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Posted: 5/9/2026 5:29:38 PM EDT
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Have a Lima Six with RECCE RPD by RRH. Also have a RDIAS that I've had for years. Did the required break in on the Lima Six/RECCE for 200 rounds in semi with basically no issues. Upper runs amazingly in semi. Went out to send some lead downrange with my sear and immediately got bolt bounce. FTF was hammer down on a live round with bolt fully closed but no bang and a slight dimple on the primer. Ammo was both M855 and M193 NATO spec. IMI and GGG. Current set up was/is an A5 buffer tube, SpringCo orange and an H3 buffer at 5.3 ounce. I watched the video on Lima Six's website for checking timing... -A 7/64" drill bit and hammer falls -A 5/32" drill bit and hammer doesn't fall. -So out of curiosity tried a 9/64" drill bit and hammer falls but I have to push a little on the charging handle to make that happen. Looks like I am in limits but just barely like by my math about .0157" barely so close to the zone where bolt bounce could be problematic. After getting home and checking parts stashes I found a couple different things I can try... Have an old AAC rate reducer I've used over the years weighing in at 5.3 oz just like an H3 buffer. Also have an old school MGI rate reducing buffer I bought from Mack a long time ago, like early 2007. It weighs in at 6.9 oz so I will probably try that one first. Note: The MGI buffer compressed length is identical to an H3. Also have a SpringCo Red spring but after reading @TonyRumore spring rate chart the red is less powerful than the recommended orange spring so not sure that will help me. I know that having a new (custom) sear trip made is an option to get the RDIAS a little more into the sweet spot but that would probably be the last thing I do if my issue can be corrected another way. If, for no other reason, finding someone competent and willing to take on a small project like mine (making a new trip) complete with heat treat seems like a lot of hassle. This RDIAS has worked perfectly on multiple uppers. Anyhow, that's where it sits. If anyone has any input or idea's I'm all ears. |
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One thing you can do is set up your phone on slow mo and record the right side of the gun. That should help determine if its bolt bounce or timing. Have you confirmed that your H3 buffer is aluminum bodied with 3 tungsten weights? And the weights can rattle freely? Have you confirmed that your hammer spring is not installed upside down? If it really comes down to it, the carrier could be machined to slightly retard the timing, but I would explore all other options first. |
https://www.limasix.com
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Thanks for your response. Wish I had a progress report but I haven't been able to get back out in the woods. Work has been in the way... The slo mo phone suggestion is something I hadn't even considered but after you brought it up these modern phones can do some cool stuff even if I'm not so modern. I can definitely give that one a shot to see what's up. My H3 marked buffer is aluminum bodied. I'll have to pop the roll pin and look inside to see what's in there re 3 tungsten weights. Hammer spring is not installed upside down. After I read that comment I wondered if it was even possible to do that but I guess anything is possible lol. Hadn't thought about machining the carrier but as you mention other options need be explored. I have confidence this thing will run. When I can get back out I have some things to try/test and will report back. |
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Originally Posted By marks: Thanks for your response. Wish I had a progress report but I haven't been able to get back out in the woods. Work has been in the way... The slo mo phone suggestion is something I hadn't even considered but after you brought it up these modern phones can do some cool stuff even if I'm not so modern. I can definitely give that one a shot to see what's up. My H3 marked buffer is aluminum bodied. I'll have to pop the roll pin and look inside to see what's in there re 3 tungsten weights. Hammer spring is not installed upside down. After I read that comment I wondered if it was even possible to do that but I guess anything is possible lol. Hadn't thought about machining the carrier but as you mention other options need be explored. I have confidence this thing will run. When I can get back out I have some things to try/test and will report back. You don't need to open it up, you can just shake it and weigh that it matches H3 weight. . Does it rattle or does the whole thing feel solid? At least, if you know it's an aluminum body and not steel (an aluminum body one would have to have tungsten weights to weigh the right amount, only a steel body one could have something other than 3 tungsten weights inside) I have one that is solid and one that shakes. The solid one doesn't work amazing on anything |
| The buffer shakes, is marked H3 and matches an H3 weight. I have no concerns that the buffer is legit. I didn't mention it but the buffer is also exactly like the H3 I purchased with my upper (along with the A5 tube) from Lima Six I just didn't have the new buffer purchased with me with me to try the day I went out to shoot. I assumed the one I brought would work. |
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