Anyone own a 7mm 300 Win Mag?

[pyroducksx3]

So here's what I think I understand..... the 300 win mag has a much larger case capacitycompared to the 300wsm, which is why I cant seem to find the supporting data of the 7mm wsm reaching these velocites. Also Im not sure how much difference it makes but if it appears it two bullets ofthe same weight in close diameters are pushed by the same powder charge , the smaller diameter willgo faster? ie .284 vs .308, so a 77 gr charge of H-1000 will push the 150 gr .284 faster than a 77 gr charge of H-1000 of a 150 gr .308. I assume this is because the .284 develops higher pressue? Also in these magnums 4" barrel length can account for as much or more than 200 fps. What really throws me is how say the 7-300 win mag using 79 gr of H-1000 in a 28" barrel can push the same bullet faster than a 7RUM using a 26" barrel using 87 gr of H-1000. as stated earlier they have a 7-300 wm with a 28" barrel using 79 gr of H-1000 pushing a 162 gr amax at a velocity of 3340 fps. Compare that the hornady manual the 7 RUM with a 26" barrel using a charge of 87.3 of H-1000 pushing a 162 gr amax to a velocity of only 3100 fps. Is this just the efficiency of the cartridge? If so somebody ie Remington, winchester missed the boat and should have made this a factory round.

 

[pyroducksx3]

Well no replys? again Im not attacking anyone. I just dont understand and when I dont understand I ask question and because of my lack of expierence I interpret data. So does any one know what a 7-300 WM would push a 200 gr wilcat ULD? If it could get 2900 fps it would be in a pretty impressive performer!

 

[Kiwi Nate]

A lot of the answers to your questions are in the article link I provided. Perhaps you missed the link, here is again:
The 7mm Practical. A Practical Magnum.

As for Remington and Winchester getting it wrong. Things are never quite that black and white. When the 7mm Rem mag was in design phase, Remington engineers pretty much had two main contendors, Les Bowman's .338 Win mag necked down to 7mm or Warren Page's favorite, the 7mm Super Mashburn Magnum which is basically the 7mm-300 Win Mag, although in those days it would have been a blown out H&H. You have to remember that H1000 wasn't around back then so the 7mm-338 Win mag was probably a lot more efficient and effective, hence the adoption of the 7mm-338 as the 7mm Rem mag.

In modern times the market has been a bit tougher. It would not be easy to convince buyers that the 7mm-300 Win mag is the bees knees and a must have. The WSM's and RUM's are vastly different from the traditional belted mags so they get plenty of attention, the premise is based on sales way before ballistic performance.

I have just, 20 minutes ago, finished my third 7mm-300 for a client. This one is shooting groups of between .420" and .465", driving the 168gr VLD at 3212fps. I will leave it at that as the barrel has yet to be fully run in.

 

[pyroducksx3]

Kiwi Nate thank you for the reply it does answer some of my questions. Do happen to know what the 7-300 would push a 200 gr wildcat at Im guessing 2900-3000 but not sure. Thank you

 

[Kiwi Nate]

Yes, you are right on the money. 2900fps and up to 2950 as a near max load.

 

[pyroducksx3]

Kiwi nate I just looked at the 7 STW and it case capasity is even greater than the 7-300 is it correct to assume that it will be capable of producing even higher velocities or does this extra case length not produce the effeciency of the 7-300? It seems to me the 7-300 is just slightly longer than the 7 rem mag with all other dimensions the same and the 7 stw is longer than the 7-300 with all other dimensions the same. Which to me means the stw would be able to match or beat the RUM but looking at the hornady manual the 7 stw using a 162 amz with 78 grains of H-1000 it produces a velocity of only 3150 with a 26" barrel so add the 35 per inch of barrel and we end up with 3240. What you have found is that the 7-300 using 77 gr gets you 3330. Seems that the 7-300 achieves the optimum case capasity for the 7mm and that you really dont gain much going bigger ie the stw, RUM is this a fair assumtion? Thank you again.

 

[Kiwi Nate]

As I wrote in the article, the STW is reliant on freebore. This can be difficult for people to understand at first so take your time to think about what this implies. I have 40 thou jump in my 7mm-300. The STW has 400 thou- nearly a half inch bullet jump. It needs this as a pressure release valve. This creates its own set of problems. Again, please refer to the article and read it carefully.

