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Posted: 2/15/2026 12:52:09 AM EDT
[Last Edit: tsymonds][Edited]
Built this rig about four or five years ago. Have always been a fan of the Fireball and have had an XP-100 for many years. The original prototype XP-100s were chambered for 222 Remington but had issue with muzzle blast and concussion from the 10.5" barrel. The 222 was shortened to make the Fireball round to solve some of that. Having run short ARs in 223 and having the same blast and concussion issues I had the bright idea that the same solution would possibly work. Had a custom 8" pipe made and converted some 223 brass which I loaded with some 36 grain Barnes Varmint Grenade pills. Runs on standard Pmags or Lancer mags with no issues and I get about 2900fps. At this point I'm at about 4-5k rounds and four classes with it. Converted brass lasts 8-10 reloads and I put it all on stripper clips for easy loading. I've run it out to 300yds or so but it"s really a 200-250yd rig and really shines from phone booth to about 200yds. A really good PDW setup. I have an identical upper chambered in 5.7 which runs the same diameter pill at 1900fps. Only advantage the 5.7 has is mag capacity. Anyway a couple pics of the current setup. 
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Originally Posted By 9D1Alpha: I like the numbers on that . Handy looking rig too . Thanks. It's definitely a handy setup and I have enough confidence in it at this point that it sits by the bed and goes in the truck. The Varmint Grenade pills are a compressed powder core hollow point and I've shot drywall and other stuff with it enough to feel good about using it for a suppressed house gun. Kinda wonder why the round wasn't looked at a bit more for this use case as I've found with the right bullet it solves a lot of the issues that crop up between normal PCC calibers including 5.7 and shorty 223. It recoils like a pellet gun, feeds from standard mags, uses standard AR BCGs, standard buffers, completely standard uppers and lowers, and normal diameter pills. I even made subsonic 221 Fireball using 77g OTM bullets. '60s tech repurposed as it were. |
Joined:
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Posts:
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NC, USA
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Years back had a 10" T/C Contender barrel in .221 Fireball. Lots of fun hunting crows with it. It is an underrated clambering. Nice rig in that pix. Not surprised that it is working for you. Keep us posted on how it goes.  ETA: the .221 F is more reloader friendly than the 5.7. |
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