375 RUM Range Time

[Richracer1]

Went out to load develope for the 375RUM yesterday. 3 different bullets tested. Here are the results, sort of:
270 TSX for a CA hog, the first charge tried was about 1 MOA 3 shot group. I called this good enough for a hog. I didn't chrono this load. THe load:
270 TSX
GM215M
97gn of RL-19
COL 3.61"

Second Bullet: 260AB using I 4350, GM215M and a COL of 3.67 (max magazine allowed length)

Set up the chrono and proceeded to shoot. Got several decent groups, around 1" - 1.25". After looking at the groups, I'm going to load up some 260s at 96gns and alter seating depth. The group size with the initial test load was 1st & 3rd shots overlapping and the 2nd shot about 1.25" away. The 2nd shot may be a result of the idiot behind the trigger. Anyway, the average velocity of the 96gn charge was about 3000 fps.

Third bullet: 300AB, I 4350, GM215, COL: 3.67"

Same set as the 260, got about the same results. I decided to work with the one that shot around 1.25". This was the 93.5 gn load. Again, will play with COL to see if this will tighten up. The average velocity for the 93.5gn load was around 2800 fps.

In regards to group sizes for this specific caliber, I will be happy if I can get 1" groups. If sub-moa is achieved, that's icing on the cake. I will be happy with 1" groups because this rifle will pretty much be used on elk/moose/bear, and at my self-imposed max range of 350yds, 1" groups are more than satisfactory.

 

[JD338]

Rich,

I bet with a little tinkering, you should get sub MOA accuracy.
Good luck with the load development and keep us posted.

JD338

 

[Richracer1]

I figured I might as well post the targets, so, here are the targets from the above mentioned loads.

260AB w/ 96gn of IMR 4350

300AB w/ 93.5gn of IMR 4350

 

[Richracer1]

Rich,

I bet with a little tinkering, you should get sub MOA accuracy.
Good luck with the load development and keep us posted.

JD338

I have plenty of powders to try if I can't get IMR-4350 to work.

 

[Guy Miner]

This is a sporter-weight rifle isn't it? Not some 20 pound, heavy-barrel bench monster? I think that given the power level of the cartridge, in a relatively light hunting rifle - you're doing great. Those big boomers are not easy to shoot from the bench... You're talking about a whole lot of power with that thing...

Big game to 300 - 350 yards? I think you're there. A little more load tweaking won't hurt, and may get you under an inch at 100 yards. That's always nice, but you're already doing plenty good for hunting big game at reasonable ranges...

Regards, Guy

 

[Richracer1]

This is a sporter-weight rifle isn't it? Not some 20 pound, heavy-barrel bench monster? I think that given the power level of the cartridge, in a relatively light hunting rifle - you're doing great. Those big boomers are not easy to shoot from the bench... You're talking about a whole lot of power with that thing...

Big game to 300 - 350 yards? I think you're there. A little more load tweaking won't hurt, and may get you under an inch at 100 yards. That's always nice, but you're already doing plenty good for hunting big game at reasonable ranges...

Regards, Guy

Guy, the rifle is Rem 700 LSS. The only thing I've done to it was have my 'smith adjust the trigger to 2.5#.

 

[JD338]

Rich,

I would re shoot the 96.0 gr IMR 4530 load as is and also play with the COL. I think you are on to a good load.

JD338

 

[FOTIS]

There is potential there for sure. We had great luck with IMR 7828.

 

[Greg Nolan]

97 gr. IMR 4350 at 3.59" OAL at 3080 fps. with CCI 250 LRM primer was the answer for my Rem 700 LSS. with the 260 gr. AccuBond. Elk love it (NOT)!

 

[Richracer1]

97 gr. IMR 4350 at 3.59" OAL at 3080 fps. with CCI 250 LRM primer was the answer for my Rem 700 LSS. with the 260 gr. AccuBond. Elk love it (NOT)!

Thanks Greg, right now I've got some loads with 96gns made up with different COLs. I noticed you have yours seated kind of deep, did you start at that COL or did you work your way to it?

