New 6.5 Idea

[sj-pratt]

Another one of RHB guys brought over an 300/700 dakota reamer and said is was as close to the 7mmRHB as he could get but without all the brass work. I chambered a couple of those rifles and I thought they were a nice rilfe for those big heavy 7's they both shot really well and would be a good choice for 190-200 gr bullets. I think RHB had a hand in that one also.
We have alot of fun here in Utah and strieve for quality longrange rifles and equipment. The Titanium Brake we put out is on the test 6.5 Idea, with a Proof Research Carbon Barrel, I blueprinted a remmy action change the bolt handle and stuck a sako extractor on it. RHB bedded it in a Manners MCS-T stock and made a few mods so I'm repainting it. Here's a look at our
Titanium Brakes Thanks for your comments.

 

[7mmRHB]

Montana, the 7mm Dakota round is smaller in length and diameter than the 7mm RHB, and holds 12+ grn less powder. The .284 Stak is a 300 Dakota Imp. with.012" of taper, necked to 7mm that I designed for a customer. It holds 4 grn less than the 7mmRHB so no, I did not reinvent the 7mm Dakota. A friends 7mm Dakota w/ 180s was at least 150 fps slower than the 7mm RHB.

The first 7mmRHB was for a friend that wanted light bullets and high velocity. ( I couldn't talk him out of it ) The slow twist bbl,140 Noslers and 80 gr RL 22 produced 3640 fps and serious accuracy. He has been shooting that load for 12 years and the brass is still going strong. I think it does exceed a( factory) 7mm RUM based on GoodGoupers load development on several Factory 7RUMs.

I have also designed the 270 AMP which is based on the 7mm Dakota case w/ 40* shoulder and reduced taper. It will push the 170 VLDs to 3050 to 3075 . Very mild load but extremely accurate. we built three of these and the guys have pushed them to 1150 yards on deer. One shot!

I didn't use the saum case as I was looking at making a smaller case than the 6.5 - 284 that had Lapua brass available. I was trying to make a round that would exceed the performance of the 6.5 x 47, 6.5 Creedmore and the 260 Remmy and still get 4 in the mag while still feeding well. I guess I'll have some answers about my little round soon. ----- 7mmRHB

 

[marioq]

I want one. Let me know when you are done.....

 

[MontanaRifleman]

7mmRHB, did you blow out the base of the 7 RUM at all, or just decrease the taper? What is your velocity for the 180 out of the 7RHB? What powder are you using?

I am going to a 7 Dakota wildcat of some kind at some point, but not sure if I'll use the 7 Dakota case or 300 Dakota. After I do a 300 Dakota Imp and see how that goes with various powders, I'll decide how to go with the 7. The 270 and 6.5 i plan to do off the 7 Dakota, very similar to your description.

Looking forward to hearing of more progress on your 6.5.

 

[elkaholic]

You haven't mentioned what length barrel you are quoting these velocities at (unless I missed it). I'm having a difficult time seeing 3075' with that little case capacity. Also, what kind of freebore are you looking at?......Rich

 

[redneckclimbing]

So you REDUCED case capacity, REDUCED pressures, and INCREASED velocity? Pardon my cynicism, but I am waving my BS flag. There is no way that all three of those things can be true.

Well, don't jump to conclusions yet. I have just started testing a similar design myself in 7mm (The 7mm GT). It is a shortened WSM case, to fit in a SA with the bullet seated long.

Anyways, the case capacity is 69.75 grains filled to the top (65.2 to the shoulder neck junction) I worked loads up to 58.5 grains of Hodgon 4831sc and got 2839 fps with a 29" barrel.

The funny thing is that, I had more case capacity left, there were no pressure signs at all! And all of this is with the 180gr Berger Hybrids jammed in the lands.

So, yes it may be possible to reduce capacity, and pressure at the same time. Although, velocity is pretty much affected by pressure. But you may be able to use a faster powder to essentially raise the pressures back up. Getting a more "efficient" burn, creating greater velocities.lightbulb (If that makes sense.)

So they may really be on to something. Keep us informed! Sounds promising to me!

 

[elkaholic]

Well, don't jump to conclusions yet. I have just started testing a similar design myself in 7mm (The 7mm GT). It is a shortened WSM case, to fit in a SA with the bullet seated long.

Anyways, the case capacity is 69.75 grains filled to the top (65.2 to the shoulder neck junction) I worked loads up to 58.5 grains of Hodgon 4831sc and got 2839 fps with a 29" barrel.

The funny thing is that, I had more case capacity left, there were no pressure signs at all! And all of this is with the 180gr Berger Hybrids jammed in the lands.

So, yes it may be possible to reduce capacity, and pressure at the same time. Although, velocity is pretty much affected by pressure. But you may be able to use a faster powder to essentially raise the pressures back up. Getting a more "efficient" burn, creating greater velocities.lightbulb (If that makes sense.)

So they may really be on to something. Keep us informed! Sounds promising to me!

A .280 Remington would do that with a 29" barrel. I guess I still am not seeing where this is going, (3075' with 54 gr. capacity) but as you said, keep us informed......Rich

 

[jwing]

Save your self time, go with a 6.5 saum. Don't go with a tight neck. Get a Wyatt ex box and you can run the Berger 140 out of it. You can get 3200, but they shoot best around 3100..

 

[barnesuser28]

tag, curios to know more.

 

[elkaholic]

Save your self time, go with a 6.5 saum. Don't go with a tight neck. Get a Wyatt ex box and you can run the Berger 140 out of it. You can get 3200, but they shoot best around 3100..

This I believe! I can get 3200' out of my case with a 26" barrel and it has very close to the same capacity (probably slightly more).....Rich

 

[Swamplord]

seems to me a Mr. Jim Sloan proved that you can shorten a case, reduce the taper, seat the bullet out and have similar velocity offa the same case........

I like your idea and can't wait to hear more info/data etc.... keep it coming !

 

[jwing]

I agree if you want to spend all your time working cases. Just saying keep it simple, and the 6.5 saum will work in a short action.

 

[sj-pratt]

I agree 6.5 saum is a good option and I also agree that if you do not enjoy these challenges you would be nuts to try them. Remember though we are taking a run at making a efficent burning cartridge designed around 6.5-140 VLD in a std short action, not just trying to throw 140's at 3200 FPS that would be to easy. When we did the drawings we elected to stay with std magazine box length first if that is not quite what we need then we have the Wyatt,s option and .110 more room, but as you will see from the cut out pictures (I didn't get post yet) we don't have much bullet in the powder column. Worst case is we spend alot of time and money and have a cartridge that won't keep up with a 6.5-284 I've done worst.
Got the stock repainted last night should have pictures and I,m hoping a velocity ladder before to long.
Thanks for all the comments I like to here what others are working on out there.

Steve

 

[7mmRHB]

JWING, as Steve said we are not looking for a bigger faster case, that's easy!! I believe as others have stayed in this thread that shortening a case allows you to get to a better burn rate in powder options and increased efficiency. Instead of having 50 gr. in a 64 gr case you can get to 47 gr. in a 54 gr case.

BY the way I do brass prep as part of my job each day. I have trued the case heads and turned the necks on over 26,000 pcs of brass in the last 17 years so it's not about the wasted time for me.It's just a fun, fact finding project, not a commercial project.

------ 7mmRHB----