7mm re-chamber question...


Well-Known Member
Oct 24, 2007
I have a 7mm RM and ordered a new Shilen 5.5 contour barrel which will be 28" finished. Should I take the opportunity to re-chamber to a 7mm RUM?? Why would you? and why wouldn't you? I've heard they are finicky barrel burners and all the rest. Just want to hear some opinions.

I like the idea of an unbelted mag shooting the 180 gr over 3000 fps as long as it's accurate. I'm lucky to have a great gunsmith that really knows how to make em shoot.

I will be using it for WY deer and UT Elk which usually means long range hunting and long range targets (1000 plus on targets). I don't mind re-barreling every few years.

Thanks in advance for your help. I'm torn!
How much over 3000 fps do you need with a 180? I put together a 30" 7 rem mag last year and it shoots the 180 VLD at 3050 @ 60 degrees with 68 gr of RL-25. Recoil is very mild and I know barrel life will be good.

Just a few weeks ago I picked up a used LSS model 700 in 7 RUM. It had a 26" barrel. For the heck of it I tried the 180 Berger VLDs. (The bullets were moly coated) Maxed out with 89 gr for a velocity of 3100 fps. A 28" barrel would give you more velocity but how much I can not say. It will also give you far more recoil.

Another consideration is magazine fit. The 7 RUM with a 180 VLD is one long cartridge. I had a wyatts box mag added to the LSS 7 RUM and still had a .140" jump to the rifling. This rifle shot well with that jump but another might not. The 7 Rem mag has extra room at the end of the mag box and currently the bullet is .035" INTO the rifling. I have lots of room to chase the throat at the barrel wears.

I am certain a few will add to this thread on velocities obtained with the 7 RUM.

Here is one comparison. 180 Berger VLD: G7 BC is .337 Using JBM's program: 4000 ft, 65 degrees:

I am guessing what a 28" 7 rem mag would do 2950 fps
7 RUM ??? ------------------------------------------------------- 3200 fps

Both rifles zeroed at 200 yds

7 rem mag:

100 yd 1.4 high
300 yd -6"
500 yd -33.3
drift in a 90 degree 10 mph crosswind 8.8"
energy at 500 yd 2391 ft/lb

7 RUM:

100 yd 1" high
300 yd -4.9"
500 yd -27.7"
drift in 90 degree 10 mph crosswind 7.8"
energy at 500 yd 2859 ft/lb

Hope this helps.
My brother has a 7mm RUM and i have a 7mm STW and i would take my STW anyday over his RUM. I shot his RUM and it has a muzzel brake on it so recoil is not too bad but then it blows your ears off. Its even loud with ear plugs in. Took the MB off and then it about breaks your shoulder. The recoil and sound on my STW is way better than his and ballistically im shooting a 168 berger vld at 3230 fps and he is shooting a 162 amax at 3350 fps so ballistically they are very compareable. So if i were you (even though you may not like the belted mag case) i would go with the stw or stay with what you got. Unless you are a really big man that can withstand a swift kick in the shoulder and are already deaf:D
Both very good responses. I hadn't considered the length problems with the RUM although I think my smith could cut the chamber to match my bullet choice. I am leaning towards keeping the 7 RM. Maybe the extra 200 to 250 fps isn't worth all of the potential problems?

Keep em coming. Hearing from those of you who have RUM or experience with them sure helps with my decision.
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