I pick it up at the gunny next week and am anxious to try it out.

I'd like loads for a 140gr bullet.

I'm thinking that since it has slightly greater case capacity than the 7mm Rem Mag, but a smaller bore, that 7mm Rem Mag loads should be about right. E.g. with a 140gr bullet, 75.0 grs of Retumbo or a case full of US869 (~80.0 grs).

I don't have a 6.5-300WM, but have a 257Weatherby with a 7 twist, and have tested and chronographed a Wildcat 142 grain ULD (from Canada) in the barrel.

Also, the owner of a 257/300WM case told me it had a capacity of about 88 grains, which is almost identical to the 87.8 grains of new 257W brass.

Also, after testing and finding that Norma 257W brass is soft, I necked down, trimmed, and formed some 257W cases using 300WM brass. The formed cases were 85.2 grains so the cases are obviously thicker and testing has shown they are stronger and permit an extra 70 - 100 fps.

So I believe that as case capacities would be very close, I believe that using data from my 257W which is built on a Rem700, with a Krieger 26 inch 7 twist barrel (no freebore) would be ok as a starting point. My data using Rem 300WM cases, Federal 215 primer:
70.0 AR2218 (H50BMG) - 3050 fps
71.0 " - 3069 "
72.0 " - 3119 fps (Near Max)

69.0 H870 - 3092 fps
70.0 " - 3110 "
71.0 " - 3150 " (Max)

Hope that the above helps, and good luck with your 6.5/300WM. Brian.

I have no direct data for the 6.5x300. I show 264 capacity of 81.5gr of water. 300 is around 90.36 so take of say 1gr for neck size you get an increase in capacity over the 264 of around 9%. In theory the loads will increase the same percent. While your comparison to the 7mag is a start the case is the size of the 264 not the 300.

As a check I ran two runs in Loadtech. Using the base 264 a 140 & H4831 then increased the case capacity by 9%. The program showed a max load increase of 8.5%,

Dear Andy,
I built one for a guy in Hawaii many years ago. He used regular 264 Mag loading for starting out. The loads in the 264 Thor were too hot. I would try and get some H-870 and use the Hornady loads as a beginning and to break in the barrel. The H-870 is a ball type powder and a bit easier on the rifling. You might just luck out and hit it right off the line? Who knows? Good luck and Aloha,Mark

Thanks guys.

Case capacity is about 90.0 grs H2O. Using a 120gr Nosler BT and an OAL of 3.360", how does this sound?

70.0 grs H4831
75.0 grs H1000
75.0 grs Retumbo
80.0 grs US869

CCI 250 magnum primers. Load densities are in the 90-95% range.

I haven't used US869, and some say it is faster burning than H870, and others have said it slower. If it was my lot of H870, I would estimate that max would be 78.0 grain, bearing in mind that 79.0 was max with the 115 BT in my 257W.

I would be using about 73 grains of H1000, as I have found that it is about 2 - 3 grains faster burning than HRetumbo. Brian.

If you do a search (back to the beginnings), there was a fellow who posted some loads. This was many years ago though, so you should just go to the last page and work forward.

Hope this helps.

This sounds like a cool cartridge, I will be eager to see how it perfoms. I have been working with a 6.5-270WSM (essentially the same as a 6.5-300 WSM), over the summer, I have logged 300 rounds so far and it is shaping up to be a great shooter.

Andy what were your thoughts on choosing the 300 WinMag, any concerns about the belt at those high pressures?

Thanks

quote:

Originally posted by roberti11:
This sounds like a cool cartridge, I will be eager to see how it perfoms. I have been working with a 6.5-270WSM (essentially the same as a 6.5-300 WSM), over the summer, I have logged 300 rounds so far and it is shaping up to be a great shooter.

Andy what were your thoughts on choosing the 300 WinMag, any concerns about the belt at those high pressures?

Thanks

could you give me some of your 6.5/300wsm loads, i'm working on Retumbo and Berger 140 VLD now

I use Norma 270 brass trimmed to 2.070, and resize with a bushing die to 6.5mm

CCI magnum primers, Lapua 139gn match bullets (I cannot get Bergers right now), and H1000 61gn.

OAL 3.080 gets me 20 thou off the lands, and a velociy ~2950 fps

quote:

Originally posted by Nitroman:
If you do a search (back to the beginnings), there was a fellow who posted some loads. This was many years ago though, so you should just go to the last page and work forward.

Hope this helps.

I believe that was me looking for loads,and somebody posted some for me.All my load info for this rifle got wet in a basement flood so I have started over.
I have carefully worked up a load of 68 gr of 7828 with 140gr rem ppcl,rem brass and a col of 3.46 250cci primers .
This is shooting into 1/2 inch at 100 yds.I have 2 more loads to try at 68.5 and 69 gr,but they may be too hot as I am probably pushing it now.I have no pressure signs but as you know that can change in a hurry.60.5 grs is max for the 264 win mag.My chrony is taking a piss again so I have no idea of speed.I am estimating 3000+to3100.This is on a 26" barrel.I would have put this on gunputz for you Andy but I couldn't find your thread.I clearcoated that thing and it improved considerable over the pic I gave you.

Rich

Just got back from my first firing - I found out quite a bit.

120gr Nosler with OAL of 3.365" (seated just off the lands). 24" barrel

H4831 - 70.0 grs - 3400 fps
H1000 - 75.0 grs - 3510 fps
Retumbo - 75.0 grs - 3370 fps
US869 - 80.0 grs - 3130 fps

like the Three Little Bears would have said, the first two loads were two hot by 2-3 grs, the Retumbo was about right for a max, and the US869 has some room to go. I plan to try H50BMG next time out.

I need to extend the throat so I can seat to 3.400" and have it 0.050" off the lands. A 30" barrel is in the plans as well.

quote:

Originally posted by brianw:
I haven't used US869, and some say it is faster burning than H870, and others have said it slower. If it was my lot of H870, I would estimate that max would be 78.0 grain, bearing in mind that 79.0 was max with the 115 BT in my 257W.

I would be using about 73 grains of H1000, as I have found that it is about 2 - 3 grains faster burning than HRetumbo. Brian. Right you were Brian!