributions up to 15%, so money is going to be good soon, but I'm being really cautious about my spending right now until I get a good grip on exactly where I am at. When everything kind of levels off, I'll be more likely to buy better equipment, but for now I'm just trying to work with what I have.
You may not need different dies or additional equipment although some way to measure your cases to establish the die adjustment necessary would make your adjustment of your dies easier. You can set your sizing die to just barely size the neck by watching how much of the neck is getting sized. Careful adjustment until most of the neck is being sized and then monitoring the fit of the case in your rifle as JBelk has recommended is likely to work fine. the only thing you have to watch for is if the bolt starts to close hard when chambering the sized case. Sizing just the neck over time may move the shoulder forward and then you can readjust your die to just clear that problem. At that point you have the dies properly set for your gun. The adjustments in that final step are very small, less than a 1/16 of a turn each step.
You don't need expensive equipment to build accurate loads, just patience and some good advice. I will defer to JBelk's knowledge as an instructor and remain quiet so you only have to listen to one voice. I do wish you the best in your loading process.
Paul
 

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Just an example of what we face with the tools for sale that 'fits them all' but overworks brass in the process.

RCBS FL die set dated '77 6mm Remington

Factory load fired in Remington M700BDL ('63) Chamber neck ID is .2798.
started out factory W-W neck dia of .2705.
Fired diameter .279.
Resized diameter .269,
after .242 expander ,neck is .270 again.
Seating the bullet gives .2705 diameter.

It was blown out by .009, sized down by .010 and expanded by .001 and expanded again when the bullet was seated.

When you adjust a die all the way down for FL re-sizing, ALL of the neck is resized, but all that's needed to hold the bullet is about .100 sized just enough to hold the bullet.

By using a neck bushing die to size to .269 the last .100 of neck, brass 'movement' is reduced by about 90%. That extends case life a LOT.

Cases cannot 'grow' in headspace length unless the gun does it first. After several firings, the tiny irregularities in the chamber will 'stack' enough to make the bolt too hard to close (Expect some feel on fireformed rounds). At that point, take the bush out of the die and carefully adjust the die to smooth the case enough to chamber easily. No shoulder has been changed UNLESS THE GUN HAS EXCESS HEADSPACE. Dies and shell holders don't allow it. They only size to zero headspace, not less than.

If your die pushes the shoulder back it is because the rifle allowed it to grow.
 

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Short enough isn't the problem, mine were too short for my chamber. My problem is consistency. I believe it is just variation of the brass. I'm hoping the annealing reduces the variation and helps with consistency.
Actually, my post #22 covered both shortening (first paragraph only) and making the head-to-shoulder distance longer (the second and third paragraph). I re-read it and realized I hadn't made the change in direction explicitly clear. I have gone back and rewrote three of the sentences to make that clear. If you reread it, you will see it addresses your problem, especially the third paragraph.

Jack is correct that you only need a GO headspace gauge (aka, a breeching gauge). The additional gauges you mentioned will only bracket your actual chamber size. You'd need a full armorer's set of gauges in 0.001" increments to get closer. There is an easier way. Rather than invest in the required pile of extra gauges, you will get better information by buying or improvising a case comparator. Just use it on your GO gauge as the zero number, then apply it to one of your fired cases that has not yet been resized. The fire-formed case will be close to your actual chamber size, less one or maybe two thousandths at most because of spring-back of the brass. You can also neck-size the brass only and re-fire it a couple of times without FL sizing to tighten that dimension within half a thousandth.

That is what is called a transfer measurement. The dimensions being measured are transferred from the chamber to the comparator via the fired case serving as the transfer gauge. A lot of comparators and the RCBS Precision Mic make this indirect measurement of chamber headspace and have called themselves headspace gauges. Because the object being directly measured is the transferring case, this has gradually misled a generation of handloaders to think the case itself has headspace. But headspace is the room needed to accommodate a case, and since the case isn't designed to have another case inserted into it, it has no headspace, despite the widespread use of "case headspace". Just replace headspace with "case accommodating room" and you will see it makes sense applied to the chamber but not to a case. I mean, sure, you could fit .25 ACP brass into .30-06 cases, but that fact has little practical value. (Someone may point out the 25 ACP case can be used as a jacket for swaged .277 bullets, but that's rather stretching a point.)

