Another 7mm- 300 WM

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Broz, Sep 2, 2011.

  1. Broz

    Broz Well-Known Member

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    Just finished this one up tonight. I am doing it for a good friend of mine that is a true 7mm lover. He already has a full custom .338 Rum, so this should fill out his long range arsenal very well. I will start break in and load development tomorrow. Have some of the new 180 gr Berger Hybrids to try. Along with some 180 Berger VLD's , H-1000 , CCI 250's and Fed 215 GM's that will go into new RWS Brass. Just finished 50 pcs of 300 Win Mag brass necked down and ready to go. I used Redding 300 win Competition bushing dies (3 die set) to do the necking down. Started with the Neck die with a .321 bushing for the first pass through, then a .312 bushing, then finished up with a .306 bushing. It all went smooth as silk. After fireforming, one pass through neck sizing die with the .306" bushing will be all they need till the shoulder needs bumped, then a seperate pass through the 300 win body die will fill that bill. This one was chambered with a custom reamer I ordered to my liking. Plenty of throat room for the long boolits and a few little things I think will make her shoot into small holes. I really have had great success with this chambering. I feel it is the perfect case volume for a heavy bullet in a 7. Not too over bore and barrel life long enough to enjoy for a good while. It will send the 180's over 3150 with ease and I think it gets some of it's inherent accuracy from the 300 win that has been a proven shooter for many years.

    Here are the build specs.

    Manners T-3 stock, action bedded in Devcon.

    Seekins DMB bottom metal and Mags

    Early Rem 700 action , trued and lapped with a lighter ejector spring so as to not dent hot brass necks upon ejection.

    One of .308 Nates custom bolt knobs for quick and easy bolt fnction.

    Timney Trigger set at 1 3/4 lbs.

    Heavy 3 pin barrel lug

    Hart 26 1/2" tube in a sendero contour , fluted and hand lapped by Hart in a 1 in 9 Twist.

    JP Enterprises brake

    Satin Black Cerakote on all metal and Olive Drab Duracote on stock.

    Nightforce NXS 5.5 ~22 x 50 with NP-R1 reticle and zero stop. Mounted with a Bedded NF 20 moa rail and in NF ultra lite 30 mm rings.

    Jeff gun)-------------------------------------------------------------------------------------------------

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  2. SidTheKidd

    SidTheKidd Well-Known Member

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    Interested to hear some results, Broz
     
  3. Oliveralan

    Oliveralan Well-Known Member

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    Very nice! I just spent the last few hours prepping 300 win nah Winchester brand brass for my 6.5-300 win mag (dubbed: 6.5mm Voodoo). Will be testing a new powder lot (Retumbo) as well as some 140gr Amaxs to compliment current diet of 140gr VLDs.

    I think when this barrel is worn out, I will try a 7-300.

    Interesting you size them down in 3 steps, I simply used a 7mm rem mag full length sizer to get them to .280 inside neck diameter, then .264 win mag die to reduce them to .261" inside neck dia.

    Ballistically I believe the two are very close, both well ahead of the 300 wm. Yours carries more energy and better barrel life, at the cost of more recoil. I think it's worth it though. Will have my suppressor anyway by the time I wear out my 6.5 barrel so recoil isn't really a consideration anymore, then the 7mm wins outright!
     
  4. pyroducksx3

    pyroducksx3 Well-Known Member

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    Isnt the 7 rem mag/ 264 mag shorter than the 300 win mg? I would figure you would be oversizing using these dies on a 300 win mag case. I guess I can learn something though. Using the redding set seems much more logical as you can use the 300 dies and just get the proper bushing to neck down. The only other step that I have heard (thats not mentioned by Broz) is to use the innovative technologies dies to size all the way down to the rim.
     
  5. pyroducksx3

    pyroducksx3 Well-Known Member

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    Oh and the gun is pretty nice for being built backwards :)
     
  6. Oliveralan

    Oliveralan Well-Known Member

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    Pyro, of course I used it backed out.. I was explaining my method of necking down. I use a 300 win mag body die to FL size.
     
    Last edited: Sep 3, 2011
  7. bigngreen

    bigngreen Well-Known Member

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    Very nice Broz! I can't wait to see how it does with that reamer design! After shooting the 7 RUM some more I'm convinced the 7-300win is the sweet spot for all round performance, which should include usable barrel life, after all you can't have a barrel smoke out will engaging a band of hostile rocksgun)
     
  8. Broz

    Broz Well-Known Member

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    Breakin is done. This Hart barrel is one of the smoothest I ever pushed a patch through. I seen a pretty large decrease in copper after the 6th shot. By the 20th it was cleaning in 3 to 4 patches. I then shot a 5 shot group and it was done. Pretty much a 5 shot ragged hole at 150 yards.

    By the time I finished break in I had found what it liked for a powder charge. I was up to 74 gr but it was happier and shooting tighter at 72 gr. of H-1000. So that is where I stayed. I just got in from shooting 3 groups at 300 yards. Off a bipod prone it shot 1 group at .2 moa and two at .3 moa. Each group was .010" different is seating depth starting at .040" off the lands and ending at .060" off the lands. The winner was .050" OL with two in the same hole and a group size of .872" @ 300. I will take it.:D

    I need to chrono again to see what the final velocity and ES is. But when I last checked it was just over 3050 fps wit an ES of 11. So the shorter barrel on this one and the reduced charge did cost about 100 to 125 fps.

    I am shooting the 180 VLD's. It didn't seem to like the 180 hybrids as well. I don't think this reamer is the best choice for hybrids. I designed it for the VLD and it works out perfect at .050" off the lands. This puts the back of the bearing surface right at the base of the neck. That gives about .200" of bearing surface in the neck.

    I am running more neck tension han I like to. So I ordered a looser bushing today. I hope that might drop the ES a bit too.

    Recoil is very light in this rifle with the JP brake. I can hold a good sight picture through the recoil and only move a few inches off point of aim. The rifle is very fun to shoot.

    All these groups were done with virgin freshly necked down RWS brass that had not been fireformed yet. So, it is looking like it will be an easy rifle to load for. She sure aint picky.:)

    Jeff gun)---------------------------------------------------------------------------------------------
     
    Last edited: Sep 11, 2011
  9. Elk Chaser

    Elk Chaser Well-Known Member

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    That's a good lookin' rifle. Looks like all the parts and pieces went together well:)
     
  10. BH Hunter

    BH Hunter Well-Known Member

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    Did you put the action on backwards?
     
  11. Broz

    Broz Well-Known Member

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    No, it's for a left handed friend of mine. Backwards would be for a South Dakota shooter.

    Jeff
     
  12. BH Hunter

    BH Hunter Well-Known Member

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    Touche'
     
  13. Broz

    Broz Well-Known Member

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    BH Hunter, Just kidding back at ya. All in fun :D

    Jeff
     
  14. SidTheKidd

    SidTheKidd Well-Known Member

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    Sounds like a shooter Broz. I coudnt get mine to stay consistantly accurate. Traded mine for a 338 Edge. Sure would like to mess around with the 7-300wm again sometime down the road again.