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· Premium Member
11,655 Posts
Discussion Starter · #1 ·
I like to design, build and test new and different calibers so I'll start with Variants I know of.
From the SPC case-
6mmHagar(30 rem case)

From the .223 case-
300 whisper

from the 220 Russian or Grendel-
6mmAR Turbo
6.5 Grendel

other cases-

358 Specter
458 Socom
50 Beowolf
500 Phantom
338 Rhino
375 Rhino
417 Rhino
458 Rhino

243 WSSM
6.5 Reaper

Cold, Marty has too many I don't know about if you'd like to add them.
Anyone else have any or wish there were different ones?

· Registered
3 Posts
I took a few minutes and came up with a short list. There are almost certainly many more that I have neglected.

Numerous .17's
.20 Vartarg
.20 Vartarg Turbo
.20 Tactical
.22 Lindahl Chucker
.22 CRT
.22 Rimless Wasp
.22 CRT
.240 Madame
6mm Vartarg
6mm Vartarg Turbo
6mm TCU
6mm CRT
6mm WOA
6mm AR
.25/222 Copperhead
.257 TCU
.25 CRT
6.5 CRT
.265 1*
7mm Whisper
7mm CRT
.30 HRT
.30 PPC
8mm HRT
.357 Auto
.38 Casull
.40 Super
.40 Extreme
.440 Cor-Bon
.475 Tremor
.500 Phantom
.502 Thunder Sabre

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1,509 Posts
Will the 6.5 reaper handle all the longer 6.5 bullets or is there a OAL magazine problem in the AR-10?

What about necking it down to a 6mm or would that just be to overbore and burn up the barrel in under 1K? I am just thinking it would be interesting to use some of Tubb's new 117 grain SMK with a BC of well over .636( which beats the 6.5 144gr Lapua bullet) developed for his 6DTAC round. They have that new boron coating which is suppose to be many time slicker than moly , doesn't come off or have acid prolems in the barrel. He will coat any bullets you have in batches of 1000. Apparently it doesn't just tumble on like moly.

I always liked the 7mm in the Short magnums. What are your thoughts on say a 7mm Reaper compared to the 6.5 given the bullet available from berger and the like? I always liked 7mm bullet as a whole they seem like the perfect balance in bc, weight, sd, and energy.


· Premium Member
11,655 Posts
Discussion Starter · #9 ·
The Reaper was designed to handle all of the heavier 6.5s but specifically the 139 Scenar at 3200fps in the AR10 platform it will not work with 100-108 gr bullets they're too short..
I think a 6mmReaper would smoke the barrel in no time but the 7RSAUM should work well.

The 243 is bad enough about burning out the barrel, the DTAC in that should be about as fast as it gets.

· Registered
51 Posts
Constructor, you load for a 6.5 Grendel and Banshee. I read a post where, please correct me if I'm wrong, you load the two .445 diameter cartridges to 10K less PSI than the 6.8. Is this pressure limit because of the thinner barrel surrounding the chamber? Assuming the bolt holds up, whats the upper pressure limit with the Grendel and Banshee?

The 6MM BR could be added to the list.

· Premium Member
11,655 Posts
Discussion Starter · #12 ·
I push every gun I have to just below case failure, ususally around 60000psi. That should be the limiting factor in all rifles, If a case fails it blows gas and black powder on me but thats better than flying pieces of bolt and receiver.
The Grendel limit was set by Bill A at 52000 to save the bolts from breaking.
I use LWRC 6.8 bolts modified to fit the Grendel so I push my Banshees to the same limit as the 6.8. Lapua brass is good and will not show sign of swipes or flat primers because of the small primer and small flash hole so the first sign of pressure with the Grendel will be case expansion of over .0005 just above the groove.

· Registered
51 Posts
I see, so the Grendel has plenty of meat around the chamber after all.

I've read a couple of 6mmBR threads and the concern that stood out to me was the thin chamber walls. At what case diameter would you start lowering pressure because of the fear of chamber wall rupture?

.450 diameter- Carcano brass
.460 diameter- 35 Rem, 308 swaged down with USB dies and 35 Rem dies, with a rebated rim.
.470 diameter- 308, -06 etc. brass

Please assume that all the brass is as hard as 6.8 or 308 brass for the sake of this discussion.

