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Posted: 8/2/2026 2:20:58 PM EDT
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It is intriguing that hyper velocities can now be obtained from standard chambers. But how can a direct impingement system handle that extra pressure? |
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Same as with 5.56 vs 223 pressure, smaller gas ports and heavier buffers, as everyone has already stated. Not that complicated once you've got a specific load dialed in, and a rifle that's designed to operate at those pressures, either through parts geometry, or metallurgy. Where it gets fucky is when contracts demand cross compatibility with standard 5.56, there's no good way to do that without adjustable gas, and the half decent options for that on an AR15 are limited. It's more likely that the HICAR will end up using a piston gun with a 2 or 3 position gas valve with standard, HV, and possibly an adverse HV position. |
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Originally Posted By 308Sako: It is intriguing that hyper velocities can now be obtained from standard chambers. But how can a direct impingement system handle that extra pressure? I thin adjustable gas will be key, and that itself - creating a 'military reliable' adjustable gas system for di - will be a big deal. Its also possible Federal PEAK uses a very fast burning powder, that has a high pressure at start, yet due to burning up quick has normal pressure by the time it reaches the gas port. That's my current hypothesis at least. |
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Originally Posted By spydercomonkey: I thin adjustable gas will be key, and that itself - creating a 'military reliable' adjustable gas system for di - will be a big deal. Its also possible Federal PEAK uses a very fast burning powder, that has a high pressure at start, yet due to burning up quick has normal pressure by the time it reaches the gas port. That's my current hypothesis at least. Yeah, from what I heard Federal is claiming no increase in backpressure. |
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Originally Posted By 308Sako: It is intriguing that hyper velocities can now be obtained from standard chambers. But how can a direct impingement system handle that extra pressure? At this point... no one is saying. NOTE... video posted , Jan. 25, 2025 Also...this is with a 64gr bullet... I strongly suspect it is a 64gr TBBC bullet... which would explain why there is "all of a sudden" so much 5.56 64gr TBBC ammo/ bullets around. Bear in mind , with that increased velocity... comes more barrel erosion over a "standard" 5.56 load. So, that will need to be addressed. ( Proof PXT / Seekins barrel tech ?... or some new barrel material / bore coating ? ) Maybe a stronger bolt material ? ( G's carpenter 158 + bolt ?... 5x the life ) "G" has produced stronger gas tubes , .812 barrels and their "Super HBAR Straight Gas Tube" "G" has also been looking at improved "barrels". So far Geissele "seems" to be making / involved in all sorts of "stronger / more durable" parts. And IMHO, that implies ( to me ) that someone ( Uncle Sugar ) wants a more durable AR capable of handling higher pressures. So... I guess I am saying.. no one has let the cat out of the bag yet. And we get to wait. ( I also would like to know and "own" a AR capable of using PEAK alloy 5.56 ) I also would like a 6.5CM AR capable of using the new 6.5CM PEAK ammo. FWIW... 6.5CM was chosen for the next PEAK alloy ammo release , over 308, because ALL 6.5CM rifles use "modern" high pressure "steels" Any previous 308 semi auto might be "weaker" or not up to snuff, given the age of various 308 produced semi autos / bolt guns. I find it interesting, that no AR manufacturer has come forward and stated that ANY AR that they make, is capable of using PEAK ammo. Including Geissele. So maybe there is some "secret sauce" needed for the increased pressure ammo in a ( any )AR . And given the videos limited info.. who knows what , if any alterations were done the the "AR" . FWIW...  Federal’s Peak Alloy is changing ammo w/ 7mm BC. This case tech increases velocity w/ similar recoil |
*Hold on to your AR-15s. Their magic must be very powerful, or they wouldn’t want them.*
JAFOM.... Just another fat old man.
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TOGC,IADC
JAFOM.... Just another fat old man.
________________________________
TOGC,IADC
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The answer to the question is: "It depends." The pressure varies as a function of time, faster powders build pressure early and then it drops off quickly, slow powders build pressure slowly and it drops off slowly. So, whether the pressure at the port is higher or lower than standard 5.56mm depends on what powder is used, and what the actual peak pressure is. How any gas system handles this will be the same, decrease port size, increase reciprocating mass, or increase the operating volume, it won't matter if it is DI or a conventional piston. |
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I will be experimenting with this soon enough. Ordered some 277 Fury brass and will resize it into 6.5 CM. A couple of rifles will be used. Bolt action first since it is easier then on to an AR10 type. 20" barrel and adjustable gas block. The plan is cut the gas to minimum and slowly increase it until the rifle functions. Of course watching brass etc. while doing so. I believe modern metallurgy has increased the strength of steels to the point they can handle these pressures, we just have to test it out and see if it works. |
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