7mm Mauser resizing issue

50 BMG, Collet, and steel reloading dies plus the Factory Crimp Dies. Also, discussions concerning the Deluxe, Pacesetter, and RGB die sets.
User avatar
RBHarter
Founding Member
Founding Member
Posts: 2040
Joined: 13 Mar 2014 19:45
My Press Choice: Single Stage
Location: The green hell 90 miles north of Texarka
Has thanked: 76 times
Been thanked: 670 times

Re: 7mm Mauser resizing issue

Post by RBHarter »

I take a deep breath .
There are several physics things happening that I lack the book learning to describe but bear with the wrench bender .......

Several points 1 is that if these were the first cast down the bore and or it was a clean bore then what you are seeing is the bullet raising pressures in the first inches of the bbl as the lead and lube , and I hate the word , season the bore . Think of it like the first time you used olive oil in your bacon grease cast iron pan ...... It's not the same but similar .
As the bullet lube gets uniform in the bore the high spikes go away because the bullet is riding on slickum' from the last shot while it adds some to replace what it squeegees off .
That sort of explains why the lessor loads did that . It's possible that the load was in a ragged edge of explosion vs burn . There are a bunch of big words but what really happens is that you have a space volume and a pressure curve that allows too much of the powder to burn before the bullet moves . Basically the powder is at peak pressure and maximum expansion inside the case instead of 2" up the bbl . Unique is fairly forgiving in this respect .
For a mental image think about the last time you kicked a solid frame panaled inside door open . That's what the charge is doing the whole thing springs then swings open .

In your 2nd load you have a 500 fps swing , not good for consistency . 1700-2200 fps . Look how your 8-9 gr loads settled down . If you reshoot the 7 gr loads I'd bet on seeing them in the middle 1200s now . I'd bet on you finding a sweet spot seated long somewhere about 8.7-9.5 if you don't get leading .
Just a Red neck,White boy, Blue blood American.....
User avatar
GasGuzzler
Moderator & Supporter
Moderator & Supporter
Posts: 2035
Joined: 26 Jan 2016 22:39
My Press Choice: Turret
Location: Cooke County, TX
Has thanked: 330 times
Been thanked: 500 times

Re: 7mm Mauser resizing issue

Post by GasGuzzler »

That helped me for otter stuff.
__________________________________________________________________________________________
I've always been crazy but it's kept me from goin' insane.
jloader
Posts: 156
Joined: 12 Apr 2016 13:13
My Press Choice: Progressive
Location: SE Michigan
Has thanked: 32 times
Been thanked: 38 times

Re: 7mm Mauser resizing issue

Post by jloader »

GasGuzzler wrote:File this under "Unique".

What did primers look like on 7/short? Were they tough to extract? Sure is the outlier with bad ES. I wonder if you had chrono fail on 7/short.
All primers came out nice and easy. Yah, that one reading of over 2000 fps, I attribute to bad reading. Not big enought sample size to take out hi and lo extremes.
jloader
Posts: 156
Joined: 12 Apr 2016 13:13
My Press Choice: Progressive
Location: SE Michigan
Has thanked: 32 times
Been thanked: 38 times

Re: 7mm Mauser resizing issue

Post by jloader »

RBHarter - thank you for all that info - it does make lots of sense. Lots of physics at play here - I love it - it feeds my analytical brain. yum yum. :)
That info gives me plenty to work with and have fun with. It was my first time playing with chrono as well.
I felt like a kid with a new Lego set under Christmas Tree...
I'll make larger number of samples to have more consistent reading...
I never knew this hobby could be so much fun...
And my 16year son was so impressed as he made a few shots from the 100 year old rifle in 3" grouping @50 yds. I think he's hooked, for now.
Ohio3Wheels
Supporter
Supporter
Posts: 888
Joined: 06 Mar 2016 16:09
My Press Choice: Hand Press
Location: SW Ohio
Has thanked: 156 times
Been thanked: 240 times

Re: 7mm Mauser resizing issue

Post by Ohio3Wheels »

Except for the out liers the rest are pretty much what I'd expect due to the difference in case volume.

Make smoke,
Curt.......makin' smoke and raising my carbon foot print one cartridge at a time +guns +guns
Post Reply

Return to “Rifle”