If things were as simple as case capacity equals velocity, we could simply neck down the 50bmg to 7mm or .30 cal and run high BC bullets at 5000fps. But what would really happen if we necked the 50bmg to say 7mm? Well, the action or barrel would blow to pieces because the gas would not be able to escape through the barrel relative to its expansion. In other words, the .50bmg case has the potential to yield X amount of energy over Y amount of time while a 7mm bore has only Z amount of potential to vent this energy. Hell I hope that makes sense to someone- LOL.

 

[Kiwi Nate]

I think one factor you need to bare in mind is- design goals. Most people who opt for the 7mm-300 do so because they want magnum power, but also want to plink/shoot a lot which in a larger capacity cartridge, is undesirable due to excessive wear. Even the 7mm-300 is pushing the limits but the people who choose this cartridge, have an idea of what to expect. On the other hand, there are folk on this forum who absolutely love the STW and RUM. They also know what to expect, strengths, limitations- they work to the strengths of their pet cartridges.

The STW and RUM get the very last few fps out of the sevens via freebore. You could actually do the same with the 7mm-300 as there is plenty of powder space. With .400" freebore, velocities are much the same accross the board. To really understand just how relevent this is, have a look at the 7mm Weatherby. The case is much the same size as the 7mm Rem Mag, but it uses freebore, allowing it to drive 160 grain bullets at 3200fps. Weatherby actually go a step further than most, utilizing a 1:10 twist rate to minimize any yaw created by the freebore/ loss of bullet to bore concentricity. Its quite a cunning design.

The other night I pumped 3 rounds through my 7mm-300 as fast as I could work the bolt, I needed goats for dog tucker. I located a mob, shot the first animal all quite like but the next two shots had to be taken quick before the mob escaped into the bush. My .308 culling rifle is having a birthday at the moment so its out of action and I am using the big seven on a week to week basis. Pumping rounds out fast like that is what killed my last 7mm RUM. So, there are many things to consider when comparing cartridges.

 

[Broz]

Broz,
Got a couple more questions on the 7mm-300 for you. What sorta groups were you guys seeing at 100 yrds with the berger? Also was the gun throated specifically for the VLD bullets? Also if you remember, how far off the lands were the VLDs when they shot the best? Where you seeing alot of runout with the RM brass?(You are right, this is what I am using.)

I guess I ask because, I was talking to a fella today who has shot alot of Bergers and swears that they will only shoot on or in the lands if the throat is not reamed for them.

Sid, I don't hardly ever shoot groups at 100. I prefer 200 or more as I feel it gives the bullet time to stabilize. I will take a .5 moa group at 300 to a one hole group at 100 any day. Just my personal preferance. That said this rifle will shoot 180 bergers into 1 1/2" at 300 on a very regular basis, and some times better.

The gun was not throated specially for bergers, but it has a long throat, this worked out well. I had the bullets close to the lands at first, but decided to back them in to see how they shoot if they would fit in the box. That came out to be .115" off the lands. That is where there are now and shoot awesome. So I don't feel anyone can say that the bergers have to be on the lands. I have seen them shoot in many rifles I own from .005" in the lands, to this rifle at .115" off. I would just use the Berger seating method and see what your rifle likes.

We were not seeing a terable amount of run out with the RP brass, but the brass was old and I am very fond of RWS and Lapua brass for the 300's. So we changed to new RWS brass. After the first firing we did see noticably less run out, probably .002~.003" less on average.

I am not suprised you are considering a little less powder charge and I doubt if you back off a grain if it will be a negative affect on accuracy. Please remember if you ever go to RWS brass you will need to back off probably 4 gr but I feel you will see very close to the same velocity as you are now.

Hope this helps.

Jeff gun)gun)

 

[pyroducksx3]

Kiwi nate nate thank you for your replies. As I stated I am learning about this and you have answered my questions. I appreciate your patience. I had heard that weaterby uses a lot of freebore I guess I didnt consider or realize that about the rum and stw. I was considering building a 338 edge or 338 RUM because I had hearn that barrel life was terrible with the 7 RUM, so this gives me another option to think about. I am also looking to build the rifle as a long range hunting/plinking rifle , gotta practice to get good right. This 7-300 with the wildcats actually better ballitics than the 338 Edge/Rum, it gives up Ft lbs but still has about 1600 at 1000. So Broz I think I'm ready to un hijack your thread now, sorry. I appreciate the help advice and patience.

 

[Kiwi Nate]

No problems pyroducksx3, you are welcome.

You can see there is a slight difference between my load data and Broz's 3174fps. This will be due to the freebore in Broz's rifle. From what Broz has described, freebore in his rifle is similar, perhaps identical to the .308 Winchester when utilized in a magazine fed action. Its certainly not excessive.

