New build: 7mm- 300 Win (long) Mag

TresMon

TresMon

Gunny Sergeant
Full Member
Minuteman
Dec 3, 2007
1,241
140
NW USA
#1
I'll say it before anybody else can chime in. Velocity is far SECONDARY to accuracy.

But just for fun:
3311smk.jpg


I was creating my own reloading data for the custom cartridge because none exists.
That load was 79 grains of retumbo behind a 180 SMK.

7mm, 180 grain match king
7-mm-300WM ("7mm Win Mag")
30" Rock 8.9 twist
Savage 110
 
#2
Re: New build: 7mm- 300 Win (long) Mag

I have toyed around with getting this round chambered in a rifle ever since I picked up a set of dies for dirt cheap. Glad to see someone is messing with the cartridge. Out of curiosity did you consider the 7mm STW?
 
#3
Re: New build: 7mm- 300 Win (long) Mag



I did consider the 7mm STD
laugh.gif


And the 7mmRM.

From my research the 7mm-300WLongMag is a bit hotter than the RemMag, but with about the same barrel life- far better barrel life than the 7mmStw...

Barrels are expensive in my neck of the wallet!
 
#4
Re: New build: 7mm- 300 Win (long) Mag

Do you have any idea what kind of speeds it should be doing with a 24-26" barrel? 3150-3200? 3300FPS is pretty impressive anyway you slice it.
 
#6
Re: New build: 7mm- 300 Win (long) Mag



3300 fps is a hot load and brass wouldn't last long. FTrecord I plan on running loads in the 3075 to 3125 if the gun likes that MV.

Thanks for the info on the guy, I will have to give him a yeall adn see what componants are working well for him.
 
#9
Re: New build: 7mm- 300 Win (long) Mag

Have you guys seen this post on the .284 Jarrett? Sounds like the same cartridge, or real close to it.
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2492051#Post2492051

Dare I ask, what might the predicted lifespan be on barrels in a 7mm-300WM cartridge? And where do I look so that I can do a bit of studying on barrel life factors, including those which come into play when developing cartridges? Especially, hot one's.

I'm thinking the back end of that rifle's likely not all that comfortable when you touch one off, given the MV's. But for that kind of speed, likely it's worth it.
 
#10
Re: New build: 7mm- 300 Win (long) Mag


MsScott,

Anybody that chambers barrels can chamber a long action Savage in this round. The catch is you'll probably have to purchase a reamer...

Jean:
Yeah the .284 Jarrett is similar. But FAR more expensive. You use standard 300WM dies for the 7-300WM (with smaller neck bushings) For the Jarrett you have to buy custom dies- and then If you get Kenny J to use his reamer your getting a throat for light hunting bullets as well as a loose neck.


Yes this is a great round. I was drilling 700 yard head shots on steel yesterday and HAMMERING a 1120 yard silhouette. I drilled The 1600 yard plate as well. Ace was calling my wind for me:

"Well, the wind here at the line is left to right, it's just &^%$#%^ swirling everywhere- else. Half way to the target the RAIN is blowing right to left, but then the %$#$$%% trees at the target and blowing the other way too...... Bang.. HIT!

But half the reason I built it was that my 300win mag barrel was on decline and I had been wanting some kind of 7mm magnum when I found my Savage Tactical 300WM for cheap.

So I already had good brass and good dies... so the 7mm-300WM made logistical & financial sense... coupled with performance it was a no brainer for me.

If your wanting a hot 7mm and staring from scratch- I'd prolly suggest just a straight tight or snug necked 7mmRM with a LONG barrel. No tedious forming of brass, etc. Just load it and go.. and it would prolly be 90% of my rifle, with less fuss.

Barrel life: There is a barrel life estimation program over on accurateshooter.com
It's an excel program that takes in several variables and estimates bore life.
2 sure fire ways to stretch bore life is 1. polish the throat of the bore every 75 rounds or so with JB bore cleaner or ISSO polish. 2. load with the SLOWEST burning SINGLE base powder you can use and get adequate velocity.

I have guy tell me "I can get 3000 f/s with 180's out of my 280 Ackley. I just nod and go on. What they don't know is they are using ultra hot ultra aggressive double based powders to do it which consumes barrels far faster.

