7-300wm or 7 Rem Mag?

[Bladestryke82]

I'm looking to purchase a new barrel for my R700 chambered in 7 Rem Mag but I'm contemplating a 7-300wm chambering when I do. I have a few questions though and figured here would be the best place to ask.

First off I'm new to reloading, I've been doing my research, but I'm wondering if neck sizing the 300wm brass might be a little over my skill level?

Is there really that much of a difference in case capacity between the 7rm and the necked down 300wm? My logical brain is telling me most of the extra case capacity would come from the .30 cal. neck diameter which is to be formed down anyways. The shoulders are different but not by much, but then again neither is the neck diameter.

In a 29inch barrel (my possible ending length) would a 7-300wm see much velocity over a 7rm both loaded with 180gr bullets?

I'm wanting a cartridge pushing 7mm 180-190gr bullets as close to or past 3000fps from my reading for ELR shooting. Am I over thinking things here?

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[LRShooter101]

Necking down the 300 WM cases to make the 7mm-300 can produce "Donuts", contrary to popular belief there is no way to say 100% sure if you will or will not get them, but you will probably get them to some degree or another. If you do, you have two choices, Neck Turn to get rid of them, or keep the base of the bullet above the Donut at the Neck/Shoulder Junction.

Below is a good discusion on the 7mm-300 (*55 pages worth!) http://www.longrangehunting.com/forums/f19/anyone-own-7mm-300-win-mag-51404/

They were getting the Berger 180s to beyond 3,000 fps with it, but you are talking about a barrel burning and potentially shoulder pounding round!

 

[ahhshoot]

I can't see the 7-300 being that much of a boost over 7mm RM, not enough to make it worth all the brass prep etc.

I have fantasized about a 338 LM necked down to 7mm though. drool

 

[Powermac]

If you want something above the 7 RM i would take a hard look at the 7 LRM really.
The 338 case for a 7 is really overkill.

 

[Bladestryke82]

If you want something above the 7 RM i would take a hard look at the 7 LRM really.
The 338 case for a 7 is really overkill.

I have but it is too long to be magazine fed, at least from what I've read in an article I can no longer find. I guess I should have mentioned that I'm mag feeding rounds.

*After a little more searching it seems the LRM has a case length of 2.514", which will not put it over the 3.6" mag length of my AI mags.

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[Powermac]

Yes it will work fine with LA AI mags, in worst case a 338 CIP mag is even longer.

 

[ahhshoot]

If you want something above the 7 RM i would take a hard look at the 7 LRM really.
The 338 case for a 7 is really overkill.

overkill? What's that? Lol. But with a long barrel velocity would be ridiculous and a great BC and sd. Would be a cool novelty if money were no problem.





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[SUIScide]

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I happened to have this photo of a 7mm mag fired in a 300WM chamber. I think it helps show how much more capacity there is in a 300 WM case (oops!). I would definitely prefer the 7mm/300WM. It would add a few additional steps to the reloading process but wouldn't be too bad. I always thought doughnuts were more of a problem when necking up or pushing back the shoulder of a cartridge.?

 

[HodgdonExtreme]

Donuts are evil and to be avoided at most any cost.

You are more likely to be forced to deal with them when necking up, but there's no guarantee you won't if you necked down.

I've recently been working on a project that really solidifies my belief you DON'T do wildcats that will have the bearing surface anywhere near the NSJ.

There's a reason they're called "dreaded" donuts.

 

[Unknown]

When considering reloading a wildcat cartridge, I like to figure out how much more range the wildcat cartridge will get me over the standard cartridge. I went through this when considering the 6.5-08 AI over the 260 Remington. I ended up with the standard 260 Remington.

My rationale was that the wildcat round would only keep the bullet from going transonic for another 100-175 yards. And the loads I wanted to use with the 260 didn't go transonic until somewhere around 1500 yards. As I rarely shoot that far, I figured all the extra work for extra distance that I would be very unlikely to use in any case. So far, in the 3.5 years since I have had the rifle, I still haven't regretted the decision.

How much extra distance will the wildcat cartridge get you, and how often do you anticipate actually using that capability? I think most guys think they want the extra capability, but they seldom use it. What this leaves them with is a rifle that requires ammo that that takes much more work than they actually need, or will even use.

