After reading all the good reviews on this spring, I bought one in hopes of fixing my short stroking issue. It worked

at fixing that issue, but the spring is to weak to reliably chamber a round. If I had more than 5 rounds in a mag, the

tension against the rounds from the mag spring was to great for it to pick up a round and chamber it. I even tried

lightening my buffer from 3oz. to 1.5 oz. That helped, but it still wouldnt cylce the bolt 100% of the time if the mag

had more than 10 rounds in it.

This spring is a MUST HAVE for all 300 Blk users....especially if you're gonna run subs (with or without can). This $16 fix solved ALL my cycling issues and my carbine runs like a thoroughbred now! Couldn't be happier.....

This spring solved all my cycling problems in my 300 blkout ar 15 pistol.Runs great now!

We built up a few AR's in 5.56, I decided to do one in 300BLK out of the same batch of parts. The 5.56's worked great but the 300 was short stroking with standard loads, checked everything, the gas port was .120" with a carbine length gas tube, everything was perfectly aligned. Tried different bolts and lowers. Nope still shot stoking. Found this spring...finally got to the range today. Started with my 150 grain, worked, zero problems, got it zero'd in, ran 10 rounds of 150, then 10 of 147 then 10 of 110 HP ZERO problems and less than 1" groups.. Then another 30 of 150. Kicks a touch more because this spring is lighter by 15% or so and about an inch shorter than a regular spring. So, if you've checked everything, try this. The picture is at 25 yards with 110 HP, bench rest with UTG bi-pod and Hypertouch 24E trigger group.

Problem solved!!! 220g. sub sonic loads now feed like butter. I have also run 50 rounds of 125g. Nosler BT through it and they feed as well. Good product!!

Tried 3 different powders for subsonic .300 blackout. 1 wouldn't eject, and the other 2 wouldn't cycle enough to pick up the next round. After reading other reviews I decided to give the NEMO spring a try. So glad I did. Works great. H4198 @ 11.0 gr. 208 Amax, A5744 @ 11.2 gr. 208 Amax, and H110 @ 9.4 gr. 208 Amax, all cycle. Thank you Brownells and NEMO for a great product that saved the day!

I built a 300 Blackout and was experiencing short cycling of the action. I increased the gas port diameter from 1/16 to 7/64th. This cured the problem most of the time. I was still experiencing short cycling on an infrequent basis. I installed this spring and all trouble have now gone away. I have run hundreds of rounds through this carbine now without issue. This is a great and inexpensive fix.

This is the spring that the online build reviews are talking about for homemade .300s. If your build is not cycling properly this is the first step to take; and will fix the problem most of the time before having to go to other alternatives (lighter buffer, lightened BCG, etc). Also make sure to shoot several different brands as one may work better than others, my favorite right now is Remington UMC; and it is available most anywhere.

Talk about an instant cure for an AR that is short-cycling with .300 AAC!

Not only did it fix the issue with my 300 blackout but it fixed the issue with a customers 7.62X39 AR short stroking.

This is a MUST for Anyone experiencing a Short Cycling AR15 that is being built in the Awesome 300 BLKOUT round, I've built four of these already in a Carbine Gas system and I can Attest that without using this Buffer Spring be ready to experience a series of issues with Cycling, ejecting and going into full battery mode, The only other Buffer Spring I've found that the AR functions Flawlessly is the JP Enterprises Silent Capture Spring downfall of going with the JP is Cost the Nemo buffer spring is a GREAT Affordable FIX!!! and your AR will function GREAT shooting Sub-Sonic or Super Sonic rounds! I've used just regular T2 Carbine Buffers and My last build I used a Spike's Tactical Tungsten Buffer and all of the AR's with using a standard Buffer spring didn't Function and when I put in the NEMO Buffer Spring they functioned and shot like a Dream!

I was having cycling problems on a new 300Blk build.Would not lock back on empty mag.I ordered this spring and installed it.Now my AR 300Blk shoots and cycles perfectly.Ordered on friday,had it on monday,thanks Brownells.

I had an older AR15 and I bought a new 300 blkout upper which can be used on the old AR15 lower assembly. I had trouble with it short cycling on the 300. I put in this buffer spring and bought a 2.9 oz buffer weight which I use when firing the 300 with supersonic ammo. The 300 now works flawlessly and is a delight to shoot.
The shorter spring and lesser buffer weight allows the 300 ( Shortened version of a 223 made to fit a 308 bullet in it ) which has less powder to push the spring all the way back to completely cycle.
I also put a light weight bolt carrier assembly in the upper. Once you get the 300 working the way it should it will become a favorite to fire.

This might seem like a good idea if you've got a 300BLK that won't reliably cycle with subsonic ammo but the spring is too light for reliable operation. I found that the spring is so light it may or may not fully strip a round from a fully loaded magazine. If it does strip a round it probably won't have enough oomph to fully close the bolt.