Breaking News* New AR15 .30 cal cartridge

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You are few years late, it's called a 6mm Hagar. The 30 Rem is nothing new.
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You need to re-read the thread. .30 RAR is not .30 Remington. The cases are entirely different.
 
Parent Case: The .450 Bushmaster. But the case head diameter was bumped up to .492” to prevent accidental chambering of other cartridges.
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I'm thinking this means that existing .450 Bushmaster magazines will feed .30 RAR. This little cartridge is catching my interest. It may not be an Elk cartridge, but a 125 grain 30 cal bullet at the listed velocities sounds good for deer. I like the idea of an AR-10, but the size and weight make the reality of an AR-10 less desirable to me.
 
I honestly wonder why they used the .450 BM as the parent case...
I would be rather surprised if you couldn't do most of what this cartridge does using a lengthened 6mm PPC case... And you could double-stack it and use Grendel mags, too...
 
Nolo said:
I honestly wonder why they used the .450 BM as the parent case...
I would be rather surprised if you couldn't do most of what this cartridge does using a lengthened 6mm PPC case... And you could double-stack it and use Grendel mags, too...
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You just invented the 7.62x39 improved, which would probably only run about 50-100 fps faster than the old 7.62x39 Soviet and wouldn't feed as reliably.
 
You just invented the 7.62x39 improved, which would probably only run about 50-100 fps faster than the old 7.62x39 Soviet and wouldn't feed as reliably.
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There is no way that's all you could get away with.
Let's look at some numbers:
6.5 Grendel: 123 grain @ 2650fps @ 45KPSI (20")
Not only are you drastically increasing the diameter of the bullet with the 7.62 version, which would increase velocity significantly, you're also increasing pressure to 55KPSI (6.8 SPC operating pressure) and the case length by 2mm. My guestimates run like this:
Add, say 75fps for the larger bullet.
Add 125fps for the higher pressure.
Add 50 fps for the longer case and much less bullet contained inside of it.
Subtract 75 fps so that the numbers are conservative.
What do you get?
2775 fps with the same exact bullet as the the .30 RAR out of a 20" barrel. To verify the numbers, I look at the .30 HRT (6.8 SPC necked up to 7.62), which is supposed to do 2700 fps with a 110-grain bullet. The estimates look valid.
As for feeding reliably, that's really an AR problem, not a cartridge problem. AR's got a lot of bugs...
 
The reason the Grendel has a lower operating pressure than the SPC is because the larger case head increases bolt thrust while removing bolt face material to fit it weakens the bolt. That is also the reason the SPC runs lower pressure than 5.56mm.

If you are dumping the buggy AR platform for one of your illustrations then there is no reason to be constrained by ether of these AR magwell compromises.

AA factory specs for the 6.5 / 123 / 19.5" are 2565 fps at 47-49k PSI.
 
AA factory specs for the 6.5 / 123 / 19.5" are 2565 fps at 47-49k PSI.
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I must say, the Grendel is one of the hardest cartridges I've ever seen to get reliable datum on...
:scrutiny:

If you are dumping the buggy AR platform for one of your illustrations then there is no reason to be constrained by ether of these AR magwell compromises.
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Well, you wouldn't be dumping the lower, just the upper, which you'd have to change anyway.

The reason the Grendel has a lower operating pressure than the SPC is because the larger case head increases bolt thrust while removing bolt face material to fit it weakens the bolt. That is also the reason the SPC runs lower pressure than 5.56mm.
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Bolt thrust and the bolt head can be compensated for, I imagine.
I thought the SPC runs at a higher pressure than the 5.56, not the other way around. I thought the 5.56 was 52KPSI and the SPC was 55KPSI.
 
Quote:
Parent Case: The .450 Bushmaster. But the case head diameter was bumped up to .492” to prevent accidental chambering of other cartridges.

I'm not even sure what the 450 Bushmaster is, but looking at the dimensions given in the Outdoor life blog link earlier in this thread, the parent case is more like an unrebated 284 Winchester or even a 376 Steyr, both of which seem to feature a .500" diameter base.
Steve
 
hey nolo, the differance between a 7mm-08 and a .308 is larger than that(from what i have heard), and you are making a even bigger jump.
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I was being conservative. If I wanted to really stretch my boundaries, I'd say 150 fps for the bullet alone.
My point is, you can get great performance our of a .30 cal AR that is way worth it over 7.62x39mm. Oh, and you can still have 20+ rounds in the mag.
 
If somebody can get me the case capacity of the .30 RAR and if Nolo can get me guestimates on the capacity of his 7.62x41 improved, I'll be happy to run things through QuickLOAD and get us some more informed guesses about the relative ballistics of these rounds.
 
If somebody can get me the case capacity of the .30 RAR and if Nolo can get me guestimates on the capacity of his 7.62x41 improved, I'll be happy to run things through QuickLOAD and get us some more informed guesses about the relative ballistics of these rounds.
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Let's see...
I think the capacity of the 7.62-PPC is gonna be pretty easy to calculate..., the Grendel's case is almost cylindrical.
Alright, the 7.62-PPC's case capacity should be about 38.5 grains of water, 35.75 grains of powder.
I would have standard operating pressure for the 7.62-PPC to be the same as 5.56, and have it utilize a 125-grain bullet.
As for the .30 RAR...
Dunno.
 
His cartridge is close, but I've still got 2mm of case and higher pressure on him.
I am pretty sure I can compensate for the increased bolt thrust (which won't be any more than 7.62 NATO, anyway, which is what we're competing against) with recoil buffer systems, and I imagine I could even fit those into standard-lower compatible upper.
Gonna need a whole new upper anyway, so why not?
Also looks like he isn't fitting those 155s into the AR-15s OAL, which means he isn't using AR-15 mags.
 
It is where I started.
Overall, I think my design is better. It can still use the big bullets without mags, just like his.
Not to mention he's only getting 2100 fps with 155s. I'd be willing to be I could get at least 2300...
 
Nolo said:
I am pretty sure I can compensate for the increased bolt thrust (which won't be any more than 7.62 NATO, anyway, which is what we're competing against) with recoil buffer systems, and I imagine I could even fit those into standard-lower compatible upper.
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Nope.

Bolt thrust is a concern for the locking lugs, it has nothing to do with recoil.

Now it is apparently possible to deal with the bolt thrust issue, because the .30 RAR and WSSM uppers have already managed it.

This is going to be my last post here, I'm moving over to http://www.thehighroad.us
 
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