Estimated reading time: 2 minutes
Last week on DemolitionRanch, Matt experimented with an ultra-high-velocity round that combines a .17 caliber bullet with a 5.56 case, resulting in a wildcat cartridge known as the 17-556.
Created by KAK Industry, this cartridge takes a tiny, lightweight 17-caliber bullet and pairs it with the power of a 5.56 casing, leading to extremely high speeds that Matt was excited to test.
The 17-556 cartridge moves much, much faster than standard rounds. Compared to a regular .17 HMR, which travels at around 2,500 feet per second (fps), the 17-556 can hit speeds of over 5,000 fps.
For reference, typical high-power rounds like .375 CheyTac or .50 BMG max out around 3,000-3,500 fps.
“It’s almost a mile per second at the muzzle,” Matt observed, pointing out the extreme velocity.
To showcase the speed difference, Matt tested both the .17 HMR and 5.56 rounds on various targets, including watermelons, ballistic gel, and bottles of Fanta.
The results were striking: the .17 HMR would puncture targets, but the 17-556 would cause dramatic explosions, showing the power increase from its incredible speed.
As Matt noted, “Exact same bullet passing through the exact same watermelon going twice as fast just made that difference. That’s insane.”
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The high-velocity rounds also performed well against different types of body armor. While the 17-556 couldn’t penetrate level IV armor, it went clean through level IIIA.
In ballistic gel testing, both the .17 HMR and 17-556 reached similar penetration depths, though the wildcat round created a larger wound cavity due to its higher speed.
In a final experiment, Matt tested different custom loads from CAC to see just how fast he could push the cartridge. Using 12.5-grain brass bullets, the 17-556 reached an impressive 5,220 fps, setting a new speed record for the channel.
The final test hit a simulated skull target, proving that even the smallest, lightest bullets could deliver substantial damage at these speeds.
With the 17-556, DemolitionRanch demonstrated the intense effects of speed and energy on small-caliber rounds.
As Matt concluded, this wildcat cartridge brings a unique approach to high-velocity shooting, showing just how much power can come from a tiny bullet when it’s moving at extreme speeds.
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The .17 cal/.22 cal case idea has been around for a long time. The .17/223 wildcat was developed in the mid 1960s. In 1968 Harrington & Richardson introduced the model 317 Ultra Wildcat in .17/223, making it the first domestic, commercially-produced rifle chambered for a wildcat cartridge. H&R then got together with Remington, made some slight changes to the case dimensions, and it became the .17 Remington in 1971. The .17/222 came along even earlier, in the 1950s.
This caliber/case concept has been around for decades. The .17/223 was developed in the mid-1960s. Harrington & Richardson introduced the model 317 Ultra Wildcat in 1968 in .17/223, making it the first domestic, commercially-produced rifle offered in a wildcat caliber. In a joint venture with Remington, some slight changes were made to the cartridge and it became the .17 Remington in 1971. The .17/222 was created even earlier in the 1950s. The .17/22 and .17/223 cases are almost identical, with only a 0.07″ difference in case length. .
“Exact same bullet passing through the exact same watermelon going twice as fast…”
I find it surprising that an “exact same” .17 HMR bullet can be fired at 5000 fps without coming apart in the air.
Just saying this, IT”S BEEN DONE ALREADY LOL!
.17 Remington
Production history:
Designer Remington
Designed 1971
Manufacturer Remington
Produced 1971
Variants 17-222/17-223
Bullet mass/type Velocity Energy
15.5 gr (1 g) BT 4,917 ft/s (1,499 m/s) 874 ft⋅lbf (1,185 J)
20.0 gr (1 g) BT 4,436 ft/s (1,352 m/s) 874 ft⋅lbf (1,185 J)
Try 110 GR in 300 win Mag
17 Remington – what’s old is new again, 53 years later. This wildcat appears to have a shorter neck and steeper shoulder for increased case capacity, but it’s otherwise similar in construction and performance. It’s appropriate to credit the lead up to new developments.
How do you figure one mile per second. Not even close. With that light of bullet can it even make a mile?
I don’t believe this is a new concept the military and experimented with tha same case and a .17 caliber bullet many years ago. You can even find a few of the original experimental rounds on Gunbroker.com
Don’t tell any psycho-Democrats about this.
Since its development in 1937 , I am certain there were those
that said ( in relation to the .22-250 ) “ why ? “
Browning began chambering for the round in 1963 , and the
rest was history . The reasons for such a round as the .17-556
are mysterious , and its use is questionable , but could we not
be witnessing the next wave in “ wildcats “ ?
Just wondering …………..
The excellerator was doing that decades ago.
I remember reading about the 220 Swift barrels back in the 70’s having a pretty bad reputation for sever throat erosion. Short of having a barrel made out of a metal like Inconel, I see the same problem, if not even worse. But I can only imagine hitting a prairie dog with that little missile travelling over 5000 FPS. PINK MIST! 🤯😱
I wonder how long the barrels last. I also wonder how well the little 17 cal bullet does in wind.
Roy Weatherby swore by high speed – high energy decades ago, most bullets were just not up to the task.
So is anyone manufacturing an AT barrel for this ammo?
220 Swift (develpoed decades ago) can push a .224 cal. 48 gr. bullet @ 4,100 fps. and a 42 gr. bullet @ over 4,200 fps. I’m quite certain the swift could push a lighter (say 30gr.) .224 projectile @ velocities matching the 13 gr. 17-556.
the custom loads were from KAK not CAC
Will the bullet stay together at that speed ? What kinda accuracy was achieved ? Because of the overbore what is the barrel life ?
I’ve been getting 4200 FPS from a 6mm for sometime now.
17 Remington with lightweight brass bullets?
So you have never heard of the 17 Remington??
Regarding the 17-556
Wouldn’t a round like that burn out a barrel fairly fast. Say after firing 500-1000 rounds?
I assume you could use half the twist to generate the same amount of spin on the bullet?
Probably faster than that, especially with brass bullets(which are harder than solid copper/copper jacketed bullets.)
Remington tried something like this with the .17 Remington introduced in 1971
Nice to see you’ve reinvented the wheel.
I’ve been using my old Lyman mold for the 145gr. Keith HP for years now.
Together with my Combat Master Piece in 38Spl. we have fed many a jackrabbit to the coyotes.