7LRM (Long Range Magnum) - Pic & Info thread

[Rockfish Dave]

I am interested in the 7LRM chambering, but there does not seem to be allot of information out there at moment.

If you have a rifle and load for it please post up the specs for those of us that are interested.

Personally I like the magnum performance in a beltless case and brass options (buy from: Gunwerks or Primal Rights, or make from 375 Ruger).

 

[AZShooter]

It would be a real chore to make your own brass from 375 Ruger brass. It isn't just necking down to 7mm but you also have to move the shoulder back .215" and trim length .066" shorter.

I neck down the 375 Ruger with no other changes and it is enough of a challenge. Best to buy the finalized case from Gunwerks.

 

[Rockfish Dave]

What would the steps be to bumping the shoulder back? Would one die do it or would it need to be in steps?

I've done the 6.5SLR and that is pretty simple.

Trimming is no big deal with a Giraud case trimmer, since I already have that.

Necking down is easy enough with a bushing die, I can just swap out bushings in steps. Neck turning is drama free as well so I'd have neck consistency.

So the only question is the shoulder bump... If a single step that would seem to be easy enough on my co-ax press.

 

[AZShooter]

If you want to form your own then call Hornady and see what dies are necessary. Not sure but it might take a couple of steps to move the shoulder.

I had a box of 375 Ruger sitting around for several years. Every so often I would look at a piece and think of necking it down to 338 or 7mm. One day I decided to try and neck it down to 7mm with dies I had on hand. If it would work then I would order a reamer from PT&G.

The reason I finally went with the 7mm-375 Ruger was brass availability. When there was no other 7mm brass on the shelves ( a couple of years ago) there was always 375 Ruger at my local Sportsman's warehouse.

In my collection of dies I had the FL 338 RCM as well as a Whidden FL bushing die for same. The 338 RCM shares the same shoulder diameter and angle as the 375 Ruger. I did notice that you have to be careful using a bushing die as it often hangs up on the case mouth. I have often thought of grinding one side of the bushing with a taper to help things along. Here are the dies I used:

1) Hornady 338 RCM FL die
2) 300 RUM FL die to taper case mouth
3)7 RUM seater followed by 7 RUM FL die to continue reducing the neck dia
4) Whidden 338 RCM FL bushing die with .312 bushing
5) open up neck dia with K and M 7mm expand iron
6) turn necks to .013" wall thickness using K and M neck turning tool
7) use 338 RCM .309 bushing

I use a 375 Ruger FL die along with a small base die to size the fired cases. I made the small base die by cutting off the neck/shoulder and some of the base of the second 375 Ruger FL die. At this point I finally had to go buy some dies I didn't own...two 375 Ruger die sets.

For seating I used the 7mm-375 Ruger reamer and recut a Redding 7mm Rem mag comp die sleeve.

It was a fun exercise.

I used a Remington 7mm Rem mag takeoff that I rethread for a Ttang safety Ruger ith a lengthen mag box. Tried the 180s but the twist is marginal so moved to the 168 Berger classic hunter. Using 86 gr of RL-33 I am getting 3265 fps from a 26" barrel.

Enjoy the fun of doing it yourself. After reading this you may decide to make a full length 7mm-375 Ruger instead.

I am very happy with the performance

 

[Rockfish Dave]

Good point regarding the bushings hanging on the case mouth, I've noticed this on other projects as well.

If I decide to form my own, I'll probably just ask whidden to champher the neck bushings used to size the neck down for that purpose, and end up with 2 7mm bushings; a final sizing bushing and finishing neck tension bushing before turning the necks.

I'll figure out the cost and see where the break even point is since the Gunwerks brass is $1.36/each piece of brass and I read in a post the Primal Rights brass is $1.30/each.

 

[Edd]

I push the shoulder back on RUM cases. To do this, I have 4 custom dies from Hornady.

 

[Rockfish Dave]

I push the shoulder back on RUM cases. To do this, I have 4 custom dies from Hornady.

Well that looks like making brass out of 375 Ruger is a last resort...

Out of curiosity, what does each die do? Only pushing the shoulder back incrementally?

 

[Edd]

My form dies don't push the whole shoulder back incrementally.

Starting at the case OD, they reduce the case diameter by pushing about .060" of the shoulder all the way back. The next die die does the same thing. After three steps my shoulder is where I want it and the neck diameter is about .350 ".

I have two fourth step dies, one of them will make a 30 caliber neck and the other one will make a 7mm neck.

 

[bigngreen]

The 375 Ruger case forms very well compared to many but not as easy as just getting LRM brass sent to your front door. I like the LRM and I'd likely still be running it if I wasn't expecting more out of it than 7 mag performance. It a solid case design, the Gunwerks reamer is set up to short, I would recommend getting a case put together and getting a reamer made for neck turned brass with the 180 Berger seated correctly not buried in the case.

 

[Rockfish Dave]

How much free bore would you recon?

I personally would like to run 140gr - 180gr.

I have not compared an 300WM AICS length 7RM to this so I could likely get my answer that way.

 

[Rockfish Dave]

No one with a rifle chambered and shooting?

 

[outdoorsmunn]

The 375 Ruger case forms very well compared to many but not as easy as just getting LRM brass sent to your front door. I like the LRM and I'd likely still be running it if I wasn't expecting more out of it than 7 mag performance. It a solid case design, the Gunwerks reamer is set up to short, I would recommend getting a case put together and getting a reamer made for neck turned brass with the 180 Berger seated correctly not buried in the case.

I am in the process of getting a 7LRM built right now. I am planning on running the Berger 180 hybrid and would like to get 3000fps or more. May I ask what your loads were like. I am certainly hoping for more than regular 7 rem mag performance. How about accuracy? Any other tips or advice before I'm in too deep?

 

[Elkhunter1983]

Is there another reamer out there that has more free bore? I am looking to do a build with this cartridge. Brass is $1.34 each and never has ran out. Am looking at shooting the 180 or even the 195 (if it ever surfaces). I am wanting to free up a little space for powder and just extend the box mag.

 

[Edd]

You can use the standard reamer then lengthen the freebore to whatever you want.