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Old January 22, 2020, 01:23 AM   #1
TruthTellers
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Best straight wall cartridge for semi auto? *READ FIRST POST*

I was thinking at work today about how I could reload the most ammo for a rifle that wasn't weak like 9mm or .40 S&W are, basically something that could hit 900 ft/lbs of energy minimum, but was available in magazines of 15 rounds or more.

I'm focusing on straight wall because it's generally less work to load that case than a bottleneck case. Inevitably someone is going to come in and say that they can load a bottleneck with less work than a straight wall and hey, good for you, I want to focus on straight wall here.

So, that led me to thinking about 10mm, both Auto and Magnum. 10mm Magnum in a rifle would be great, but there are really no magazines available to use that long cartridge, so 10mm Auto is really the only option and it is still a good option. Still, 10mm Mag in a rifle... that'd be cool.

Then I thought about the .350 Legend. That's got some darn good power, better trajectory than 10mm, and is certainly more accurate at ranges over 150 yards. The only problem is I don't know if there are any magazines available for it that hold more than 10 rounds. Same issues with .450 Bushmaster and .50 Beowulf.

I thought about .30 Carbine and we know it's quite effective with soft points, but it's really stuck in the M1 as nobody seems interested in making a modern rifle for the cartridge.

I must be forgetting some obscure cartridge, but as of right now, it seems 10mm Auto is the only option that fits my criteria.
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Old January 22, 2020, 06:30 AM   #2
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I would like to see more guns in 30 carbine. The M1 are expensive in GI or repros. There are a lot of m1 carbines out there. I have a couple and would give a good look at a lower cost modern rifle.

I dont get the big deal in 10 vs 15 round magazines. I expect with how the 350 legend is catching on there will be many AR options soon. With google, 15 round:

https://shopwilsoncombat.com/AR-Styl.../TR-350LMAG15/

This maker says "20 round coming soon":

https://dura-mag.com/product/duramag...ainless-steel/

Too bad I was pulling for the 30 carbine.
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Old January 22, 2020, 02:41 PM   #3
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If .350 Legend is going to have 15 or even 20 round mags coming out, then I think I found what I'm looking for. 10mm is great, but .350 Legend is built specifically for AR's, so it's going to work with minimal issues. 10mm... IDK.
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Old January 22, 2020, 04:26 PM   #4
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The Ruger AR pistol in 350 Legend is sounding better and better.
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Old January 22, 2020, 04:39 PM   #5
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Kinda "old school", but 45 Winchester Magnum would be interesting. It would fit in an AR, overall length loaded is just over 1.5", and it can generate 1,500 ft-lbs of energy out of a 6" barrel, let alone out of a 10" AR pistol barrel. It's kinda the idea behind the 450 Bushmaster, so I guess magazine capacity would be about the same as the 450.

I personally think the 350 Legend is going to be disappointing long-term. It is basically a 200-250 yds cartridge, kind of a copy of the old 351 WSL. I know, I know, Winchester told us it will shoot 4 miles and hit a gnat in the backside, then make a sandwich and crack open a cold one for you . . . .
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Old January 22, 2020, 05:01 PM   #6
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If you really want big boom strait-wall in an AR; give Carl a call at Accuracy Systems and ask him about his 450 Marlin AR 10.
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Old January 22, 2020, 06:47 PM   #7
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I think of the 350 legend and the 450 Bushmaster as the modern day brush gun cartridge. Probably has to do with my affinity for the 35 Remington. I could see myself with a 350 legend bolt gun and at least a complete AR style upper chambered in the same, although I don't live in a state where straight walled cartridges are required for hunting. It's a caliber I'll keep an eye on.
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Old January 23, 2020, 01:10 AM   #8
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Originally Posted by Scorch View Post
Kinda "old school", but 45 Winchester Magnum would be interesting. It would fit in an AR, overall length loaded is just over 1.5", and it can generate 1,500 ft-lbs of energy out of a 6" barrel, let alone out of a 10" AR pistol barrel. It's kinda the idea behind the 450 Bushmaster, so I guess magazine capacity would be about the same as the 450.

I personally think the 350 Legend is going to be disappointing long-term. It is basically a 200-250 yds cartridge, kind of a copy of the old 351 WSL. I know, I know, Winchester told us it will shoot 4 miles and hit a gnat in the backside, then make a sandwich and crack open a cold one for you . . . .
A 200-250 yard range isn't a detriment to me, the goal here isn't to be 500 yard capable or knock your socks off energy like .45 Win Mag has, it's practicality, ease of reloading, and price.

I made this thread thinking 10mm is the way to go, but .350 is really starting to get my attention. I could set up a progressive press and crank out 200 rounds in 90 minutes using .357 Mag bullets I already have and have a hell of a day at the range.
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Old January 23, 2020, 04:32 PM   #9
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I worry that the 450 would just be too hard on the AR lower and me plus the bullets cost a lot (I'm not a reloader). 350 Legend seem to have rather soft recoil, more than the 5.56 but nothing like the 450. Both do seem to burn well in short barrels and in the pistol platform (at least much better than a 5.56 in a short barrel). I'm not looking for range, mostly good penetration with a bigger projectile than 5.56/.223. Looks like all one needs is the new upper and new magazines. No extra tuning required if I understand correctly.

