Does brass fired in my chamber make more accurate reloads?

[westernrover]

I suppose that brass fired in my chamber fits tightly compared to factory-new brass or loaded cartridges that must fit in a SAAMI minimum-dimension chamber. This tighter fit should result in less movement of the brass during firing and more consistent/accurate results. However, I must resize the brass at least some if I am to expect it to chamber reliably.

I could practice neck-only resizing, though I understand that has fallen out of favor to the point of being mocked and ridiculed. Instead, I have used a Redding body die to bump the shoulder. I don't bump by the thou, but so that the bolt handle (with the spring removed) drops on all cases without resistance. In my experience, this has required bumping most cases a couple thou so that there are no cases that aren't bumped enough. As long as I am using a bolt gun, I will check with that. For a semi-automatic, I suppose I would have to bump 2 or 3 thou to ensure all the cases would chamber without issue.

I recently bought a full-length bushing type sizing die (for a cartridge different than any I previously loaded). I am lacking a comparator insert for the case (out of stock), so I haven't been able to adjust the die precisely yet. What I've noticed is that the body diameter is being resized back to factory cartridge dimensions. This means it's going to fit loosely in the chamber, except for the headspace against the neck which I will be able to control when I'm able to set the bump.

Should I hone the full-length sizing die out so the brass is squeezed down less and fits more tightly? Or is just bumping the shoulder no more than necessary sufficient to achieve a fit in the chamber that will provide the best accuracy?

If my un-honed die is going to resize the body to a loose fit, and only the shoulder will be fit to my rifle's chamber, do I really need brass fired in my chamber to make accurate loads, or can I just use brass fired in any chamber so long as I can set the shoulder datum to some spec?

 

[Jim Watson]

Gee, I don't know because I have not done it any other way. Any centerfire rifle I shoot carefully at a target has its own brass.

 

[westernrover]

What are you accomplishing by dedicating brass to a particular rifle? Do you neck-only size? If not, what dimensions are matched to the chamber and how?

 

[Skgreen]

.

 

[westernrover]

What is the difference between bumping and full-length sizing? How can a case be bumped and not full-length sized?

Are you saying that if a full-length sizing die is adjusted to bump the shoulder 10 thou the results will be just as accurate as if it were adjusted to bump it 2 thou?

 

[Skgreen]

What is the difference between bumping and full-length sizing?

Should be able to find more info on that using the Search feature.

 

[Jim Watson]

I neck size for bolt actions because that was the standard when I learned to reload. Partial sizing with a "bump" is the current fashion.

I full length size for my hemi semi demi auto target rifle, but it still has its own lot of brass, weight sorted at that.

 

[Walkalong]

What is the difference between bumping and full-length sizing? How can a case be bumped and not full-length sized?

Are you saying that if a full-length sizing die is adjusted to bump the shoulder 10 thou the results will be just as accurate as if it were adjusted to bump it 2 thou?

10 thousandths would be waaaay too much.

You can make very accurate ammo with any decent brass, whether it’s new, once fired in your rifle, or fired brass from another rifle.

“Bumping” the shoulder just mean’s adjusted the full length sizer die to only move the shoulder from brass fired in your rifle a couple of thousandths. If you have some way of measuring where that is, you can size brass from other rifles to the same spot.

 

[westernrover]

Should be able to find more info on that using the Search feature.

My point is that there is no difference. Am I mistaken? Bumping the shoulder is not partial-length sizing. It sizes the full length of the case and pushes the shoulder in. I've never seen a die that would bump the shoulder without the die touching the shell holder and full-length sizing the case. It's possible to partial-length size a case, but the shoulder won't be bumped at all and I can only imagine it being relevant to tapered straight-wall cases.

 

[JerkyFreak]

Unless you bought a so-called small base die, I don't know of any bushing dies that size back to minimum SAAMI specifications. I may be misinformed.

That said, take some measurements from a fired case and compare it to a sized case. Mostly interested in the shoulder diameter and 0.2" above the rim. You may find that the case is not such a loose fit as you imagine.

If it is sized too much for you to be happy with, then get yourself a Forster bushing bump die. It sizes the neck and bumps the shoulder back; that's it. Does not size the body. Provided you do not load the cartridges too hot, you won't have to use the body die at all.

 

[westernrover]

10 thousandths would be waaaay too much.

You can make very accurate ammo with any decent brass, whether it’s new, once fired in your rifle, or fired brass from another rifle.

“Bumping” the shoulder just mean’s adjusted the full length sizer die to only move the shoulder from brass fired in your rifle a couple of thousandths. If you have some way of measuring where that is, you can size brass from other rifles to the same spot.

