I figured it would be better to start a new thread instead of derailing jezzolo’s 300 win mag build.
I’ve owned 3 of these over the years, all lefties, one standard and 2 mags. 2 got away from me, I still have one. I got the 300 H&H bug sometime back, still waiting on a barrel and will update that thread when I have more parts.
Anyway, I hope to pass on some useful information for those considering the action for a build.
The factory sent out the 300 Win Mags with the standard length 3.4 mag box, that is to say the same length as 30-06, 7RM, 338 WM, etc. The 7STW was sent out with the 3.6 length H&H length mag box. They also opened the ejection port to the rear, making the rear scope base holes closer together than the standard. This can cause frustration when ordering scope bases.
In my opinion, putting the 300 WM in the standard length action was a mistake, especially if one is to take advantage of all the case capacity the WM offers and wishes to use the LR bullets that are all the rage. Why else use a 300WM, right?[emoji1]My good buddy has one, and he can’t get within .200 of the lands due to mag box length, so his rifle is basically a single shot. With the pre-64, it’s a big deal to remedy. With the Classic, it’s still some work but much more do-able.
If one desires to leave the action alone for collector value, or if using long skinny bullets successfully to full value in your 300WM is not a concern then stop here. I’ve learned a few things that make them work. I write this only because of everything I’ve read that says this is a plug and play modification. This was NOT my experience at all...
The 1st thing to do is remove the block in the rear of the “ML” mag box. It is spot welded in 6 places. The spot welds can be drilled out with a good center punch mark and careful drilling. Go slow. Or if you can find an E box, that works too. Last I checked they were available from Midwest Gunworks. Also, the bolt stop and ejector blade will have to be shortened, I believe by about .100 but don’t use that number as gospel. You might get lucky here and have a rifle that feeds correctly without any further work. For me, Murphy rules so I had to go deeper into the job by milling the feed rails aft another .200 or so to clear the belt on the case. This is not rocket science and can be done with a Dremel with a small carbide burr or a mill. Proceed with extreme caution though or you will have a single shot. Additionally, there is a square “bump” machined into the rear of the mag box opening that may also give your follower problems. This bump is about half thickness on the H&H length actions with a ramp cut starting at the edge of the middle action screw. Again with Murphy ruling the day, my standard magnum follower would not work so I had to source a H and H length from Sunny Hill Enterprises as the factory 7STW length is unavailable. The Sunny Hill is a work of art, and they are an awesome company to deal with. Pricy at $50. Finally, after all that, I had to change to a Remington 700 follower spring and the angle of the feed ramp as the bolt was riding over the cartridge in the magazine.
This will get you a 3.6 mag length that feeds right. If you really want to take advantage of the cartridge, Wyatt’s Outdoors makes a box that goes to 3.8. With this you can have a rifle that feeds with Jeff Brozovich’s famous 300WM reamer pattern for 215 Berger hybrids which end up at 3.7-ish LOA.
So my advice is this for everyone who stuck with this boring write up: if you want a 300 mag in a Winchester 70, use the 30-338 wildcat or 308 Norma. Both are near identical and with a reamer with .100 leade, one can get pretty close to the lands with a ELD. Mine (Remington 700 action) has a .120 leade, and rides the lands at 3.5 OAL with the 212 ELDX, and yields 2850fps with IMR4350. That’s about as good as a 300 WM. Down side is that you’ll be reloading everything.
If you want to stretch one out, Lee Christianson in WI is one of the best Model 70 smiths around.
Wow, done[emoji1]
I’ve owned 3 of these over the years, all lefties, one standard and 2 mags. 2 got away from me, I still have one. I got the 300 H&H bug sometime back, still waiting on a barrel and will update that thread when I have more parts.
Anyway, I hope to pass on some useful information for those considering the action for a build.
The factory sent out the 300 Win Mags with the standard length 3.4 mag box, that is to say the same length as 30-06, 7RM, 338 WM, etc. The 7STW was sent out with the 3.6 length H&H length mag box. They also opened the ejection port to the rear, making the rear scope base holes closer together than the standard. This can cause frustration when ordering scope bases.
In my opinion, putting the 300 WM in the standard length action was a mistake, especially if one is to take advantage of all the case capacity the WM offers and wishes to use the LR bullets that are all the rage. Why else use a 300WM, right?[emoji1]My good buddy has one, and he can’t get within .200 of the lands due to mag box length, so his rifle is basically a single shot. With the pre-64, it’s a big deal to remedy. With the Classic, it’s still some work but much more do-able.
If one desires to leave the action alone for collector value, or if using long skinny bullets successfully to full value in your 300WM is not a concern then stop here. I’ve learned a few things that make them work. I write this only because of everything I’ve read that says this is a plug and play modification. This was NOT my experience at all...
The 1st thing to do is remove the block in the rear of the “ML” mag box. It is spot welded in 6 places. The spot welds can be drilled out with a good center punch mark and careful drilling. Go slow. Or if you can find an E box, that works too. Last I checked they were available from Midwest Gunworks. Also, the bolt stop and ejector blade will have to be shortened, I believe by about .100 but don’t use that number as gospel. You might get lucky here and have a rifle that feeds correctly without any further work. For me, Murphy rules so I had to go deeper into the job by milling the feed rails aft another .200 or so to clear the belt on the case. This is not rocket science and can be done with a Dremel with a small carbide burr or a mill. Proceed with extreme caution though or you will have a single shot. Additionally, there is a square “bump” machined into the rear of the mag box opening that may also give your follower problems. This bump is about half thickness on the H&H length actions with a ramp cut starting at the edge of the middle action screw. Again with Murphy ruling the day, my standard magnum follower would not work so I had to source a H and H length from Sunny Hill Enterprises as the factory 7STW length is unavailable. The Sunny Hill is a work of art, and they are an awesome company to deal with. Pricy at $50. Finally, after all that, I had to change to a Remington 700 follower spring and the angle of the feed ramp as the bolt was riding over the cartridge in the magazine.
This will get you a 3.6 mag length that feeds right. If you really want to take advantage of the cartridge, Wyatt’s Outdoors makes a box that goes to 3.8. With this you can have a rifle that feeds with Jeff Brozovich’s famous 300WM reamer pattern for 215 Berger hybrids which end up at 3.7-ish LOA.
So my advice is this for everyone who stuck with this boring write up: if you want a 300 mag in a Winchester 70, use the 30-338 wildcat or 308 Norma. Both are near identical and with a reamer with .100 leade, one can get pretty close to the lands with a ELD. Mine (Remington 700 action) has a .120 leade, and rides the lands at 3.5 OAL with the 212 ELDX, and yields 2850fps with IMR4350. That’s about as good as a 300 WM. Down side is that you’ll be reloading everything.
If you want to stretch one out, Lee Christianson in WI is one of the best Model 70 smiths around.
Wow, done[emoji1]
