C'mon, Bill. I'd buy a 300 if I didn't have the 7.62, but really, there is little compelling reason for the 300. Using the 4:1 rule of thumb for velocity gain, you gain what? About 2 grains with the 300? That's 8% on a 25gr baseline load. So, that's a potential 2% velocity increase. I'm getting over 2,500fps with 125s and I've loaded some of my cases 3 times now. So, that's about a 50fps potential gain.
You don't need new cartridges to use different twist rates or throat geometries either. I'm just wondering what it's reason for being is. It's not easy or cheap to launch new cartridges. I just don't see what the payoff was for this project.
I assure you that you can't come close to 300 HAM'R velocity with the 7.62x40WT at the same chamber pressure. If you want to compare 7.62x40WT over pressure loads to 300 HAM'R safe pressure loads, then yes they can be very close.
Some of the loading data I saw is identical.
Not sure where your getting your load data? I've got a LOT of experience with both cartridges and I've never seen pressure tested load data that shows any 125gr 7.62x40 load at 2500fps with pressure under 57,500PSI (not even in a 20" barrel), but I do have data on a specific 125gr 300 HAM'R load at 2550fps at 56,000PSI. Trust me, if your loading a 125gr to 2500fps your loads are over pressure, especially if your using A1680.
As to the WHY of the 300 HAM'R, there are several reasons. The main ones are:
7.62x40WT is a un-marketable caliber name and was brought to market at the worst possible time due to the .300 Blackout introduction.
The original goal was to equal .30-30 velocity with comparable bullet weights in the same barrel length. This can't be done with the 7.62x40WT, but can with the 300 HAM'R.
While the 7.62x40WT and it's 1-12 twist is usually pretty accurate, after extensive accuracy testing with the following twist rates we found 1-15 to have a substantial advantage in accuracy potential with bullets in the 110-135gr range, while still shooting 150gr bullets as well as the 1-12. We tested 1-11, 1-11.25, 1-12, 1-13, 1-14, 1-15
We found the increased powder capacity to have a huge positive effect on chamber pressure.
