gerritm Posted December 29, 2014 Share Posted December 29, 2014 I have always had standard low profile gas blocks with good luck. Guns always run. I have a lightweight 16" Eotech rifle that I built for fast hoser type matches. I had a standard 16" 1-9 twist M4 barrel, carbine length gas system that I put on it with a Nordic Tactical SS Comp. Very fast and fun to shoot, but tinkering with it to get out the muzzle movement I put a RCA adjustable gas key on the BCG. Went to the range Friday, adjusted it per instructions with several different types of ammo and it ran great. Turned it out an extra 1/2 turn and locked the 2nd screw with Loc Tite per instructions. Temp was 75 degrees. Took it to a match Saturday and it was 45 degrees. First stage single shot, could not get it to cycle. Got a reshoot with my standard BCG back in it and it ran 100%. Question? What do you guys that run adjustable gas blocks/keys do in colder weather. I am assuming that was the cause of the problem. gerritm Link to comment Share on other sites More sharing options...
dauntedfuture Posted December 29, 2014 Share Posted December 29, 2014 Lucky you got a re-shoot. In general when shooting in cold weather your ammo will develop slightly less pressure. If its real real cold any lubrication that you have will not work as well. If you are in arctic conditions, the grease will freeze, but I don't think that's the case here. In cold weather metal will also "stick" together. There have been a few reviews of the adjustable gas key here. I don't think they are all that glowing as initial reports are that the adjustments come loose. I think the consensus is that its good in theory but in practice it does not work so well. I would try adjusting the gas key and finding a way to mark the setting with a scratch etc. Shoot some and see if things work loose. You also need to adjust the gas so things work and the gun runs at full power, ie not a sluggish carrier, and then give the gas another 1/2 turn and lock things down. If you are right on the edge of cycle/ no cycle then if you don't lube the gun right or it gets too dirty It will choke. Link to comment Share on other sites More sharing options...
TonytheTiger Posted December 29, 2014 Share Posted December 29, 2014 Where you using the same ammo at the match that you used to tune it with? I'm just getting into rifle tuning and I've learned the hard way that all our go fast parts narrow down your operational window and something as simple as small ammo differences can ruin your day. Link to comment Share on other sites More sharing options...
gerritm Posted December 29, 2014 Author Share Posted December 29, 2014 Same ammo. Next day. Pretty sure the adjustment didn't change. Gun locked open on all ammo then turned it 1/2 turn further out. Only real difference was the temp.When I tested it I ran several different types and quality including the ammo I shot at the match. I will pull it apart and check the adjustment. Not used to colder weather. I use no grease and Mobile 1 for lube. gerritm Link to comment Share on other sites More sharing options...
TonytheTiger Posted December 29, 2014 Share Posted December 29, 2014 Interesting. Only thing I have to add is that cheap steel cased ammo runs fine in all my guns in normal temps. Once it drops below 30 degrees they tend to go into single shot mode. I gave up on that junk... Link to comment Share on other sites More sharing options...
bikerburgess Posted December 29, 2014 Share Posted December 29, 2014 Did you fire it after installing the locking set screw? I think you can inadvertently move the first set screw when you are tightening the second one. Link to comment Share on other sites More sharing options...
MickB Posted December 29, 2014 Share Posted December 29, 2014 Exact same behavior with my JP15. Shot fine and locked back at 80 degrees, but testing the next morning at 55 degrees caused it to be a single shot till I turned up the gas. This was with factory IMI M193 5.56. Interesting observation with a .308 G2 and using Australian ADI F4 ball ammo. This rifle has an SLR SA7 adjustable gas block. My belief is that the lower temps are causing lower gas pressure to cycle the action (PV=nRT), ie. gas volume is directly proportional to temperature. Here's the interesting part - the .308 performance didn't change at all at lower temps. Why? Australian powders were developed to be relatively temperature insensitive due to the climatic variations across the country and to maintain performance with the L1A1's adjustable gas system. This turned out to be the case with my G2 and lower temperatures. The same powder is loaded in the Australian Outback range of .308 and .223 that is sold here in the USA. It would be interesting to see if the same effect could be made with that series of ammo in a .223/5.56 rifle. If so, the next question is where can I buy the powder for my reloads! Mick Link to comment Share on other sites More sharing options...
gerritm Posted December 29, 2014 Author Share Posted December 29, 2014 Did you fire it after installing the locking set screw? I think you can inadvertently move the first set screw when you are tightening the second one. I will check this. Possibility cause I didn't fire it after installing the set screw with loc tite. Did not feel like it moved. gerritm Link to comment Share on other sites More sharing options...
dauntedfuture Posted December 29, 2014 Share Posted December 29, 2014 ADI powders makes Hodgen extreme series, ADI 2208 is Varget here in the USA. Link to comment Share on other sites More sharing options...
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