.30 BRX (7.62x41mm) in an AR15 rifle

[Bruce Drake]

From top to bottom
308 Win with 150gr Spirepoint
308 Win Case
308 Win trimmed to 41mm (308x1.5”)
308 Win first form
308 Win neck and shoulder formed for 7.62x41
308 Win inside neck-reamed and final trimmed
7.62x41 final formed and loaded with a 110gr RN

My great idea....has been thought of before. A decade ago a national champ in Benchrest Rifle developed the .30 BRX from the .30 Benchrest for use in 300M international use in a bolt rifle and the gunsmith who developed the 300Blackout about that same time tried to develop a 30BRX AR15 upper at the same pressure levels as the bolt rifle (55PSI) but it didn’t work well for him as it required a thickened upper receiver and a high-strength bolt which made it too much $$$ for commercial use. That said, I intend to develop the 7.62x41 load as a 30-30 Winchester equivalent and same pressure levels (42K PSI limit - also due to the 450 Bushmaster AR15 bolt I'm using) which would mean it outperforms the 7.62x39 at least which the 7.62 Herrett Rimless was about equal to in performance in my 16" barreled AR15 upper.

A slightly bigger cartridge and slightly more powder than my earlier post about my 7.62 Herrett Rimless wildcat (trimmed down and necked up 6.8 SPC) but with the 450 Bushmaster bolt and a 6.8 SPC magazine for my AR15, it runs pretty smoothly. Some days, you don’t need the fastest and hottest cartridge to be an effective deer and pig cartridge. Now I actually do have a "30-30" AR15

(and forgive the jacketed bullets in the pictures. I'm doing cast loads in the next round of testing.)

Bruce

 

[Ian]

Ahh, the things we do for love.

There are at least half a dozen ways to turn an AR-15 into a .30 WCF (the 7.62X40 WT and 7.62X39 Soviet are fine examples), and I get a kick out of it every time a new way is dreamt up.

 

[CZ93X62]

The 30/30 WCF performance envelope is a very capable bracket to play within. Cast bullets of conventional construction work well, and it is easy to engineer a jacketed controlled-expansion bullet for that velocity range.

 

[popper]

Or 7.62x41 with 358 bore?

 

[Bill]

Already been invented and abandoned, it was called 30 remington

Bill

 

[Bruce Drake]

loaded at 2100fps with a lyman 311359 over 23gr of Accurate 1680.

Regarding the post about .30 Remington. That would be the .30 Remington AR which was built off the rebated rim 284 Winchester case. That case failed for multiple reasons:
non-popular base cartridge (how often do you find .284 Win brass available on local gunshop shelves for reforming)
unique magazines with limited capacity (4 rounds in a standard AR15 10-round magazine size)
Remington loaded the original commercial ammo to too high of a pressure which caused multiple issues with the bolts failing along with brass flow issues.
Inordinate expense (Only Remington made the R25 rifle)

Using .473 parent cases allows me to easily trim back 308Win or any other .473 case head cartridges back to the 1.5" case length
Using the .450 Bushmaster bolt carrier group forces the cartridge to stay within the 42K PSI limit its rated for but well within the same 30-30 winchester pressure levels of the lever-rifles its loaded for. The case also provides more space for powder than a 7.62x39 cartridge which also allows the reloader to use starting loads for 7.62x39 while dropping pressure lower than the x39 case puts out. USing 125-170gr bullets in a 1-8" twist barrel should allow me to duplicate the 30-30 Ballistics

But hey, its a WILDCAT. If you want an easy 30 caliber AR15 chambering, go with 300BLK or 7.62x39. I've gone past those initial offerings.

I own 4 AR15 rifles in 308 caliber (300BLK, 7.62x39, 7.62 Herrett (.308-6.8SPC trimmed down) and now .30BRX.

I'm a retired Army Ordnance Officer, experimenting with calibers is what I do in my free time.

Bruce

 

[Bruce Drake]

Or 7.62x41 with 358 bore?

I guess you could start with 35 Herrett load data but finding a 35 caliber AR15 barrel with a gas port would be a custom barrel from the start.

Bruce

 

[Bruce Drake]

Ahh, the things we do for love.

There are at least half a dozen ways to turn an AR-15 into a .30 WCF (the 7.62X40 WT and 7.62X39 Soviet are fine examples), and I get a kick out of it every time a new way is dreamt up.

the 7.62x40WT/.300HAMR is a way to get better performance than the 300BLK but its still a 5.56 parent case so very limited on powder selection and powder space and it doesn't equal the 30-30Win in performance past 100 yards.

 

[CZ93X62]

You KNOW you're in fast company when Caliber Wars morph into tech-speak half-way through the thread's first page.

