10mm Case variation

[preventec47]

Somewhere from a forum I copied the following text and I want to
know what brand "R-P brass" is as I think I want to use it too?


"I've been loading 10mm for years and pretty much settled on the
200 gr. XTP, 13.2 gr AA9, WLP primers and had been using R-P brass
until recently. I changed to Winchester brass and found that I
was lucky to get 12.5 gr.'s in there with the bullet seated
to 1.260. any more and the bullets get distorted because the
powder is so compressed." ( source unknown )

[Ctk1981]

Remington-Peters brass.

You can get a lot of variation between cases. I have a 1000 pieces of starline and doing a random sampling they weighed in at 70.5 AVG grains......Also have a 1000 pieces of Top Brass from scharch and they weighed in at 74 AVG grains. I liked the starline better as they had tighter control on the variation in weight, the top brass had a wider variation. I'll probably weight sort the top brass but Im not worried about it too much.

[Alk8944]

That is not unusual. Regardless of caliber R-P brass seems to be thinner at the mouth and have slightly higher internal volume as it is thinner, actually, all over. Most likely he is seating to an OAL where the bullet is getting into the tapered area of the case, not that the powder is being compressed that much. If it were the powder being compressed that much he is compressing the cahrge in the Remington case too, maybe just not as much.

Interestingly Accurate lists 12.5 AA-9 as maximum for the same 200 gr HDY XTP bullet in their manual, without specifying which case they used!

[BruceM]

Preventec47:

Rule #1: Handloading data is just that, data. It is NOT a recipe although that term is starting to worm it's way into the handloading vernacular and inexperienced people are taking the term literally.

Rule#2: Start low and work up. Do not just copy somebody else's load. See rule #1.

Many moons ago I tried to duplicate a maximum .44 magnum load from the Sierra manual using the 180 grain JHC. I used the identical brand, style & weight bullet, powder and case. After I dropped this maximum charge of W296 into the case, I could NOT seat the bullet & crimp. The case was too full. All this means is that although you match everything, lot to lot variations can make load duplications tricky at times & even impossible.

Yes R-P denotes Remington Peters. The nature of your question suggests you are pretty new to handloading. Follow the rules, do some research/reading of manuals and be careful.



Bruce

[preventec47]

I have done a lot of hi end load development in Magnum Rifles
but this is my first with pistols.

So far I checked with MidWayUSA and Graff and neither carry
the Remington Peters cases anyway. I am pretty conversant
in internal ballistics at least with rifles and there is this weird
gottcha with case capacity. Although more can be good
in terms of keeping pressures down, more case capacity
means weaker cases ( all other things equal ) Now it
could be Remington Peters uses a superior alloy or heat
treating to overcome less material .... or they could simply
achieve more volume with distribution of material like
the earlier guy said about thinner case mouth walls.

In some instances like the .45 Super compared to regular
.45 ACP, you know in advance that by building up the
strength of the case head you are going to give up some
volume in the case.

I wonder how the different brand 10mm cases compare
if you did cross-sections to measure thickness in
all the areas?

Midway has Winchester and Starline 10mm brass. What
are sources for other brands of 10mm brass that have
decent reputations?

[Ctk1981]

Scharch.com for top brass. Starline from grafs, midway, or order direct. Starline is generally considered high qaulity in every caliber they produce.

[oldRoger]

I have an Accurate Listing which shows substantially different maximums for Speer 200 FMJ and Hornady 200 XTP both at COL 1.25”.
The Speer 13.5 grs @1200 fps & 36,300 psi: HDY 12.5 @ 1170 & 37,000. I suspect the Hornady Bullet is longer hence seated lower. I do not have either bullet at hand.
+1 for Starline, who is about ready to make a run of 10mm.