[panatomicx]

Always thought the AR-15 lineup was missing a link at .40-caliber, but now there's the 400AR that uses a Carcano parent case. Any thoughts or opinions?

 

[broom_jm]

Not sure who wrote that article, but there is no such thing as a "458 Bushmaster". There is a 450 Bushmaster and a 458 SOCOM, which the writer seems to have gotten confused, but that's not a big deal.

Overall, the cartridge is "OK", but I've never been a fan of higher pressure rimless cartridges that headspace on the case mouth. They are a pain in the neck to reload because case length is so critical.

A rimless 35 Remington would be a much better choice, given the limited selection of suitable bullets available in 40 caliber. For that matter, the 358 Gremlin wildcat (7.62x39 necked up) would be a very good choice. I know you couldn't double-stack, but in hunting situations, more than 3 or 4 rounds is almost never indicated.

Not a total waste of time, but not something I'd get all that excited about, either.

 

[Big Bore]

TROMIX is doing preliminary testing on the 10 mm SOCOM, a .458 SOCOM necked down to .400. The biggest two problems we are expecting are: will the bullets stabilize and shoot accurately, and will pistol bullets hold together at twice the velocity they were designed for. While a 1:15 twist is fine for a 200 gr. bullet at 1200 fps, is it going to be too fast for the same bullet at 2300 fps, we think. Twist calculators say a 1:22 to 1:32 is needed but the only barrels we can find are either way too fast or way too slow. The rifles are built and the ammo loaded, now we need a break in the weather for testing which should happen in the next week or two. This is not expected to go into production but that could change if the accuracy is better than we think it will be and the bullets hold together.
It's going to be a fun project regardless. Test results can be followed on the 458socomforums.

FYI, headspaces on the shoulder, case length is therefore not critical, and it operates at the same low pressure as the .458 SOCOM, .475 TREMOR, and .375 SOCOM, 35-37.5K psi. Brass will last forever at this level and it is common for .458, .475, and .375 brass to last over a dozen loadings, especially if you anneal after forming. And it uses unmodified AR-15 magazines and to convert all you need is a barrel and bolt and to enlarge the ejection port.

 

[Big Bore]

I got to test the 10mm SOCOM today and it performed better than I ever dreamed it would. Here is a link to the results.

 

[broom_jm]

Any plans to test with the ML bullets, Big Bore?

 

[Big Bore]

ML? Muzzle loader? Not sure what you mean. The only bullets I am testing are the 200 gr XTP and the Sierra 135 gr Sportsmaster HP.

I did water and penetration tests today and I got results I never dreamed I would. They are posted in this thread

 

[broom_jm]

ML? Muzzle loader? Not sure what you mean. The only bullets I am testing are the 200 gr XTP and the Sierra 135 gr Sportsmaster HP.

I did water and penetration tests today and I got results I never dreamed I would. They are posted in this thread

https://www.midwayusa.com/product/1...in-hollow-point-flat-base-lead-free-box-of-24

https://www.midwayusa.com/product/4...liber-200-grain-super-shock-tip-sst-box-of-20

Of the two, I would expect the SST bullets to work very well and not cost as much as the all-copper Barnes option.

 

[carpooler]

reformed Kalisnakovs

Its been written about, but I haven't tested it, that you can re-form the AK round into 401 WSL's, by using the brass cases only. This one should have very close to the case capacity of the 41 S&W magnums. Seating out the 0.410 caliber bullets, brings things up to the 401 WSL's capacity. This one may have to head space on the case mouth, but shooting these in an original Win. M-1910, means that it head spaces on the cases' semi-rims, only.

I've been angling for a left ported AR-15, which is chambered for the 401 WSL. The originals put out too much fire and sparks right in front of my nose. I used to have the Lyman 410426 R.N. mold. Cast soft, it dropped bullets right at 250 grs. This would be a handful at 1650 fps, out of an AR-15. It would duplicate the original Black Powder Express load ( 265 gr. F.P. lead bullet ) shot out of a 40 - 82 Win.

A real "Old Timer", the late Gaye Randall, told me back in the late Sixties, that his dad's, M-1886 used these 265's to put paid to numerous Grizzles, on the Randall Ranch, which is now the N.E. Corner of Yellowstone Nat'l Park. He said that they later came out with a 300 gr. bullet, but that it didn't kill the Great Bears with the same proficiency.

So there's a sweet spot for bullets around 40 caliber, weighing 250 to 265 grs., at around 1650-1750 fps. So if you can match these old 40-82 Win. express loads, in the AR-15, then you are really doing something.

