7mm build

[Deleted member 25294]

I have a MRC in 7RM. Will shoot sub 1/2" with 162 ELD-X. But the case expands in front of the belt requiring the case to be swagged at that area. Another step and it drives me crazy. No more belted cartridges for me. 28 Nosler next step up.
Just Saying.

Thank you
I'm glad some one else is willing to admit it..
I was starting to think I was the only one who's had that issue!

 

[MudRunner2005]

Thank you
I'm glad some one else is willing to admit it..
I was starting to think I was the only one who's had that issue!

If a reamer/chamber is cut properly the swelling is minimal to non-existent. I have never had any swelling issues with belted magnums because of anything other than ****** brass. I had some Federal STW brass that swole up bad and had case/head separations after only a couple firings (from factory ammo that I bought and fired from the same rifle). I chunked them, and started using Nosler brass, and had no more problems. I think brass quality has a lot to do with the issues everyone keeps talking about having with belted cases. Once I swapped to good high-quality brass, I never had any issues after that with any caliber/cartridge. I don't use Federal, Remington, or any off-brand (CBC, GWB, etc...) brass in anything I load for. The ONLY exception being Remington .30-06 brass for my .30-06 AI, simply because over the years I had picked up tons of them for free at the range. And I don't shoot that rifle very much...Maybe only a couple hundred rounds for fire-forming and load development, but that was about it. Haven't really shot it since I found a good sub-MOA node that will get me by in a pinch. I've got others that need more extensive load work, so I concentrate on those.

 

[TXAoudadKlr]

I have a 7RM, after some debate I plan on sticking with it once I get my barrel. Thinking 26" 1.8.7 bartlien 2b or #3. Not the biggest, baddest or latest but it works

 

[sfdoc2000]

My 7RM is a Bartlein 28" Rem varmint contour 1-9 on a Rem 700 accurized action, MDT stock with a Magpul PRS rear and a Vortex Gen 2 Razor. Shooting Berger 180 LR hunters .005 off lands with Nosler brass and 7977 powder. Have some pretty extreme temp changes where I am and the temp range of the powder is an advantage. 2900 FPS will shoot all day at 1" groups at 300 and pop steel at 800-1000 with a rare miss. The ballistic chart on iSnipe is right on.

 

[ENGUNEER]

I will throw in a vote for a 7mm practical or the slightly improved 7mm Rogue for shooting the heavies. They both run just shy of a STW. And 300 WM bras is a dime a dozen and easy to find. However I built my Rogue just before the 28 nosler came out. Had it arrived prior to the build I may have went that way.

I also love the 7mm Practical (7-300 Win Mag). It is easy to form cases (just neck size a 300 WM to 7mm) and it is accurate (I have 2 of them both easily shooting <1/2MOA) and they are as fast or faster than the 7 STW with 180's.

 

[WildRose]

What is your definition of ridiculously long neck?? I know nothing about the 7LRM but the most accurate cartridges today have looooong necks - 6PPC for example. I also like long necks for chasing the lands and there are some - that are more knowledgeable than me say longer necks are easier on throats.

A lot of people say a lot of things that don't hold up to scrutiny and can't be supported scientifically.

Neck length should be equal to caliber which is what the "experts" have been saying for decades which makes perfect sense to me. There needs to be enough neck to properly hold and align the bullet and case to the chamber properly, I see no utility in more.

What I see in the case of the 7LRM is a ridiculously long neck and a waste of useable case volume as a result.

As far as longer cases reducing or retarding throat erosion goes I've yet to see any evidence to show that to be the case, assumptions and "I Heards".

 

[WildRose]

I understand what you are saying but your example was way over the top. This cartridge will only shoot jammed so technically the extremely short neck has little to do with holding or aligning a bullet.

Like I stated above I like a long neck mostly for chasing the lands. Also, a properly sized case neck will not have issues with crooked or bent necks. If someone is having this problem they shouldn't be handloading.

You can chase the lans with any length of throat. The case OAL is the same irrespective of neck length or can be.

All else being equal a shorter neck simply gives you more case capacity.

 

[coyotezapper]

You can chase the lans with any length of throat. The case OAL is the same irrespective of neck length or can be.

All else being equal a shorter neck simply gives you more case capacity.

