Calibers .25x45, 6.5mmx45, 6mm-6.8SPC, .25-6.8spc, 6.5mm-6.8spc for an upper.

[1stmarine]

I have been considering a few alternatives for the next AR barrel/upper including the creation of a new round if needed. (Fun autumn project)

So, for you wildcatters does anyone have any experience with any of
these variations?

A) from the .223 case
================
1- The .25 caliber with the same angle on the shoulder or slightly improved, I would say no more than 30 or 35 degrees?

2 - 6.5mm with the same angle on the shoulder or slightly improved.


B) from the 6.8 SPC case
==================
1- 6mm caliber with the same angle on the shoulder or slightly improved.

2- .25 caliber with the same angle on the shoulder or slightly improved.

3- 6.5mm caliber with the same angle on the shoulder or slightly improved.


I have been playing with QL and I believe with the 6.8 case could yield some interesting results. I believe it is doable a 100gr .25 pill safely achieve the 2800+fps with a very decent sectional density.
I prefer slight variations that do not require fireforming and still give decent results so the TCUs are excluded.
My believe is that the 6.8 case has a lot going and the 6.8 bullet is not helping 'her'.
It is just like Robert Withley said about the grendel case... "The grendel almost wants to be a 6mm"... LOL

Any experience anyone would be great. I am not afraid to spend for the sake of experimentation even if I have to order reamers and dies from scratch.

If someone asks why I would say why not.
Only healthy dialog please or move on to another posts.

Cheers,
E.

 

[451 Detonics]

the 6.5 MPC (6.5X45) is an easy one as it uses standard BCG and magazines.

95gr at 2800
110gr at 2730
120gr at 2400

this is from a 20 inch barrel

brass is very easy to form, just neck up and trim 3mm, square and make cases consistent oal.

 

[1stmarine]

Hey thanks! that sounds interesting. I didn't know the put a name MPC already!? Everyone is labeling the military based wildcats so fast these days.
I have several in 6mmx45 and I am very happy with them. Probably do not need much more from the AR-15 but you know, curiosity.

Do you know the dies and reamers / barrels where they can be ordered?
Also any first hand real data on loads and spreads?

thanks.

 

[451 Detonics]

MPC stands for multi purpose cartridge but there have been several just called the 6.5X45 as well. I ma sure Clymers can supply the reamers, RCBS the dies and 6.5 barrel blanks are available.

SSK Industries was the main promoter of the caliber and I have one in the plans as soon as my suppressed build is done.

 

[1stmarine]

Thanks again! that is what I was thinking for the reamers clymers. For the dies I didn't know but I would have to check with RCBS.
I do believe the 6.5 over 6.8 is not a huge gain other than a much better assortment in the category and grain range. That is why I would like to also research what the .25 could do.
This would be all for moderate range hunting and some fun with moderate to mid range with a tad gain in Sectional Density and ballistic coefficients for all purposes. That is the simple idea. nothing huge just some modest gains out of these baseline casings.

 

[NG VI]

It'd be interesting to see what the 6.8 case could do vs. the x45 in a few different calibers.

Whatever you go with, keep us updated!

 

[dc.fireman]

I think LE Wilson uses this company for a lot of their reamers:

http://www.pacifictoolandgauge.com/index.htm

Their prices are certainly reasonable enough...

 

[1stmarine]

I am still testing the last one in 6x45 (3 different barrels at the moment).....

http://www.thehighroad.org/showpost.php?p=7265166&postcount=127

And the russian upper compared along with others here...

http://www.thehighroad.org/showpost.php?p=7299232&postcount=44

I am still waiting for the blackout but looking for some other alternatives in the list here.
I just realized I need to update the other projects with more pics and results.

 

[1stmarine]

I have been playing with CAD and QL and I think that an optimal cartridge for a short / middy barrel would be a tad sorter version of the 6.5mm TCU. The thing is that I do not like the sharp shoulder so I am thinking how I could push the shoulder down and keep it at 30 degrees.
Anyone any experience with the 6.5 or 7mm TCU?
According to my calculations this would make it an excellent choice for 95gr vmax and 90gr TNT pills. Additionally I am working in a solution for a magazine that is going to allow 2.4 COAL.
Any ideas are greatly appreciated.

 

[1stmarine]

I have narrowed this down to several options.

6mm.
6x45 slightly improved.
6.8 SPC case necked down to 6mm and change in lenght and in shoulder angle.
.264LBC necked down to 6mm. Different to 6mmAR.

6.5mm.
6.5TCU with change in length and shoulder angle.
6.8 SPC case necked down to 6.5 and change in shoulder angle.

6.8mm.
6.8 SPC case improved with change in shoulder angle and length.


7mm
7mmTCU with change in length and shoulder angle
6.8 SPC case necked up to 7mm and change in shoulder angle.
.264LBC necked up to 7mm.


There is one that it seems a no brainer without touching shoulder angle

It seems to me that the .264LBC like the grendel are screaming for a change in clothing. Some got the 6mm covered that to me is one of the best (if not the best) bullet departments out there.
Now the next logical step is to neck up that baby to 7mm.