 

[Big Bore]

I am not personally interested in testing them for two reasons, neither is available (I have not looked elsewhere) and they are a lot more expensive than normal .400 bullets. If I were going to use those types of bullets I'd break out the .458 SOCOM, 300 gr. TTSX at 1700 fps or the 250 gr. Hornady GMX at 2000 fps. Or the .375 SOCOM with a 200-220 gr bullet at 2350/2150 fps respectively.

After a night of thinking about those ML bullets, I think I will test them out if I can find any. Why not? It would certainly make this a longer range rifle and much more suitable for deer. The handgun bullets explode so rapidly that penetration is quite limited and I am not sure I would want to use them on larger game, but the ML bullet might be just the ticket. I don't see it doing anything the .375 or the .458 cannot also do but since when does that matter?

Thanks for putting the bug in my ear.

 

[broom_jm]

I am not personally interested in testing them for two reasons, neither is available (I have not looked elsewhere) and they are a lot more expensive than normal .400 bullets. If I were going to use those types of bullets I'd break out the .458 SOCOM, 300 gr. TTSX at 1700 fps or the 250 gr. Hornady GMX at 2000 fps. Or the .375 SOCOM with a 200-220 gr bullet at 2350/2150 fps respectively.

After a night of thinking about those ML bullets, I think I will test them out if I can find any. Why not? It would certainly make this a longer range rifle and much more suitable for deer. The handgun bullets explode so rapidly that penetration is quite limited and I am not sure I would want to use them on larger game, but the ML bullet might be just the ticket. I don't see it doing anything the .375 or the .458 cannot also do but since when does that matter?

Thanks for putting the bug in my ear.

Now yer talkin'!

I was mostly thinking they would be the right weight/length for the ROT in the barrel. Also, it would make for yet another Indiana-legal option, presuming the necked down case doesn't exceed 1.800"?

 

[nvshooter]

Is there a .358-caliber mildcat for the AR platform? Could use AK brass... maybe?

 

[Big Bore]

The max case length is 1.590" with a TTL OF 1.580".

With the way IN laws are changing with HB-1231 who knows what will be legal by deer season?

The .358 SOCOM is doable and would work in an AR with no mods except barrel and bolt and enlarging the EP, the same as with all .458 SOCOM cases variants.

By the way, I found some of those H 200 gr ML bullets in stock. I wish they were heavier than 200 gr., like maybe 250 gr., but at least they have a better BC than the XTP and are designed for higher velocities than the XTP.

 

[panatomicx]

When asked if the .40 SST ML bullets could be purchased by themselves, Hornady sales answered, "We do not sell this bullet by itself, we apologize for any inconvenience this causes." Perhaps if they received more inquiries...

 

[broom_jm]

Is there a .358-caliber mildcat for the AR platform? Could use AK brass... maybe?

Like this?


358 Gremlin, the 9x39 USA

 

[Big Bore]

When asked if the .40 SST ML bullets could be purchased by themselves, Hornady sales answered, "We do not sell this bullet by itself, we apologize for any inconvenience this causes." Perhaps if they received more inquiries...

Nosler said the same thing about their 300 gr. .458 diameter ML bullet but after being deluged with phone calls and email requests, they did release it without sabots, at least for a while. I don't know if they still sell it without sabots or not because I have not followed this bullet, so if Nosler will do it, you can bet Hornady will also IF they think it will increase sales and turn them a profit.

IF, and it is a big IF, if a group buy were to be arranged with a minimum order of 10,000 bullets, or whatever Hornady would set as the minimum, then one could very likely get a special run sans sabot (how about that, mixing English, Spanish and French).
Graf & Sons price per 20 (C&R dealer) was less than $11 so at that price I can toss the sabots or give them to someone who might use them in their ML.
And here is a thought, put a bug in Graf & Sons' ear because they are well known to do bulk buys for groups wanting special quantities of not exactly off the shelf items. They did this for Starline nickel .458 SOCOM brass and I am 90% certain they did this for the Nosler .458 300 gr. ML bullet sans sabot.

 

[panatomicx]

It's Alive!

Congrats on the birth of your new 10mm SOCOM wildcat, Big Bore. Enjoyed your reports, especially the water jugs.
FYI A sample of Thompson Center ML bullets (from Buds) measured .4000 in the majority, while the Hornady ones were mostly .3995. Hope you try some on the jugs.
Mentioned in the now abridged report is that with 135gr pistol bullets, the 400AR had a velocity of 3,042 fps, but with its greater capacity, it'll be interesting to see what yours can do.