 

[Missionary]

Howdy Bruce
Keep at it ! Forget the "Nay-Sayers". Why if no one ever ventures down the unknown paths who will ever see where it ends up.

 

[CZ93X62]

No doubt about it, Missionary. Rabbit holes are fun, interesting places.

 

[Bruce Drake]

You KNOW you're in fast company when Caliber Wars morph into tech-speak half-way through the thread's first page.

War? not even.

 

[Hawk]

I load the 7.62x40WT and it's great.
5.56 cases, magazines, BGC etc., but more power than a 5.56 or .223.
2" high at 100 yards equals 2" low at 200.
A great pig gun.

 

[Ian]

I enjoy AR-specific wildcatting immensely and am glad I'm not the only one on this rock
who does, so I'm not naysaying at all.

On the .30 Remington, I have no experience with it but thought it was the .30-caliber version of the rimless .35 Remington that was introduced in their self-loading rifle sometime about 1908 IIRC. The RAR being a totally different animal.

Bruce, I know you've been working quite successfully with powder-coated cast bullets in several cartridges and look forward to more reports on this new toy, please keep 'em coming!

 

[CZ93X62]

25-30-32 Remington were birthed in direct competition with Winchester's rimmed levergun rounds of similar caliber in the 1894-series arms. The Rems were rimless for self-loading rifles, and the calibers matched each other closely in terms of velocity between diameters and makers. All three used the .422" head diameter now seen in 10mm and 40 Short & Weak pistol rounds. Remington also recycled the head size in its 6.8 x 43 SPC series cartridges. Nothing new under the sun, sports fans.

 

[RBHarter]

32 Rem ,30 Rem fired , 30-30 , 32 Rem factory , 6.8 SPCII .

They may share data , but they aren't the same really .

 

[fiver]

Already been invented and abandoned, it was called 30 remington

Bill

and reinvented as the RAR when Remington redid it in the AR.

 

[Bruce Drake]

I load the 7.62x40WT and it's great.
5.56 cases, magazines, BGC etc., but more power than a 5.56 or .223.
2" high at 100 yards equals 2" low at 200.
A great pig gun.

and the drop at 300 yards is....
The WT is an improvement on the 300BLK but will never equal a 30-30 Winchester with 150gr bullets.
Wilson doesn't even provide 150gr loading data on its website (https://shopwilsoncombat.com/762x40-WT/departments/411/)
That said I used their own load data as the basis of when I was experimenting on a .30 Apache chambered AR15 (30 Apache is a full length 5.56 case opened up to 308 but is limited to 125gr or less bullets in an AR15 due to magazine OAL restrictions) a few years back. I ended up pulling the barrel as the shoulder on that wildcat was too far forward and too small for effective and consistent headspacing.
Attached are the factory ammo drop and drift tables (a&b) for 7.62x40WT (100 and 125gr bullets) and then the D&D table for the factory hornady 30-30 150gr RN (c) and my starting load for my 155gr Lee Spirepoint poly-coated cast bullet at 2200fps with Accurate 1680 (d) and my 30-30 matching load with the same bullet at 2350fps with H4895 (e)
a b c d e

That increased case capacity of the 30BRX does come in handy in comparison to those smaller cartridges trying to match the 30-30 loads.

 

[CWLONGSHOT]

Already been invented and abandoned, it was called 30 remington

Bill

I was gonna suggest that one. I picked up a small bunch if brass one day. There was 6mm PPC AND GRENDELS AND 30 AR. I didnt know the 30 AR was so fat! Its a chopped 30/06-308 .473 head isnt it??
I have never been a 270 guy and pupu the 6.8 for years. Going with the Grendel. But recently I was sorting a pail of brass only to find about 4/500 6.8 & 7.62x39 Brass cases!! Now I got my brain swriling do I now "need" a 6.8 & Ruski??

CW

 

[Bruce Drake]

I was gonna suggest that one. I picked up a small bunch if brass one day. There was 6mm PPC AND GRENDELS AND 30 AR. I didnt know the 30 AR was so fat! Its a chopped 30/06-308 .473 head isnt it??
I have never been a 270 guy and pupu the 6.8 for years. Going with the Grendel. But recently I was sorting a pail of brass only to find about 4/500 6.8 & 7.62x39 Brass cases!! Now I got my brain swriling do I now "need" a 6.8 & Ruski??

CW

the 30RAR put out by Remington is a 284 Winchester case cut-down and reformed to 30 caliber with a rebated .473 rim.
both the 6.8SPC and 7.62x39 are great little cartridges to experiment with. I never really delved into the 6.8SPC or the 270 because of the lack of cast bullet molds in that caliber. I think RCBS puts out one mold, SAECO another and then Lee recently added one. other than those three, its a custom mold route for 270 caliber bullets I feel.