Straight walled cartridge idea

A

Andy1

New member
Straight walled cartridges get a lot of attention lately. Mostly because of relaxed regulations for deer hunting. Especially the ones that are AR compatible. I'm underwhelmed with the 350 Legend and the 450 BM can be too much for new, young, or sensitive shooters.

I'm thinking of a new, similar cartridge slotted between these two. The .22-250 case has a standard .473 rim. Using it's .470 base, it can be tapered to a .454 neck and use a .429 bullet. There is no shortage of .429 bullets for weight, profile or usage. Case length and pressure TBD.

This would offer less recoil than a 450BM, more power than a 350 Legend, with plenty of speed and energy deer, hogs, etc. As well as an additional AR chambering.

I was going to submit this idea to Federal's idea submission portal. Any thoughts?
 
You are essentially talking about .44 Auto Mag. Based on a cut-back 308 case necked to 44 caliber, generates about 1500 fps out of a 6" barrel, probably 1800 fps out of a rifle or mid-length barrel. Duplicates 44 Mag pretty well. But it has a shoulder for headspacing, so I don't know how the "straight-walled only" states would respond.

You could also look at 45 Win Mag, it's straight-walled and designed to headspace on the case mouth.

Or just shoot 10mm out of your AR, 40-caliber bullets are out there.
 
I have a 10mm, .450BM and a .450 Corvette in the straight walls. The 10mm is a DI gun, so it is a lot more powerful than what can be obtained in the blowbacks. I have found it suitable for Deer and Pigs out to about 100 yards. Much prefer it to the 300BO it replaced.

I really like the .350Legend in concept as well as some of the others, like the 6.5PCC and the 6mmARC (just introduced) in that they maintain the .223 case as the parent. That reduces cost of ammo, manufacturing, and builds since all one needs is a barrel. That is, IMHO, a big deal. A barrel swap only in the AR15 platform is something really will increase interest and sales as it is just a barrel. Plenty of shot out .223Rems around that can be rebarreled as well.

My .450BM and .450Corvette are in my "to be sold" pile and I will eventually replace it with a .350L once it gets through the growing pains. Other than 9mm and 10mm, I have lost interest in anything for the AR15 platform that does not have the .223 as the parent case.

In addition, your solution would not be a straight wall, so would not be legal in the "straight wall" legal for hunting states that have recently passed such laws. DOA.
 
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I really like the .350Legend in concept as well as some of the others, like the 6.5PPC and the 6mmARC (just introduced) in that they maintain the .223 case as the parent.
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Unless something has recently changed, the 6.5 PPC ans the 6mm ARC use the 7.62X39mm as the parent case, not .223 Remington.
 
Scorch, the 6.5 Patriot Combat Cartridge has always been on the .223 Case. I made a typo in my post and wrote PPC, should have been PCC, which is what I actually have.

No one has a SAAMI spec 6 ARC yet as it was just discovered to have had the patent applied for in January, but no guns or ammo. I don't know much about it, but the case head is in fact .441, so yeah, not the .223 Case, my error.

I should have had that 2nd cup of coffee. Thanks for cleaning that up for me.
 
You are essentially talking about .44 Auto Mag. Based on a cut-back 308 case necked to 44 caliber, generates about 1500 fps out of a 6" barrel, probably 1800 fps out of a rifle or mid-length barrel. Duplicates 44 Mag pretty well. But it has a shoulder for headspacing,
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Nope. It is a very slightly tapered case. M. Ayoob had a Model 29 cut for full moon clips and shot .44 Automag in it on an African safari.
 
Jim-
You made me think!! OW OW OW OW!! You're right, I was confused with the 357 Automag.:o
Scorch, the 6.5 Patriot Combat Cartridge has always been on the .223 Case.
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There have been a number of 6X45 and 6.5X45 and 7X45 cartridges over the years (TCU, Ingram, etc). They work OK, but never really caught on. When you start to complicate an established system, some jump on board, others just walk away.
 
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I think FrankenMauser has it right. 44/45 what's the difference?
Bigger than 35, smaller than 45, I'm a bit surprised there hasn't been a 40 cal (10MM) with 5.56 length to run in an AR.
 
I think FrankenMauser has it right. 44/45 what's the difference?
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That is exactly why Tony Rumore didn't go any farther than a chamber drawing for the .44 caliber version of .458 SOCOM, known as ".44 Fury".
It is so close to the parent, with only a few bullets suitable for feeding in an auto-loader (ARs specifically, of course), that the caliber change wasn't worthwhile.
 
The 10mm is a DI gun, so it is a lot more powerful than what can be obtained in the blowbacks.
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I'm (politely) interested in why you say the DI (by which I assume you mean locking lugs extension to bolt) is much more powerful than blowback, mostly because I've pushed more than few to failure and basically what I've found is the case itself can't handle that much more pressure (+/- 4000 psi) than the SAAMI specs for max pressure.
 
When I was thinking up the design I knew it wouldn't be far off the 450BM. But with the wide array of .429 bullets available I was going for versatility. It would duplicate .444 Marlin specs in a rimless AR length case.

The other idea I had was similar to the AR400. Instead of the Carcano case it uses the .220 Swift case. This has the .473 rim, .450 base and would taper to .425 neck and use .400 (10mm) bullets in a 1.7" case. But there are way less bullet designs suitable for velocities this high. I think this would be a great cartridge. Better than the .429 in design and use but not for reloading.
 
I'm (politely) interested in why you say the DI (by which I assume you mean locking lugs extension to bolt) is much more powerful than blowback, mostly because I've pushed more than few to failure and basically what I've found is the case itself can't handle that much more pressure (+/- 4000 psi) than the SAAMI specs for max pressure.
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I'll admit to being a bit of a 10mm fanboy and a moderate PCC fan as well. The key in that statement is "what can be obtained" and I should have added "being reasonably safe", in a blowback.