 

[Big Bore]

Congrats on the birth of your new 10mm SOCOM wildcat, Big Bore. Enjoyed your reports, especially the water jugs.
FYI A sample of Thompson Center ML bullets (from Buds) measured .4000 in the majority, while the Hornady ones were mostly .3995. Hope you try some on the jugs.
Mentioned in the now abridged report is that with 135gr pistol bullets, the 400AR had a velocity of 3,042 fps, but with its greater capacity, it'll be interesting to see what yours can do.

First of all, this is not "my" wildcat but dreamed up by Tony Rumore of TROMIX. Tony got a hair over 3000 fps with the 135s but at higher pressures than 35-37K psi, probably up around 42K psi. In fact, using a 22 inch barrel QL says you get 3042 fps at 42000 PSI with N200. This load would be a mild load in a bolt action but creates way too much back thrust on the AR-15's bolt for sustained use. It might hold for several hundred rounds but it won't hold forever before the bolt lug fatigues and breaks. At 35-37K PSI ANY SOCOM based round will give the same backthrust as the 5.56. The .400 AR sounds like a ballistic twin of the 10mm SOCOM with these notable exception.
1. The 10mm SOCOM works at pressures at 35-37.5K psi so at those pressures it is likely a little slower than the .400AR operating at much higher pressures.
2. The 10mm SOCOM is a bottleneck cartridge that headspaces on the shoulder, not the mouth, therefore, case length is not as critical.
3. Standard AR 5.56 mags are used with no mods.
4. Since it works at lower pressures, case life will be very long.
5. Since it operates at lower pressures there will be less stress put on the AR platform. While the .400AR is currently operating at over 50K, I don't personally expect a long and uneventful bolt life unless they are using special bolts and BEs. This is the same problem the .375 REAPER guy ran in to but refused to admit it, and eventually went belly up. If you tone down the .400AR to more conservative working pressures that do not put excessive backthrust on the bolt, then a slight edge on velocity will go to the larger capacity 10mm SOCOM. That is not a slam on the .400AR, just physics and since the 10mm SOCOM is not planned on being put into production, it will not be a competitor to the .400 AR.
6. It feeds and function with all bullet weights tested, Tony has tested loads with bullets as light as 135 gr.
7. The only down side is that there are no CURRENT plans to make the 10mm SOCOM a production item.

 

[nvshooter]

Like this?


358 Gremlin, the 9x39 USA

Exactly, Jason! What a perfect idea. Not that I'd ever want one. I was just wondering...

 

[panatomicx]

The 400AR has a case head of .447, while the 6.5 Grendel has .445 and is SAAMI rated at a maximum average pressure of 52,000 psi, so does the 400AR max of 50,000 seem excessive? Also the 400AR case hasn't got a shoulder and very little taper, so doesn't that combine to produce less thrust on the bolt? And is it really fair to compare a .308 parent case wildcat like the .375 REAPER to 7.62x39/400AR-sized cartridges?
Anyway, it'll be interesting to see how the 400AR, the 10mm SOCOM and other wildcats develop to fill in the AR-15 10mm/.40 caliber gap.

 

[broom_jm]

The 400AR has a case head of .447, while the 6.5 Grendel has .445 and is SAAMI rated at a maximum average pressure of 52,000 psi, so does the 400AR max of 50,000 seem excessive? Also the 400AR case hasn't got a shoulder and very little taper, so doesn't that combine to produce less thrust on the bolt? And is it really fair to compare a .308 parent case wildcat like the .375 REAPER to 7.62x39/400AR-sized cartridges?
Anyway, it'll be interesting to see how the 400AR, the 10mm SOCOM and other wildcats develop to fill in the AR-15 10mm/.40 caliber gap.

Take a look at all the available rimless rifle cartridges over the last 100 years or so, and notice how few of them are straight-walled jobs. There is an excellent reason for this. A rim provides a good means of headspace and a datum on the shoulder an even better one. The case mouth itself, by comparison, is a poor means of headspace, especially if one reloads.

In fact, there is but one high-pressure rifle cartridge that was relatively popular while being both rimless and shoulder-less...the 30 Carbine. If you have ever reloaded for 30 Carbine, you know how critical it is to measure case length each and every time, making it a pain in the thumb, so to speak.

The 400AR is a non-starter, for me and I suspect the general shooting populace will feel the same.