Barrel production

Each barrel’s production story starts with a piece of steel. This careful attention ensures that the final barrel gives a consistently high caliber performance. All MullerWorks barrels are made from 416R stainless steel manufactured in the United States.

"You have to be able to adapt to what the steel is telling you at each stage of production. The ideal barrel is one that is forgiving -- you don't want it to be finicky with the bullets and powder you use. It has to shoot accurately with a broad range of loads," Dan says.

Dan designs and makes all the tooling for the cut rifling process. The tooling is inspected via measuring microsopes and an optical comparator to ensure the uniformity and correct sizing. The button tooling is designed and manufactured to his specifications on direct drive CNC grinding equipment to assure correct sizing and an absolute twist rate.

Drilling: Blanks are drilled on a modified double spindle Pratt and Whitney gun drill, and each barrel blank is inspected for run-out and straightness. After drilling and inspection, the next step can either be reaming or contouring.

Reaming: Reaming is done on a CNC machine which Dan designed and built using bore reamers which have been designed and manufactured to his specifications. Dan selects the reamer based on whether the finished product will be a signle point cut or button barrel.

Contouring: Contouring is done on a Hardinge model 1078L slant bed CNC lathe utilizing a pair of hydraulic steady rests for consistency in the tapers and size as well as to minimize the amoutn of induced stress during the contouring process. This allows for a precise and consistent barrel profile.

Initial hand-lapping: Blanks are inspected with a bore scope and precision measuring tools to check the quality and size of the ream plus ensuring a uniform bore from one end to the other. After inspection, each blank is hand lapped to remove all tool marks and inspected again to prepare it for rifling.

Rifling: There are two types of rifling - single point cut and button.

• All single point cut rifling work is done on a CNC rifling machine which Dan designed and had built to his specifications. This unique machine allows Dan to select the twist rate and number of grooves as well as the depth of cut per pass, the number of cycles, the cutting speed and cutting foces. The rifling machine components were welected for a high degree of accuracy and smoothness during operation.
• For button rifling, Dan developed a special lubricant which significantly reduces the pull forces during the buttoning process, which ensures that a consisten pressure is maintained as the button travels through the entire length of the blank. This machine has the capability to produce a broad range of twist rates. After inspection, the button rifled blanks are heat-treated in a small furnace on site. Heat treating ensures that the stresse that are put into the steel blank during the rifling process are removed. Afterwards, heat treated blanks are inspected again for sizing and any imperfections.

Final hand-lapping: The final part of the production story is that each barrel is hand lapped to remove tooling marks form rifling. Handlapping ensures that the barrel has the proper taper as well as a uniform internal surface finish from the breach to the muzzle.