Author Topic: 7mmBRM (Read 2785 times)

onesonek · « **on:** June 10, 2003, 01:52:32 AM »

Well, I sold my 280AI, one of those offers I couldn't refuse deals. Sooo, what to replace it with. I don't do much 300yd+ hunting,so the 280's power wasn't needed. I still love the .284 bullets for deer,so I decided to have EABCO build a Encore 7mmBRM. Plenty of power for deer. Shoots flat enough to 300yds. With alot less recoil, (9.5 to 12 ft lbs), pending on bulet weight used. Should be a REAL pleasure, to shoot extended bench sessions. Can't wait to see if it shoots like the 6mmAI they built me. On

onesonek · « **Reply #1 on:** October 04, 2003, 02:20:30 AM »

Well, it got here Monday. Going to do some fire forming after work today. Load up some work-up loads tonight.

onesonek · « **Reply #2 on:** October 05, 2003, 03:11:52 AM »

I'm excited, took two boxes of 7-30 waters for fireforming. I fired two fouling shots,and waited two minutes. 38 rounds fired at two shot, two minute intervals,at a 100 yds. The remaining hole in the target, could easily be covered by a 50 cent piece. I wish I had D/C, so i could post a pic :-D

Bandito · « **Reply #3 on:** October 27, 2003, 12:39:33 PM »

Which bullets are you using and what are their velocities? 'Dito

onesonek · « **Reply #4 on:** October 27, 2003, 02:51:10 PM »

I used Federal factory loads 120 gr. Sierra BTSP. I didn't chronograph these. I've been too busy for shooting reloads. I hope too get similar groups with 120 X's,at 2800+. We'll see, if not on to plan "B", whatever that maybe. Maybe 140 NP's

stratocaster · « **Reply #5 on:** January 15, 2004, 03:28:47 PM »

Onesonek,
So, it looks as if Mr. Brown's BRM are necked down 30/30 cases? If that's true, it looks as if I will be ordering one of his 224BRM tomorrow.
Thanks for the feedback on your 7BRM!

onesonek · « **Reply #6 on:** January 15, 2004, 05:00:23 PM »

You're welcome Stratocaster.
And yes, the 30-30 is the parent case. The 224 BRM should be a good one. Wouldn't mind having one my self, except I already have a #1 in a 220 Swift.

Graybeard · « **Reply #7 on:** January 16, 2004, 06:31:00 AM »

What is the real difference in Eben's round and the 7-30 which BTW I sure don't consider a 300 yard capable round? Shorter neck? Less taper? Do you know how much extra powder capacity you gain?

What's it doing over the chrono?

GB

onesonek · « **Reply #8 on:** January 16, 2004, 12:37:40 PM »

Hi GB,
I never really did compare the factory rounds to the fireformed one, just didn't think about it. But, in general it has about .010" taper. From rim to shoulder it is about 1.665". From the rim to shoulder/neck juncture, it is 1.760", with what appears to be a 35 degree shoulder. I started 2 grs. below Waters max, with Varget/120 BT combo. Got to a (very) slightly compressed charge of 40 grs. The Encore opens easy, and cases extract likewise. Chronograph read an average 2875 fps with a variation of less than 10 fps. This is out of a 24" barrel with a long throat. Three shot groups been hovering a tad over .5" at a hundred yards. I am happy with the load, to say the least. But I'm going to give 120 gr X's a whirl, for curiosity sake.
I don't do much hunting/shooting of big game at beyond 250 yds anymore. It's more fun to get closer, much closer most of the time. But with that load above, it should point blank on a 4 1/2"- 5" target at 250, and not have to take the cross hairs off the deer at 300. With enough energy to get the job done. At least according to the ballistic program. But honestly I haven't shot it over a 100 yet, so we will see when I start moving the target back. I don't take bal/programs for granted. I will shoot up to 200 rounds at paper at various ranges before I hunt with it.

onesonek

Graybeard · « **Reply #9 on:** January 17, 2004, 05:07:26 AM »

Those dimensions give it mighty darn little extra capacity over the Waters. I doubt you gained as much extra as the amount of powder you're putting in. Don't think the load would work safely in a Contender but then you aren't using it in a Contender. If we were using the Waters in a stronger action like say the Encore I suspect you could likely get about that same charge in it (if it would fit) and be safe.

Guess that's about what I figured Eben was doing with those BRM rounds of his. Did he provide loading data? Seems I recall it used to be available on his site. The Waters and I'm sure the BRM is a nice mild recoiling little round that will do most of what folks really need a round to do.

