ActionGunner
JP-5/MP5 Lock Piece, 40 Degree
JP Enterprises
Rifle Parts & Upgrades · USPSA
SKU JP5-LP40

JP-5/MP5 Lock Piece, 40 Degree

$99.95

// PROOF, NOT ADJECTIVES
JP 40 degree lock piece for the JP-5 and H&K MP5, a new release below the old 50 degree minimum. For higher-pressure loads or a gun that cycles too hard. Check bolt gap after install.
The lock piece is the JP-5's tuning knob. JP compares it to an adjustable gas block on an AR: swap the angle and the recoil impulse changes to match the ammo. This is the 40 degree piece, a new release and the lowest end of JP's range, which means more delay and a slower-opening action than the 80 degree piece a JP-5 ships with.
JP's rule is that a larger angle opens easier. Weak or unreliable cycling calls for a higher angle; a gun that cycles violently and slams the buffer tube calls for a lower one. JP lists 80 as the standard and notes that competition shooters often drop to 70 for recoil reduction with standard-pressure loads. Going this far down is for hotter loads or a shooter chasing a flatter gun who is prepared to test.
One thing to know, straight from JP: under-delaying the JP-5 with high-pressure ammo can damage the gun. A 40 degree piece adds delay, so the failure mode is the other way, weak cycling with soft ammo. Either way, a lock piece change can shift bolt gap, so measure it after the swap. JP lists its lock pieces as compatible with the H&K MP5 and with clones that accept H&K lock pieces.
The trade-off is that $100 buys a tuning step, not a guaranteed improvement. A shooter who does not know their current angle and ammo velocity should start there before buying.
JP-5 and MP5 shooters tuning recoil for a specific load: the 40 degree piece suits higher-pressure ammo or a gun that still cycles too hard at 50 or 55.

Out of stock

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SKU JP5-LP40 Categories , Tags , , , , , , , , , , , , , Brand:
Manufacturer JP Enterprises
Model JP-5 Lock Piece
Manufacturer Part # JP5-LP40
Angle 40 degrees
Angles Offered by JP 40 through 120 degrees
JP Standard Angle 80 degrees
Material Proprietary steel, nitride finish
Platform JP-5; H&K MP5 and clones that accept H&K lock pieces
Country of Origin USA

Description

The JP-5/MP5 Lock Piece in 40 degrees is one of JP’s interchangeable lock pieces for tuning the recoil impulse of the JP-5 roller-delayed carbine, and a new addition below the previous 50 degree minimum. JP machines the lock pieces from a proprietary steel and finishes them with a nitride coating for low wear and low friction.
The larger the angle, the easier the action opens. Higher-pressure ammo pairs with lower angles; lower-pressure ammo pairs with higher angles. JP lists 80 degrees as the standard configuration and notes that competition shooters often run 70 for recoil reduction with standard-pressure loads. If cycling is weak, move to a higher angle; if cycling is violent with buffer impact, move to a lower angle.
JP warns that under-delaying the JP-5 combined with high-pressure ammo can damage the gun, and that switching lock pieces may alter bolt gap, which should be checked after any change. JP lists its lock pieces as compatible with the H&K MP5 and with non-H&K clones that accept H&K lock pieces.
What’s Included:
  • One 40 degree lock piece
What’s NOT Included:
  • Bolt gap gauges (see JP-5 Bolt Gap Gauge Set)
  • Other angles (each angle is a separate part)
  • Tools
Disclosure: Action Gunner is an authorized JP Enterprises dealer and stocks this part in the Pro Shop. Product facts on this page come from JP unless noted.

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