I ask these questions because I've often thought of a cartridge and reamer that would clean up the 6.8 SPC chamber and add capacity due to the larger base. It should function from a 6.8 or 6.5 magazine. This larger capacity cartridge was important back before I understood why the 6.8 got loaded down and less important now that the 6.8 is getting it's legs. But since I see you discussing variants I'd like to know what you think of the ARs ability to handle a larger diameter cartridge.


· Premium Member
11,655 Posts
Discussion Starter · #14 ·
The Air Force shooting team uses 6BRs full strength so the .473 case should be good. Others have used the WSSM loads with the Oly bolt and extensions. I have a HK 308 which has a very thin barrel so I don't think barrel strength is an issue.

Marty at Teppo Jutsu has done alot of large bore wildcats you may contact him or look for his site for more info.

You sound like someone on another forum. Are you?

· Registered
51 Posts
LOL Bigfoot or slight variations are the only handles that I use. I did see someone asking about the 6mmBR and pressures in the AR someplace else tonight. Someone else thinks like I do, poor guy. :)

To be perfectly honest I haven't got my head around exactly what OLY and DTECH do to make the WSSM work in the AR. This goes for the big thumpers as well. I was under the impression that the WSSM ARs used a larger diameter barrel along with the larger bolt head. I thought that I read that DTECHs 6mmBR bolt head is the same as the WSSM just cut different so I assumed that it used a larger barrel as well. Bad assumption?

I was completely unaware that the Air Force team shoots the BR. Do they use the standard AR 1" barrel diameter at the chamber?

· Premium Member
11,655 Posts
Discussion Starter · #16 ·
You are correct about Dtech and Oly, the extension, carrier, bolt, and upper receiver are larger in diameter. the barrel I measured was the same at 1". The 308 HK I have is smaller although I can't get a caliper in to measure it.
I have a 6BR bolt for that OLY system, I was going to build a 6BRX but just lost interest because of the lack of mags.
I have read post by others who are thinking along the same lines.
M9 wanted to use the carcano case to get rid of a Grendel barrel he was very unhappy with.
If you need any help with the cat just let me know, it takes 3 phone calls and about 8 weeks to make it happen.
Pacific tool for custom reamers
Hornady for custom dies
and someone to chamber a barrel

· Registered
51 Posts
I finally found some details on the WSSM conversions last night. The standard AR barrel holds up to the WSSM case diameter and high pressure so it will certainly last with anything that will double stack in a 6.8 or 6.5 mag.

I'd guess that the Carcano brass whether Norma or Pivi would be fairly soft but I could be wrong.

Thanks for imparting your knowledge. I come from a long line of inventors/fabricators and I have the same tinkerers curse. I can't let an idea go until I've fully scratched the itch. However the smart play is to wait and see what your barrels can do. Let the 6.8 be what it is, a mid-range carbine cartridge and don't try to make it into an elk getter. Let the -06 do that stuff.

Thanks Again

· Premium Member
11,655 Posts
Discussion Starter · #18 ·
Just for that 6.8 VS 6.5 argument straight from the horses mouth.

Senior Member Join Date: Oct 2004
Location: Virginia
Posts: 663


Nuff said for a forum! Remember we only make hunting rifles for civilians and the military/LE does not, never has, nor will it ever have, an interest.

What I am trying to see is how this would be recieved by general shooters, who have to save their own dollars and who are deciding what to buy.

Here is an example based on my use. I shoot only for hunting or occasional targets. I have a hunting carbine that will see less than 100 rounds this YEAR and most of those are loaded in fives or threes. Suffice to say I have no use for the cost of a piston in this application but would spend the dollars for a better barrel.

The Grendel is not a 5.56 and the market does not obey many of the dynamics so I am bouncing ideas as I run trials

Bill Alexander

Bill A. has posted this several times on the Grendel forum.

· Premium Member
11,655 Posts
Discussion Starter · #20 ·
paulosantos said:
I read that before. Did Grendelizor ever read that? LOL.
Yes, even though Bill A. and Arne of CSS developed it John has claimed it as his baby. John and Bill both spend a lot of time promoting it and the 6.8 really has no one to do that. We experiment but we don't send letters or emails to writers or TV shows like future weapons to get publicity.
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