If you do the math on the blowback design, you need a 3 pound bolt for the 10mm with a 180 at 1250 fps. That is THREE pounds of cycling mass, or about twice what you need in a 9mm. If you lengthen the barrel and up the powder charge with a slower burning powder that number goes up. Full power 10mm from a 16" barrel with a fairly slow powder is pushing 6 pounds for the cycling mass. Yes, you can cut mass a little with the spring, but when you do, the risk of deep seating of bullets goes up. Frankly, the .40S&W is right on the edge of the safety with a blowback and a 10mm has to run neutered rounds or they become unsafe, tear up brass and don't last.

With 180s in my DI gun I am up over 1600 fps and with the 115 grain solids, in the 2400 fps range. Not overpressure and my brass is pristine. Run those loads in the CMMG, MecTech or HiPoint and you will get significant case damage and or case ruptures.
 
When I was thinking up the design I knew it wouldn't be far off the 450BM. But with the wide array of .429 bullets available I was going for versatility. It would duplicate .444 Marlin specs in a rimless AR length case.
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Due to bore expansion ratio, bore friction, and the pressure limitations of such a large diameter cartridge in an AR, you wouldn't be able to match .444 Marlin performance levels safely.
2,000 fps would probably be a safe bet, maybe 2,100 fps.
But I believe that ~2,200+ fps would be pushing an AR too hard.

The thin shank of an AR 15 barrel, due to the necessity of having a barrel extension around it, limits maximum safe pressure with cartridges larger in diameter than .223/5.56. In addition, when the bolt face is opened to .473", it can't take as much abuse, either.
These are the biggest reasons why .450 BM is limited to 38k psi and .458 SOCOM tops out at 35k psi.


At best, you'll get .44 Mag rifle level performance.
 
You are essentially talking about .44 Auto Mag. Based on a cut-back 308 case necked to 44 caliber, generates about 1500 fps out of a 6" barrel, probably 1800 fps out of a rifle or mid-length barrel. Duplicates 44 Mag pretty well. But it has a shoulder for headspacing,
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I see you were corrected on the "shoulder", part, there is no shoulder on the .44 Auto Mag, there is on the .357 Auto Mag.

I need to correct you on another small point. .44 AMP cases are not "necked". to .44 caliber. The rifle brass is cut to 1.298", then inside neck reamed, to allow a .44 slug to fit. Original .44AMP loads got 1600fps+ from the standard 6.5" barrel. "Full house" .44 AMP runs at the same pressure level as the .308Win (50,000psi + depending on how you measure it) Loaded to potential, the .44 AMP does not duplicate the .44 Magnum, it exceeds it. :D

The .45 Win Mag throws a 230gr @ 1500fps from a 6" tube. Either one would give you 1800fps from a carbine, without breaking a sweat. :D

The 10mm is a DI gun, so it is a lot more powerful than what can be obtained in the blowbacks.
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I'm (politely) interested in why you say the DI (by which I assume you mean locking lugs extension to bolt) is much more powerful than blowback,
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DI = Direct Impingement It refers to the direct impingement of gas on the bolt carrier operating the mechanism, rather than the gas impinging on a gas piston and that piston (usually via a connecting rod) operating the bolt.

"DI" has NOTHING to do with how, or where the bolt locks up. It refers to the method of using gas pressure to operate the gun.

The 10mm is a locked breech gun, due to the pressure involved and it is the locked breech that allows higher pressure than a blowback (of practical weight) not the method of gas operation. You can build a DI 10mm or a piston driven 10mm, as far as handling the pressure of the round, the method of gas operation is machts nichts.
 
I'm underwhelmed with the 350 Legend...
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Are you sure? Mine is launching 170gr bullets at 2400-2500fps....I think the key is the Winchester XPR....longer oal, longer 22” barrel, and somehow a fast barrel. All this with a pretty good 3.5lb trigger.
 
These are the biggest reasons why .450 BM is limited to 38k psi
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Nope. Tim LeGendre designed the Professional at much higher pressures, but Bushmaster wanted a carbine gas system, not a mid length. The pressure into the gas tube and thus the carrier was too high and too long which resulted in unlocking before the pressure had dropped. So they took out powder.

I have a .450Corvette, which is one step the other way. Rifle gas, and it operates at the higher pressures, no issues with the bolt, or brass. The "rim" of the cases do not expand and even flat faced bolt AR15 systems have been tested without any ill effects. Shearing off the lugs is due to excessive overgassing, not insufficient thickness of the wall on the bolt face.
 
Are you sure? Mine is launching 170gr bullets at 2400-2500fps....I think the key is the Winchester XPR....longer oal, longer 22” barrel, and somehow a fast barrel. All this with a pretty good 3.5lb trigger.

I am sure. I'll take my .35 Remington model 760 any day over a 350. When it first came out I was hoping for something in between .35 Rem and .358 Win. But it's not.

Due to bore expansion ratio, bore friction, and the pressure limitations of such a large diameter cartridge in an AR, you wouldn't be able to match .444 Marlin performance levels safely.
2,000 fps would probably be a safe bet, maybe 2,100 fps.
But I believe that ~2,200+ fps would be pushing an AR too hard.

You're correct and I should've been more clear. I'm not an AR guy but that seems to be pushing the trend. But the 450BM has AR and bolt action power levels and that what I was thinking.

I haven't learned how to quote others text so sorry if this seems confusing.
 
I’ve done considerable thinking on subject of straight cases since now legal Ohio deer gun.
I had 45/70 when laws came out and promptly got 44mg and 375Win. I decided the 375W was the one to get the most out of. I’ve now thinking sweet spot to be .40cal.
 
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