lablover Posted May 21, 2015 Report Share Posted May 21, 2015 Bolt won't lock back on last round So first let me start by saying new build was working great with the Federal Factory ammo. The first 20 shots went great without any issues. I used factory ammo to be on the safe side. I also shot some of my reloads after the box of factory and she ran like a champ. So, being I couldn't leave well enough alone. I decided to change out the fixed gas block and A2 stock. I installed a Syrac Gen 2 adjustable gas block and a Magpul PRS stock. Keep in mind I did not change the spring that I got with the DPMS Stock, buffer, spring Buffe tube kit from DPMS for 308. Anywho. I loaded the following loads new loads so I was starting low and worked up. Clean BCG and Rifle First load was with the Syrac gas blocked closed half way. Load was as follows First load was..... 40.5 Gr IMR 4064 175 gr SMK all single loaded all fired and bolt locked back on each round. Pretty happy so went to the next load 41.0 gr IMR 4064 175ge SMK First shot..bolt locks back but not all the way back. I figured I was on the raged edge with the gas block so opened up a few click. Every shot after that no bolt lock back.....grrrrrr Decided to open the block up all the way and fire the next groups 41.7 gr 4064 175 ge smk. Bolt wont lock back. Had the rifle on the bags so I even tried it off the bags..No lock back. Here are my questions. Is this just a break in issue? Are my loads ...wimppy. I even tried some Ball LC ammo and it locked back but once it failed too Tried a different Mag...Worked fine but one didn't lock back I thought when I first did the build with the fixed gas block all went great with the Fed gold medal match and no issues at all. I did not try to load more than one round until I get this figured out. I'm gonna take the Syrac block off and make sure I have everything ligned up correct. I did use a different gas tube with the Syrac too..Not sure that matters. Not even sure the MAgpul PRS can be an issue because with the A2 stock it worked fine with the spring/buffer I have. All ears guys. Lookin for some suggestions. I will say the 41.0 gr load was a hammer..Stuck all 5 shots in one single ragged hole at 100. Mega Arms Megalithic upper and lower (set) Mega Arms 20" Barrel BCM GAs Block..Fixed.....Now Syrac gen 2 Adj. Surefire SFMB-762 Muzzle Break LMT BCG and Bolt Vortex Viper pst 6-24 FFP ADM 20 MOA rings and Base set Giesslee 2 stage Match trigger Not sure what I might of forgot? Thanks for listening Joe Quote Link to comment Share on other sites More sharing options...
lablover Posted May 21, 2015 Author Report Share Posted May 21, 2015 Something I need to check is when I installed the new Syrac gas block I seated it all the way agaist the slope of the barrel. I have a feeling I need to measure how far back the whole is in the block then measure how far back the hole is from the barrel shoulder. Why do I know this is the issue...LOL Still all ears. Quote Link to comment Share on other sites More sharing options...
blue109 Posted May 21, 2015 Report Share Posted May 21, 2015 You havnt tried the FGMM with the new gas block? I'd say go back to the known good ammo and go from there. Run it wet. I'd suggest banging a couple hundred factory rounds to loosen her up before you start pulling stuff apart. Quote Link to comment Share on other sites More sharing options...
lablover Posted May 21, 2015 Author Report Share Posted May 21, 2015 (edited) You havnt tried the FGMM with the new gas block? I'd say go back to the known good ammo and go from there. Run it wet. I'd suggest banging a couple hundred factory rounds to loosen her up before you start pulling stuff apart. I will say I had lube on the bolt but it wasn't like dripping wet. Makes me ill to buy a box of ammo these dye when reloading is a but cheaper. I'll give that a try however. Edited May 21, 2015 by lablover Quote Link to comment Share on other sites More sharing options...
blue109 Posted May 21, 2015 Report Share Posted May 21, 2015 Many of us have found that a new 308 build tends to like lube. As in...drop your carrier in a quart of mobile1 the night before the range. Wake up, give it a good shake, and drop it in the gun. Quote Link to comment Share on other sites More sharing options...
