JP5 Ultralight – Locking Pieces.. and a bit more..

The JP Rifles – JP5 just released the ultralight weight barrel and there are a lot of questions surrounding which locking piece should you use. Let’s spend a few moments and I will share my experience with different combinations.

Most 14.5″ JP5s are shipping with an 80 locking piece. This will work with most ammo off the shelf. I will note that all of my JP5s seem to be slightly different when it comes to which locking piece is best. I have one of the first pre-production JP5s with a 14.5″ pinned comp and this one likes a 70 locking piece with a ‘white’ AR 15 SCS spring to run PNR Ammo 135 Gr (https://pnrammo.com/product/pnr-ammo-9mm-135gr-pcc-1000/ ) which is going around 840 FPS and this setup also works for the PNR Ammo 100 gr Steve Foster Edition https://pnrammo.com/product/9mm-100-gr-steve-foster-edition-500-rds-reman/ . which runs around 1100 FPS. In my 2nd JP5, which is a production model, the 14.5″ barrel runs with an 80 locking piece for both sets of ammo. When you buy your JP5 order the AR 15 SCS Alternate Spring Pack which comes with 5 springs. Think of the changes in springs to be micro adjustments between locking pieces.

My Ultralight JP5 came with a 90 locking piece. This proved to work well with off the shelf ammunition. In doing some testing, the 100 gr ammo from PNR worked best with the 100 locking piece and I added the JP white spring. After doing some testing I ended up with the 120 locking piece for the 135 gr PCC ammo from PNR. I decided the leave in the white recoil spring with great results.

Every JP5 is slightly different, but these are the configurations I have tested and are running for the world speed shoot next weekend. Through your own testing, you may find a combination that works for you. While testing, make sure the spent casing lands 2′ or more from your feet. Even the best do it your self reloaders will find a little variation in your loads and you don’t want to be on the firing line with a slightly under powered round that causes you precious seconds!

I hope this helps!

See you out on the range soon!
Steve