Combine the Grendel diameter with the 6.8 length and bullets. Capacity should be 40.6 gr and beat the SPCII by 200 fps. Shoot most of the 130s at 2700 fps.

You get the diamater and length by taking 7.62x39 blank brass, http://www.prvipartizan.com/blank_brass.php cutting it to length and fireforming in the rifle. Resize in the dies and load.

I have two versions, one SPC length so SPC owners could rechamber to it and one with a bit shorter neck so that more of the 130s will fit.

I'd use one of AR Performance's Superbolts.

This is interesting!
You could use 6.5 Mannlicher-Schoenauer cases too.
What would be the capacity? Grendel about 35 grains so maybe a short neck and about 40 grains?
What would be the projected velocity gain with 85, 100 and 115 grain bullets?

Capacity 40.6 gr.

I have some new Norma 6.5 Carcano cases that are a touch wider at .450 but two things about them. I've read that the Grendel mags are tight. I have a CP Grendel mag but I haven't cut down 25 Carcano cases to check fit, besides the case head and extractor groove needs to be turned down to fit the Grendel bolt. The long 7.62x39 brass works in the Grendel bolt and extractor as is. Cheaper too. Plus it rquires no forming, just cut it to length and fireform it.

Cris Murray wrote that he's using that long 7.62x39 brass for his 7x46mm UIAC because 7.62x45 brass bacame to hard too find. Slick idea.

The 200 fps increase is what Constructor projected for his 6.8 BRX and this case has the same capacity due to it's longer length. He has far more experience with wildcats in ARs and projecting velocities than I do. I'd expect close to 2950 with 110s, well over 3000 with the 95 gr TTSX and the 100 Accubond. The SPCII can drive the 85 TSX over 3200 so it would scream even more here. I like the idea of 130 Partitions and Accubonds at 2700 for hunting.

I would load it to SPC velocity for defence and general shooting and it would do double duty as a fine lightweight hunting rifle when loaded to full velocity.

HA! I was .6 grain off.
How far can you move the shoulder without issue with the inside rib on the mags???

I left the shoulder/neck junction at the same point as the SPC so the reamer would clean it up. I cut the neck down .040 to bring it back behind the front ribs but after looking at some mocked up cartridges I think that the full length neck will stack just fine in the 65G mag. I measured the inside distance between the front ribs and there was very little difference between the C-Products Grendel mag and the PRI waffle style 6.8 SPC mag, sorry but I don't remember the exact difference right now.

I used the same case taper as the Grendel.

Some SPC reloaders shoot the 130 Ballistic Tips accuratly from the SPC length neck but I prefer the shorter length neck to keep the ogive outside the case.

I think you are on to something good.
Have you calculated the projected point blank range with the diff bullets?

So the grains capacity
223 Rem 28.5
6.8 SPC 33.5
6.5 Grendel 35
6.8x42 40.6

So that is a tad over 20% capacity increase over the 6.8 SPC
The case capacity of the 6.8 SPC over the 223 is 20% so in comparison over the 223
There will be about 42% increase capacity of the 6.8x42 over the 223
I bet there will be good cart efficiency with the 6.8x42

Two thumbs up

For small deer
110 Accubond @ 2950 3" ^ @ 150yd 3" v @ 298yd
Minimum Expansion at 1800fps which is at 540yd

Big Deer
130 Accubond @ 2700 3" ^ @ 141yd 3" v @ 277yd
Min Expansion 1800 @ 476 yd

I don't really see this as a 300 yd elk cartridge but here it is anyway.
130 E-Tip @ 2650 3" ^ @ 132yd 3" v @ 275yd
Min Good Expansion 2100 @ 295 yds

I think that the premium 130s are the best weight for this capacity although the heavies could be used.

The 16" SPCII maxes out around 2550 with 130s so these # are conservative, it might get over 2750 w 18" barrel.

Where will you get the brass?

So.. how close is this to PPC cases or 7mm BR.

How deep are 130's seated in a 42mm case??? passed the ogive :-)

quote:

Originally posted by richj:
How deep are 130's seated in a 42mm case??? passed the ogive :-)

Depends on the bullet. The bullet exposure is only .050 less than on the 270WSM. Almost all 130-150 gr .277 bullet ogives will be outside the case including Bergers. The tipped Hornadys, the Scirocco and a couple others are too long though.

Privi Partizan sells the brass. It's linked in the OP.

The PPC and BR cases are both 1.52". This is essentially a stretched 6.8PPC.

I tried a 7mmbr in an ar mag with 130's, it fit, barely. I couldn't find the capacity of a 7mmbr but I think a 30br is about 37.5gr.

Here's a fella with a similar idea. He's just necking up Grendel brass and he's getting velocities equal to my goals with the lighter weights. 95 TTSX at 3100, 110s at almost 3000. http://www.ar15.com/forums/top...l?b=3&f=121&t=499778

Remember that the 6.8x42 is .10" longer at the shoulder and mouth and has almost 5 gr more capacity. And he's running a weaker bolt so I'd guess that he isn't hot rodding it.

The 130gr Berger has it's ogive at .627" so it will fit easily even with a shortish 2.25 OAL.

BTW he has a 7mm version that shoots 120s at over 2800 so 5 more gr capcity should get my high BC 130s to over 2800.

http://www.ar15.com/forums/top...=121&t=397161&page=8

Interesting about the 6.8 Grendel. I posted about idea a while back. A 308 based case with 6.8 SPC dimensions but fatter could yield you enough capacity to push up to 150 grain 270 bullets. That could be pretty sweet on a Ruger bolt action conversion.
Pushing the 115 grain 6.8 bullets at 3,000+ fps.
Kind of like a longer 6.8 BR
Hmmmmm that would be sweet
can someone help me figure out what capacity that would yield.
I am guessing maybe 43 grains. The 30-30 is about that so maybe a 308 version would be interesting too. Heck I'll have to have an imaginary whole breed of these SBC carts from 22 on up. That would be tredding on 30 RAR territory.
Let's call it the 6.8 SBC instead of 6.8 SPC