lablover Posted May 21, 2015 Author Report Share Posted May 21, 2015 Pretty excited. I'm almost sure I just figured it out. I took the Syrac gas block off and measured the distance from the hole to the edge of the gas block that goes against the barrel shoulder... If you remember I said I pushed the block all the way against the barrel shoulder...Big mistake. the hole was .035 off So, that being said I was not dead center hole for hole on the barrel and block. I have to think .035 off would make a huge difference in the way the block functioned..or in this case didn't. Cant wait to try her out again...I have no doubt that was the issue Quote Link to comment Share on other sites More sharing options...
blue109 Posted May 21, 2015 Report Share Posted May 21, 2015 Hope that works! But generally speaking, the hole in the block is a bit bigger than the hole in the barrel allowing for that slight difference. I butt all my gas blocks up to the shoulder. I know some guys use a business card in the gap when setting it up. Quote Link to comment Share on other sites More sharing options...
FaRKle! Posted May 21, 2015 Report Share Posted May 21, 2015 (edited) I know some guys use a business card in the gap when setting it up.You can also flip the block so it's upside down, align the rear-most set screw hole with the gas port (the set screw hole and gas block opening on the opposite side should be perfectly aligned which makes this method work) and then pencil in an index point on the barrel so you know how far to slide the block on. Edited May 21, 2015 by FaRKle! Quote Link to comment Share on other sites More sharing options...
lablover Posted May 21, 2015 Author Report Share Posted May 21, 2015 On the fixed block the hole is way bigger than the hole in the barrel. The Syrac, not so much Quote Link to comment Share on other sites More sharing options...
lablover Posted May 29, 2015 Author Report Share Posted May 29, 2015 Plan B It wasn't the gas block alignment. I tried the reloads again and no bolt lock back. Fed 168 GM and no probe...hmmmmm Is 41.7 gr of 4064 that freakin light? 175 Match Kings Damn, what a bummer. I will say every once in awhile it would lock back. Grrrrrrrrrrrrrr Quote Link to comment Share on other sites More sharing options...
98Z5V Posted May 29, 2015 Report Share Posted May 29, 2015 You happen to measure the diameter of the gas port in the barrel, by chance? Quote Link to comment Share on other sites More sharing options...
survivalshop Posted May 29, 2015 Report Share Posted May 29, 2015 (edited) Fed 168 gr. GM & the bolt locks back every time ? Your hand loads might need some inspecting , I would not think 41 gr.'s of 4064 is a weak charge with 175 gr. bullets , maybe something with sizing or COL , just two things to look at . Have you tried M80 milSpec ball ammo ? Edited May 29, 2015 by survivalshop Quote Link to comment Share on other sites More sharing options...
lablover Posted May 29, 2015 Author Report Share Posted May 29, 2015 You happen to measure the diameter of the gas port in the barrel, by chance? Did not but I can. What should it be Quote Link to comment Share on other sites More sharing options...
lablover Posted May 29, 2015 Author Report Share Posted May 29, 2015 (edited) Fed 168 gr. GM & the bolt locks back every time ? Your hand loads might need some inspecting , I would not think 41 gr.'s of 4064 is a weak charge with 175 gr. bullets , maybe something with sizing or COL , just two things to look at . Have you tried M80 milSpec ball ammo ? I'm pretty anal about my reloading. COL is 2.800 and I F/L resize lake City brass. I'm going to grab a box of factory ammo again today and give it a go. I'm also going to bring the fixed gas block I had on it originally and never had any issues. After I built it with the fixed gas block and it worked flawless....I changed 2 things. Added Magpul PRS stock and changed gas block to a Syrac adjustable block. It's gotta be one of those 2 things. My reloads functioned fine with the fixed gas block. I'm at a loss....The Syrac is wide open as well Edited May 29, 2015 by lablover Quote Link to comment Share on other sites More sharing options...
