Home Forums Reloading Big Game Rifles New powder for 7mag w/ TSX's

Norma powders are now available again and MRP & MRP II are supposedly temp stable.

In all cartridges that I've used MRP in over the years, the load data and performance has been the same as RL22.

Besides that grains are more uniform and it meters better than RL22.

I've managed to keep a small supply over the years for my 270s, 280s & 338's.

I don't shoot my long throated 7mag enough to go to the effort of changing from RL22 but I strongly suggest you give it a try.

If you do, let me know what happens.

MM

I just loaded up 28 rounds of Retumbo from 70-73 grains in .5 grain increments with the Barnes TSX 140gr and CCI Magnum Primers. I haven't been to the range yet.......Is there any reason that no one is using this combination? I thought Retumbo was the most accurate powder they tested.

Thanks,

I've never worked with Retumbo......let us know how it performs for you.

MM

50-100fps seems bit small to triffle over for a hunting load, but I understand pursuit of perfection. I know of few powders not somewhat affected by cold, but a few are far less affected by heat. Even the Hodgdon powders lose a bit of velocity in cold weather, they just don't get as spunky in hot weather. YMMV on that.

For me these days, whatever R-19 and R-22 will do, VV-N160 and N165 will do as well or better. I aint tried the N560 yet but plan to. 3300 is doable in a 24" 7mmRM with 140s...if your gun will do it, N160 will do it smartly. Consider it a tad faster than R-19, but a tad slower than H4350. Its "personality" changes dependant on case size. A buddy of mine actually has used it with R-22 data in his 7mmRM, but in smaller cases it seems a tad faster. Screaming hot velocities every time I use it though!

I like Alliant's RL25 for bullets 150gr on up in the 7RM, usually gives better accuracy and higher velocity than RL22. I just worked up a RL25/150BT load for my 7RM. Under a .5" at 3200fps using a 25" PacNor SS:


Will re-chrono this load when the weather cools to see how much velocity loss occurs.

MtnHtr

Montana Man,

Will do.

Ty at Barnes recommended the powder so we will see how it does. Barnes recommendation of IMR 4831 for the 300WM 168gr TSX worked out well for me today with a little over .25" group.

All the IMR powders are good performers........only problem is that they are a bit more temp sensitive that the Hodgdon, Ramshot & Norma lines, and RL22, but where you're at, prolly doesn't matter.

IMR4831 is just a tad faster than H4831.

Here's link to a good chart for comparing burning rates of powders easily.

Powder Burning Rates

MM

I'm using it. Settled at 73.5 grains, which shot around 3215 FPS with the first lot I used. The new lot is going about 50 FPS slower, but to the same point of impact, and both lots shoot just under an inch.