Home Forums Hunting & Shooting Long Range Hunting 7mm-300 weatherby

I've aquired a 7-300 weatherby 9tw and fire formed some brass with 180 hornady and magpro from 74-78 gr with no signs of pressure.

I'm looking for load data for this case and bullet. I have magpro, 7828, h1000, h4831, rl22, rl26 and imr 4831 to work with. The gun shot magpro well enough but I don't have a lot of experience in temp swings with it. I don't mind burning the h1000 up if it is the right choice.

Anyone have any recipes to share or ql data?

Thanks in advance.

I don't have any data to share but I believe you're really about the same capacity as a 28 Nosler. Maybe take a few cases and weigh H20 in them and compare to what's on Nosler's Data for the 28 Nosler. Might give you some good information or at least get you in the ballpark of what right looks like.

Curious myself

some of the older Sierra manuals have 7mm-300 Wby data in them

of course you could just use starting 7mm STW load data & work up

BR Cental 7mm-300 Wby data

7mm-300 Wby

Wouldn’t that be close to a Mashburn super???

It is closer to the 28 Nosler than the Mashburn Super. It is virtually identical to the bigger cased Mashburn round. Art Mashburn called the middle sized case the Super back in the day though.

Was the Mashburn case the full length case like a 300H&H?

The Super was 2.6" case. I use the 300 Win Mag and reform it a bit. Back then they used the H&H, and trimmed it down, then fireformed it.

There were two other 7mm Mashburns, one was basically the same as the 7 Rem Mag, the other was the blown out H&H case. Art Mashburn dubbed the Super as the middle one since back then, with powders available he got similar speeds to the big case with 140-175's. Said in order to get everything from the bigger case would require a 26" barrel and then it would beat the Super Mag, but only marginally.

I have loaded for the 7mm/300 Weatherby for the last 25 years or so. My go-to powder has been IMR7828 with the 162-grain Hornady BT Interlock. The rifle belongs to a younger brother who I load for. My suggestion is to use 7MM STW load data as a starting place. I advise caution because the chamber and throating are all over the place. I know that the smith who chambered my brother's rifle used what amounts to free bore.

Mine does have a good bit of freebore. I haven't cast and measured, but the scope shows it.

The only 7mm pills around are 180eldm.

My first 7x300 WBY. was built in 1973 by the late Howard Wolfe of Mifflinburg Pa.
It became a very popular long range cartridge in Pa when Hornady introduced the 162 gr BTHP match bullet.
It also became the cartridge that caused the demise of the 6.5x300 WBY for long range hunting in Pa.
There were actually no good powder choices available that would maximize the cartridge potential at that time. H 570 was pretty good but also hard to come by.
H870 was also pretty good and easily available at that time.
But when 7828 came along it really improved the performance of the 7x300 WBY.
Today i have 2 7x300s, one has a 30” barrel, and the other has a 27” barrel.
Velocity is the same in both guns with the same load.
My current load is 78 gr 7828 with the 162 gr bullet using a 215 primer.
I strongly recommend using caution when working up a load with 7828.
We still use the 162 gr bullet for hunting because it shoots flatter than the heavier ones out to about 1200 yards. And when you get to 1200 yards, its time for a better gun anyway.
I would recommend starting at 75 gr with the 162 gr bullet.
Load just one, then one each with 1/2 gr increases till you see pressure signs like a sticky bolt.
First sign of pressure, STOP, back up a half grain and use seating depth to find accuracy before changing the load.
Shoot everything over a chronagraph, a target isnt necessary initially, a dirt pile is all you need.
Your looking for velocity first, tuning the load can come later.
When you find the velocity, then load 3 and shoot them for a group.
As stated, play with seating depth before changing the powder charge.

I run a 7mm stw, basicaly the same case less the double radius shoulder, H1000 is the go to powder

You've [bleep] up,the ONLY three fhuqking things that matter. Hint.

1) RPM

2) Throat geometry

3) COAL constraints


Fhuqking LAUGHING!...................

Try reloaded 25. My 7 rum loved it with 168 vlds.

It was a buy I made for parts. Mk5 in a brown pounder for 7 hundo.....couldn't screw that up if it was shot out. I will cook this one out and it'll become a stubby 375.

Till then, I expect to burn it down with 180s.

How do you like the Brown's pounder on your MK 5?

Hal

I feel your pain. I recently had to give $499 for this 7mm RemMag,in it's MacaMillion handle. Hint.(grin)



My 21" LW 375 H&H AI,was a fhuqking HAMMER,in it's Fibergrain MacaMillion AWR handle. Hint..............

I scored this one for tree fiddy. https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/14415989/re-nome-cl-lambert-rifle

Nice "problems" to have. Hint.(grin).................