Some nice bullet options...

http://www.hornady.com/store/7mm-.284-120-gr-V-MAX/
http://www.speer-bullets.com/ballistics/detail.aspx?id=43
http://www.nosler.com/Bullets/Ballistic-Tip.aspx ...7mm 120gr Ballistic tip. Look at those numbers!!!!

QL says it can be done and when you get into the big boys w/o getting in the huge sections. There is nothing any .308 bullet can do better in the AR15 other than suppressed work. (Excluding all exotic single stack cases)

These are the proposed numbers...

7mm-264LBC - TNT 110gr bullet. - 100yds zero.
Range Velocity Energy Impact
0 2850 1984 -0.5
100 2571 1615 0
200 2316 1310 -4.79
300 2076 1053 -16.12
400 1851 837 -35.58
500 1644 660 -65.25
600 1458 519 -107.84
700 1298 412 -166.81
800 1169 334 -246.4
900 1075 282 -351.24
1000 1006 247 -485.85

7mm-264LBC - Nosler BT 120gr bullet. - 100yds zero.
Range Velocity Energy Impact
0 2600 1801 -0.5
100 2387 1518 0
200 2190 1278 -5.64
300 2001 1067 -18.58
400 1823 886 -40.24
500 1657 732 -72.41
600 1504 603 -117.28
700 1367 498 -177.52
800 1250 416 -256.32
900 1153 354 -357.24
1000 1079 310 -484.06


I think it could give the grendel and 6.8 a run for the money for a deer/black bear AR rifle. I don't care too much about the 1000yards shooting with an AR15 but care a lot about what type of mail can be delivered within the 300 yards range.

There are folks there ready to help us. I am working with a few barrel options.

 

[Kachok]

I would go with a 5.56 case necked up to 25 cal. It would vastly improve on the terminal ballistics of the 5.56 and not sacrifice magazine capasity. With an improved shoulder you should be able to compete with the external ballistics of the old 250 Savage with 100gr bullets, that would make it a real dual purpose AR setup and much like the 6.8 SPC it would finction nicley in carbine length barrels. I would love an AR that could serve as my deer/hog rifle. The SPC does that as well of course but looses a little magazine capasity and the ability to use 5.56 brass. I would normaly opt for the 6.5mm bore, but even with an improved shoulder I don't think it has the case volume to effectily handle the 120gr bullets, shame really because I love the 120 Ballistic Tips.

 

[Z-Michigan]

Your options look interesting, but why did you rule out the 6.5 MPC? That to me looks like nearly the ideal all-around AR15 cartridge, and I am puzzled why it seems to have gone exactly nowhere in the US.

 

[1stmarine]

Many thanks for your feedback. Great suggestions.

These are my initial thoughts...

Yes I read about the 6.5 MPC but cannot find any reliable data for it. I am surprise more folks do not use it. Anyway, not a great fun of proprietary cartriges here that might not add much value as a wildcatter so I rather to work it up with the baseline cases. I leave other exotic candidates out on purpose.

Regarding the 25x45/44/43. I also thought about this one but the 6mm 100gr bullet at 2600fps is hard to beat. Also the 6mm 95gr Berger VLD.
Even the 87gr v-max has a BC of .400. I am looking at energy retention at 300 yards limit for deer and 500-600 yards for occasional coyotes in the plains. For this one I do not care about a longer barrel as I might shoot from the truck bed.
The .25 bullet needs to be a higher grain than 100gr to be a little better than 6mm at moderate ranges. At short range is a very good choice but I am looking for a little bit more versatility.
Same ailment that we have with the 6.8 SPC sometimes although what the 6.8 sometimes looses in SD it gains in wound channel width.

Nothing wrong with either one gentelman! ..I am looking for something with a bit more substantial advantage than the 6x45 that is already an improvement of a very good cartrige that is the .223rem case.

Modern .223 is very different from the ones used in Vietnam or the 55gr value packs. Only for some inexplicable reason is not allowed for hunting
in many places at moderate range.
I have .233 rem 70gr TSX moving at 3,000fps. The problem with the hunting bullets in .223 (not the target ones) is that .223 stops almost where the 6mm starts with dozens of amazing options in this 6mm department.

 

[MAF]

6.5x45

A question if you don't mind; after all your research what do you think about the 6.5X45? SSK makes ammo and brass and that is one heck of a round. It is also about half way between the 5.56 and 7.62 so it seems like it might be a tad better than the 6 or the 300. I'm building now and was stuck deciding between the 6 and the 300 and now I'm thinking maybe I should consider this instead. Here is what I am shooting for:

1- Light, easily carried/manipulated, indoors or in urban terrain (CQB)
2- Fast follow up shots, even for my 13 YO son (or wife or daughter)
3- Hunting for game in Virginia, i.e. deer mainly
4- Marksmanship training on varmints, i.e. groundhogs or coyote
5- AR platform with maximum parts commonality (mags, bolt, etc.)
6- Easily reloaded ammunition options
7- Self-defense either at home or “worst case scenario”
8- Good amount of aftermarket parts and accessories
9- Option of a piston drive over DI
10- Maybe playing with a suppressor…