Do you think minimally sizing the brass, whether by neck-only, bumping, or using a honed-out die that more closely matches the chamber -- do you think that any of these processes contribute to accuracy or do they merely reduce the work-hardening of the brass? If you believe they contribute to accuracy, which process does so? It seems evident that neck-only doesn't contribute to accuracy or competitive shooters wouldn't have abandoned it -- I'm not claiming that it's results in any flaw, but that it doesn't seem to be required for accuracy. So does a close-fitting die contribute, or does minimally bumping contribute, or none of it makes any difference to group sizes?

 

[Carl N. Brown]

I keep my fired brass with the gun it was fired in (6.5 Carcano in my Model 38, .30-30 in my Marlin 336, ..303 Brit in my No.1 Mk III*) and neck size only for consistent neck-bullet fit.. It doesn't hurt accuracy and is a lot less work.
Only down side is that my reloads in .30-30 won't fit my son's Marlin 336 which has a minimum size chamber.

 

[Bill M.]

I do not know the answer. I learned reloading in the 60's. Once fired brass that was neck sized only was thought to be the only way to good groups. You were considered "slow" if you did not do it that way. Now the people on the forums say that is totally wrong and you should full length resize everything. Me, I still neck size when shooting paper and full length resize when loading for game. I cannot do a direct comparison because I use different bullets and loads for each purpose.

 

[Varminterror]

@westernrover - to start this discussion, what standard of precision are you trying to achieve? If you're shooting shortrange benchrest with custom built rifles, punching groups regularly into 0's and 1's, then the discussion is very different than if you're shooting ~1moa with a factory rifle.

But I'll make a few relatively broad comments:

1) Do not only neck size. It was a silly thing we all did for a handful of years a billion years ago because one dude won nationals with neck sized ammo. A lot of new reloaders get misled by a few manuals which propagate the myth of "chamber fit" by neck sizing only, and it does get kicked around online far too much as the "best known practice," but those claims completely ignore contemporary competition and record-setting performance reloading practices, which use full length sizing dies. Even in a bolt gun, you will eventually run into chambering issues where the body expands and headspace stretches just enough to cause issues, then you have to go back to a full length die, so the internal capacity of your brass is slightly growing over a few firings, then you have to smash it back down to reset the clock, and it starts growing again - rather than having the same internal capacity every loading when FL instead.

2) Do not body size and neck size in separate steps. You're introducing opportunity for eccentricity by sizing these independently. If you want to control those dimensions independently, use a full length sizing die with a neck bushing, and float your neck bushing as you see fit. Or instead of the bushing, send your desired neck dimensions and your die to the OEM and have them hone the neck - typically done for free, just at the cost of shipping. This minimizes your neck travel in sizing, and allows control for setting your neck tension. Honing, as opposed to using bushings, does not allow the reloader to adjust the tension as brass hardens from one firing to the next, and does not allow adjustment for changing brands or lots of brass which might have different neck dimensions.

3) The best chamber fit you can possibly find is to send a few pieces of 3x fired brass to your preferred die maker (such as Whidden) and have them cut a custom sizing die for your chamber.

4) If you're not neck turning and don't want to order custom dies then your best opportunity is to FL size with a neck bushing die, or at least honed neck die, only bumping the shoulder 1-3 thousandths, then mandrel expand to set neck tension. This pushes imperfections in brass neck thickness out to the exterior surface, making a more uniform interior surface for more uniform bullet grip (reminding that the sizing die pushes the imperfections to the INSIDE during the sizing stroke).

4b) Bail on the expander ball in your sizing die. It's not doing you any favors.

5) Just a note here - I shoot groups sub-half moa as a habit, out of premium barreled rifles, VERY frequently putting 3-5 shots into 1/4moa or less, and I'm not terribly certain I could shoot the difference between ammo loaded with custom dies vs. Redding Type S bushing dies which have been mandrel expanded to set neck tension. A lot of us make reloading WAY more complicated than it needs to be. I was guilty of ALL of the reloader's voodoo in the past, trimming meplats, pointing bullets, weight sorting primers, neck turning, etc - all just dropping into factory rifles, and praying for 5 shots to fall into 1/2-3/4moa... praying for groups that I'd consider a "bad day" these days, without doing ANY of that work, just stuffing bullets into cases.

6) Another note - prioritization of influence of different reloading techniques is pretty critical. Weight sorting cases, as an example, tends to be relatively fruitless while neck tension tends to be one of the top influences of load performance, so as an example, weight sorting cases without tuning neck tension would be completely upside down.

So maybe in summary, two points: In the first, best known reloading practices are full length sizing with minimal shoulder movement ("bumping") using a die with a targeted neck diameter, whether you're chasing with a mandrel or just sizing down to your targeted diameter. And in the second, don't over think it - it's really not so complicated to achieve extreme precision, and most of the knobs reloaders turn first simply burn energy, and don't actually move the needle.