GB

onesonek · « **Reply #10 on:** January 17, 2004, 08:01:07 AM »

I agree GB. But 40 grs. does fit, with out major compression. The load data is Hodgdon, which shows a compressed load at 37 grs. Varget in the Waters. Eben's load data is 39 grs VV150, for the 97 D rifle, at 2820 fps which isn't as strong as Encore. Eben just told me to use 7-30 Waters data and work up carefully. Which is what I do with all the Imp. rounds I've had. I'm sure my load would be too much for the Contender. I do believe there is some merit to the theory, that less tapered case, has less thrust on the frame though.
It may prove to be even faster with H4895, but I didn't buy this barrel for speed anyhow. And I may back off if case life is overly short. It's primary use is for timber still hunting, but with alittle range capability, for clear cuts and fire lanes. Quite honestly, a 120 gr. at 2800 fps, or a 140 at 2600 fps is all I really need for this setup. Either or, it looks to me as an impressive deer round, with extremely mild recoil, enough power. and flat enough for modest ranges.
If you want I'll send you one case, so you may get a hands on look at it.

onesonek · « **Reply #11 on:** January 18, 2004, 06:43:54 AM »

Not that it makes a world of difference. But after thinking and looking at it. I wonder if the name Bench Rest Mag, implies (uses) a 30 degree shoulder, taken from the Remington BR rounds.

stratocaster · « **Reply #12 on:** January 18, 2004, 08:57:57 AM »

I thought the exact same thing. Anyway, I went ahead and ordered a .224BRM for the encore. This should be fun!

onesonek · « **Reply #13 on:** January 18, 2004, 10:20:26 AM »

Keep us informed. I for one would like to know how it does.

stratocaster · « **Reply #14 on:** January 21, 2004, 02:36:59 AM »

Onesonek,
Did you order the 7BRM dies from EABCO as well? Just curious what kind of quality they are? Any idea who makes them? I ordered a set with the .224BRM barrel, but asked him just to ship them when he sends the barrel.

onesonek · « **Reply #15 on:** January 23, 2004, 12:34:43 AM »

Hi SC,
Yes I got the dies there also. I don't believe anybody else has them. From what Eben told me he assembles these. He had asked a couple different mfgr's to make them, but the cost were too high. So he had Lee do the bodies, and put Hornady guts in them at a lower cost. I think he said the difference was close to $200 .00.
I think the dies are just fine. The interior finish of the sizer looks good. The seater is the floating type, simple to use, but different from what I am use to. Make sure to read the instructions.

7bru · « **Reply #16 on:** January 29, 2004, 03:48:09 AM »

hey onesonek, I have a 7brm in a bf pistol,15 inch barrel. I shoot the sierra gk 160 hpbt molycoat with 40 .2 of vv160.velocity is 2150. shoots like a dream. I have taken 4 deer from 255 to 295 yards. with a sand bag of course. it kills hogs and deer like lightning. I was kind of skeptical about eben's so called hangtime song and dance but the proof is in the pudding you can make the brass from 375 win I hear. did you fireform with factory 7-30 waters or did you load them. I have never shot any 120 bullets because it shot great with 160's. bru

onesonek · « **Reply #17 on:** January 29, 2004, 02:27:11 PM »

Hi 7,
I have fireformed factory, and have partially formed cases from Eben.
I'm reserving the 120 gr. BT's for Prairie Goats. I'm now working with 120 gr. X's. But weather has kept me from shooting them so far. If they don't meet my expectations, I have 140 gr. PT's and 150gr. Scirocco's for Deer. I've heard some promising reports on the Scirocco though. I may pursue that one more intensively, soon.
Personally I don't see a need for forming 375 cases. I know they are stronger. And one may get longer case life, but I don't have the time for the extra work.
But the round it's self, deffinately looks like a winner in my books

7bru · « **Reply #18 on:** January 29, 2004, 02:58:23 PM »

yes onesonek i totally agree about the 375 brass. I was looking for a way not to buy the brass from eben. I use to have a 7-30 and have lots of brass and dies still. I guess i should use a fast powder with a medium charge to form with. I tried 154 sst hornady's and they shot pretty good. but not as well as the 160 game king hpbt. I am going to get a 6mm brm in a encore this summer. BRU

onesonek · « **Reply #19 on:** January 30, 2004, 01:47:50 AM »

I haven't found a source for 7-30 brass. The least expensive route is likely necking down 30-30. As forming 375 would be somewhat labor intensive. I know Eben's brass at $35/ 100 seems high. But with all factors considered, it's not a bad price. The only reason I fireformed the factory rounds I did, was one, I got it cheap, and two, I wanted to make sure I could.
And I think the brass in his chambers, will have a fairly long life. Unless one pushes the limit with fast powders. At which point, not only the brass will be stressed.
I know what you mean about "hang time". It goes against the accepted norm of high velocity of somewhat lighter bullet. But it does have a logical sense about it, which has been proven for years. IMHO, speed only assist in range, not so much in lethality. More important, is bullet choice.

