Different Cases, Different Grains

[ADL]

I recently tested out how much grains of the BL-C(2) my new PMC cases would hold versus the winchester cases.

Win = 57.1gr

PMC = 53.7gr

That is quite a bit!

So if my normal winchester loads are 45gr would people normally reduce their holads to mach the case capacity in this case PMC loads would be 41.6gr?

Thanks for your input!

[jsizemore]

Looks like your PMC case is about 94% of your Win case. That puts your PMC load at 42.3 BUT you need to drop 10% and work up (if 10% reduction is safe for the powder/case/bullet your using) and work back up to your 42.3gr max load. Powder/case/bullet combo may react a bunch different then the old case.

Chronograph will tell the story. Chamber pressure reading would be even more better.

[Neverhome]

I’d agree with above to go by percentages instead of actual difference.
BL-C2 is a fairly fine grained powder and probably gives you decent volume data because it likely settles well in the case HOWEVER using a powder to find volume is typically not the most reliable method. The rate you pour it in matters. Fast pour sits higher than slow pour hence drop tubes. Water is a better medium because it always fills the case the same.
The 10% rule that jsizemore mentioned should be adhered to for sure

[17nut]

Now an actual case would be nice for us impared with Quickload and acces to actual loading data, instead of just wag! And then exact bullet used too.
Data!

If not then it's: Is my Ford faster than what my neighbour has or the one he wants to buy?
Data!

Most anything is: Crap in = Crap out.
Data!

[CastingFool]

Weigh the cases and the heavier one will have less internal capacity. Ideally, you want both to be recently fired from the same rifle, or full length resized, trimmed and chamfered.

[tazman]

I recently loaded some PMC 30-06 cases with the identical load I use in Remington cases in my match rifle. This load uses H414 and is about 2 grains under listed max with a 168 grain SMK. With the Remington cases, this load puts all the rounds into 3/4" at 200 yards on a calm day.
I had it out on the range and when I switched to the PMC cases, I immediately noticed a problem. Impact point shifted noticeably(nearly 3 inches high right) and the group size opened up.
I inspected the cases and found that the primers were fully flattened.
I didn't have my chronograph with me that day so can't say what the velocity change was.
Good thing I only loaded 10 rounds of those. I pulled the last five apart when I got home.
I didn't expect a case change to make that much difference with a "light" load.
The warning others have given about reducing and working up again is good advice.

[Ozark mike]

Jus put some high pressure loads through em they will thin out:bigsmyl2:

[ADL]

Well, it seems 43.5 worked well.

263566

[jsizemore]

It's been so long ago I can't remember the powder, manual or bullet. But it was 308. I was using the published starting load but in Lake City brass. The long kernels of powder were slow going through the funnel throat. I didn't look directly down in the neck but there was space. I usually load 3 and adjust my powder scale. When I looked in the case the powder was half way up the shoulder! My next powder increment was .5 grain and now it was at the neck shoulder junction. Uh-oh.

When I looked at my manual I discovered at the beginning of each round they said they used x case with y primer trimmed to this length. That Lake City brass was made to run through a machine gun and had a monster web and case walls.

When I started shooting matches, I discovered that the internal volume of cases varied lot to lot and there were odd balls in a particular lot too. Not enough to be dangerous but for sure would blow the group. Got a half dozen with no flash hole.

Weight sorting is a quick way to check for oddballs. Shooting is the best test. If I got a load that works with a particular brass lot/ bullet lot and I have a flyer, that piece of brass gets set to the side for press setup or fouling shots for conditioning the bore.

Like most things, when you get used to doing it, it's not that big a deal. It matters if you care about where your shot goes.

A guy at my club I used to belong to trimmed his cases each time he reloaded. I asked him why. He said " The reloading is the easy part so I'm gonna do everything in my power to make that round as consistent as I can." I believed him since he was world champion a few times.

[MostlyLeverGuns]

Case weight does vary substiantially by make. Whenever I change cases, I weigh ten or more. I have 308 cases that vary from 159 gr to 180 gr. My 444 Starline is heavier than my 444 R-P by about 5 grs. 358 Win, 243 Win, 300 Savage all vary enough that working near max loads require separate work-up by case make. My BOOLIT loadings do not approach levels of concern, but impact on target at 100 yards can vary 1/2 -3/4 inch. I do try to use a single case make for a particular rifle to avoid these concerns. I do usually weigh brass on 1st loading and remove outliers. I too pull brass that cause fliers. Annealing new brass, then on a schedule also seems to reduce group size.

[charlie b]

These guys have a list of average case volumes for the .223. Varies by quite a bit.

https://www.6mmbr.com/223Rem.html

Changes in case volume are a big issue if you want to shoot small groups or if you load near max pressure. If you load near max then you need to sort your cases at least by brand and if you are at max then you should probably weight sort as well. When working at max loads, changes in case volume can make your load dangerous to shoot in your rifle.

I have always sorted my brass by brand. If military surplus then it is sorted by headstamp.