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Another 7mm- 300 WM

 
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  #1  
Old 09-02-2011, 11:11 PM
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Location: Townsend, Montana.
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Another 7mm- 300 WM

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 -------------------------------------------------------------------------------------------------



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  #2  
Old 09-03-2011, 12:43 AM
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Re: Another 7mm- 300 WM

Interested to hear some results, Broz
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  #3  
Old 09-03-2011, 01:26 AM
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Re: Another 7mm- 300 WM

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!
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Old 09-03-2011, 02:30 AM
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Re: Another 7mm- 300 WM

Quote:
Originally Posted by Oliveralan View Post
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!
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.
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Old 09-03-2011, 02:33 AM
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Re: Another 7mm- 300 WM

Oh and the gun is pretty nice for being built backwards
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Old 09-03-2011, 07:57 AM
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Re: Another 7mm- 300 WM

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.
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Last edited by Oliveralan; 09-03-2011 at 04:43 PM.
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Old 09-03-2011, 08:24 AM
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Re: Another 7mm- 300 WM

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 rocks
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