Langenator Posted June 30, 2015 Share Posted June 30, 2015 I'm building an upper. I have a Nordic 18" barrel, Carbon Arms gas block, and I'm planning on a Seekins LM BCG. I shoot factory ammo (Freedom, unless I find a significantly better price). Which JP captured spring should I used - standard or heavy? Link to comment Share on other sites More sharing options...
BitchinCamaro Posted June 30, 2015 Share Posted June 30, 2015 Does the SCS come with multiple springs now, or do you have the spring pack? Adjust gas for your ammo and see if your bolt locks back on an empty mag. If it doesn't, try the next lighter spring or increase your gas volume a bit. That's just how I tuned it for minimal gas, but there are plenty of "intermediate" tuning options that may work better for you. Link to comment Share on other sites More sharing options...
TennJeep1618 Posted June 30, 2015 Share Posted June 30, 2015 I bought the spring pack, installed the lightest spring and tuned the gas block for that spring. It has resulted in a very soft shooting rifle, so that's what I would recommend. Link to comment Share on other sites More sharing options...
BitchinCamaro Posted June 30, 2015 Share Posted June 30, 2015 That's pretty much my same setup. I'm going to try one or two spring rates up and tune up the gas to lock back the bolt. The lightest spring "feels" laggy, though it does chamber rounds with authority from a locked bolt. I don't think I can outshoot this current setup with my splits, but I feel that there has been some unidentified compromise in tuning with the lightest spring. I only have about 400 rounds with it so far though. No malfunctions but I feel that it could be better. Link to comment Share on other sites More sharing options...
Langenator Posted July 1, 2015 Author Share Posted July 1, 2015 JP's web site shows the SCS being available in two different weights, in addition to the spring pack with differing spring weights. Standard: http://www.jprifles.com/buy.php?item=JPSCS-15 Heavy: http://www.jprifles.com/buy.php?item=JPSCS-15H The site doesn't list specs. Link to comment Share on other sites More sharing options...
TennJeep1618 Posted July 1, 2015 Share Posted July 1, 2015 JP's web site shows the SCS being available in two different weights, in addition to the spring pack with differing spring weights. Standard: http://www.jprifles.com/buy.php?item=JPSCS-15 Heavy: http://www.jprifles.com/buy.php?item=JPSCS-15H The site doesn't list specs. I believe that equates to a standard vs heavy buffer. Since you're going with a low mass BCG, then I'd go with the Standard. Wouldn't make much sense to go with a low mass BGC and a heavy buffer.... Link to comment Share on other sites More sharing options...
Gunnar Posted July 1, 2015 Share Posted July 1, 2015 http://jprifles.com/1.4.7.2_os.php Click on the FAQ tab to see the difference. But TennJeep1618 is right on the money when it comes to competition setup. Recommended use for Heavy buffer SCS includes: Short-barreled Rifles (SBR) Suppressed weapons Rifles that are recommended for use with H2/H3 buffer Select-fire Rifles Piston-operated systems Link to comment Share on other sites More sharing options...
Langenator Posted July 1, 2015 Author Share Posted July 1, 2015 So, standard SCS, and buy the spring package to tune it. Link to comment Share on other sites More sharing options...
Gunnar Posted July 1, 2015 Share Posted July 1, 2015 If you get an adjustable gas block, you do not need the spring pack. Link to comment Share on other sites More sharing options...
BitchinCamaro Posted July 1, 2015 Share Posted July 1, 2015 If the spring pack wasn't available I would have been fine with the stock spring and adjustable block. But it is, so now I'm chasing the mo' better. Link to comment Share on other sites More sharing options...
Langenator Posted July 1, 2015 Author Share Posted July 1, 2015 I've got a fixed block. Springs it is! Probably cheaper, at any rate. Link to comment Share on other sites More sharing options...
flyfishdave Posted July 1, 2015 Share Posted July 1, 2015 Set up my rifle as follows: * JP 18" ultra match barrel with LMOS carrier and headspaced bolt * JP SCSS with OE (100%) spring * SLR sentry adjustable GB Using Freedom .233, needed 8 clicks from closed to hold open on an empty mag. Shot with ZERO issues using two different comps/brakes for 3 matches so far. Hardware is solid......the software can use some work. Anyway, just swapped the OE (100%) spring for the 90% SCSS spring. GB needed only 5 clicks open to lock the bolt back on an empty mag. No issues stripping a round from a full mag when dropping the bolt and the buffer tube didn't explode. Don't remember what it felt like with the 100% spring and haven't shot it much in that configuration, but I think there was less felt recoil, more of a quick slap vs a thud and a push using the 90% spring. Time permitting, I'll try the 95% spring, hopefully before the next match. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
BitchinCamaro Posted July 1, 2015 Share Posted July 1, 2015 Flyfishdave, why haven't you tried the 80% and worked up? I'm not saying anything is wrong with your method, I'm just wondering for data's sake. Link to comment Share on other sites More sharing options...