You can buy the Hornady or Sinclair case comparators or an RCBS Precision Mic in your chambering, but here is an improvised approach to try. Just fine a spacer about the diameter of the middle of your case shoulder. It may not be exact shoulder datum diameter, but this is a comparison to see how many thousandths longer than the GO gauge your fire-formed shoulder is, so just zero the caliper on your GO gauge and measure your case:


 

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What I have sized for my 30-06 pre-64 has no issues chambering in either of my O3-A3's. Not so the other way around.

My 270 #1 is very tight and has to be FL sized all the way to the base which is why I have to keep them and my Model 70 brass separate.

I have a pair of 25-06...one a #1 and one a custom Mauser. They both love the same ammo and if a load shoots well in one...it will in the other. I wish all were like that. :D

Joel
 

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Discussion Starter #50
Short enough isn't the problem, mine were too short for my chamber. My problem is consistency. I believe it is just variation of the brass. I'm hoping the annealing reduces the variation and helps with consistency.
Actually, my post #22 covered both shortening (first paragraph only) and making the head-to-shoulder distance longer (the second and third paragraph). I re-read it and realized I hadn't made the change in direction explicitly clear. I have gone back and rewrote three of the sentences to make that clear. If you reread it, you will see it addresses your problem, especially the third paragraph.

Jack is correct that you only need a GO headspace gauge (aka, a breeching gauge). The additional gauges you mentioned will only bracket your actual chamber size. You'd need a full armorer's set of gauges in 0.001" increments to get closer. There is an easier way. Rather than invest in the required pile of extra gauges, you will get better information by buying or improvising a case comparator. Just use it on your GO gauge as the zero number, then apply it to one of your fired cases that has not yet been resized. The fire-formed case will be close to your actual chamber size, less one or maybe two thousandths at most because of spring-back of the brass. You can also neck-size the brass only and re-fire it a couple of times without FL sizing to tighten that dimension within half a thousandth.

That is what is called a transfer measurement. The dimensions being measured are transferred from the chamber to the comparator via the fired case serving as the transfer gauge. A lot of comparators and the RCBS Precision Mic make this indirect measurement of chamber headspace and have called themselves headspace gauges. Because the object being directly measured is the transferring case, this has gradually misled a generation of handloaders to think the case itself has headspace. But headspace is the room needed to accommodate a case, and since the case isn't designed to have another case inserted into it, it has no headspace, despite the widespread use of "case headspace". Just replace headspace with "case accommodating room" and you will see it makes sense applied to the chamber but not to a case. I mean, sure, you could fit .25 ACP brass into .30-06 cases, but that fact has little practical value. (Someone may point out the 25 ACP case can be used as a jacket for swaged .277 bullets, but that's rather stretching a point.)

You can buy the Hornady or Sinclair case comparators or an RCBS Precision Mic in your chambering, but here is an improvised approach to try. Just fine a spacer about the diameter of the middle of your case shoulder. It may not be exact shoulder datum diameter, but this is a comparison to see how many thousandths longer than the GO gauge your fire-formed shoulder is, so just zero the caliper on your GO gauge and measure your case:


I think JBelk has me on the right track as far as resizing goes.

I understand that I only need a go gauge. If I do decide to get the others, it's only because I like buying tools for no other reason than I like tools. I bought a table saw and a generator a few years ago, I've still never used either one. The generator was still in the box up until recently. I got the box wet so I got it out and put it together. It still has never had gas in it. I should probably test it out.

I have a similar custom made comparator. I turned mine out on a lathe and slotted it on a mill, then tapped it for a bolt to hold it in place. It's not perfectly at .400" but it's close enough for comparison of fired cases. I gave mine a smaller diameter hole up above the neck so I can check seating depth too.
 

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Discussion Starter #51
What I have sized for my 30-06 pre-64 has no issues chambering in either of my O3-A3's. Not so the other way around.

My 270 #1 is very tight and has to be FL sized all the way to the base which is why I have to keep them and my Model 70 brass separate.

