Rule of Thumb?

[GameHauler]

Is there a general rule of thumb as to case capacity differences between manufactures?
Lets say I had worked up a good load using Remington brass that just happens to be pushing max but I scored on a boat load of Federal brass and want to load up a bunch.
I know to always back off and work back up but is there a consistent that would say:
If going from Rem to Fed you only need to back off a half grain.
BUT if going Fed to Rem you better back off 2 grains.

Guess what I am asking for is a list brass manufactures that show relative case capacity.

[Castaway]

Only rule I know of is if using military brass, back off 10%

[stimpylu32]

Mike

Nope , there are even case cap diffrences between lots of the same brand , the problem is that no two lots of metal compound are the exactly the same , thus when its drawn to form cases it pulles to diffrent levels of thickness . 

stimpy

[GameHauler]

Thanks Lou but do not the different Manufactures have a set thickness they are trying to obtain with one being more or less than other?
Or both trying to obtain the same but with better equipment?
There for Fed always has less capacity than Rem. (example)

[cwlongshot]

Mike

Nope , there are even case cap differences between lots of the same brand , the problem is that no two lots of metal compound are the exactly the same , thus when its drawn to form cases it pulls to different levels of thickness . 

stimpy

I completely agree, even different lots from the same manufacturer can be different.

One thing I have found is Winchester tends to be most cap and Fed least in calibers I have checked. Not allot and not what I would call a "rule". At least not across the board for all calibers...

CW

[stimpylu32]

The only hard and fast rules to brass are that it must meet the SAAMI chamber dimensions and pressure requirements , other than that the companies are free to make their brass as thick or thin as they want .

stimpy

[bilmac]

I don't think I would want to be running so close to max that case capacity is going to make any difference. I do think that it may get important if you are trying to wring out the last bit of accuracy.

Also, I do adjust my charges according to case capacity just to make them more practical. A lot of my loads fill the cases up into the neck. But with some brands of cases the same powder charge will be right to the top or over. I reduce the charge for those headstamps so that they fill the case about the same as the higher capacity cases.. That does two things in my mind, they are just a lot easier to handle rather than having to tap the case in order to settle the powder, and it kind of meets the rule to reduce the load for the smaller case. I can't say that I have ever shot the smaller charges side by side with the larger charges at targets to see if they group in the same place, I just take them to the dog town and shoot them interchangably. Seems like one splatters as many P dogs as the other.

[AtlLaw]

Wallll boys, another thread on the primer pockets in military brass got me thinkin on the subject... And you know what happens when I gets to thinkin!   

I recollect onec't way back in the day when I managed to come up with about a thousand pieces of lake city 7.62 brass.  Well I thought I done died and gawan to heven!  They was all marked LC 60 some odd or early 70 something.  I figgured now that I got 'em I might just as well prep 'em all and be done with it.   

Now the first thing I done did, or tried to do, was to depriming them little buggers!     Naturally you got to empty the pocket before you can swage it.  So, after messing up a couple a depriming pins on my sizing die I decided to do it the old fashioned way.  I pounded out each primer using a Lee I think it was, hand tool; sit the shell in a base, drop a punch into the case, center it in the flash hole and whack it with a hammer.

Okay, I figger that was the hard part.  It'll be easy getting rid a them durn PP crimps!  But little did I know they is aggravatin devils they is!     Anyway I perloins me a pocket swager and commence to swagin!  Do y'all have any idea how long it takes to swage the pockets on 1000 +/- cases!?   Or how hard that lever is to push after a few hundred of 'em!? 

But over the course of time I finally got a thousand (+/-) pieces of GI brass with swaged pockets.  'course I also got a right hand that by this time I would swear would never hold a beer can, or other vital items of similar shape, again...   

Now, being the perfectionist that I and all hand loaders are, I couldn't resist checking to see how well I did my work up to that point.    So I pop a primer into the tool and ram it into the primer pocket, expecting the former to slip into the latter slicker then... well,  easily!     HA!     Think not reloading rookie!     The primer was crushed trying to penetrate the outer edge of it's explosive little hearts desire!     

Moving along and trying to get to the point, if I can remember what that point may be, I ended up using a chamfering tool to bevel the rim of the primer pocket.

So, after completeing the rest of my perp procedure, to include deburring the flash hole and triming all the cases, I decided (heaven knows why) to sepreate the brass by year.  Once that was done it was a logical leap to wonder if the year lots varied in weight any.    So, I broke out my handi dandi 5-0-5 and commenced to weighing each case and recording the weights of each case in that case's year group!

A course by this time I'm swearing I will never use another piece of GI brass which was kinda stupid since I had yet to drop the first bit of powder in one!   

But the point is that the weights were pretty consistant within a given year but varied noticably from year to year.  I will spare you all, gentle readers, the details of the next logical step; comparing weights of GI brass with Commercial brass and commercial brass by headstamp...  but will tell the OP that, in my experience, case weights, by brand and even by different headstamps within a brand, vary. 

BTW, the only rule of thumb, y'all know where that phrase came from dontcha?  The only rule of thumb is if you hand load by rule of thumb you're liable to loose one!   

[fastbike]

That rule doesn't work today. I've had civilian cases with consistently less volume than some military cases. However, differences have been small. I try not to load right to max because a small change in volume can make a big pressure change and there are too many ways to get that small change in volume.

Only rule I know of is if using military brass, back off 10%

[Steve P]

The rule of thumb:  If you change anything in your reloading recipe, drop your load 10% and work your way back up......except with 296 or H110 powder. 

Change primer, work back up.
Change brass, work back up.
Get new lot of powder, work back up.
Use a different brand of bullet, work back up.

I do this on all of my reloads that are pushing the pressure envelope.  I have many many loads that are well under book.  With these loads, I will load a few rounds and test them.  If no suprises, I go ahead and reload like normal. 

If you are within that top 10% of book load, or at or near max book load, always work back up to your load to confirm no surprises.

Steve

[AtlLaw]

You're right!  That's a good "rule of thumb!"   

[wncchester]

"The rule of thumb:"

What everyone is saying, sorta, is there are NO rules of thumb for any aspect of changing any component used in reloading.  Things change and that's why the ONLY rule we can depend on is to make the change you wish and back off on the charge to see how it affects your load.