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KAC had a bad run of extractors, a while ago, that caused exactly that problem. Also the same batch needed a gaskey re-tighten and stake.
New extractors were sent from factory.
BTW if you can't sort out a feed/extract/eject issue.. dig film it & play it s l o w later.
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Thanks for the additional info...
I personally sealed and staked the gas key on my LMT enhanced carrier, so that rules out a leak at the key. Also the extractor functioned fine without the supressor installed, could it be marginal and adding the supressor brought out the problem? I'm tempted to order a SR-15 field repair kit and swap extractors just to see if anything changes. The gun was cycling way too fast and way too hard the way it came from KAC which leads me to belive it was overgassed. I am happy with the H3 / H&K red spring combo in their now and will continue running ammo through the gun suppressed to ensure it's stays reliable.
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Email me -- I know we talked, but in checking with our Engineering Test and Evaluation Depertment, I think you may need need extractor and spring.
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suppressing will, of course, increase back pressure, speed up the action and exacerbate any issues.
A heavier buffer will slow it a bit, but the increased spring power of the HK spring may not help.
BTW I have had good luck using the A5 system to slow overgassed piston guns. a 416 with suppressor can get to 1200+ rpm
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Kevin,
Just fired off an email in your direction.
Dano5326,
Can you elaborate on why a heavier spring may not help?
It seems like it really tamed the violent cycling I was experiencing...
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Increased resistance in spring strength will also lead to increased speed going forward. To what exact degree, and with consideration to buffer weight & configuration, I cannot say.
No significant engineering background here..
I have tried springing and buffer-weight or configuration variances. More luck varying weight.
Also, you may have some difficulty resolving an issue with a vendor.. after a mix and match of makers & components.
Of note the LMT cam path is nonstandard and there is a lip on the carrier where the bolt goes in. Additionally the KAC Bolt pin hole and extractor is proprietary.. so it may not permit proper movement or tension.
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Gotcha - I'll keep an eye on it feeding and try several different magazine types to ensure the increased spring force is not causing additional issues. Thanks for your insight! Knight's is also sending me a new extractor to swap into the gun to ensure it is not compounding the problem. I will post updates as I get more time to shoot the gun and will share any findings along the way. I will also double check the parts compatibility to ensure there are no mechanical problems with the mating of the LMT carrier and KAC bolt / cam pin.
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Dano that was a really clever suggestion; I just pulled apart my BCG to inspect all of the components to ensure there is no mechanical contact or abnormal wear on any of the parts , paying close attention to the extractor arm, the BCG alignment ring machined into the front of the carrier, and the cam pin and cam pin tract. Everything looks 100% good to go, but I will check it again every few hundred rounds to ensure perfect continual compatibility. Interestingly enough LMT has chamfered the interior of the BCG "ring" to provide additional clearance for the extractor arm, something I have never noticed until I looked at it this afternoon.
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120 more rounds (XM193F in one session) through it with the H3 and H&K red stripe spring - no malfunctions... Haven't had much time to go to the range the past week but this week looks promising.
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Another 120 rounds of XM193F and no extraction issues but two failures to lock back on empty the last two mags.
I've got a hunch that the H&K spring is a tad too strong as I'm losing consistent lock back on an empty mag now that the action is filthy; where is the best place to pickup a blue and red SpringCo CS carbine spring and have them delivered with a quickness? (Ignore my question - just placed an order direct from SpringCo - picked up a green rifle length in case I go A5 and the blue and red carbine... )