7mm build

[WildRose]

11 pages of some really great options on 7mm cartridges. The one that really sticks with me for an upgrade from either of my (2) 7mmR.M.'s is the 7mm Practical. I just took a 300 win mag case, neck sized it to 7mm, pressed a 180 Berger in it and just stared at it next to a 7mmR.M. for a while. Other than length, the cases are about identical on body size. I popped it into the mag box, cycled the bolt slowly and it fed fine up to the longer OAL. Nothing there to worry about feeding it.
The brass is plentiful and cheap for 300 Win. It just seems to be a natural, elegant way to get more performance out of a 7 mag I currently own. The only downside to convert an old rifle is re-chambering (and/or a barrel) cost, and buying dies. (assumptions here, subject to my smith). For a hunter, that's a big jump in performance, IMO. Interesting discussion and thanks!

If you have a good barrel I see no reason why you shouldn't be able to get someone to simply rechamber it as is unless you have a whole lot of rounds through it. If the latter is the case and there's significant carbon buildup you might have a hard time getting it done because it can be pretty hard on tools.

The more I work with the .375 Ruger case the more I think of doing exactly the same thing staying with the original neck vs the ridiculously long neck of the 7LRM.

 

[Bob Wright]

I took a borescope to my old 82 vintage 700 Rem and it appears to have a lot of "heat checks" in the leade. Looks like surface cracks. I am relly anal about cleanliness.
What is that crazing stuff?
This old barrel has unknown round count and will only shoot a 168 berger at a mild speed of 2835 fps, but very accurate. Everything else in lower grain weights is a joke.....I don't know, but maybe retire that barrel? It checks on twist at 9.25 with cleaning rod/tight patch.

 

[highdrum]

11 pages of some really great options on 7mm cartridges. The one that really sticks with me for an upgrade from either of my (2) 7mmR.M.'s is the 7mm Practical. I just took a 300 win mag case, neck sized it to 7mm, pressed a 180 Berger in it and just stared at it next to a 7mmR.M. for a while. Other than length, the cases are about identical on body size. I popped it into the mag box, cycled the bolt slowly and it fed fine up to the longer OAL. Nothing there to worry about feeding it.
The brass is plentiful and cheap for 300 Win. It just seems to be a natural, elegant way to get more performance out of a 7 mag I currently own. The only downside to convert an old rifle is re-chambering (and/or a barrel) cost, and buying dies. (assumptions here, subject to my smith). For a hunter, that's a big jump in performance, IMO. Interesting discussion and thanks!

You are aware the 7mm Practical is more than just a necked down 300win? They improved the shoulder to 30° and lengthened the neck. A standard 7-300 win just requires neck down, no fireforming, and ADG brass is the bomb. It's a great setup!

 

[WildRose]

I took a borescope to my old 82 vintage 700 Rem and it appears to have a lot of "heat checks" in the leade. Looks like surface cracks. I am relly anal about cleanliness.
What is that crazing stuff?
This old barrel has unknown round count and will only shoot a 168 berger at a mild speed of 2835 fps, but very accurate. Everything else in lower grain weights is a joke.....I don't know, but maybe retire that barrel? It checks on twist at 9.25 with cleaning rod/tight patch.

When I see what looks like alligator skin in the throat area I start thinking it's close to the end. You're still getting good accuracy though so I wouldn't worry about it too much.

Talk to a good smith about just rechambering it and see what they tell you as sooner or later you're just going to run out of room chasing the lans.

 

[Bob Wright]

No I didnt! I have not studied the designs of the cases. I just got caught into dreamland here a bit and just studying the 300 win/7mag case side by side. Step one I guess.

 

[WildRose]

I took a borescope to my old 82 vintage 700 Rem and it appears to have a lot of "heat checks" in the leade. Looks like surface cracks. I am relly anal about cleanliness.
What is that crazing stuff?
This old barrel has unknown round count and will only shoot a 168 berger at a mild speed of 2835 fps, but very accurate. Everything else in lower grain weights is a joke.....I don't know, but maybe retire that barrel? It checks on twist at 9.25 with cleaning rod/tight patch.