 

[GeoDudeFlorida]

Marlin 336 which has a minimum size chamber.

wow. He must have The minimum chamber Marlin 336
When I loaded for military rifle shooting the old timers said to neck size until you got tight bolts, then flame them and F/L size. And always keep your brass with your gun. Enfield chambers are cut for French mud crusted ammo.
That still works, by the way.

 

[Walkalong]

Do you think minimally sizing the brass, whether by neck-only, bumping, or using a honed-out die that more closely matches the chamber -- do you think that any of these processes contribute to accuracy or do they merely reduce the work-hardening of the brass? If you believe they contribute to accuracy, which process does so? It seems evident that neck-only doesn't contribute to accuracy or competitive shooters wouldn't have abandoned it -- I'm not claiming that it's results in any flaw, but that it doesn't seem to be required for accuracy. So does a close-fitting die contribute, or does minimally bumping contribute, or none of it makes any difference to group sizes?

Do you have a true match grade barrel on a known accurate action in a good stock? If not, you're over thinking it.

 

[Walkalong]

If you're shooting shortrange benchrest with custom built rifles, punching groups regularly into 0's and 1's, then the discussion is very different than if you're shooting ~1moa with a factory rifle.

Yep.

And as he continues, there are a lot of things that have to add up properly together to be accurate.

 

[Walkalong]

then get yourself a Forster bushing bump die. It sizes the neck and bumps the shoulder back; that's it.

Yep, and will cause you issues in the long run.

 

[JerkyFreak]

Yep, and will cause you issues in the long run.

How long is "the long run"? And what issues?

So far I am on 10 uses for one batch of cases and 6 on another over the space of 8 years. Still using the same bushing even. So far no issues. Which is infinitely better than when I used hornady dies...

 

[Varminterror]

When I loaded for military rifle shooting the old timers said to neck size until you got tight bolts, then flame them and F/L size.

Bingo - and herein lies the problem with neck sizing, because EXACTLY this will happen, every time. The brass grows more and more with every firing, and then suddenly doesn't fit the rifle any more, so you smash it back and reset the clock, meaning you never had consistent internal capacity for any sequential firing, anywhere along your way... What a waste...

 

[Varminterror]

How long is "the long run"? And what issues?

neck size until you got tight bolts

Even in a bolt gun, you will eventually run into chambering issues where the body expands and headspace stretches just enough to cause issues, then you have to go back to a full length die, so the internal capacity of your brass is slightly growing over a few firings, then you have to smash it back down to reset the clock, and it starts growing again - rather than having the same internal capacity every loading when FL instead.

 

[JerkyFreak]

Have you used a Forster bushing bump die before?

 

[Varminterror]

Have you used a Forster bushing bump die before?

Redding and Forster bumpers, both. Physics doesn't change.

 

[JFrank]

I suppose that brass fired in my chamber fits tightly compared to factory-new brass or loaded cartridges that must fit in a SAAMI minimum-dimension chamber. This tighter fit should result in less movement of the brass during firing and more consistent/accurate results. However, I must resize the brass at least some if I am to expect it to chamber reliably.

I could practice neck-only resizing, though I understand that has fallen out of favor to the point of being mocked and ridiculed. Instead, I have used a Redding body die to bump the shoulder. I don't bump by the thou, but so that the bolt handle (with the spring removed) drops on all cases without resistance. In my experience, this has required bumping most cases a couple thou so that there are no cases that aren't bumped enough. As long as I am using a bolt gun, I will check with that. For a semi-automatic, I suppose I would have to bump 2 or 3 thou to ensure all the cases would chamber without issue.

I recently bought a full-length bushing type sizing die (for a cartridge different than any I previously loaded). I am lacking a comparator insert for the case (out of stock), so I haven't been able to adjust the die precisely yet. What I've noticed is that the body diameter is being resized back to factory cartridge dimensions. This means it's going to fit loosely in the chamber, except for the headspace against the neck which I will be able to control when I'm able to set the bump.

Should I hone the full-length sizing die out so the brass is squeezed down less and fits more tightly? Or is just bumping the shoulder no more than necessary sufficient to achieve a fit in the chamber that will provide the best accuracy?

If my un-honed die is going to resize the body to a loose fit, and only the shoulder will be fit to my rifle's chamber, do I really need brass fired in my chamber to make accurate loads, or can I just use brass fired in any chamber so long as I can set the shoulder datum to some spec?

Maybe this has been mentioned idk..The reason we full length size is not for accuracy it’s to cycle freely before and after ignition, fighting the bolt upsets the rifle from tracking and takes longer to back on the target, I bump the shoulder back .002 from a no resistance bolt drop and don’t worry about loose chamber gunsmith stuff.

 

[JerkyFreak]

I know Redding and Forster both make neck dies and Redding make bushing neck sizing dies, but I am not aware Redding made bushing bump dies.

Perhaps you are confusing the neck die for the bump die...