Home Forums Reloading Big Game Rifles 7mm Rem Mag at 64-65,000 PSI ?

Bob,
It is a pleasure to read all of these posts especially when working up loads for a new rifle in 7MM Rem Mag. Have some interesting data. Went to the range the other day and ran some Nosler 140 C-T's and RE22. I was a little shy about using a bunch of RE22 as my experience with another rifle (Mark X action and a 24" Douglas) made me that way. Couldn't put a tenth more in that one over 65.5g with a 145 Speer or the base of the brass would burnish @ 75 degrees.
Anyway here it is. RE22 140 Nosler C-T. CCI Mag Primers. W-W Brass. Bullets seated .020 off the lands.
67g 2931. 67.5g 2940. 68g 2986. 69g 3031.
Barrel was allowed to cool between shots and none of the powder charges gave any indication of being too much. Looks like another grain will yield close to 3100 so I thought RE19 may be the ticket and have loaded a few to test starting at 66g.
The barrel on this rifle is a Spencer and is not 25" as previously posted but 24 1/2" measured from the end of the threaded "tenon" to the muzzle. The throat is deep. A 150 Nosler BT seated @ 3.920" -.020" off (Comparitor)is at the bottom of the neck. A 140 Nosler (not a C-T) is too short to be gripped by .200" of the neck unless it is seated -.130" off.
140 C-T's, 150 Nosler and Sierra, 160 Speers are all OK as far as seating goes and these 7's will shoot about anything but I am a little miffed about the velocities I am seeing. Also, the chamber in this barrel won't accept a FL resized once fired brass shot in a different gun. I have nothing to bump the shoulder's with other than "over camming" the press.
150 Nosler's w/ 64.5g IMR 4831 are right at 3000 to 3040fps and shoot great. Tried adding with this combo and the group size doubled. What do you think about this deal and the velocities I am seeing. If anyone has any suggestions please do not hesitate.
Thanks,
Dave

RaceTire,

I think there's a typo re: the OAL of a 150 BT.....with the bullet seated to the base of the neck, it's around 3.536.

That's 1.307" for the bullet + 2.229" for the case length to the base of the neck.

I like to be in the range of .020"-.050" of the lands in hunting rifles......with the preference for the lower end of that range of it works.

In the 7mag, I've generally found that RL25, H4831 and IMR7828 are better than the slightly faster powders like 4350, IMR4831 and RL19 with bullets of 140 grains & up.......YMMV.

IMR4831 is an excellent powder and I'm suprised that your accuracy got worse by a factor of 2x with it above 3000 FPS....however as already said, it is not in my top tier of powders for the 7mag and that does happen sometimes with certain guns & powders.

I do have to say that my accuracy with 7828 has not been as good as with RL22 though.

As for sizing cases not fired in a given gun, and not fitting after FL resizing, I've had this happen on a couple of guns with SAAMI minimum or near minimum chamber.....it can happen.

Here's a link to something that might help...... no guarantees, but it's worked for me in the past.

Belted Magnum Collet Resizing Die

MM

MM,
Appreciate the input. My post was a little confusing regarding OAL as I did not make it clear regarding my use of a Stoney Point Comparitor and my use of the dimensions it produces. The true OAL of the loaded 150 Nosler BT in this rifle is 3.495" which is 3.920" when the comparitor is attached to the calipers.
I use what I call the "pushback" method along with the bullet blacking method to determine where the bullet hits the lands and can get pretty close. 3.920"/3.495" in my 7 is .020" off as best as I can determine.
I haven't worked with the IMR4831 enough to give it a good opportunity to give me the right velocity and good accuracy. Actually stumbled on to the 64.5g load in doing some load work and it is real accurate. Can probably add more powder to get the v up and work with bullet seating depth to get it as accurate as possible. Deal here is going to be to get it to shoot in the mid 2's (like it does @ 3000fps) which won't be easy.
Looks like it's going to take at least another grain of powder to yield 3100fps.
Thanks for the recommendation on the tools to help to get some of the brass I have to work.

Dave

Well, after two trips to the range with the 140TSXs, here's what I've found with my rifle:

1. Retumbo at around 3000-3025fps was very accurate. But I seen no advantave since I already shoot 160g North fork at that velocity.

2. H4831, H4350 and H1000 all got me 3150 to 3303 but accuracy was not what I wanted with any of them. H4831SC and H1000 showed promise but the second trip failed to verify anything but good velocity.

3. My conclusion is my rifle just doesn't care for the 140g TSXs, a surprise, because TSXs shoot well in my .257 Roberts, .308 Win, .30-06, and 300 Win Mag.

I'm going to try 140g North Fork bullets instead. If they don't work I'm going to stick with the tried and true 160s. Might just cut my losses and do that anyway.

Very interesting post Gents, wished I had seen the post earlier...was wondering the same about the 7RM and the Weatherby.