Reading that again, if you do rebarrel go with a faster twist if you ever intend on shooting bullets heavier than 180gr.

 

[MudRunner2005]

No I didnt! I have not studied the designs of the cases. I just got caught into dreamland here a bit and just studying the 300 win/7mag case side by side. Step one I guess.

Might as well just go .28 Nosler or 7mm STW... Personal opinion.

 

[Bob Wright]

When I see what looks like alligator skin in the throat area I start thinking it's close to the end. You're still getting good accuracy though so I wouldn't worry about it too much.

Talk to a good smith about just rechambering it and see what they tell you as sooner or later you're just going to run out of room chasing the lans.

Yes, that's what it looks like. My buddy sold it to me complaining it wouldnt shoot. He was right to a point. The berger worked but I bet this was "shot hot" and dirty many times and just may be tired now.

 

[WildRose]

No I didnt! I have not studied the designs of the cases. I just got caught into dreamland here a bit and just studying the 300 win/7mag case side by side. Step one I guess.

I've been doing the same thing for years. Back in the 90's the STW bit me hard and I had to get one, about the same time friends started wildcatting with necking down both the 300wm and 300wby attempting to compete with it.

I started looking at the .375 Ruger about six years ago right after I first heard of it and started imagining in my head it's practicality as a parent case for 6.5's, 7mm's, and .30's so trust me, I get it. The only way I can see to improve the original case would maybe be to slightly alter the shoulder angle to around 40-45deg.

 

[WildRose]

Yes, that's what it looks like. My buddy sold it to me complaining it wouldnt shoot. He was right to a point. The berger worked but I bet this was "shot hot" and dirty many times and just may be tired now.

Well if it could be set back a couple of turns and rechambered to the practical you'd probably have a rifle that will last you the rest of your life and without the cost of a new barrel.

Might be worth talking about with a good gunsmith, at worst they'll say, "You need a new barrel".

 

[CMRHG]

What powder/ load are you using? I'm jealous. You're getting 150fps more than I'm getting in my 7RM with 195's.

Retumbo 73.6 grains. New Norma Brass, Federal 215M Primer. Ive built 4 7RM that shoot this same bullet between 2930-2960 fps. I just built a 300-7 shooting the 195. 85.5gr RL33, necked down new Norma Brass, 215M primer, between 3110-3115FPS. In 25 shots thru it, got it down to a 1/4"moa. I work hard to find a simple load that is accurate but easy to put together for my clients. My 270 win builds push the 170 gr berger eol at 2950 as well and are low recoil tack drivers. Simple load as well...

 

[Bob Wright]

Yes Mudrunner, saw a lot of discussion on the merits of STW and the 28. My custom is a 7mm RM Krieger barrel at 8.5 twist. It makes a fine hunting rifle using the 175 Nosler LR. still tweaking slowly to improve but nowhere near the speeds I see in this thread. Those are impressive speeds and groups. I settled for 2935 fps at .75 groups using RE 23. Good for hunting, not for records LOL.

 

[Bob Wright]

I have a rifle builder in Prescott AZ. He's a 30 cal guy and loves/builds Dangerous Game guns. I'll have to listen to his reasoning why the 7mm sucks, but then he'll give me his opinion. Love this guy anyway. He's that good.....

 

[MudRunner2005]

Yes Mudrunner, saw a lot of discussion on the merits of STW and the 28. My custom is a 7mm RM Krieger barrel at 8.5 twist. It makes a fine hunting rifle using the 175 Nosler LR. still tweaking slowly to improve but nowhere near the speeds I see in this thread. Those are impressive speeds and groups. I settled for 2935 fps at .75 groups using RE 23. Good for hunting, not for records LOL.

If looking for more speed, I would try a slower powder like IMR 7828 SSC, 7977, or H1000.