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Posted: 7/22/2026 2:36:01 PM EDT
[Last Edit: man_o_brass][Edited]
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For background, Henry Supreme lever actions use a standard AR-15 bolt and barrel extension. We've been having problems with sticky bolts in Supremes chambered for 6 ARC and 338 ARC. We've ruled out enough things that we currently believe that this problem is being caused by the cartridges stretching excessively when fired and leaving the boltface under mechanical pressure. (We sometimes see a very similar issue in bolt action magnums with stretchy titanium actions) edit: I should add that we aren't the only ones seeing this problem with ARC calibers in the Supreme. As the post title says: who makes the toughest, stiffest barrel extension that might help minimize any excessive cartridge stretching? JP was my first thought, but they only sell AR-10 extensions. |
| You're quite right. We've tried chambering one so tight that it was snug on the go gauge, and closing the action on a live round required a slight but noticeable amount of extra force. This reduced the issue, but didn't resolve it. |
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There are not very many actual manufacturers of barrel extensions, especially after Whitworth Tool and Decimet both quit. You're left with Asteroid Precision and Slabe Machine, that I know of. You'll need to buy 384ea at one time from Slabe. Not sure on the minimum quantity for Asteroid, but it's probably at least 100. If you just want a couple, you're a pimple on the bull's ass with these guys. Tony |
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Originally Posted By HighpowerRifleBrony: It is not the lack of primary extraction? Originally Posted By HighpowerRifleBrony: It is not the lack of primary extraction? We've ruled out primary extraction. Unlocking the bolt still takes excessive force even when the extractor and ejector are removed. Once the bolt is opened, the spent cases will fall out of the chamber by gravity alone. At the moment, all signs are pointing to an extra thou or two of chamber stretch during firing due to the increased bolt thrust of the ARC rounds. Originally Posted By TGWLDR: Some are utilizing 17-4 PH SS citing superior tensile strength and corrosion resistance compared to standard 8620. I have read this anecdotally, but I have yet to find anyone openly selling 17-4 extensions. The search continues. Originally Posted By lfagan: Phoenix Weaponry makes an S7 tool steel extension. I have used a few for 6mm & 22 ARC barrels. They are very consistent and so far they seem pretty solid. Thanks! I just ordered one for testing. |
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Please return and let us know if that S7 extension is working for you! Blackout Defense/Blackout Dynamics out of Arizona makes a proprietary 17-4 tapered barrel extension for their rail system but they also make a standard flat 17-4 barrel extension for barrels they sell that are going on standard AR15 receivers. You may want to contact them and see if purchasing their 17-4 standard AR15 extension is a possibility. Their extensions are also EDM cut and can be spec'd oversize for thermal fit. While 8620 case hardened exterior is stiffer than 17-4 at H900, the 8620 has a soft core and is tempered at 250-300F so it will slowly loose hardness with high temp exposures and the overall piece will give more right from the start. The 17-4 is through hardened and unaffected by 300F temperature exposures so it should give less, have a +20% safety margin and maintain that performance. Are you seeing a plastic deformation of your barrel extension lugs over time? Is the headspace measuring an extra thou after X number of rounds? If that is the case, a 17-4 extension should solve all your problems and at all possible firing schedules for your action. |
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Originally Posted By man_o_brass: We already buy them by the hundred. I'm mainly concerned with what material they're made out of, and what the elastic modulus of the material is. Properly hardened? Parkerized, or nitride and who knows what that heat did to the hardness? |
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