Bein old and grey I remember the fuss the 7RM brought about. Early on they actually chambered pretty deep expecting the belt to headspace. This made for some extra case capacity which we used with the old 4831. Mine was not so long throated but the best bullet we had at the time was the 175 grain Nosler partition and it was a semi-spitzer and I mean semi. It was a 2 inch rifle with this bullet but it killed well and penetrated really well. I would be surprised if I was getting 2900fps though. This rifle was a tackdriver with the 160 grain Sierra Gameking and with a max load of old 4831 this bullet was real hard on deer to way out there.

Very interesting what you have done with the barrels.

280Rem is right.
In the late 70's, a retired owner from Illinois of a tool and die company moved in on our road. His primary customer was Remington. He had access to Remnington's ballistics lab and showed me printouts of pressure curves of the 7RM--the first time I had seen or heard of such exotic stuff

He said back then Remington had been seeing some unpredictible pressure spikes they couldn't explain. Ultimately Remington reduced the charges in their factory loads in the late 70's and again in the early 80's. If you ever take a look at the old Remington brochures the advertised velocity of 150gr Core-lokts went from 3300fps in the 60's and eventually to 3110fps in the early 80's.

Maybe you discovered something, free bore and different lands may be a method to "circumvent" the pressure spikes.

Allegedly, Remington never had a definitive answer as to the why the pressure spikes were occurring.

Casey

Casey: Been going back and forth with Montana Man on this barrel issue and am presently working with a 9 twist Krieger 24" CM barrel on a M70 Classic action. The throat is on the long side, and the 160 NP is seated as long as a 30/06-length box will handle.I have so far worked with RL22,25,7828 and H4831; gradually working up and watching the chronograph, pressure signs, primer pockets, etc.

Best combo of accuracy and velocity has been 70 gr-H4831-160 NP for about 3100. I know this is over what the books call for, but so far primer pockets are tight on firing #3.

Curious thing about the load is this rifle demonstrates that peculiar characteristic of shooting only so-so at 100 and 200;but groups at 300-500 are hovering around MOA or less. I fired the other day at 300,400, and 500, and the biggest group was about 6" at 500 yards.Groups fired the day before were similar. Wish I knew the reaon for this. Boddington recently wrote in G&A that it's the crown....I don't know.

Casey: All this ballistic "gack"(as Dober would call it) over the 7 rem mag, and 30 years with the cartridge has led me to some conclusions(not that they count for much, and not to take away from the game-getter ability of the cartridge).

First, I think the Mashburn may have been optimum in terms of what a big 7 should do, but it's a wildcat.

The STW is great but requires a H&H-length action and seems to need a 26" barrel, which is sort-of a drawback.

The 7mm Dakota may be the best factory-produced big 7 of all time, but is proprietary and not commonly available.The 7mm Weatherby is simply the 7 Rem Mag with a long throat.

So, I want a 30/06 length big 7 with a tad more capacity than the Rem Mag, with industry-standard throat/leade dimensions,commonly available factory brass, and cabable of an honest 3150-3200 fps with a 160, and 3050-3100 with the 175,from a 24" barrel. This will still leave recoil a notch below the 300 mags,while providing all the ranging ability and lethal effect necessary for most game in most situations.I THINK, but don't know for sure (I am no ballistician)that the 375 Ruger necked to 7mm can provide this, which is why I want to see it standardized.

Till then I'll just wallow around with the 7 Rem Mag.

Talked to Mike at North Fork today and ordered some 140g bullets. He indicated he is changing the ogive on them (pending test results) to give them a higher BC.

Once I get them I'll repeat some of my tests with the TSX to see if I get better accuracy with the North Forks.

Still not sure why I'm doing this except that I shoot 165's in my .308 Win and .30-06 and 180's in my .300 Win Mag. The 140's, if I can get good accuracy at the velocities I want, would be my flattest shooter. The 160 North Forks give me a tad over 3000fps and .5" accuracy - I guess the 140's are just something to play with...


BobinNH -
I agree with you about the various 7mm's. Wanted a Dakota for some time and considered rechambering but there were issues with the bolt face, magazine capacity and so on that kept me from doing so. A .375 Ruger necked down to 7mm is the perfect solution. I think we'll see factory offerings of necked down .375 in several calibers over the next few years.

Bobo-the Mashburn is a wildcat??? grins

Dober

Dober: How can it be a wildcat?You make it, right?.....

Coyote: See no reason the North Fork should not be great, though I have yet to try them.GO RUGER!

Mark, How about a quick synopsis on the Mashburn. Have read about it in the past but was a while back and memory is a little fuzzy. I call it information overload.

I tried to google it. Find plenty of references to it, but no real info. Also saw a "7mm-06 Mashburn." Same or different cartridges? I thought the 7mmRM was Remmy's factory version of the Mashburn. Are the ballistics much different?