A Lesson in Case Capcity

MacD · Posted: Mon Sep 02, 2013 12:29 pm Post subject: A Lesson in Case Capcity

So. I was loading up some .308 using some 1X fired mixed brass. All cases were fl sized and trimmed as necessary. I used a published load for the 130 grain bullets and IMR 4320. The first case filled right to the top with a load of 2 grains less than max. Checked powder, recipe and even my electronic scale using a balance scale. All checked out. Okay empty case and have a look. Head stamp is a "N" left, a "7" right and .308 on the bottom. Not NATO or other military I presume but not common. So time to weigh the cases. Using Winchester cases for comparison which averaged 157 grains these cases came out at 177. A load of powder down another 2 grains and they filled up to the same level as the Winchester cases. Going to be interesting to see how the two loads compare over the chronograph. Lesson learned is that it is not only military brass that has reduced case capacity.

One question for you grizzled vets. The max load for that powder/bullet combination (which I declined to actually use) filled the Win cases to the brim. The specified seating depth would have pushed this down to about where the shoulder becomes the neck. This just looked wrong but I have no experience with highly compressed loads. So is this within normal parameters?

TRBLSHTR · Posted: Mon Sep 02, 2013 3:10 pm Post subject: Re: A Lesson in Case Capcity

Although I never use 4320-I have however found volume vs max load differences with .308 win when using varget,4895,3031,4064!Sometimes when it looks like it could be a problem I just back it down till it's at the top of the shoulder.The bullets generally seat clear into the powder anyway-so no problem of a too light load!They say it is easier to blow up a rifle like a grenade by undercharging and having all of the powder ignite at once from a flashover.Some of the newer reloading manuals list the 308 at up to 60kpsi-with max loads.So I would believe that they are using compressed charges as mine with middle of table charges are usually mid neck height with powder!

wncchester · Member Joined: Apr 08, 2006 Posts: 160

Personal opinion, 4320 is a tad too slow for a 130 gr. bullet in that case. A slightly faster powder should fill the case properly and reach sufficent pressure to insure a consistant burn. Maybe 4064 or Varget?

MacD · Posted: Thu Oct 17, 2013 11:47 am Post subject: Re: A Lesson in Case Capcity

wncchester wrote:

Personal opinion, 4320 is a tad too slow for a 130 gr. bullet in that case. A slightly faster powder should fill the case properly and reach sufficent pressure to insure a consistant burn. Maybe 4064 or Varget?

Coincidental you replied to an this thread just as I loaded up bunch with IMR3031. I will report results.

chambered221 · Posted: Thu Oct 17, 2013 4:52 pm Post subject: Re: A Lesson in Case Capcity

Stick powders will often require lightly tapping the case to settle the powder !!!

I load IMR 4350 in my 30-06, when I pour the powder into the funnel it often bridges plugging up. I tilt the case and lightly tap it on the bench till the powder settles just below the neck.

slimjim · Posted: Thu Oct 17, 2013 8:09 pm Post subject: Re: A Lesson in Case Capcity

The case with less capacity will have a different pressure response than a case that has more volume. That is why you start below max an work up. MacD, I assume you aren't mixing brass manufacturers using the same load? I found I could not load .308 Federal cases to max with the powders I used.

SingleShotLover · Posted: Fri Oct 18, 2013 4:50 am Post subject: Re: A Lesson in Case Capcity

chambered221 wrote:

Stick powders will often require lightly tapping the case to settle the powder !!!

I load IMR 4350 in my 30-06, when I pour the powder into the funnel it often bridges plugging up. I tilt the case and lightly tap it on the bench till the powder settles just below the neck.

This is also the reason that some loaders use extended drop-tubes when using "stick" type powders in cases of smaller calibers. I still use IMR 4064 in my 22/250 (mostly because I'm trying to use it up) and a length of tubing I picked up many years ago really helps it feed. It also tends to impart a "swirling" motion to the powder which allows it to settle into the cases better. Without the tube, using stick powders in a case with that small of a mouth is a lesson in patience. And just think, IMR 4064 is also used by some in .17 Remingtons! Now that spells dedication!