7bru · « **Reply #20 on:** February 01, 2004, 09:10:53 AM »

from what i understand about the 375 brass is no fireforming and not a lot of trimming. and maybe only 2% loss due to creases in the neck. I am going to find a few or borrow a few from someone and give it a try. bru

onesonek · « **Reply #21 on:** February 01, 2004, 12:34:56 PM »

Iwould be interested in how it works for you. Let me know.

onesonek · « **Reply #22 on:** February 08, 2004, 03:53:01 AM »

Well, I found a general purpose load. 37.6 grs. of Varget with a 150 gr. Scirocco at 2625 fps, +or- 5 fps. Shoots three shot groups, into .6". With no sticky bolt or extraction problems showing.

GBO MGMT · « **Reply #23 on:** February 08, 2004, 07:24:22 AM »

WOW! that sounds HOT!! for a case that small and a gun with the pressure limitations Eben seems to indicate it has. Or perhaps it is more a case of small cases than pressure?

That's fully what a .300 Savage will do and almost what a .308 Win. will do. That tells me pressures have to be greater since case is smaller.

GB

onesonek · « **Reply #24 on:** February 08, 2004, 10:57:06 AM »

Just got done with some calcuations. If this were a standard chamber, slide rule calcs. at 48,000 cup. But being this is a "imp" chamber, pressure would be less. But for safety and curiosity sake,( and I don't trust one method, specially slide rules) I mic'd the heads for comparision to a fireformed load. The reading I got varied from 0 to .0001". That is not the correct way of comparing casehead expansion. But does indicate the barrel isn't over stressed, as you can can get .0001" variance in brass alone.
Now the 300 Sav. at 46,000 cup is hardly a "bolt sticker", and the Encore can handle a 300 Win Mag, that measures .532". So I don't think a 7-30 rim at .506 is going to pose much of a pressure problem, unless I push the heck out it with something like H4895.
If I get good case life out of the load, then I'm not too worried. But if primmer pockets are loose after 2-3 loadings. Then I'll back off a .5 gr..
One must remeber also, Eben's data is max in the 97 rifle. Which is more comparable to the Contender in strength. Being a small framed falling block.

GBO MGMT · « **Reply #25 on:** February 08, 2004, 04:11:13 PM »

This thread has gone on so long I guess I've forgotten where we started. :eek: I was thinking you had it in a Model 97. You mention Encore so I guess maybe I was mixed up on that? Yup if an Encore it really shouldn't be too much I guess.

Have you compared case capacity of it to others? Say on the '08 case? Should be interesting to see what the water capacity is compared to say a 7-08

GB

onesonek · « **Reply #26 on:** February 08, 2004, 04:32:38 PM »

No I haven't GB. Isn't the 7-08 in area of 51 grs. of water to the neck? Going on memory again, not all that reliable as usual :lol: I'll try to weigh up the 7BRM in the next day or two.
One thing continually remind myself though. I didn't set this up to compete with the 7-08, ( but look at the difference between the 7-08 and .280 with lighter bullets, not much). I just wanted a solid 250yd. rimmed 7mm. Which the BRM shows promise with room to spare. My original thoughts were on a 7-40 Krag AI, which for all practical purpose's, would equal a 7-08. I'm glad I went with the 7BRM, it's a real pleasure to shoot.
On

onesonek · « **Reply #27 on:** February 09, 2004, 01:03:15 PM »

GB, They measured 42.3 grs. H2O to the neck.
On

onesonek · « **Reply #28 on:** February 14, 2004, 04:12:58 AM »

GB,
I forgot to ask, what is the case capacity (H2O) of your 7-30 Waters to the neck?

onesonek · « **Reply #29 on:** September 07, 2004, 02:10:26 PM »

Update, 150 gr scirocco's likes h4350 even better! :wink: