JP Silent Captured Spring alternate spring pack.

[BitchinCamaro]

I have the JP SCS in my current rifle- 18" rifle length barrel, JP Lmos, JP adjustable gas block, miculeck style brake (suppressor mount). I got the SCS because I'm a total nerd and fanboy, and some pro on the internet said it's cool.

The block is turned down to just cycle commercial XM193, and the felt recoil at the buttstock is virtually zeroed out by the comp. There is a lot more kick when I shoot with a suppressor, but I've yet to experiment with gas settings with the can.

The alternate springpack was on backorder when I got all my parts, but it came in unexpectedly yesterday and now I'm unsure if I really need to screw around with spring rates.

The only reason I'm not sending them back is because when I hit the bolt release on a full magazine, the top round can be a little sluggish to go into battery. I'm using a side charging upper so it's easy enough to push the entire BCG home, but I'm wondering if a heavier spring would be a fix without compromise. Plus, there are five alternate spring rates. One of them has to be better for my rifle because I'm a very special snowflake, right?

I imagine the ideal is to have the lightest weight BCG with the spring that just allows the action to cycle with a given amount of gas. I think I hit that sweetspot with the stock spring rate- It cycles the "buffer" without bottoming out, and the BCG moves back into battery with 100% reliability and what I'm assuming to be minimum forward momentum.

With more springs, I really just don't know what I'm supposed to be tuning for anymore while juggling spring rate, cycle time, gas volume, suppressed vs. unsuppressed etc.

Edited April 5, 2014 by BitchinCamaro

[BitchinCamaro]

It's definitely a first world-problem- but I'm working graveyard shifts right now and I have a lot of time to kill thinking about carrier/buffer cycle dynamics.

Plus, I don't mind being a guinea pig since the product is sort of new and there isn't a ton of information out there.

[Steve RA]

Sounds as though the gun is freshly built, I've got an LAR side charge upper and same JP spring you have and mine really shoots pretty softly. I'd get some more rounds through it before changing springs.

[BitchinCamaro]

Yup. Defintie Cabin Fever build over the winter.

I too have the LAR ambi upper. With the gas tuned it's pretty much recoilless unless the can is on.

Admittedly I don't have anything specific to accomplish with different springs. I was just wondering if there was a theoretical sweet spot. I'm probably already good with this stock spring; the guys at JP told me the stock is made for the LMOS BCG and a longish gas system.

I'm going to go to the range in about an hour and really break down the feel of the trigger and reset and in relation to the timing of the action.

[gmg]

This may be a very stupid idea but why don't you try what we do in USPSA at the "Make Ready" command. Load one rd out of a another mag then exchange for a full mag. First mag being a 20rd mag downloaded to say 5rds.

[gondo]

I have that sluggish first round out of the mag sometimes too as i only have about 500 rnds through my newest build. I know this isnt the answer you want probably but for me it never happens when its good and clean and well lubed (i just run it dripping now and clean it after every match). Also really let that bolt slam home when charging. I used to baby mine down (i guess because we spend so much money on these things) but that is not the right way and it will bite you in a match by not having a round fully seated when the buzzer sounds (experienced it). What you want to do is look at your mag, see which side the last shell is on, put it in the gun and let the bcg slam it home, then pull out the mag and see if the first shell is gone.... and reseat mag really good... at least this is what i see the better players doing... seems they have learned through experience like I am...

[BitchinCamaro]

Stripping the round isn't a real issue, just something I noticed. One of the incidental benefits of having the ambi upper is that I can see the top round strip and slide into he chamber from the left side of the reciever. Just a nudge from the charging handle is usually all the check I need to make sure everything's gonna go bang after the buzzer.

I'm not trying to baby it by any means. It's run hard and put away dirty. I try to clean it before matches and definitely after-it functions 100% regardless. Shooting suppressesed makes things so dirty so quickly though, I may start cleaning more.

GmG, I do that out of habit with all my pistol stages regardless of round count. I used to think it was weird, but pretty much everyone I'm squaded with for the day starts doing the same thing one they watch me do it.

I put a few magazines of XM193 through yesterday and turned the gas almost off with the can. It still cycled reliably but the overall cycle time was noticeably longer than unsuppressed with XM193. I get the sensation that the gas is bleeding into the gas tube instead of freely blasting into it. I don't think the buffer is bottoming out, but it's either moving slower or traveling further than when the gas block is tuned for shooting without the can. I like it- it's like a sewing machine in action insteas of the soft "snap" of before, but part of that perceptikn is due to the fact that I'm not losing half my senses with the concussion of a compensator.

[BitchinCamaro]

So now it's a year later and my spelling has improved since that last post . 2 matches in for 2015 and I still have the JP spring pack sitting on the shelf.

My current reload in .223 is somewhere in the 24.6 to 24.8 grains of Tac with Wolf primers under a 55 grain Xtreme FMJ. It's chronoing in the low 2900s. 18" barrel, 1:9 twist, rifle length gas system.

There aren't any reciprocating issues with this load, but I sense that the gun worked slighter better with commercial XM193 when shooting sub .2 splits into a 3gun nation target. When everything aligned correctly I felt like the rifle would sort of "spit out" 2 rounds in controlled accurate fire, putting 2 holes within 2 inches of each other at 25 yards with multiple targets to transition between- It was smooth and effortless.

Shooting splits like that with softer load feels less automatic, and requires a bit more attention like a true "eyes on sight" doubletap from a pistol. It may be the lack of gas blasting through the (miculeck) comp, and I'm sure a bit of user input is in there too.

I'll be dinking around with the load for accuracy, then work with the gas and spring pack over the next few weeks to see what happens. If anyone has any experience messing with the alternate spring packs please post here with your experiences. Thanks!

Edited May 22, 2015 by BitchinCamaro