I have a pair of 25-06...one a #1 and one a custom Mauser. They both love the same ammo and if a load shoots well in one...it will in the other. I wish all were like that.




Joel
If they were all like that, reloading would be a LOT easier, but probably not necessary. We could just buy precision ammo.
 

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Here's the SAAMI page for the caliber. This tells all we need to know about fit of chamber and case.

Notice, the fit of the case to the headspace dimension can be as much as .014 in a factory gun shooting factory ammo. What dimension is the die?
 

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Discussion Starter #53
Here's the SAAMI page for the caliber. This tells all we need to know about fit of chamber and case.

Notice, the fit of the case to the headspace dimension can be as much as .014 in a factory gun shooting factory ammo. What dimension is the die?
I'm not sure what dimension the die is. I've ordered some cerrosafe so I can hopefully get a good idea. It should be here Thursday.
 

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To make a 'Field' gauge, simply stick three layers of masking tape (.003) to the rear of a GO gauge. If the bolt closes without 'feel' on that, the gun is unsafe to shoot.
That is not the best option but for someone that that does not have shop skills that is the best it is going to get.

Unsafe to shoot? To avoid looking/sounding ridiculous you should avoid talking about head space.

F. Guffey
 

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Discussion Starter #55
JBelk, I tried to neck size only, by taking the guts out of my sizing die and backing the die off until it just started to touch, but it touches the body long before it touches the neck or shoulder. Here is a picture of a piece of brass I marked with a sharpie so I could see what was going on, and a pic of how far it goes into the die before it touches.
20200607_193705_1591573388241.jpg 20200607_194127_1591573409490.jpg
 

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YIKES!! Either the chamber is big or the die is small (more likely) but they're severely miss-matched either way.

You say a fired case will rechamber so the chamber is round. What you need is a larger die but one not quite as large as your case. The best way to do that is send three fired cases to a die maker and let them match you up. They 'can be' lapped, but it can't be rotary motion, but reciprocating 'piston' motion instead that does it. It's slow, tedious, repetitive and prone to failure, but if you can find and old die to experiment on and have a drill press, it's worthwhile. I'll write instructions if you want to tackle it.
 

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Discussion Starter #57
YIKES!! Either the chamber is big or the die is small (more likely) but they're severely miss-matched either way.

You say a fired case will rechamber so the chamber is round. What you need is a larger die but one not quite as large as your case. The best way to do that is send three fired cases to a die maker and let them match you up. They 'can be' lapped, but it can't be rotary motion, but reciprocating 'piston' motion instead that does it. It's slow, tedious, repetitive and prone to failure, but if you can find and old die to experiment on and have a drill press, it's worthwhile. I'll write instructions if you want to tackle it.
The instructions would be great. I might try it. Either it will work, or I screw up a die, and I'm right back where I am now, and need a new die.

Strangely enough, this would be the third Hornady die that was too small, that I have bought. I had two 22-250 FL dies that were too tight before I bought the neck die from RCBS.
 

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Lapping Dies

It would be hard to say the dies you bought were 'too small' without measuring them. It is more likely the chambers to your rifles were over-sized. One of the disadvantages of 'less body taper' is that cases don't go as far in the die without running into the walls. (A 30-06 case will slide further in the die than a .308 due to body taper even though both expanded the same amount.)

To start, you need accurate measurements of the chamber and the die. I use sulfur because it's cheap and readily available and just as accurate as any other substance. The critical measurement is at the shoulder/body junction, but that is one of the hardest measurement to make accurately so you need to make a 'gauge'.

The gauge is made from a case fired in your rifle with a full load. Carefully cut off the neck and shoulder leaving the full body. It's handy to drill and tap the primer pocket so you can screw in a 'handle' for the rear. Pour the case full of molten sulfur or epoxy to make it 'hard'. THAT gauge is your rifle's chamber size. If it slips into the die with exactly .125 left sticking out of the die, it means the chamber and the die are the same size. You want to leave the die slightly SMALLER than the chamber to give the clearance you want in loaded ammo.

