Is my logic dangerous…?

[18Echo]

I have a 7-300WM being built.

Internet search and google-fu shows H1000 and Retumbo as the powders of choice and all the load development and load data shows these two powders. We all know H1000 and Retumbo have taken on magical unicorn / unobtanium status.

IMR 7828ssc has a burn rate near H1000, each burn chart I see has it north or south of H1000. I just bought 16lbs of it.

since the 7-300WM is just a necked down 300WM, can I use the load data in the Berger manual for a 300WM shooting a 185gr VLD with IMR 7828ssc as a starting point for the 7-300WM shooting a 180gr VLD with IMR 7828ssc?

 

[Rob01]

I wouldn't use .30 data for a 7mm round.

Isn't the 7mm Rem Mag basically the same? Could you use that data if you can't find 7-300WM data? Does the smith building it have any data for it if he chambers rifles in that cartridge? You might also want to call Hodgdon and ask them. They have data for Hodgdon, IMR and Win powders.

 

[Asperly Aimless]

I would call Hogdon.

 

[Garyc]

NO!!! DO NOT DO THAT!!!

You'll likely be dangerously overpressure by doing that. Go to Hodgdon's site and compare loads for IMR7828 and 140 gr bullets in the 7mm rem mag and 264 Winchester mag. The 264 win mag max load is 11 grs. less than the 7mm rem mag. They both use essentially the same case and it's very similar to what you're talking about, the same case but different bore diameters. The difference is that with the same weight bullet the 264 has a smaller cross sectional area and a longer bearing surface, which both add up to more pressure with the same powder charge. Same thing with the 300 win mag and your 7mm-300 win mag, smaller cross sectional area and longer bullet means much higher pressure. If you use 300 win mag data you're going to be loading WAY too hot.

You'd be a lot better off using 7mm rem mag data and working up with a chronograph. The 7mm-300 win mag is very similar to an older round called the 7mm Mashburn. It's a wildcat that's been around for many years, do an internet set of 7mm Mashburn and you'll likely turn up lots of data.

A quick search yielded this load using a 175 gr. nosler partition (I DO NOT vouch for this, use with caution):

Load 580 detail in caliber 7mm Mashburn Super Magnum

Backing down from that and working up with a chronograph would be a good ballpark place to start.

Hodgdon's website also lists the 180 Berger VLD/IMR 7828 max load for a 7mm weatherby mag as 68.1 gr at 2948 fps. The 7mm wby is just a few grains less case capacity than the 7mm-300 Winchester mag so you could draw some insight from that too.

Here's a thread over on longrangehunting.com that goes 69 pages on the 7mm-300 win mag, there should be some good info in it too:

http://www.longrangehunting.com/forums/f19/anyone-own-7mm-300-win-mag-51404/

 

[18Echo]

NO!!! DO NOT DO THAT!!!

You'll likely be dangerously overpressure by doing that. Go to Hodgdon's site and compare loads for IMR7828 and 140 gr bullets in the 7mm rem mag and 264 Winchester mag. The 264 win mag max load is 11 grs. less than the 7mm rem mag. They both use essentially the same case and it's very similar to what you're talking about, the same case but different bore diameters. The difference is that with the same weight bullet the 264 has a smaller cross sectional area and a longer bearing surface, which both add up to more pressure with the same powder charge. Same thing with the 300 win mag and your 7mm-300 win mag, smaller cross sectional area and longer bullet means much higher pressure. If you use 300 win mag data you're going to be loading WAY too hot.

You'd be a lot better off using 7mm rem mag data and working up with a chronograph. The 7mm-300 win mag is very similar to an older round called the 7mm Mashburn. It's a wildcat that's been around for many years, do an internet set of 7mm Mashburn and you'll likely turn up lots of data.

A quick search yielded this load using a 175 gr. nosler partition (I DO NOT vouch for this, use with caution):

Load 580 detail in caliber 7mm Mashburn Super Magnum

Backing down from that and working up with a chronograph would be a good ballpark place to start.

Hodgdon's website also lists the 180 Berger VLD/IMR 7828 max load for a 7mm weatherby mag as 68.1 gr at 2948 fps. The 7mm wby is just a few grains less case capacity than the 7mm-300 Winchester mag so you could draw some insight from that too.

Here's a thread over on longrangehunting.com that goes 69 pages on the 7mm-300 win mag, there should be some good info in it too:

Anyone own a 7mm 300 Win Mag? - Long Range Hunting Online Magazine

I joined, and posted in that long range hunting forum, and already got an answer back with some quick load data. Thanks for the help.

 

[BuzzBoss915]

Why a 7/300WM when you can build a standard 7MM Rem Magnum? And, lots of data. Having a rifle built, you can pick anything you want. You aren't punching a 7X57 bore to the dimensions of the 300WM case in an existing barrel, or something like that? I'm not getting it? What's the advantage of a 7mm-300WM over a 7MM REM Mag.? BB

 

[Rob01]

Why a 7/300WM when you can build a standard 7MM Rem Magnum? And, lots of data. Having a rifle built, you can pick anything you want. You aren't punching a 7X57 bore to the dimensions of the 300WM case in an existing barrel, or something like that? I'm not getting it? What's the advantage of a 7mm-300WM over a 7MM REM Mag.? BB

I was thinking the same thing but to each his own. People build all sorts of different calibers for different reasons. I like stuff that's more readily assessable and mainstream so I would have went 7mm Rem Mag myself.

 

[Wildboarem]

The 7 mm rem mag is not the same case as the .300 win mag. The win mag is slightly larger in case capacity and can push the heavier 7mm bullets a little faster.

Sent from my KFTT using Tapatalk 2

 

[BuzzBoss915]

Sure, but there are standard chamberings, 7mmWeatherby, Lazzeroni and others that solve the desire for more capacity, if the sole reason is more capacity than a 7mmRemMag. But, like Robo said, everybody has a dream, like something different, exotic etc. Of course, those exotic chamberings become a liability when you consider resale. Nobody likes your dream rifle, you will find out. BB

 

[Wildboarem]

Lazzeroni? Standard clambering?
Anyhow, 7828 is a great powder I think you'll like it. After during a little googlefu, it looks as if 65 gr of 7828 will be a food starting poin to work up from.

 

[Bob L Swagger]

How about the 7STW?

 

[Kinsman]

For questions such as this, I usually refer to my friendly Sierra Ballistic Technician.
800-223-8799

Very helpful people.

 

[1J04]

Exactly. If not a 7MM Rem Mag, 7 WSM, or 7.21 FireBird then why not step up to a 7 STW which is of course a monster of a case (8MM) necked to .284 ? It's a frigging whopper fo sho. But, I must be getting old cuz the 7MM Rem Mag is still my go to popper for EVERYTHING. Love It ! Oops, forgot the 7MM RUM and all it's extra fealt foot lbs of whackage for not a whole lotta difference cept mo $$$$$$

How about the 7STW?

 

[BuzzBoss915]

Sorry for interjecting a little logic. Let the man spend his money on what he wants. Put me down: I don't get it...on this one, for the sake of "more capacity". BB

 

[1J04]

+1 ^ No doubt. Hey, if a guys flush and wants a "fill in the blank" then hell, get one. Not hating, just thinking out loud I suppose. Enjoy New Toy.

Sorry for interjecting a little logic. Let the man spend his money on what he wants. Put me down: I don't get it...on this one, for the sake of "more capacity". BB