Converting from 7mm STW to 300 Win Mag

TackDriv3r

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Hello, I am new on this forum, after I just read one article and seemed like a nice place to join a long range shooting forum. Sorry to make this little interesting article too long but its a pretty good read for those who have a 7mm STW.

I always used Rem brass for my 7mm STW for 20 years and looks like its on its way to its 4th barrel soon, until I wanted to check out Nosler's new brass they made for the STW, so I ordered 3 boxes from Nosler but those new brass is not what it seems to be. I have always used Remington brass and its what the rifle likes for .4 to .5 MOA 3 shop group for hunting using RL22 and 150 Scirocco. As of now Rem brass is hard to find and currently discontinued on Midway, so I used the new Noslers and handloaded 20 rounds with max loads of RL22 and 7828 tipped with Swift Scirocco. When I arrived at the range, fired off the first round, closing of the bolt was normal,,on the 2nd round the bolt was pretty hard to close, did not worry too much about it and fired it, on the 3rd round it was very hard, so I extracted it and put in a 4th round, the bolt won't close at all, ***, so I put in a 5th round, it was very hard to close too, so I extracted it. I sorted out the remaining, so 13 rounds was very hard to close and 5 was not able to close at all, and only 2 closed fine. This is ridiculous because I went home and resized my fired and new Rem brass, and they all were fine. Even tried to screw in the dies down more and bump the shoulders on the Noslers, nothing seemed to work. I got on the phone and spoke to a friend who is a local gunsmith, low and behold, he was also working on a customer's gun which is a STW 7mm, and he has the same issue with Nosler brass. Nosler brass worked find on my 7mm Mag, but not the STW. Gunsmith says that the belt of the case is 25 thousands longer over specifications. So I called Nosler and the smart *** representative says " We have the best engineers who design and make our brass, so the problem is your gun" What a jackass because its nothing to do with my gun so I sent my rifle to New Mexico to have a gunsmith look it over and I am pretty sure I shot the barrel close to its final worn stage, since he has the gun and wanted to convert it to a different caliber such as a 300 Win Mag, but I would like you guys to chime in and say what you would want to do if you were in my shoes since 30 caliber has a very long list of brass and bullet manufactures over 7 mm and to eliminate the brass issues from Nosler and shortage of brass for the STW. My other issue is 300 Win Mag is a little shorter by about an inch and may be loose in the magazine and will it have chambering issues? Is the action too long for 300 Win Mag? Hope you guys choose what caliber you would convert it to and Thanks for the chime if any.

TackDriver:cool:
 
Brass is hard to get for the 7stw at present. I have some supply for my rifle but I suggest people form theirs from 375h@h if they don't have any. I just loaded a bunch of test loads for the 175 eld-x into converted RP 375h@h brass for my rifle (a lh m700 wearing a 8" twist 27" long shilen barrel- Manson 7mmstw reamer) this morning.

You didn't list an action in your post but if you are on a m700 action the 300win will work as well as the 7mmstw in it. The 300 win is only a quarter inch shorter (the 300wsm is another story though)...

You are going to have to make the decision if forming brass is worth your time or not... If not, I suggest a 7rem, 7x300win (simple neck down-no fire forming), 300win, etc....
 
You didn't list an action in your post but if you are on a m700 action the 300win will work as well as the 7mmstw in it.

My action is a Remington 700, it used to be a Sendero when I bought it back in the 90's.

By the way, I have three bags of new Quality 7mm STW brass, 3 full boxes of new Nosler's, and about 60 fired once cases of Remington brass plus the Redding Competition die set once the STW rifle is converted to 300 win Mag, just give me a holler when you need those items for your STW since brass is hard to find these days. I won't be using the STW components anymore.
 
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I had the same problem with Nosler brass in STW. Everything chambered fine but the Nosler. We gave up on it.
 
Never had a single problem with Nosler brass in any caliber, including my STWs... Maybe y'all just got a bad batch?

As for converting it to a .300WM, all you will need is a new barrel blank and a good gunsmith.
 
Sounds like the belt is to tall (or to Long) since that is where the cartridge head spaces, That would explain why you cannot size the case to fit. Measure the belt height from cartridge base to front edge of belt, and compare the new Nosler against the Remington. It would only take a 2 or 3 thousands to make a too tight fit in a close spec. custom chamber. Sounds like the barrel is to far gone to worry about opening up the chamber to use this brass.

Since the 7mm STW 2.850 case it takes a full length Magnum Action. You would have extra room to not loose case capacity seating long heavy bullets deep. You and your smith will have to choose the Chambering Reamer carefully to get the throat cut to get the bullets to set off the lands or touch the rifling for accuracy, and not loose case volume. You may want to make a dummy cartridge to show the smith, at your first meeting.

Good Luck on this project.
 
Since the 7mm STW 2.850 case it takes a full length Magnum Action. You would have extra room to not loose case capacity seating long heavy bullets deep. You and your smith will have to choose the Chambering Reamer carefully to get the throat cut to get the bullets to set off the lands or touch the rifling for accuracy, and not loose case volume. You may want to make a dummy cartridge to show the smith, at your first meeting.

Good Luck on this project.

Are you referring to use a long throat chamber for the .300 Win Mag to use long heavy bullets to seat into the rifling?

What would be the difference between a short throat and a long throat chamber?

Will the 300 Mag work in a long throat chamber in a STW action? Will the bullets be able to fit in the magazine if I were to use a long throat chamber for the 300 Mag?

I was not so sure about it yet, hope you can fill me in.
 
Are you referring to use a long throat chamber for the .300 Win Mag to use long heavy bullets to seat into the rifling?

What would be the difference between a short throat and a long throat chamber?

Will the 300 Mag work in a long throat chamber in a STW action? Will the bullets be able to fit in the magazine if I were to use a long throat chamber for the 300 Mag?

I was not so sure about it yet, hope you can fill me in.

He's simply saying that you can use a custom reamer with a bit longer throat to take advantage of your action length and seat your bullets out a bit. You would get a bit more case capacity doing this too. You don't have to use anything but a standard reamer though; there are thousands of rem700 rifles in 300win and 7rem with normal chamber dimensions and they work just fine- and both are a bit shorter than the action's length constraints.
 
Are you referring to use a long throat chamber for the .300 Win Mag to use long heavy bullets to seat into the rifling?

What would be the difference between a short throat and a long throat chamber?

Will the 300 Mag work in a long throat chamber in a STW action? Will the bullets be able to fit in the magazine if I were to use a long throat chamber for the 300 Mag?

I was not so sure about it yet, hope you can fill me in.

A Rem 700 magnum long action has the same magazine dimensions regardless of cartridge...Unless it is a .338 Lapua.
 
He's simply saying that you can use a custom reamer with a bit longer throat to take advantage of your action length and seat your bullets out a bit. You would get a bit more case capacity doing this too. You don't have to use anything but a standard reamer though; there are thousands of rem700 rifles in 300win and 7rem with normal chamber dimensions and they work just fine- and both are a bit shorter than the action's length constraints.

Gotcha, I assumed its what he meant, just making sure. I believe the 300 Mag is .230 shorter than the 7 STW. Thanks Lefty
 
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