Your missing the whole picture here. With a longer neck you keep more of the bearing surface in contact and properly seated for a longer time as you are chasing the lands. There comes a time when the throat erosion will not allow the bullet to be seated at the needed length for accuracy. I recently - a year ago set the barrel back on a 308 with .370" throat erosion including original freebore. I could not seat the bullets out far enough for them to shoot well. A longer neck would have helped extend barrel life before a set back was needed.

Your second point is apples and oranges. What your saying here is that if the 7LRM had a shorter neck then it would have more case capacity all other things being equal. Neck length has nothing to do with case capacity unless you are fire forming to an improved case so in this case it does not apply. You did not think that comment through very well. If the 7LRM neck is a product of sizing up or down or fire forming the parent case then the neck length can be trimmed to whatever length the case designer wants. Maybe the designer was going for a longer neck. Does not make it ridiculous.

 

[coyotezapper]

Ok, I see now why there are certain attitudes toward the 7LRM. It's because it was a Gunwerks design.

 

[MudRunner2005]

Ok, I see now why there are certain attitudes toward the 7LRM. It's because it was a Gunwerks design.

I could care less who designed it and put it out. I was interested in building one for a while...Until I did my research. My issue with it was that for a long time they were the only ones who had brass for it, and they never had it available on their website. So if you didn't have any, you would play hell finding it, because it was a single-source, and not a very large source at that... Also, Hornady was making their brass...Which didn't turn out to be the highest quality stuff from what I've read.

I don't care who designed or built something, long neck cartridges are a waste of possible powder room. If you keep the cartridge the same OAL, but push that should up more and shorten the neck's length, you gain a significant amount of powder capacity. That's what WR is talking about.

 

[WildRose]

I have a MRC in 7RM. Will shoot sub 1/2" with 162 ELD-X. But the case expands in front of the belt requiring the case to be swagged at that area. Another step and it drives me crazy. No more belted cartridges for me. 28 Nosler next step up.
Just Saying.

Been shooting and reloading belted magnums for over 30 years and have yet to have to "swag" the belt are for any of the more than a dozen different rifles including those I own now.

Either something is wrong with your dies, now they are setup, or your method.

 

[WildRose]

Ok, I see now why there are certain attitudes toward the 7LRM. It's because it was a Gunwerks design.

For my part it has absolutely nothing to do with who designed it, it's the design itself which wastes a good bit of what would be useable case capacity and makes it very difficult and expensive to form your own brass from the parent case so you are stuck buying their overpriced Hornady brass.

 

[coyotezapper]

I could care less who designed it and put it out. I was interested in building one for a while...Until I did my research. My issue with it was that for a long time they were the only ones who had brass for it, and they never had it available on their website. So if you didn't have any, you would play hell finding it, because it was a single-source, and not a very large source at that... Also, Hornady was making their brass...Which didn't turn out to be the highest quality stuff from what I've read.

I don't care who designed or built something, long neck cartridges are a waste of possible powder room. If you keep the cartridge the same OAL, but push that should up more and shorten the neck's length, you gain a significant amount of powder capacity. That's what WR is talking about.

The neck length from what I can tell is .380" which is just under .100" longer than caliber which has been stated as the standard. How much more powder capacity do you think you will get with .100"?? I shoot a couple of different Ackleys and these only get 4-7% more capacity than the parent case and these not only change the shoulder but reduce taper in the case also, much more than just moving the shoulder up, the case is blown out also. The 7LRM from what I can tell has a 90 grain case capacity so I would guess that just moving the shoulder forward .100" would add maybe 2-3% and that's a big maybe so that equates to 2.7 grains. Not really significant.

 

[WildRose]

The neck length from what I can tell is .380" which is just under .100" longer than caliber which has been stated as the standard. How much more powder capacity do you think you will get with .100"?? I shoot a couple of different Ackleys and these only get 4-7% more capacity than the parent case and these not only change the shoulder but reduce taper in the case also, much more than just moving the shoulder up, the case is blown out also. The 7LRM from what I can tell has a 90 grain case capacity so I would guess that just moving the shoulder forward .100" would add maybe 2-3% and that's a big maybe so that equates to 2.7 grains. Not really significant.

No, according to the drawing the neck is .118 longer than .264.

The shoulder is also pushed back .211 and the angle is changed from 60 deg to 30 deg.

Compare the parent case to the 7LRM.

The neck is much longer, less capacity, the shoulder is bumped back considerably, less capacity.

Now if you like I can fill a case full of powder for each and weigh it out if you really want to know exactly how much difference there is but even a couple of grains could make a significant difference in performance.