 

[idahoorion]

Hmmm, I can get 3000 fps with 180's in my RM, it's got a freebore of ,188 perfect for 168's and a little short for 180's and that is not a max load.

IdahoCTD on this site, has made a bunch of 7/300's and he get's great accuracy, and speed. I would pm him for the insight on that. He just might sell you a muzzle brake tho.

LOL I think you can get the lead/freebore to match what ever you want. this could help that donut? issue.

Idahoorion

 

[Weaselthis]

I've put over 1000 rounds thru my 7mm/300WM in a 26" factory 7mm Remmy bbl. reamed out with 180g Bergers at 3050 fps. Shot into .9-1.1 MOA. Took it to Africa last year for a shit load of plains game. Hammer of God on Kudu, Wildebeast, Gemsbok, Hartebeast, Impala, Eland, Zebra, and Duiker. I NEVER was able to get my 7mm RM up to 3000fps with 180g.

Just re-barreled the old Rem 700, 1980 era action and BDL wooden stock, w/ a new Bartlien ,#3 countour w/ 28.5" of rifling and a Vais brake, done by Francios at GAP in 7/300WM. Got high hopes for 175g Long Range Accubonds and the 190g VLD Bergers if they ever materialize. With 4.5x14x44 Zeiss Rapid Z 800 it comes in at 10 lbs. +/- and should be a pleasure to shoot.

You mention you're new to reloading. In the past, because this was all I had for dies/equipment, I've run 300WM brass thru a 7mm RM neck die and load em up! EzPeeze. No doughnuts to date. After firing, I run them thru a 300 WM FLS die for a .002 bump with the stem removed, and then the 7mm RM neck die. I use the 300Wm seater die w/ 7mm RM stem. Pretty low tech, but has worked ok so far. I sent 2 fired cases to Hornady to make me a custom COAL gauge for their tool and will do so again for the new barrel. Right at $16 to my door.

I'll probably get a set of 300WM micrometer seater die and use a 7mm stem, a 300WM micrometer neck die w/ appropriate bushings, and a 300WM body/bump die this go round. I want to give the Bartlien bbl. all the opportunity to shine it can do.

7mm RM will prolly do anything you want to do, but IF you like the quirky stuff like me, this is a no brainer. More oomph will little effort and a LOT of satisfaction, IMO.
Good luck in whatever you decide.

 

[Skyking]

I have one of each, and my buddy end up building on as well. I think the 7/300 is has a lot more performance over the 7rm. Travis at What?s New » R Bros Rifles has a great design going with the 7/300. Also here is s'more more info. 7mm Practical

Here is my gun
http://www.snipershide.com/shooting...n-rifles/181779-7-300-win-bighorn-action.html

 

[Nortex]

If you are going to do a wildcat 7mm mag why not throw the 7mm Mashburn into the ring as well.

 

[Bladestryke82]

I sent 2 fired cases to Hornady to make me a custom COAL gauge for their tool and will do so again for the new barrel. Right at $16 to my door.

Is it really that easy to get custom dies made too or is that a bigger ordeal? Does anyone make 7/300wm dies with out a custom order?

Also, is the shorter neck of the 300wm really as much of an issue as I've read on some websites?

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[Bladestryke82]

If you are going to do a wildcat 7mm mag why not throw the 7mm Mashburn into the ring as well.

I have looked into the Mashburn but the lack of dies kind of turns me off some. I know you can get custom dies but I don't know how much of a hassle that might include too.

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[Weaselthis]

I've never had a custom DIE made for me. Just the COAL gauge. The fact I could use my existing 7Rm dn 300WM dies was a big plus for me in the decision. I would think w/ enough time/money it would be "that easy". Time/money usually does the trick. I were you and wanted a set of custom dies, I'd contact Pacific Tool & Gauge (I ordered my 7mm/300wm reamer from them), Hornady, or Redding see what they say. Good luck.

Is it really that easy to get custom dies made too or is that a bigger ordeal? Does anyone make 7/300wm dies with out a custom order?

Also, is the shorter neck of the 300wm really as much of an issue as I've read on some websites?

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