Anybody worked with a 7mm-300WM?

TresMon

TresMon

Gunny Sergeant
Full Member
Minuteman
Dec 3, 2007
1,241
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NW USA
#1
Supposed to be 150fps hotter than a 7mmRM.

It's time to rebarrel my 300WM.

I'm pretty sure I'm going to build one. I want to drop from 30 cal to 7mm but am heavily invested in 300WM with Reddy bushing dies and my good brass & all. So this is the fix. Just use smaller neck bushings and I'm good to go.

Anybody got one?

Thanks,
T
 
#3
Re: Anybody worked with a 7mm-300WM?

What I have is the 7/300wsm but, what you are suggesting will work. The 7/300wm is a great cartridge and since you already have the 300wm type S dies and brass your set. Neck down and run it. The only thing I'd do different is try find a 7mm neck die that would work with your 300wm brass. The bushing dies wont size the neck down to the shoulder, this will leave a slight buldge that may cause initial feeding issues.

Kicked this one around myself. Kenny Jarrett builds something simular and calls it the 284 Jarrett.
 
#4
Re: Anybody worked with a 7mm-300WM?

Thanks guys.

Roscoe (I'm a machinist) do you think if I grind most of the the slight rolled edge off the Reddy bushing dies that would size it on down to the neck?

I also have planned to make a bushing for the dies with a tapered hole to neck down the brass instead of having to buy a fist full of bushings from Redding to get from .308- .284

Thanks so much yall,
Tres

What about a Lee collet?

I have to get around the die issue. I just barely have barrel money. Don't know where the reamer $$ is gonna come from. Can't spent money on dies.
 
#5
Re: Anybody worked with a 7mm-300WM?

Here is a post on long range hunting forums about a 7mm-300WM. This guy is pushing the 180 VLD @ 3175fps in a 28" barrel with 77 gr H1000 and no pressure. What do you think the barrel life would be on a similar load? That velocity with the 180 VLD sure has the potential to do some damage a hell of a long way from the muzzle!

http://www.longrangehunting.com/forums/f19/anyone-own-7mm-300-win-mag-51404/
 
#6
Re: Anybody worked with a 7mm-300WM?

From a ballistics standpoint, a really fast 7mm *seems* like a great idea. In practicality, if you push 180's that fast, you'd better buy multiple barrels at a time.

My shooting partner had a 7STW and yes, that thing was a laser. But barrel life was measured in dollars/hour of range time.

Your 300WM is probably the point where performance and expense curves cross.

John
 
#7
Re: Anybody worked with a 7mm-300WM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">Roscoe (I'm a machinist) do you think if I grind most of the the slight rolled edge off the Reddy bushing dies that would size it on down to the neck? </div></div>

Negative.

The problem is the way the bushing is held in the die. You'll need a standard neck die that will hit the bottom of the neck. Maybe a 7WSM die would work as your only needing the neck to make contact. and not the body. As long as the shoulder angle is same/same it should work. The initial neck sizing would be the only time you need to use it.
 
#8
Re: Anybody worked with a 7mm-300WM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wnroscoe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">Roscoe (I'm a machinist) do you think if I grind most of the the slight rolled edge off the Reddy bushing dies that would size it on down to the neck? </div></div>

Negative.

The problem is the way the bushing is held in the die. You'll need a standard neck die that will hit the bottom of the neck. Maybe a 7WSM die would work as your only needing the neck to make contact. and not the body. As long as the shoulder angle is same/same it should work. The initial neck sizing would be the only time you need to use it. </div></div>

I'm pretty sure what the WSM case is 28 deg. WM is 25 deg. Or does it matter Roscoe, as long as the neck/shoulder junction comes down and touches the bottom of the neck?

Perhaps a RM die. Might have to cut it off or open the body so it doesn't over size the base of your brass. Might work fine as is though, as the RM is shorter than the WM.

John
 
#9
Re: Anybody worked with a 7mm-300WM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body">I'm pretty sure what the WSM case is 35 deg. WM is 25 deg. Or does it matter Roscoe, as long as the neck/shoulder junction comes down and touches the bottom of the neck?</div></div>

You are correct, it doesn’t matter if the shoulder angles are different. It wont really matter as long as the WM brass has less shoulder angle than the shoulder in the die being used. The neck is all that matters since your just trying to avoid that dreaded bulge at the bottom of the neck. It's a one step process as step #1 to be never repeated on that particular piece of brass.