Without getting deep in the weed with trigonometry and sines and cosines and complications, we'll make an educated guess that you want the body of the case at the shoulder to be resized .002 smaller than your chamber. A wild guess at the geometry says the base of the case should stick out of the die about .100 when the surfaces meet, so a total of .225 from the base of the case. That should allow about half the neck to be resized before the 'point' of the body-shoulder makes contact with the die. It looks like you might have .500 sticking out now.

TO MAKE THE LAP--

You'll need at least three laps.
Drill and tap the primer pockets to attach a drive rod. Trim the case back to the point of the shoulder-body junction. Split the case into four 'fingers' back to where the case head starts getting thicker. Be sure to de-burr the cuts so the outside of the split case is smooth. Hold the drive pin in the drill press chuck and set the die up in a Vee block on the table so you can plunge straight into the die accurately with the quill. Clamp stops to the table so you can removed the case and vee block together for cleaning and testing and replace them to the exact same place under the quill.

You should be able to push the lap into the die with the drill press handle and feel the 'spring' of the 'fingers' as they're forced into the die (drill press NOT running yet). Get a feel for how much material has to come out of the die by how much compression you feel on the lap. Set the down stop so the end of the lap has to stop at the point of the shoulder.

Smear some 320 valve grinding compound on the lap, turn the drill press on the lowest rpm, add a squirt of light oil to the die and start lapping by going in and out with the rotating lap untli you feel it start to 'relax' in spring the die gets bigger. The lap will stay the same size but gradually lose it's 'spring' in the fingers and have to be changed to a new one to continue cutting. Add a little oil so you can 'feel the grit' and keep it juicy and in suspension.

Lap for about five minutes then remove the die and vee block, flush out the grit and wipe the inside of the die clean and check your gauge to see how much progress you've made.

When you gauge is sticking out about .250 (.025 short of the goal), switch to a new lap and finer grade lapping paste. I like 40 micron diamond for step two. (ebay $10). Keep it juicy and don't 'let the lap ride' in one place. Keep the in and out motion to keep the body straight and true. The inside of the die should show criss cross polishing marks just like the inside of an engine cylinder. Lap with this grade until you gauge sticks out about .230 then switch to a finer grit like 10 micron diamond paste. Carefully lap in and out while rotating slowly until the gauge finally sticks out the proper (guessed at) amount. You can test the die anytime you like by re-sizing a case, but be sure to use a lot of really good lube because the die is not finished polished yet and cases can stick easily.

When it all looks and gauges properly, use a piece of 3/8 wooden dowel with a split in the end to polish the die with 600 wet or dry, in and out by hand to smooth and polish the die to near the original finish.

To make a neck size only die is considerably easier because you don't have to split the laps into fingers, just use a fired case (cut back to the shoulder) to lap until it the gauge stick out .125 and you have a die that no longer sizes the body but still sizes the neck and leaves the shoulder un-altered.
 

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Discussion Starter #59
Wow, that's pretty in depth. Given the amount of play in my drill press, and the cost (although low) of materials, I think I will probably just buy something like a Lee collet die, since it's cheaper than the lapping compounds.

The 22-250 die issue was really weird. It was like it was too long but too skinny as well. The brass took an excessive amount of force to resize, but once resized it would not chamber in my rifle or it would chamber, but really hard. I borrowed a good set of RCBS FL match dies and everything worked just fine.
 

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Ive had much 'problems' w/ case expander ball coming out of case w/ difficulty, lots of force req.


Ive settled on a small ointment jar w/ 7.5 or 8 birdshot in it. About the shot from 2 12 ga shells (2 oz or so). Just fill the jar 3/4 full of shot.

A friend gave me a nice quantity of graphite and I added about a nice TEAspoonful to the birdshot in the oint jar. Before starting to load turn the jar upside down (w/ lid on of course), shake a few times and then dip the case mouth into the graphited birdshot and resize. Add graphite as needed to get some on the inside/outside of each case.



Be careful NO birdshot hang up in the case as it will ruin the decapper pin.




It does req tumbling after sizing to clean cases, IMHO. I like clean cases.


I have to find some lanolin for the outside of cases. The stuff Ive been spraying is no good.
 
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