Langenator Posted July 2, 2015 Author Share Posted July 2, 2015 Hey BC, just for my edification... Did you run over my neighbor? Link to comment Share on other sites More sharing options...
Steve RA Posted July 2, 2015 Share Posted July 2, 2015 I've got a Nordic 18" barrel, Carbon Arms gas block and a JP captured set up and am running it the way it came. Seems to work very well as is. This isn't to say that you could not play around with the spring set if you wished. Link to comment Share on other sites More sharing options...
flyfishdave Posted July 7, 2015 Share Posted July 7, 2015 I wish I had some cool scientific literature and references to support my choice but I was busy watching the USA vs Germany semi-final when picking a spring - the green striped 90% was the easiest to discern in the pack. The 80% spring might be more suited for a lighter carrier but if I get a chance, I'll try them all. Not sure if less gas through the GB means more left over to work at the comp/muzzle brake and vice versa The SLR Sentry 7 adjustable GB works as advertised and does so very well. A little tight dialing down at first, but after some 'clicking' in both directions to loosen carbon fouling, the screw was easily turned. Flyfishdave, why haven't you tried the 80% and worked up? I'm not saying anything is wrong with your method, I'm just wondering for data's sake. Link to comment Share on other sites More sharing options...
shooterrdy Posted July 9, 2015 Share Posted July 9, 2015 the Spring rate will vary with the weight of your BCG, Gas Block/Length, Brake etc. the spring pack is handy they are a bit of a PIA to change they require heat to remove them once you get the one you like You will have to adjust on it when you change ammo speed/weight, I shoot 75 grn. for targets beyond 200 yd. and 55 grn at everything else right now I am using the spring just lighter than stock (forget the color code) But I am using an aluminum Whiskey Arms BCG its one of the lightest out there. with a Syrac gas block the Syrac is not as adjustable as some but very proven no to move and no PIA brass set screw. in short you need allot of things set to get the best results Link to comment Share on other sites More sharing options...
flyfishdave Posted July 25, 2015 Share Posted July 25, 2015 Update: So, played with all the springs in the calibration pack days before the Armalite 3M3G match. Yeah, flirting with a potential disaster messing with the rifle before a match but nothing bad happened. My 'counting' of clicks was probably not correct and consistent, and likely didn't have the proper 'closed' position (likely due to some fouling) when counting clicks with the first test because regardless of which spring was used (80, 85, 90, 95, 100) the GB needed the same setting to get the bolt to lock open on the last round with all the springs. In retrospect, I guess it makes sense since it's the same bolt mass that needs to be moved. At this point, going to a lighter carrier may be the only way to reduce the amount of gas. To justify the wasted time and ammo, installed the 95% spring instead of going back to the 100% spring. The changes imparted by this new spring is similar to putting in a 13 lbs recoil spring in a G34 - a slightly faster return to target. The enemy of good is perfect. Link to comment Share on other sites More sharing options...
hercster Posted July 25, 2015 Share Posted July 25, 2015 I'm upgrading my 16 inch Stag with a steel LW BCG and the Heavy version of the Silent Spring. These were the recommendations of the JP CS himself. I was open to all options including the more expensive aluminum BCG. The rep didn't hesitate to steer me away from the aluminum option and was equally emphatic on the "heavy" spring package which uses tungsten weights. The silent spring has been on B/O for some time. I have the JP adjustable gas block and the plan is to shut the gas to "off" and then loosen by one full turn until the gun cycles every time. Then I'll tighten down by a half turn until it fails and go back up by 1/4 turns until I get reliable cycling even when dirty. When fine tuning like this, I'm sure the degree of "dirtiness" will make a difference. Without getting too nerdy, I expect to get a very reliable and smooth gun. Link to comment Share on other sites More sharing options...
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