TTSX, IMR 4831, 7mmRM, crazy load data?

L

Leatherstocking

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BC Rockies
From Barnes:
IMR 4831
54.5 min
2709 FPS
60.6 max
2958 fps

From Hodgedon:
BULLET WEIGHT150 GR. BAR TTSX BT
ManufacturerIMR
PowderIMR 4831
Bullet Diameter.284"
C.O.L.3.225"
Starting Load
Grains60.4
Velocity (ft/s)2,848
Pressure49,600 PSI
Maximum Load
Grains65.0
Velocity (ft/s)3,075
Pressure59,600 PSI


So, the Barnes max is 60.5 grn, the Hodgedon min is 60.4

Barnes min is 10 percent below Hodgedon min

Does this make any sense?

Same bullet, same powder.
 
well I would not discount the Hodgedon's data. IMR powder is made by Hodgedon

Barnes is working with their powder and it looks like they are a little more adverse to possible variations.


Just works up your loads watching for signs of over pressure.

I use IMR4831 in my 300WM and I have worked up to well over some published data and still no issues. I backed it off a little to improve accuracy.
 
Find a accurage spot for your recipe. Even if its a rather light load by manual standards, it will still beat factory. My experience is that most accurate loads are at or above listed maximums.

Lawyer friendly data, i have some old reloading manuals, much more potent powder charges. Some starting loads, now, dont even cycle semi auto actions.
 
Thanks for your ideas gentlemen.
I have settled on 60.5 grn of IMR 4831, not because of the data, it seems most accurate. 1 1/4 in at. 100 yds
I tried loads from 56.5-63.5 with no signs of excess pressure
Might try tinkering with seating depth,now using 0.05 per Barnes recommendation
 
The max powder charge is the max for THEIR rifle. No one says it is max for YOUR rifle.

All manuals say start low and work up. Work up to the max velocity they publish, if you can, without pressure signs.

Rifles (identical) typically vary by 100 to 200 fps with the same ammo.

I used to build identical rifles in 3s. (Me, Wife and son.) Identical quality barrels. Typically varied by 150 fps. Each required a unique load for accuracy.
 
Leatherstocking said:
Neither one lists the brass.
Click to expand...

I began reloading with a .300 Wby two years ago. My first batch of brass was Hornady; then I switched to Weatherby brass. I discovered that I reach max pressure in the Hornady brass at a full two grains less powder than in the Weatherby brass (while still achieving very similar velocities). I probably wouldn't expect the differences to be as great in your 7mm, but they could still be significant, especially when coupled with the possible variations in chamber size, etc.
 
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