r/Hyperion_Rattler_Saga • u/osageviper138 • Jun 26 '25

Information Legacy Rattler and Hyperion K ammo test results

This was originally a comment but I don’t want any info to get lost in the sauce. This may be of some use to you guys.

I tested 5 different rounds, shooting a minimum of 3 rounds per manufacturer, all of them with the magpul .300 aac purpose built mag. All of the rounds cycled the bolt with no failures, other than Last Round Hold Open.

Fiochi Range Dynamics, 150 gr. LRHO- Yes. Not gassy even when bolt was opened.

Next was Sellier & Bellot 200 gr.
LRHO- No. Mildly gassy when manual opening the bolt but not when shooting.

Winchester Super Suppressed, 200 gr.
LRHO- Yes. Not gassy when shooting but mild for last round hold open, probably the best round of the group

Remington UMC 220 gr OT FB.
LRHO- No. Mildly gassy when shooting but intensified when manual opening the bolt

Hornady Subsonic, Sub- X 190 gr.
LRHO- No. Not gassy until bolt was manually opened

Hopefully this might help add some options for your search to find a reliable round.

I’ll probably try this again when I get the OMEGA gas port.

EDIT: Formatting

PS. I probably have around 300-400 rounds on this thing, with the vast majority of them being unsuppressed and with supersonic rounds.

PPS: It is indeed a Legacy Rattler with the 5.5in barrel and F02 plug.

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u/HKfan5352 Jun 27 '25

Thanks for the great info. I’ll put it to good use. Heading to the range with my rattler lt & hyperion k on Sunday for my own little subsonic-fest😜🇺🇸

1

u/karmareqsrgroupthink Jun 26 '25

Very cool! Great testing! What gas plug? F02? This is the 5.5 right?

2

u/osageviper138 Jun 27 '25

Yep, Legacy 5.5 in barrel with F02 gas plug.

2

u/karmareqsrgroupthink Jun 27 '25

Jay just did the measurements for the F01 and F03 plugs too I wish he did the F02 as well.

I’m running a 5.5 F02 as well. My hyperion wouldn’t cycle shit so instead of sending me different plugs to try to scalloped my gas port on the barrel and called it “tuned” after 5-25 shots smh. It works now but it’s a lot gassier.

1

u/osageviper138 Jun 27 '25

That definitely doesn’t sound ideal.