7mm RM w/ IMR 4350 weirdness..

BongoBob

BongoBob

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So, I worked up a load for my Winchester M70 7mm Rem Mag using the following:

162gr Hornady Interlock bullets
IMR 4350 Powder
CCI 250 primer
Federal cases

Following the Speer reloading manual, I started with a charge of 54 grains and worked my way up to 58 grains in .5 grain increments.

Here's where things get weird. I chronographed every shot, but the velocities I got don't make sense. You would think the fps would be higher the more powder I used, but that didn't really happen. For example...I got consistantly higher fps with 54.5 grains than I did with 58. Any clue why this might happen?
 
Unless you are playing with 120 grain bullets IMR-4350 is a bit too fast for the 7mag.
So you get twitchy results.

IMR-4831, IMR-7828, RL-19, RL-22, H-4831, and H-1000 are all better choices.
 
When you approach the too hot area for a particular load/rifle combination there is frequently a node where more powder yields little or no increase in velocity. Also an indication that your not using the optimal powder for the case and bullet weight.
 
Thanks for the info!

There were no pressure signs at any time...in fact, the whole series of shots felt pretty tame for a 7mm Rem Mag.

I'll try another work up with RL 19 and RL 22 and maybe some 4831.
 
I have had great luck with my winchester model 70 7mm
Fed cases
cci 250 primers
65 gr imr 4350
140 gr accubonds
getting dime size 3 shot groupes 3175 fps.
Maybe you need a lighter bullet??if you want to use 4350.
 
As the others have said, 162 grain bullet, use 4831, you can get 2900 FPS quite eaily and great accuracy. 4350 is too fast for that weight. I also have a couple that like 7828 for the 162s and 175s. Never tried Reloader powders but have heard great things about it in the magnums.
 
As well as burn rate barrel length plays a small role, which yes, has to do with the burn rate.I have seen 2" in barrel difference completely destroy any consistency in rifles of the same caliber using the same powder.
 
Rembo said:
try Rel22 with 162's......I use 69grs with 140's for 3250ish.....I plan to try Rel 25 someday.
Click to expand...

RL 25 is awesome in my Rem 700. My go to load for a couple years was RL 22 and the 160 Accubond. Accuracy was great, but it topped out at 2820fps. Then a friend of mine recommended trying RL 25, and I'm sure glad I listened.
3000fps (+/-15) with no pressure signs, and 3/4" 3-shot groups at 200 yards(not a misprint, 200 yards!!). Went as high as 3050, but accuracy dropped off quite a bit.

As mentioned, 4350 may be a little fast. I would try the 4831's, RL22 and 25. Never tried H1000, but have heard good things about it. Good luck!!
 
crazydave said:
Those loads are low for a 7mm mag, even the hottest load you used is 2 grains below my manuals min load
Click to expand...

What manual are you using? I'm planning on loading 160 grain nos partitions with IMR 4831 and most load data I've found max's out around 61 grains.

The nosler manual, however, states 63 as the max as well as most accurate.

I've read lots of guys are using up to 64. Since I want to make some OCW testing loads and start plugging away I'm lost as to where to set my max for calculating load weights. I understand about watching for pressure signs and all that but what's the deal with these variances?
 
Welcome to reloading for the 7mm Rem Mag :D

Honestly, I'm using data from my older manuals, and don't tell anybody, but I'm using 67gr of IMR4831 behind my 160gr bullets. I wouldn't suggest this unless you have a chronograph and you know what kind of pressure signs to look for.
 
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