When I sized down 300WSM brass for my 7-300WSM I simply ran the brass through my 300WSM FL die with a bushing change for the 7mm. I ran into the same issue and still had a bulge at he base of my neck. I neck turn anyway so it was a non issue.

The OP can try running the brass through his die first with just a bushing change to see what happens. If they chamber great, if not, he knows what to do. Non-the less, I think the 7/300WM will be a great caliber for LR. 180 Bergers at 3,000+ fps is never a bad thing.
 
#10
Re: Anybody worked with a 7mm-300WM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body">From a ballistics standpoint, a really fast 7mm *seems* like a great idea. In practicality, if you push 180's that fast, you'd better buy multiple barrels at a time.

My shooting partner had a 7STW and yes, that thing was a laser. But barrel life was measured in dollars/hour of range time.

Your 300WM is probably the point where performance and expense curves cross.

John </div></div>

Barrel life issues are one reason I chose .300 WSM over the 7mm builds. Of course, I'm the new guy at the 1,000 yard matches with a $300 scope, too. Think about it: if a rebarrel is $600+, and effective barrel life is under 1,000 rounds, you're talking about ~ a buck a shot plus ammo, not to mention turn around time for the work. Ouch.
 
#11
Re: Anybody worked with a 7mm-300WM?

[/quote]

Barrel life issues are one reason I chose .300 WSM over the 7mm builds. Of course, I'm the new guy at the 1,000 yard matches with a $300 scope, too. Think about it: if a rebarrel is $600+, and effective barrel life is under 1,000 rounds, you're talking about ~ a buck a shot plus ammo, not to mention turn around time for the work. Ouch. [/quote]


I REALLY, REALLY, REALLY didn't want to think about it that way. You are such a downer!!!!! lol!
 
#12
Re: Anybody worked with a 7mm-300WM?

Barrel life:

with a 28" barrel this think makes STW velocities with 16 less grains of powder.

So less powder = more barrel life.

I'm gonna build mine with 32" barrel and run REALLY slow single base powders.

So with the extra barrel still yet and the powder iIm still freeing up more and more barrel life. And I don't have to run it hot. I can load it to HOT .284Win MV or normal 7mmRM velocity and it just be cruisin along.

Over on 6mmbr.com an engineer posted a free barrel life estimation program. I ran the numbers on a normal 300WM & 7mmRM and got life expectancy to be in the 1800 round range which as about right to real world. This one was estimated about 1300 rounds accurate barrel life. So if I throttle her back and run slower and less agressive (single base instead of double base powders) powders- which is fine with a really long barrel- I'm expecting to get near or more than 7mmRM barrel life.

A 180 vld @ 2900-3000 is what is winning and setting record in 1000yards bench rest right now, so it would be more than adequate for 1000yd. F-class, hunting and tactical matches. If I ever needed more, for some Ultra long range session I'd prolly have another 200fps on tap to draw on....

The 7mm-300 loaded near max with a longer barrel is supposed to generate 7RUM velocity from a standard rifle, with more barrel life than a RUM- which is not saying much.

I'd like to try the 7mm, 200 grain Ultra low drag bullets from wildcat custom bullets. Field generated bc value in the .88-.9 range (!!!!!!!) That would be very forgiving in the wind, but they are 80cents a pill............
 
#15
Re: Anybody worked with a 7mm-300WM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BLK7</div><div class="ubbcode-body">[/quote]

Barrel life issues are one reason I chose .300 WSM over the 7mm builds. Of course, I'm the new guy at the 1,000 yard matches with a $300 scope, too. Think about it: if a rebarrel is $600+, and effective barrel life is under 1,000 rounds, you're talking about ~ a buck a shot plus ammo, not to mention turn around time for the work. Ouch. </div></div>


I REALLY, REALLY, REALLY didn't want to think about it that way. You are such a downer!!!!! lol! [/quote]

The "waiting" part would be the real downer. Some of these barrel shops have long wait times it seems.
 
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