Rem 300 Ultra Brass Weight Variance

[Brent]

I never made it to the range today because of the weather and brass delemas. I weighed cases from two boxes of once fired factory brass. The results are less that exciting.

The cases weighed from 275.1gr to 279.4gr. The boxes were not from the same lot but weighed in the same range so I decided to weigh them all full of water and see if this weight corralated with its case weight.

Cases with water weighed from 391.6gr to 394.9gr and did indeed corralate to within a tenth grain or two of the expected weight accross the whole board.

Here's my delema. I only have this brass to load so far and I cant even get twenty cases within 1gr and worse it's almost a full two grain spread.

Question is, if I use these cases and load up one round each in .2gr increments from starting load to max load to see where the sweet spot is, do I start with the highest case volume and the lowest charge wt together and end up with the lowest case volume and highest charge wt together thus increasing pressure a little faster than if I combined them in the opposite way that would in effect almost cancel each other out?

I realize that some may feel this is splitting hairs, but it will have an effect and skew the results if not accounted for especially while looking for consistant grouping over a range like this.

I usually develope a load like this with case and bullet weights within .5grs and just note the weight range used for later adjustments if anything weighs different and accuracy isn't there anymore.

At this point a couple hundred rounds of brass would be the answer but I don't have any yet.

To those that weigh your brass for the ultra, what are you experiences and practices?

 

[Boyd Heaton]

Brent,I have found it does not make any difference if you weight the brass or not.I shot a 1000 yard match with brass in half grain inc's.#1 was the lightest to #10.I saw no difference.Also shot those ten brass over a chrony.E.S. WAS 8fps.I also don't think you need to go up .2gr at a time.With a case that big a half grain or even a full grain would save you some barrel and powder.....What bullet are you shooting????

 

[speedbump]

I bought 500 cases to reduce to 7mmRUM & found the same variance. I separate the best I can & don't worry about it - there's not much else you can do.... Due to slightly increasing pressure I usually use the heavier cases in the mornings/ cooler weather & lighter ones in the PM or hotter weather. Like Boyd, I haven't noticed much of a difference - partly due to the huge case capacity. Also, I've never split a case neck, nor have I pierced a primer. However, the primer pockets loosen up FAST!

It works the same for a hotter chamber, so if that's all the brass you've got, & you insist on doing something, I'd use the heavier brass 1st & lighter last.

 

[Brent]

Well I have good news, but I can't explain it though. The cases I weighed spanned 4 grains. If you go back and read my previous post I said the cases with water spanned 4 grains also. I looked at it totally *** backwards, probably because I expected the results to be what everyone might think, all the lighter cases would have more internal capacity, right? Wrong.. the cases that were 4 grains lighter were still 4 grains lighter with water, meaning that internal capacity was EXACTLY equal! Each case was lighter by the same amount with water as the case weight itself indicated. Am I making sense? It wasn't the other way around. The average water weight itself was 115.7gr. Maybe some of you guys can check yours too and see how consistant accross the board this 300 ultra brass is. Mine was filled to the top with water in an eye dropper with a drop of dish soap mixed in to break the surface tension, no bubble on top, just flush with the mouth. They fireformed once and had fired primers in them at 2.840".

Boyd, this explains why you find no difference at 1000 yards. And we all frowned on the Remington brass. I am totally amazed to say the least. I might add that this was two boxes of brass from different lots too!

This may be an end to my weighing cases if this proves to be true the next few times I check some. These cases were all within +or- 3 tenths of a grain in internal capacity on cases that had a 4gr spread, WOW!

I thought you all would appreciate hearing this.

 

[Mysticplayer]

Brent,

Welcome to the world of slightly less A-retentive reloaders. What you have observed is probably common to all brass made by all manf. The only thing that matter are the consistency of the metal/annealing and the true internal case capacity. As long as the above are the same, the presure and release of the bullet will also be the same. This assumes no major physical flaws with the brass like being out of round or offset flash holes (although not sure how important that is too - another story).

Try this experiment with a old magnum case. Measure the weight, then cut a slot on the rim and reweigh. Bet you it will show a change of 1/2 grain or more. How could that affect the internal capacity of the brass? So slight manufacturing differences will show up as differece in case weight, even though internal capacity is the same.

By this same argument, cases that weigh the same may not necessarily have the same internal volume. Think about that one.

What I do to test my cases is, find a good accurate load and fire all the cases with the same load. Any shot that is sig. out of the group ie flyer, I mark the brass. When that brass is reshot, if it is still a flyer, into the garbage it goes. The further you shoot on a calm day, the better the results. I use 200yds as a baseline.

When I start to get a neck split or two, all that batch of brass gets annealed. If problems occur elsewhere, I toss the batch and start with fresh brass.

The RUM I am working on is showing signs of being a 1/2 MOA gun. This is with once fired range brass from who knows how many lots, batches, or firearms. At least your stuff came from the same box.

Enjoy...

Jerry

 

[Brent]

Thanks for the tip, I'll add that to the routine as well. I just could not believe that the case weight was in no way indicative of it's volume what so ever, and more astonished they were SO close in internal capacity. This will make loading for this alot easier, and faster.

I try to do all my testing at 200 yards as well, so bullets have stabilized, sometimes 300 yards if wind is insignificant.

The more important thing for me has been to keep brass seperated by the number of times shot because of the different pressures they cause, ie. neck tension. This is pretty easy to do.

 

[kraky]

FWIW-I was bored a couple weeks ago on a rainy day and compared internal capacity of once fired win 30-06 brass to never fired rem nickel cases. The rem cases weighed about 12 grains more and I figured the 1x fired deal would add even more internal capacity. They both held exactly 67.5 grain of water. SURPRISE!! (at least to me it was!!))