For those who suggest why not the .300 Blackout I respond, don't care to confuse bullets with the 5.56/.223 and blow myself up.
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Old January 23, 2020, 10:25 PM   #10
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A 10mm would be fun, but I would not be happy with the short effective range.

A 30 carbine would also be fun, but again I would not be happy with the short effective range.

A 350L is a lot more of a gun. The good (for now) is that brass and components are ok and getting better. However, the round has enough taper such that it requires a full length steel sizing die. Loading is not near as easy as 10mm. I would consider this round to be just as involved as loading for say a 300 BO.

I have a 357AR that can use 223 basic brass and be loaded with 357 mag dies. It would be hard to recommend this wildcat now that the 350L is out.

A 450 seems to be a bit much for the desired application.

I really do not have any great suggestions that line up with the OP. A lever action 357 or 44 might actually fit better than an autoloader.
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Old January 24, 2020, 12:54 AM   #11
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Originally Posted by P Flados View Post
A 10mm would be fun, but I would not be happy with the short effective range.

A 30 carbine would also be fun, but again I would not be happy with the short effective range.

A 350L is a lot more of a gun. The good (for now) is that brass and components are ok and getting better. However, the round has enough taper such that it requires a full length steel sizing die. Loading is not near as easy as 10mm. I would consider this round to be just as involved as loading for say a 300 BO.

I have a 357AR that can use 223 basic brass and be loaded with 357 mag dies. It would be hard to recommend this wildcat now that the 350L is out.

A 450 seems to be a bit much for the desired application.

I really do not have any great suggestions that line up with the OP. A lever action 357 or 44 might actually fit better than an autoloader.
I agree, but I've already got the Henry in .327 and will be getting a Rossi .45 Colt in the Spring. My thoughts were a semi-auto rifle that would be less work required on a bottleneck to reload. I did see that only steel dies are made for the .350 which kind of stinks, but hopefully carbide dies will come in the future because my idea was to load on a progressive.
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Old January 24, 2020, 09:51 AM   #12
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Loading them on a progressive is not that big of a deal.

I load .30-30, .308., 6mm Remington and 5.56X45 on a Dillon.

I just FL resize first, then go to the Dillon. Sure, it';s an extra step, but once you start doing it, it's no big deal.
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Old January 24, 2020, 11:01 AM   #13
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For the 350L, I do not expect that carbide sizers will ever be available for a reasonable cost. The round is just too long.

Actually now that I think about it, there is a wildcat that does fit the OP pretty good, the Mini Mole. It is made using the 357AR reamer, but it is not run in as deep. It uses a much shorter case (same length as 360 Dan Wesson). With the longer case and higher allowed pressure, power level is closer to the 357 maximum than the 357 magnum. Since you are cutting the entire neck & shoulder off of 233 brass it is a whole lot easier to make than the necking up required for my 357AR. You load ammo using standard 357 pistol bullets seated deep enough so that the nose is just short of the side rib of a 223 magazine (Similar to the 300 BO concept). You get full capacity out of standard 223 magazines.

https://mdws.forumchitchat.com/post/...40174?trail=25
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Old January 24, 2020, 02:18 PM   #14
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There is no "best" anything.
"...M1's are expensive in GI or repros..." Some places think they're too evil to own too. And too many people believe the nonsense about frozen Chinese quilted jackets stopping Carbine bullet. And that the .30 Carbine is a pistol round and isn't powerful enough for deer(some of those places will let you use a .22 calibre varmint cartridge with no stipulation about the bullet though.).
The Carbine doesn't come anywhere near 900 ft-lbs at any distance, except ME. ME doesn't prove much of anything.
"...kind of a copy of the old 351 WSL..." So is the .30 Carbine. And the .401 SL.
"...350 Legend..." Is a 200 to 250 yard cartridge. However, the whole thing is dependent on what one intends doing.
"...900 ft/lbs of energy minimum..." At what distance? A 400 grain .45-70 has a bit over 1,000 ft-lbs left at 200, but drops 16.5".
Does "straight walled" to you mean handgun cartridges?
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Old January 24, 2020, 02:25 PM   #15
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Noreen has a 30-06 and I think a 338 lapua and maybe Cheytac in a AR platform

