This is for a small ring Mauser with a .98" 12tpi thread. It will also work with Gewehr 88s.

The plunger is a welding tip from a Bernard q-gun. A 5/16" bolt could also be modified to work. The plunger can be 3d printed. https://www.amazon.com/10-pk-Welding-Contact-Bernard-Centerfire/dp/B088FPFQ4M/ref=sr_1_1?keywords=bernard+centerfire+tip&qid=1636247065&qsid=146-3924171-3245601&sr=8-1&sres=B088FPFQ4M%2CB004HF66DE%2CB07H1YXCJG%2CB01M11WHON%2CB07H22CKQK%2CB00JDSTW0Y%2CB07D9BQY4K%2CB07F1DQR5Y%2CB001AIULYG%2CB002ORB2G8%2CB07FY5KCFK%2CB07THWMZ7R%2CB07F1KG6RS%2CB07F1CMT43%2CB07BLQFQNN%2CB005FTPZSS%2CB003GM9Q1S%2CB004HM5ZQ6%2CB07SC5QN64%2CB07THZC1PM

For the bolt I used a bolt from a vise grip. The tip of the bolt is reduced and the spring slides on. The knurling on the bolt also makes it easier to use. A standard 7/16" bolt could also be used. The bolt can be 3d printed. https://www.amazon.com/Irwin-Tools-2071910-IRWIN-ITEM/dp/B001NNGJ9E/ref=sr_1_5?keywords=vise+grip+screw+replacement&qid=1636247872&qsid=146-3924171-3245601&s=hi&sr=1-5&sres=B001NNIL1S%2CB0002JT60E%2CB07678B78G%2CB001NNGJ9E%2CB0002JT604%2CB00004YO5M%2CB01EVQH42U%2CB00YS401X0%2CB018QNM7V2%2CB007PB2ONS%2CB0000TFGFU%2CB088LYPS1T%2CB0925SWPFN%2CB00XWCEI8S%2CB0000T4TSU%2CB0015SBILG%2CB01FT2QTDA%2CB002L6HJAA%2CB000OQ21CA%2CB0002JT5ZK

The spring is a 9/32" by 3/4" long. It came from the Harbor Freight assorted spring set. A longer spring can also be used, though it might need to be cut down. https://www.harborfreight.com/200-piece-assorted-spring-set-67562.html

The lapper body has knurling to make it easier to use. The rear also has flats for a 1" wrench if needed. After printing the plunger hole will need to be cleaned up with a 5/16" drill bit. The bolt threads will also need to be cleaned up with a 7/16"-14 tap. The barrel threads may need to be cleaned up with a file.

The Fusion 360 file is included. To change for a different barrel thread search for Change Parameters. Under User Parameters barreldiameter is the od of the barrel. Type in the new barrel od. If it's in inches type in after the dimension. Barrellength changes the length of the treads. Thread changes the number of revolutions per inch. Metric pitches will need to be converted to inches.

Print Settings

Supports:

No

Notes: