Anyone own a 7mm 300 Win Mag?

[Kiwi Nate]

When PTG create the neck diameter for these 7mm wildcats, the neck is generally tight, but without need of neck turning- for the most part.

A while ago I came across a batch of Nosler .300 Win Mag brass that was too tight, jacking up pressures and limiting accuracy potential. The client was given two options, either stay with Nosler and neck turn or change to Winchester. The clientg opted to change to Winchester. This brought groups down to sub quarter MOA with a gain in velocity of 100fps. So- be weary when it comes to brass brands for the various 7mm-300's.

.284 has offered more useful info regarding the goal of versatility. Good things to keep in mind.

 

[18echo]

When I called Dave at PT&G I told him I wanted a 7-300 reamer that would allow me to shoot the 180 berger VLD's and would fit into an AICS magazine. He sent me the "Bison Barrels" reamer with .095 of freebore. Shorter than what most are using here but we'll see how it works. Worst case scenario I'll have a smith dial in a little bit more with a thrifting reamer.

 

[1simplemann]

Kiwi nate, I sent you a PM. thanks

 

[joeycoates]

Well, this is the caliber that I am going to use after reading the whole thread and developing a slight headache in the process... I was going to chamber in 7stw, but I think that the 7-300 has a lot to offer, it will allow me to use my existing DBM with a 3.715" magazine for a 300WM, and brass should be easier to find.

But holy cow there seem to be more variations than you can shake a stick at! I have been reloading for several years, but this will be my first go around with a wildcat cartridge. I would think that to keep it simple, and since I can find dies for a 7-300, that it would be easier just to go with the "normal" 7-300? I know that many have had good results with the improved shoulders, but to do that you would be looking at custom dies correct?

I am going to use a 28" 5c 8.5 twist barrel, either from Brux , Benchmark or maybe Pac-Nor. Probably in a light varmint or maybe a Sendero contour. I do not yet know what smith I am going to use, but if they already have a 7-300 reamer, do I need to buy one from PTG, or is that normally done just so you can have your own specific reamer for an improved version of the 7-300? I would assume if they have a reamer that they can set the throat up to shoot the 180gr Bergers or the 195's if they ever come out?

I guess if I go with Benchmark or Pac-Nor then it looks as if they already have the reamers so maybe I can just have them do all of the gunsmithing to simplify things. This is really a whole different ball game for me so I have so many questions, and I would much rather do it once and do it right.

I have read where some people are stepping down the neck diameters when re-sizing, and it seems that others just run it through the 7-300 dies to get it right. I already have a neck reamer so I can do that, and I have annealed several of my existing cases with a simple drill and torch setup so that is taken care of, but I have never used a bushing die setup. I understand how it works, just never used one. I guess that I could buy a bushing die and do it like Broz has done, stepping down bushings to get the neck diameter to where it needs to be, I just do not know if this is necissary.

Thanks for whatever guidance you guys can offer. I guess it will be done one step at a time and then it will get there!

 

[Planenut]

I have a Sendero II in 7mag. It shoots fine but if I wanted to convert it to a 7-300, is it worth reaming the factory barrel? It only has about 120 rounds down it so far.

Also, Are reamers available to rent or would I have to purchase one?

Thanks!

 

[calib]

I would say so if you have a smith that will

 

[Nimrod]

But holy cow there seem to be more variations than you can shake a stick at! I have been reloading for several years, but this will be my first go around with a wildcat cartridge. I would think that to keep it simple, and since I can find dies for a 7-300, that it would be easier just to go with the "normal" 7-300? I know that many have had good results with the improved shoulders, but to do that you would be looking at custom dies correct?

The 7mm Mashburn Super Magnum uses a standard die set from RCBS and Redding may list it as well but I'm not sure. PTG has the reamer print. There are a lot of variations on the .300 WM case but from what I have seen the ballistics are all similar. I went with the Mashburn mostly due to nostalgia but it is a very good round any way you slice it IMO.

Bob

 

[fmajor]

Well, this is the caliber that I am going to use after reading the whole thread and developing a slight headache in the process... I was going to chamber in 7stw, but I think that the 7-300 has a lot to offer, it will allow me to use my existing DBM with a 3.715" magazine for a 300WM, and brass should be easier to find.

I'm in a similar position as well - I'm sitting on ~350 (same lot) new WW .300 Win cases (and have another ~100 which have 2x or 3x firings) from when I last reloaded (it's been way too long.......). The 7mm-300 WinMag seems like such an easy upgrade from the 7mm Rem Mag - especially for those who hand-load.

Though hand-loading for the 7mm Rem Mag to it's more realistic potential (which is radically different from the anemic hand-loading manual suggestions) vastly improves from what's available over-the-counter.

But holy cow there seem to be more variations than you can shake a stick at! I have been reloading for several years, but this will be my first go around with a wildcat cartridge. I would think that to keep it simple, and since I can find dies for a 7-300, that it would be easier just to go with the "normal" 7-300? I know that many have had good results with the improved shoulders, but to do that you would be looking at custom dies correct?

True, True, TRUE!!!!

........ and I have annealed several of my existing cases with a simple drill and torch setup so that is taken care of, but I have never used a bushing die setup. I understand how it works, just never used one. I guess that I could buy a bushing die and do it like Broz has done, stepping down bushings to get the neck diameter to where it needs to be, I just do not know if this is necissary.

I used to use the RCBS Precision Mic bullet seating die (on advice from my hand-loading teacher/mentor) which is a bushing die. Though I suppose this different than the forming die you're mentioning..... oops

The 7mm Mashburn Super Magnum uses a standard die set from RCBS and Redding may list it as well but I'm not sure. PTG has the reamer print. There are a lot of variations on the .300 WM case but from what I have seen the ballistics are all similar. I went with the Mashburn mostly due to nostalgia but it is a very good round any way you slice it IMO.

Bob

Bob - please excuse my ignorance..... but, how does the 7mm Mashburn Super Magnum compare to the 7mm-300 WinMag?

Pragmatically, does it have greater ballistics than the 7mm-300 WinMag?
Does it have more of shoulder angle/lack of body taper?

Anyway, thanks in (hopeful!) advance

frank

 

[Kiwi Nate]

Hi guys, sorry to interupt, just wanted to let folk know that I have revised the 7mm Practical article on our site to make it more user friendly (hopefully).

New article is here:
http://www.ballisticstudies.com/Knowledgebase/7mm+Practical.html

 

[fmajor]

Hi guys, sorry to interupt, just wanted to let folk know that I have revised the 7mm Practical article on our site to make it more user friendly (hopefully).

New article is here:
http://www.ballisticstudies.com/Knowledgebase/7mm+Practical.html

Broken linky......

 

[Kiwi Nate]

Thanks fmajor, my bad, I did not use the LRH forum hyperlink properly.

7mm Practical

 

[Nimrod]

Bob - please excuse my ignorance..... but, how does the 7mm Mashburn Super Magnum compare to the 7mm-300 WinMag?

Pragmatically, does it have greater ballistics than the 7mm-300 WinMag?
Does it have more of shoulder angle/lack of body taper?

Anyway, thanks in (hopeful!) advance

frank

Frank,

The Mashburn tapers to .494 at the body/shoulder junction and has a 30 degree shoulder. This is another neck down in the FL sizer and shoot wildcat boasting speeds of over 3000 fps with the 175 grain Partition from a 24" barrel. Dave Kiff already has the print for this one it's #15106.

With new WW Super brass, trimmed to 2.600" and sized in the Mashburn FL die H20 capacity is 84 grains, with the same case fireformed in the Mashburn chamber is 90 grains H20. The trim length on the Mashburn is actually 2.625 but my brass didn't clean up there. The late Warren Page was reported to have killed in excess of 700 head of game with his 7mm Mashburn (Old Betsy)

I was ready to pull the trigger on Nate's 7mm Practical but I stumbled across an article on the Mashburn and things just fell into place from there.

Bob

 

[Petersen]

Tried RL25 in mine today and it went great. I know it can be sensitive to temp whereas H1000 is not. I have a couple pounds of the RL25 and figured why not try it.

Berger 180 gr. vld hunting
71 gr. shot a little over 1/4MOA @200 yds.
72 gr. shot under 1/4MOA @200 yds.
73 gr. shot 1/2MOA @200 yds.

Later in the day I took it out to check velocity. Loaded 72 gr. and shot it @540 yards. Drop shows it is going a little over 3100fps. Seems to be a mild load with no hint on pressure. It held under 1/2MOA and it was a little windy.

This is with cci magnum primers and Norma brass and I am currently using a Forster bump-bushing die. I bump the shoulder back a thousandth and have a couple thousandths of neck tension.

New batch of Brass had the 'donut' in the inside at the neck shoulder junction. A round file worked well removing them.


Impressed with the caliber so far. Took a sheep in 2012 @320 yards, a mule deer this year at a little under 600 yards, and also a cow elk at about 830 yards.

 

[Petersen]

Tried RL25 in mine today and it went great. I know it can be sensitive to temp whereas H1000 is not. I have a couple pounds of the RL25 and figured why not try it.

Berger 180 gr. vld hunting
71 gr. shot a little over 1/4MOA @200 yds.
72 gr. shot under 1/4MOA @200 yds.
73 gr. shot 1/2MOA @200 yds.

Later in the day I took it out to check velocity. Loaded 72 gr. and shot it @540 yards. Drop shows it is going a little over 3100fps. Seems to be a mild load with no hint on pressure. It held under 1/2MOA and it was a little windy - temp was 60 degrees

This is with cci magnum primers and Norma brass and I am currently using a Forster bump-bushing die. I bump the shoulder back a thousandth and have a couple thousandths of neck tension.

New batch of Brass had the 'donut' in the inside at the neck shoulder junction. A round file worked well removing them.


Impressed with the caliber so far. Took a sheep in 2012 @320 yards, a mule deer this year at a little under 600 yards, and also a cow elk at about 830 yards.