98Z5V Posted May 29, 2015 Report Share Posted May 29, 2015 Gas port on that barrel should be north of 0.080". 80-thou. That's a Mega 20" barrel - I imagine it's rifle-length gas? Quote Link to comment Share on other sites More sharing options...
lablover Posted May 29, 2015 Author Report Share Posted May 29, 2015 Gas port on that barrel should be north of 0.080". 80-thou. That's a Mega 20" barrel - I imagine it's rifle-length gas? 89 thou Rifle length Quote Link to comment Share on other sites More sharing options...
lablover Posted May 29, 2015 Author Report Share Posted May 29, 2015 So, went to the range again today with a box of Fed GM 168gr Fired without a problem...Tried one of my reloads...Fail to lock back. Had one fail to lock back on the factory so I re-lubed up the BCG etc and no problems. Hell, I even shut the gas block down by half and the Factory Fed GM still functioned...Loaded up 5 rounds and all fired without a hitch..Pretty Stoked. Bad thing..WTF is up with my reloads? Gotta be something on the powder burn rate or the heavier bullets are not as snappy as the Fed Gmm. When I shut the gas block down half way I about poop myself when the Fed Gmm still functioned. So, I think my build is fine....I think my build needs broken in...LOL I think my reloads has an issue and can't figure what..I have a sneaking suspicion it my be be only bumping the brass back 3 thou and its not brass originally from my rifle...hmmmmmmm Bet it is. I'd like to think I don't need small base dies? I'l scoot the die down a little bit more so it cams over on the ram. Barley bumping the ram now. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted May 29, 2015 Report Share Posted May 29, 2015 I cam over all my Sizing dies over , slightly , even my SB dies . Are your reloads having any problems feeding into the chamber ? You also said you changed to a PRS Stock , did you change or replace any Buffer assembly components ? Quote Link to comment Share on other sites More sharing options...
lablover Posted May 30, 2015 Author Report Share Posted May 30, 2015 I cam over all my Sizing dies over , slightly , even my SB dies . Are your reloads having any problems feeding into the chamber ? You also said you changed to a PRS Stock , did you change or replace any Buffer assembly components ? I did not replace..They were all Rifle parts...Or, Rifle length parts...Buffer, spring had an A2 stock. Quote Link to comment Share on other sites More sharing options...
392heminut Posted May 30, 2015 Report Share Posted May 30, 2015 I cam over all my Sizing dies over , slightly , even my SB dies . I do the same as SS does and it works for me. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted May 30, 2015 Report Share Posted May 30, 2015 Powder and/or primers are contaminated. Only thing it can be. The powder, 4064, is a good powder for the heavies, so it's not powder type. What primers are you using (brand/type)? Never saw mention of that detail in this thread. Quote Link to comment Share on other sites More sharing options...
lablover Posted May 30, 2015 Author Report Share Posted May 30, 2015 Powder and/or primers are contaminated. Only thing it can be. The powder, 4064, is a good powder for the heavies, so it's not powder type. What primers are you using (brand/type)? Never saw mention of that detail in this thread. CCI 200 Quote Link to comment Share on other sites More sharing options...
MikedaddyH Posted May 30, 2015 Report Share Posted May 30, 2015 (edited) CCI200 has a smaller flash than other primers ! I have used ; Fed 210M Rem 9 1/2 CCI 34 Win WLR On my 168gr Projo loads with IMR 4064 powder. Edited May 30, 2015 by MikedaddyH Quote Link to comment Share on other sites More sharing options...
lablover Posted May 30, 2015 Author Report Share Posted May 30, 2015 CCI200 has a smaller flash than other primers ! I have used ; Fed 210M Rem 9 1/2 CCI 34 Win WLR On my 168gr Projo loads with IMR 4064 powder. I need to be on the prowl for other types...I'm not real fond of the CCi's Quote Link to comment Share on other sites More sharing options...
MikedaddyH Posted May 30, 2015 Report Share Posted May 30, 2015 Posted a thread on primers last weekend, lots of info. Check the Reloading section. Quote Link to comment Share on other sites More sharing options...
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