Vince · Posted: Fri Oct 18, 2013 6:35 am Post subject: Re: A Lesson in Case Capcity

Like Slim says Mac...tapping the bottom of the case lightly on the bench settles the powder down into the case and the little air spaces between the "sticks". I always do this to any cases that appear to have slightly more powder in them when I check prior to seating a bullet.

Give Varget a try mate. The Aussie Army use it in their 7.62mm NATO rounds and these rounds are considered "match grade" amongst the "belly flopping" target shooting fraternity. I know...I always push Varget as a great powder, but in reality it is a most versatile powder that delivers great accuracy over a number of calibres.

stovepipe · Posted: Fri Oct 18, 2013 11:08 am Post subject: Re: A Lesson in Case Capcity

MacD wrote:

One question for you grizzled vets. The max load for that powder/bullet combination (which I declined to actually use) filled the Win cases to the brim. The specified seating depth would have pushed this down to about where the shoulder becomes the neck. This just looked wrong but I have no experience with highly compressed loads. So is this within normal parameters?

MAX published.
Interesting topic.
Same's based on someone else's findings using that recipe, in that chamber/bbl comb.
I've yet to find a load that's more accurate than around the "middle" of the published recipe's charge weights in off the shelf firearms.

I start at an avg. of START recipes and go from there. then, if the case tops off and it's not bridging I back it way down. I mirror what Chambered, Slim and SSL said too. And, in a lot of cases, if it's not a super slow mag powder you can go 10% below START and still be OK. Compressed loads are sketchy. Get it wrong, a in too little powder and it'll KB big time- from what I hear. I don't compress loads. Too many variables. I move over to another powder rather than compress. It's just safer that way IMHO.

For your 7N cases, reduce by 5-10% and look for pressure, not at the chrony sheet, leave that in the truck til the load is proven safe. Pressure goes up exponentially, not gradually, when there's a component change- esp in the brass dept. Next to powder the case will make the biggest difference, all other factors being the same.

MacD · Posted: Fri Oct 18, 2013 12:32 pm Post subject: Re: A Lesson in Case Capcity

Thanks for the comments. I have made a few notes in my mental reloading book.
1. Stick to brass I know. I use mixed brass for practise ammo but stay at or near starting loads.
2. Just because a powder is listed for a given bullet weight doesn't necessarily mean it is a reasonalble choice.
3. No case should be filled past the bottom of the neck. This still means an occasional lightly compressed load when using extruded powders. I already tap cases when I drop powder. I also use a slow drop and pour high on the funnel which gives the powder a slight swirling motion.
4. Stick to bullets more within the usual weight range for the caliber being loaded. I loaded 168 grain A-Max with the same powder and they shot great without any case filling issues.

As an aside but related, I found that my 99f may have a tight chamber but it has generous headspace. FL sized cases trimmed to 2.010 stretched as much as. 010 with only a light loading. I checked them for the telltale case head ring but none had it. I have changed my FL die to just touch the shoulder and retrimmed the brass. With the shoulders mored forward I expect fewer case capacity issues? The completed rounds chamber with a slight resistance just as the lever/breech bolt come to the locked up position.

Elvis · Posted: Fri Oct 18, 2013 1:14 pm Post subject: Re: A Lesson in Case Capcity

Maybe a partial length resize may be a better option????
a wise man once said "many a great load has been ruined by a chronograph"
some fellas get all hung up on velocity at the expense of accuracy.

stovepipe · Posted: Fri Oct 18, 2013 1:20 pm Post subject: Re: A Lesson in Case Capcity

Elvis wrote:

a wise man once said "many a great load has been ruined by a chronograph"
some fellas get all hung up on velocity at the expense of accuracy.

Bingo....