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10mm big bore cartridges

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11 October 2025, 04:57
boom stick
10mm big bore cartridges
One thing I love is pistol bullets being used in big bore cartridges. 10mm Auto and 400 Legend is becoming more popular and thus more pistol bullets available. I was thinking that like the 40 BSA there can be more .400” or 10mm big bore cartridges. 10mm-308? 10mm Whelen? A 10mm Whelen with pistol bullets should be able to use short actions (2.8”-3”) a 308 cartridge could just be necked up with the same shoulder diameter and have a small shoulder like the 400 Whelen has. On the 06 case, a 10mm bullet would be a tad larger than the 400 Whelen. I think a 10x57 would be a great cartridge for Mauser actions and fit nicely in short actions. A good pig smashing round to be sure. 10mm Njiri? That’s what they call a warthog in Kenya. A good Pumbaa cartridge. Disney would send a cease and desist letter if I did that Big Grin 10mm Kiboko (Hippo in Swahili) would be a good name for a 10-9,3x62 variant. Just a simple neck up. There could be a good argument for the resurgence of the 40 BSA from 1921. The 40 BSA is .400” bullet with taper and no shoulder on a 375 HH case but I think it was around 2.6” case length but not sure about that.


577 BME 3"500 KILL ALL 358 GREMLIN 404-375

*we band of 45-70ers* (Founder)
Single Shot Shooters Society S.S.S.S. (Founder)
11 October 2025, 06:53
shootermetal
Well some of the stuff you wish sorta exists, almost. The 10mmx57, there's the 9.3x57. Also there is a 400 Whelen. You might like the 375 Raptor, look it up.
11 October 2025, 06:58
Kyler Hamann
Don't forget the 10mm Magnum. I've been playing with it in a revolver lately. Starline makes brass.


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11 October 2025, 14:53
p dog shooter
I have shot thousands of pistol bullets in rifles.

I have found the that the performance at rifle velocities leave something to be desired.

Fun to shoot, cheaper to shoot but then performance on larger game can be lacking.
11 October 2025, 20:32
boom stick
Yes, some pistol bullets are not good at large game but the 10mm has bullets literally meant for bear. I would find out what the bullets do at higher velocities and adjust. My initial thought was to make a 30-30 straight wall with 10mm bullets. I think that would be a fun round and probably push 180 grain bullets around 2,000 fps at the muzzle easily.


577 BME 3"500 KILL ALL 358 GREMLIN 404-375

*we band of 45-70ers* (Founder)
Single Shot Shooters Society S.S.S.S. (Founder)
12 October 2025, 15:17
p dog shooter
quote:
My initial thought was to make a 30-30 straight wall with 10mm bullets. I think that would be a fun round and probably push 180 grain bullets around 2,000 fps at the m


Yes that would be a fun round.

Meant for bear at pistol velocities is different then meant for bear at rifle velocities.

Over expansion and under penetration can be a problem when using pistol bullets at rifle velocities.

I am not against it and it can be a lot of fun.

Just be careful
12 October 2025, 19:56
shootermetal
I built a 35-40 last year on and cut down old Krag rifle I had. Very impressed with it.
13 October 2025, 17:35
buckdeer
A 405 winchester short using 303 brass and 405 dies maybe worth a look at. Not .400 but very close and you can use pistol bullets
13 October 2025, 20:58
buckdeer
303 tapered not necked to .400 would work as well but would require a reamer and custom dies. Would be legal to deer hunt with in several states as well.
13 October 2025, 23:12
boom stick
quote:
Originally posted by p dog shooter:
quote:
My initial thought was to make a 30-30 straight wall with 10mm bullets. I think that would be a fun round and probably push 180 grain bullets around 2,000 fps at the m


Yes that would be a fun round.

Meant for bear at pistol velocities is different then meant for bear at rifle velocities.

Over expansion and under penetration can be a problem when using pistol bullets at rifle velocities.

I am not against it and it can be a lot of fun.

Just be careful


Solid copper or brass would obviously be best at high velocity but hog velocity could be 2000 FPS at the muzzle and much less at 100 yards. I think the best use case would be a 30-30 case and a 308 or a 57mm case unless you are swaging down 405 bullets to match the 405 Win in a smaller package.


577 BME 3"500 KILL ALL 358 GREMLIN 404-375

*we band of 45-70ers* (Founder)
Single Shot Shooters Society S.S.S.S. (Founder)
13 October 2025, 23:14
boom stick
quote:
Originally posted by buckdeer:
303 tapered not necked to .400 would work as well but would require a reamer and custom dies. Would be legal to deer hunt with in several states as well.


Lots of fun options have been bouncing around in my head like a sped up pinball machine


577 BME 3"500 KILL ALL 358 GREMLIN 404-375

*we band of 45-70ers* (Founder)
Single Shot Shooters Society S.S.S.S. (Founder)