 

[Greg Nolan]

Rich
I worked my way to it. I started closer to the lans at max magazine length which was still .017 jump but as I worked shorter and longer I did the best at 3.59 which is almost right on the 3.6 max for both Nosler and Hornady. The ogave difference would suggest at least a little difference but SAAMI specs seem to rule. I have been surprised more than a few times that the SAAMI max ends up the best after all my hi-tech :roll: reloading efforts. Weatherby and Winchester are usually the exceptions but not always. Let me know what works out for you. I use CCI primers and I believe you choose Federal so there will be a learning experience for me. Thanks
:grin: Greg

 

[Richracer1]

Well, here's the results of todays shooting. I may go play with the remaining loads I made up with varying COLs, but I can live with this.

375RUM
Rem Brass 2.83"
GM215M
96gn of IMR4350
260AB
COL: 3.630
Velocity: around 3000 (I need to re-chrono this as I lost my previous fps data)

 

[Antelope_Sniper]

Yep, that's a nice group for an artillery piece. :grin:

 

[Greg Nolan]

Richracer1
That looks like a lot of tasty elk meat in the making :wink:

 

[JD338]

You're there Rich.
Nicely done.

JD338

 

[Richracer1]

Went out today to try some 300ABs loaded up with IMR-7828SSC. IMR-4350 didn't work out. Anyways, here's the scoop:
Rem Brass - 2.83"
GM215M
99.5gn of IMR7828SSC
COL: 3.63"
Velocity: Not yet, the battery died in the chrono.
I'm guessing around 2800 to 2850fps.

I'm very happy with this load.

 

[JD338]

Rich,

Still a good start at 1.0". Try adjusting the COL. The 300 gr AB at 2800-2950 fps is some serious horse power.

JD338

 

[Richracer1]

Thanks Jim. I think I'll call this load good as the 300AB is my secondary bullet for this rifle. My primary is the 260AB. Plus I'm getting low on 300ABs and Nosler hasn't put any 2nds up for sale yet. If I can aquire some 300AB 2nds, I may play with it some more, but for my artillery gun, that's pretty darn good IMO.

 

[FOTIS]

Cartridge : .375 Rem Ultra Mag
Bullet : .375, 300, Nosler PART SP 44845
Cartridge O.A.L. L6: 3.600 inch or 91.44 mm
Barrel Length : 26.0 inch or 660.4 mm
Powder : IMR 7828 SSC

Predicted data by increasing and decreasing the given charge,
incremented in steps of 3.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-30.0 73 69.65 1999 2661 23151 6975 82.9 1.922
-27.0 76 72.64 2085 2897 25657 7427 85.5 1.846
-24.0 79 75.62 2173 3146 28443 7867 87.9 1.772
-21.0 82 78.61 2262 3408 31540 8287 90.2 1.701
-18.0 86 81.59 2351 3683 34990 8685 92.3 1.632
-15.0 89 84.58 2441 3970 38839 9055 94.1 1.559
-12.0 92 87.56 2531 4268 43141 9391 95.7 1.484
-09.0 95 90.55 2621 4576 47960 9690 97.1 1.414
-06.0 98 93.53 2711 4895 53372 9946 98.2 1.347
-03.0 101 96.52 2800 5223 59469 10156 99.1 1.284 ! Near Maximum !
+00.0 104 99.50 2889 5559 66361 10316 99.7 1.224 !DANGEROUS LOAD-DO NOT USE!
+03.0 108 102.49 2977 5903 74181 10422 100.0 1.167 !DANGEROUS LOAD-DO NOT USE!
+06.0 111 105.47 3064 6253 83098 10476 100.0 1.113 !DANGEROUS LOAD-DO NOT USE!
+09.0 114 108.46 3150 6610 93312 10511 100.0 1.062 !DANGEROUS LOAD-DO NOT USE!
+12.0 117 111.44 3236 6974 105087 10534 100.0 1.013 !DANGEROUS LOAD-DO NOT USE!
+15.0 120 114.43 3321 7347 118726 10544 100.0 0.967 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 104 99.50 3012 6043 81025 9845 100.0 1.134 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 104 99.50 2709 4888 53601 10281 95.0 1.342

 

[DrMike]

For sure, that load will work for anything on this continent. Still a good group.