Oops my bad... those are not straight walled caetridges

Last edited by Old 454; January 24, 2020 at 02:32 PM.
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Old January 24, 2020, 04:24 PM   #16
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Originally Posted by T. O'Heir View Post
There is no "best" anything.
"...M1's are expensive in GI or repros..." Some places think they're too evil to own too. And too many people believe the nonsense about frozen Chinese quilted jackets stopping Carbine bullet. And that the .30 Carbine is a pistol round and isn't powerful enough for deer(some of those places will let you use a .22 calibre varmint cartridge with no stipulation about the bullet though.).
The Carbine doesn't come anywhere near 900 ft-lbs at any distance, except ME. ME doesn't prove much of anything.
"...kind of a copy of the old 351 WSL..." So is the .30 Carbine. And the .401 SL.
"...350 Legend..." Is a 200 to 250 yard cartridge. However, the whole thing is dependent on what one intends doing.
"...900 ft/lbs of energy minimum..." At what distance? A 400 grain .45-70 has a bit over 1,000 ft-lbs left at 200, but drops 16.5".
Does "straight walled" to you mean handgun cartridges?
I agree, no best anything, just what's best for me.

Muzzle energy, don't care much what energy is at distance, just muzzle given it's easier to measure.
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Old January 24, 2020, 04:27 PM   #17
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Loading them on a progressive is not that big of a deal.

I load .30-30, .308., 6mm Remington and 5.56X45 on a Dillon.

I just FL resize first, then go to the Dillon. Sure, it';s an extra step, but once you start doing it, it's no big deal.
I've never used steel dies before. Correct me if I'm wrong, but the cases only need to be lubed for resizing correct, not expanding/seating/crimping?

I'm okay with doing the resizing on a single stage and the rest on a progressive or the Lee turret press I have.
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Old January 24, 2020, 09:37 PM   #18
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One of the easiest ways to do a big batch would be to

Clean the batch
Apply a lube that you can tumble and then let dry
Then run the batch through your Lee turret press.
  • Size & de-prime
  • Expand & bell (if needed)
  • Charge
  • Seat
Then wipe off the brass if desired.

If you are open to this approach, the 300BO, 7.62x40, 300Ham'r, 350L are all medium rounds that work in an AR-15 platform with a standard bolt. Of the above, I like the performance and flexibility of the 7.62x40 (if you are willing to make you own brass from 223).

Last edited by P Flados; January 24, 2020 at 09:47 PM.
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Old January 24, 2020, 10:16 PM   #19
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It sure would be fun to start out with a clean piece of paper and deep pockets and come up with a 1.80 length (Mich) straight walled cartridge. Just about all the straight walled cartridges I've looked at still have some room for improvement (my 2 cent's) from the .357 Max to the .450 BM and all the "G Wiz" in between. Can we do better "Hell Yes" all it takes is Deep Pockets and someone that has a little time behind the "Wheel" using those kind of rounds.
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Old January 25, 2020, 01:40 AM   #20
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Quote:
Originally Posted by P Flados View Post
One of the easiest ways to do a big batch would be to

Clean the batch
Apply a lube that you can tumble and then let dry
Then run the batch through your Lee turret press.
  • Size & de-prime
  • Expand & bell (if needed)
  • Charge
  • Seat
Then wipe off the brass if desired.

If you are open to this approach, the 300BO, 7.62x40, 300Ham'r, 350L are all medium rounds that work in an AR-15 platform with a standard bolt. Of the above, I like the performance and flexibility of the 7.62x40 (if you are willing to make you own brass from 223).
If that's all it is, I could do this with other calibers and not have to get into buying brass for .350. One appeal to the .350 tho is .357 bullets compatibility.

I'll have to think on this more. The .350 has its advantages and disadvantages, while 10mm has them too.
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Old January 25, 2020, 09:13 AM   #21
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Quote:
Originally Posted by P Flados View Post
I really do not have any great suggestions that line up with the OP. A lever action 357 or 44 might actually fit better than an autoloader.
This
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Old January 25, 2020, 09:26 AM   #22
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Quote:
Originally Posted by TruthTellers View Post
I've never used steel dies before. Correct me if I'm wrong, but the cases only need to be lubed for resizing correct, not expanding/seating/crimping?

I'm okay with doing the resizing on a single stage and the rest on a progressive or the Lee turret press I have.
You only need to lube for resizing. I clean, resize/decap, tumbke to remoce lubs, then load normally.

One little tip I learned. Tumbling after resizing will often result in a granule of corn or walnut in the flash hole. So I remove the sizing die from the first station of the Dillon and screw in a RCBS universal decapping die. that knocks anything in the flash hole out.
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Old January 25, 2020, 12:09 PM   #23
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I built a 10mm gas DI AR and it is pretty amazing. On a 10" plate at 330 yards, I can go 10 for 10. I will eventually sell off the rest of my .450 Bushmaster stuff and go to .350 Legend.
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Old January 25, 2020, 08:41 PM   #24
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Bear in mind... most pistol bullets will probably expand very rapidly , and have shallow penetration at greater then their design envelop velocities.
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Old January 26, 2020, 05:59 PM   #25
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For 10mm, I have run 180 and 200 XTPs to just under 2000 in testing, they hold up. For 115s, I use a solid, and it performs perfect up over 2000.
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