Shot this yesterday, same freebore as Broz's rifle. Its a Howa I tricked up a couple of years back which has come in for a birthday:

 

[pyroducksx3]

Well the more I research everything it looks like this 7x300 WM will do everything the stw will do, possibly even better. It appears the 7 stw has more case capasity but is not really able to take advantage of it, or make any significant gains with it compared to the 7x300. It appears to me that the 7x300 is more effecient and makes up for it slightly smaller case capacity and gives up nothing to the STW and maybe only +/- 150 fps to the 7 RUM. Plus I like that I can get 300 WM brass from anyone ie nosler, norma, winchester compared to the stw only from remington and nosler. Is anybody seeing flaws in what I'm finding thinking, thanks.

 

[SidTheKidd]

Sid, I don't hardly ever shoot groups at 100. I prefer 200 or more as I feel it gives the bullet time to stabilize. I will take a .5 moa group at 300 to a one hole group at 100 any day. Just my personal preferance. That said this rifle will shoot 180 bergers into 1 1/2" at 300 on a very regular basis, and some times better.

The gun was not throated specially for bergers, but it has a long throat, this worked out well. I had the bullets close to the lands at first, but decided to back them in to see how they shoot if they would fit in the box. That came out to be .115" off the lands. That is where there are now and shoot awesome. So I don't feel anyone can say that the bergers have to be on the lands. I have seen them shoot in many rifles I own from .005" in the lands, to this rifle at .115" off. I would just use the Berger seating method and see what your rifle likes.

We were not seeing a terable amount of run out with the RP brass, but the brass was old and I am very fond of RWS and Lapua brass for the 300's. So we changed to new RWS brass. After the first firing we did see noticably less run out, probably .002~.003" less on average.

I am not suprised you are considering a little less powder charge and I doubt if you back off a grain if it will be a negative affect on accuracy. Please remember if you ever go to RWS brass you will need to back off probably 4 gr but I feel you will see very close to the same velocity as you are now.

Hope this helps.

Jeff gun)gun)

Yeah I will keep that in mind Broz,
Where were you finding that RWS brass? I have googled it and cant find the stuff. I guess I was asking about the seating depth because I had the best results so far with the 180 VLD's at .083 off. I am going to lower the charge another .2 an take them in and out .002 to see what happens. I hope I can get some groups closer to a quarter. Maybe I will try grouping out further too. That is something I have been meaning so try too..Thanks for the info again.

 

[Weaselthis]

What a wealth of info you guys have here! I really appreciate everyone sharing such insight and experience. THANKS!

I got into this thread and went off the deep end....just so happens I found out my ole 7Remmy was shot out for the first 2.5 inches! And the same day I see someone had a brand new 7RM take off bbl. for sale cheap. Voila! New toy ordered. Smith has the old rifle and the new bbl. awaiting arrival of the 7/300 reamer. Meanwhile, I go out and get some new Winchester 300WM brass so as to get ready for the new toy.

Here's my dilemma:
I ran 6 brass thru my7RM neck die and did not use any lube (never did before) and collapsed one case and had a bulge on another that REALLY shortened up the brass. SO, I figgered I'd anneal the rest of the batch before anymore sizing. And I lightly lubed the outside of the necks. Lost 15 more to bulges & collapse!??

Also, the brass is very short after sizing. Of the 33 left, 18 are under 2.610 (Most are under 2.60) and the longest was 2.617. ???? Aargggh.....

My questions:
Anyone have any input as to technique, what I'm doing wrong, what I SHOULD do right, or any other instructions w/ regard to brass prep? ALL ideas, input is appreciated. I've been reloading for 25+ yrs. but am a novice at this wildcat stuff & am always willing to learn new things.

I asked my smith to make a set of dies w/ the reamer for the build. IF he is unable to do so, any leads on how to get dies from a commercial source?Do you guys just use a 7RM neck die to size and/or 300WM for a FLS w/ a 7mm stem? How about a seater die? IF you don't have a set of 7/300 dies, how do you do operate?
(Speaking of that, how would you get a few loaded rounds to fireform in order to send cases to have them built).

Any suggestions on the remaing brass I have prepped? I can't trim/true up the mouths on the shorts ones and I THINK there may be a slight bulge on one side of a few of them. Would fireforming iron out this problem, or result in a "Kaboom"?

LOL...STARTED to call the smith and just tell him to leave it 7RM, buth then the stubborness in my showed up and NOW it's a challenge! One that I'm sure I can meet by using all the wealth of help on this forum.

Hey, guys, thanks in advance for all your help! Take care.