7mm-300 win mag

rfurman24

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I need some opinions/advice. I am not trying to reinvent the wheel here. I am just looking for simple. I had pretty much made up my mind on a straight 7mm-300 win mag and had talked to Dave Kiff about the reamer. I was necking down some 300 win mag brass to seat some bullets to find the freebore I need. I got lazy and used my 7mm wsm sizer, as it already had a .313 bushing in it. I got it sized and a 180 vld seated. I assumed when I did this it would just size the neck down and leave the shoulder alone. What I got was a ~35 degree shoulder and a neck @ .313 with no visible donut. I, then, went ahead and put the .313 bushing in my 300 win mag dies and necked some cases down. This method leaves a donut on the outside of the neck/shoulder junction that I believe would have to be turned. I have the equipment I would just need a 7mm pilot. I really do not desire to turn though. At this point I am leaning towards the 35 degree shoulder and just sending Dave a couple dummy rounds. I would then neck all my brass down using the 7wsm dies and use these dies to bump the shoulder when needed. For all other sizing operations I would use the 300 win mag dies. I will be using 180 hybrids I just don't have any lying around right now.
 

rfurman24

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image-2798407110.jpg

From left to right
Sized with WSM dies, sized with 300 win mag dies, and straight 300 win mag.
 

.284

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You could try sizing down in a couple steps with your300 WM die using a couple different bushings to avoid the donuts. That's how I do it anyway.

I haven't put a lot of thought into the 7wsm die being used but how would you full length size or use a body die when needed if you change the shoulder angle?
 

Lefty7mmstw

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I don't think that's a donut on the middle case... I'm thinking you haven't gotten the brass necked far enough back.... It looks rather much like some partially formed 7stw's made from 375 h&h that we've done
 

rfurman24

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Regardless of the route I go I am going to get a "middle" bushing to help keep necks straight. As far as I can tell from all the measurements I took I would be able to neck size and bump the shoulder with the WSM dies and full body size with my 300 win mag dies. After you size down with a few steps do you not have a donut or unsized part? How does it chamber at that time? As a side question what is everyone using for freeborn with the 180 hybrid?
 

Broz

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I would not worry about it. I use Redding bushing dies and get the same thing. It has never caused a chambering issue and goes away after the first firing. I have done tons of them using 300 win dies. That ring you are referring to is not like an internal donut and goes away. I have never had a donut inside either.

Jeff
 

rfurman24

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Thanks guys that is really what I was wanting to know. I have read every page of the 7mm-300 thread but it all starts to blur after awhile. Just so I understand correctly you just neck down using 300 win bushing dies, in at least two steps, then seat a bullet and shoot?
 

rfurman24

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I have to say I do like the idea of the slightly longer neck with the 35 degree shoulder.
 

.284

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Thanks guys that is really what I was wanting to know. I have read every page of the 7mm-300 thread but it all starts to blur after awhile. Just so I understand correctly you just neck down using 300 win bushing dies, in at least two steps, then seat a bullet and shoot?
Yes sir. No donuts at all. In fact newly sized brass shoots just the same as once fired in mine

If you had a 35 degree shoulder from sizing with a WSM die I'm not sure that a standard 300 WM body die would be able to size the entire case for you?
 

Broz

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Thanks guys that is really what I was wanting to know. I have read every page of the 7mm-300 thread but it all starts to blur after awhile. Just so I understand correctly you just neck down using 300 win bushing dies, in at least two steps, then seat a bullet and shoot?
Yes, I like 3 bushings best, about .010 steps, but 2 will do it just fine. Load and shoot.

Good luck with the "freebore" , not actually free bore, it is throat length. I have yet to get one like I wanted from Kiff. I am using another reamer mfg this time.


Jeff
 

Broz

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Seat a dummy with the bearing surface about .060" below the neck shoulder junction and tell them to put it on the lands. That in my mind would be perfect, if they get it right.

Jeff
 

rfurman24

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From all measurements it appears the neck is getting longer as the angle gets pushed to the WSM shoulder. Without firing it I can't be sure but it appears the 300 win mag dies would size all but the shoulder and a small portion of the neck. Over all I still like the simplicity of the straight 7-300 Win Mag. Who are you using for reamers? I called Clymer and they did not make me feel warm and fuzzy.
 

.284

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I used PTG but I had them make me a separate throating die so that my smith could set the distance to the lands off of a dummy round. I did basically what Broz suggested by seating a 180 Berger's bearing surface about 50 or 60 thou below the neck and asked for that to touch the lands. This way you can chase the lands as the throat erodes later and still have the bearing surface in the neck as you seat the bullet out further. There is more than enough case capacity to seat the bullet deeper in case if your rifle wants a jump to the lands without crowding the powder.

It's a great round. You might consider a barrel with the required twist for Bergers 195's if/when they ever show up. Those will keep up with a 300 grain 338 round with the exception of ft/lbs of energy.

For what it's worth I'm getting about 3130fps from a 27 inch tube using H1000.

I used nosler brass because I liked the consistency of it but my primers pockets are done after 3 loads so I would recommend starting with something else
 

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