180's @ 3300fps: Yes I did it. But don't build a rifle for those numbers. At that speed it would be junking brass and probably torching barrels. I'm looking for my match loads to be running 3050-3125. Just whatever the rifle likes.

DO build it with the longest barrel you can afford to buy. 32" !! or 30 like mine. I sure wouldn't go less than a 28".

Recoil is not bad at all on my rifle: I'm running a holland style muzzle brake, 30" AMU profile heavy barrel= all works out to be a 16# package.
 
#11
Re: New build: 7mm- 300 Win (long) Mag

WOW! That is amazing if even just from a purely academic standpoint.

I enjoyed talking to you about this round last month at Park Mammoth. It certianly is an interesting magnum option.
 
#12
Re: New build: 7mm- 300 Win (long) Mag

Tres thats certainly a potent long range hunter you have there.

Shame its not easy enough to come across heavier 7mm pills than the 180 grain... I know there are 190's around but I havnt seen any.
 
#13
Re: New build: 7mm- 300 Win (long) Mag


Bob Cauterucio out of California makes custom bullets under his own last name.
He makes 189 HPBT bullets with Sierra Jackets. I also had in WildCat Custom bullets 200 grain Ultra low drag bullets in mind for this build......

Thanks guys.
 
#14
Re: New build: 7mm- 300 Win (long) Mag

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">the .284 Jarrett is similar. But FAR more expensive.</div></div>

I called Jarrett about cutting me a barrel and they said to true my Savage action and cut one of their barrels they wanted $900! I picked myself up off of the floor and politely said no thanks.
 
#15
Re: New build: 7mm- 300 Win (long) Mag

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">
MsScott,

Anybody that chambers barrels can chamber a long action Savage in this round. The catch is you'll probably have to purchase a reamer...

</div></div>

I guess that was my question ..... did you buy your own reamer or which gunsmith did you use that has it?
 
#16
Re: New build: 7mm- 300 Win (long) Mag

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Training Wheels</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">the .284 Jarrett is similar. But FAR more expensive.</div></div>

I called Jarrett about cutting me a barrel and they said to true my Savage action and cut one of their barrels they wanted $900! I picked myself up off of the floor and politely said no thanks. </div></div>

Haha, good job Jarrett. Way to instantly kill off your own caliber.
 
#17
Re: New build: 7mm- 300 Win (long) Mag

Very nice TresMon! I have kicked around the idea of the same for my first Savage long action. A modest 3100 give or take should provide better barrel life that any of the other hot 7mm rounds from what I have heard. Looking forward to some pics of that rifle and some targets.
 
#19
Re: New build: 7mm- 300 Win (long) Mag

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">I'll say it before anybody else can chime in. Velocity is far SECONDARY to accuracy.

But just for fun:
3311smk.jpg


I was creating my own reloading data for the custom cartridge because none exists.


That load was 79 grains of retumbo behind a 180 SMK.

7mm, 180 grain match king
7-mm-300WM ("7mm Win Mag")
30" Rock 8.9 twist
Savage 110 </div></div>


Hi TresMon,

I keep coming back to the 7mm-300W for pretty much the same reasons you decided to try it.

Substantial velocities.Easy to find and relatively inexpensive brass.One neck down from 30 to 7mm.Perfect feeding from AI 300WM mags.

My only complaint is the belted case.No biggy.

I do wish Ruger would come out with a 7mm version of their 375R case.It would be the perfect sized 7mm cartridge.It holds about 5 grains more powder with a longish neck enabling 180-190 to be seated above the neck/shoulder junction and feed from the mag.The brass isn't too expensive either.I can't talk myself into necking down from 375 to 7mm though
crazy.gif
...Arggg.

Let us know if you are still liking the cartridge compared to others in the near future please.

Thanks
 
#20
Re: New build: 7mm- 300 Win (long) Mag


Will do partner. As soon as I can get around to doing & finalizing load development I'll report back.

I hoping to have this rifle/cartridge doing all it is capable of by the TN f-class Regional champion ship in a couple of weeks.
 
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