Krieger Criterion Shop Tour
By Jon Y. Wolfe
On the morning of September 27, 2007 a little past 6:00 AM, I spent some time with Steve Dahlke, the President of Criterion Barrels in Richfield, Wisconsin. The night before Steve and I had dinner at a small town restaurant that was jam-packed with local flavor and close-knit hospitality. Steve was evidently a regular as he had his own booth and all the staff knew him on a first name basis. We had a few drinks, an appetizer, soup, salad and prime rib; yet we did a lot more talking than eating or drinking. By the conclusion of our meal, my appetite and my quest for information were equally satisfied. I had a full belly and a mind full of very interesting, first-hand information about the evolution of Krieger and Criterion Barrels.
Steve, who runs the day-to-day operations of both Krieger and Criterion, has been working with and for John Krieger since 1978. The two have made an obviously potent duo when it comes to making high quality barrels, but as with any successful company, what you start out doing isnít what always ends up making you successful. The original company formed by John Krieger was set up as a machine shop to manufacture a fully enclosed gearbox. By the time that contract ended, Krieger had begun the process of making rifle barrels. In 1982 the company conceptualized the process to produce high quality rifle barrels and it wasnít until 1984 that all the bugs had been worked out. From 1984 to the present, Krieger has been a highly respected name in high quality rifle barrels.
The creation of Criterion was a joint venture between John Krieger and Steve Dahlke. It has its beginnings in the production of rifle barrels for Weatherby Rifles. Initially the contract was for the lightweight Mark V and non-magnum rifle barrels. Over time, Weatherby contracted all of their rifle barrel production to Criterion and they continue to use Criterion barrels on the majority of their rifles.
In my discussions with Steve, it became apparent that good old fashioned American ingenuity is the driving force behind the companyís success and their high quality barrels. Whatís more, their process of rifle barrel making is ďa knowledge base of expertiseĒ with a breadth and depth that is rivaled by few. They are master artisans when it comes to rifle barrel production, and they make some of the best rifle barrels in the industry.
A primary purpose of my visit was to see the production of M14/M1A barrels first hand because of my passion for the M14 type rifle. This is how my connection with Krieger/Criterion began. In the process I discovered just how many different barrels Krieger and Criterion were producing for the industry at large. Iím not sworn to secrecy, but as a matter of principal I wonít divulge the names of their customers, However, it should suffice to say they are doing some very interesting projects for a wide range of customers, making barrels from 5.56mm up to .50 cal, as well as a special barrel project for a tank weapons system used for military training purposes. I was humbled by the quantity of barrels they were producing during my visit.
With respect to the M14/M1A barrel production, I had an opportunity to meet with the folks who perform the different operations on the barrels. Without sharing too much proprietary information in this public forum, Criterionís process for M14/M1A barrels involves a heat treatment of the steel by the manufacturer, which occurs before Criterion takes possession of the steel. The blanks are drilled, button rifled, honed, heat treated, honed again, turned and then chambered. (I may have one or two out of order as this process was very extensive.)
Criterionís process for button rifling is proprietary in nature and was developed and implemented in order to obtain a more consistent twist rate and to ensure the tightest bore and groove tolerances possible. Traditional button rifling can have large variances in actual twist rate. Changes in the barrel can cause the button to skid. At Criterion, the twist rate is more consistent because of their system to drive the button while turning. This has the result of improving twist rate consistency from barrel to barrel.
Their bore and groove dimensions are set to achieve the minimum diameter for the particular caliber. This process provides Criterion barrels with longer barrel life because both groove and bore diameter are at the minimum tolerance and as the barrel wears, it wears from a minimum bore and groove diameter as opposed to starting life mid-stream. According to Steve, consistent bore and groove diameter, end to end is more important than bore and groove diameter alone. That is, if the bore is slightly larger in diameter, as long as it is consistent end to end, it will have a much better potential for accuracy.
Chambering is done as a final process before the barrels are sent for chroming and phosphating. An experienced, conscientious machinist does the chambering. For optimum quality control, a production barrel nut and a control barrel nut are used to ensure correct headspace. The production barrel nut is used on each barrel, and the control barrel nut is used on a sampling of the lot. The barrel nut width closely approximates the distance between the barrel shoulder and the bolt face. This establishes the zero for the gauge that is used to measure the chambering depth and provides a reference for cartridge and bolt interface, thereby allowing a very precise approximation of finished headspace.
Without using the barrel nut, the gauge would rest on the breach face of the barrel, which may have a slightly longer or shorter distance from the shoulder. This is why the use of the nut is crucial. Otherwise, additions or subtractions must be used to calculate the approximate headspace before chroming. Criterion makes most of their own gauges for ensuring correct tolerances and they have made new tools over the past few months that aid in correctly chambering barrels that are going to be chrome lined.
As an example, their chambers are cut within a range of 4-6 thousandths deep. This represents a pre-chromed and pre-installed headspace of 1.634-1.636. This headspace measurement typically drops by 3 to 4 thousandths after chroming and installation. All else being equal, a cut depth of four thousandths would yield a finished headspace of about 1.631 and a depth of six thousandths would yield a finished headspace of 1.633. The calculation for those who are interested goes like this; four thousandths deep (1.634), plus 2-3 thousandths crush plus 1 thousandth for the chrome yields a finished headspace range of 1.630-1.631. This of course can vary depending upon the receiver, bolt, crush and actual thickness of the chrome. Although I did not see an inspection of timing using an actual control receiver, it is my understanding that this inspection is done for each barrel.
Krieger barrels and Criterion barrels share floor space and personnel, but the clear difference between the two processes is cut rifling versus button rifling. Krieger barrels use steel (raw blanks) that has been cryogenically treated and then re heat-treated, whereas Criterion barrel material is not cryogenically treated.
The cut rifling process is exactly what it sounds like. A single cutter is passed through the barrel with cutting oil being injected from inside the cutter tube. The cutter makes a full length pass in the direction the bullet travels and the machine indexes to the next point to cut the next groove. This process takes significantly longer than button rifling but does not introduce additional stress into the barrel. A cut rifled barrel can be rough turned before the cut rifling process, a button rifled barrel is not turned until after it has been rifled in order to maintain a constant bore and groove diameter.
During the button rifling process, the rifling machine exerts over 1 ton of pressure on the button that is pulled through the barrel. If the barrel had already been turned, the contour at the back would be thicker than at the front. This variation would allow the button to move more metal at the front than at the rear, therefore creating a different bore diameter from front to back. The button rifling implement uses a carbide tip attached to a steel rod that is pulled through the barrel at the appropriate twist rate. This "irons" the rifling into the barrel, rather than removing steel by cutting.
In addition to the above differences, Krieger barrels are lapped twice whereas Criterion barrels are honed. Krieger pre-laps the barrels after rifling using a lapping machine that spins the lapping bit in the barrel. The final lap is done manually in the direction the bullet travels down the barrel.
Also housed within the Krieger/Criterion facility is an underground 300 yard firing tunnel. There Krieger technicians do accuracy and velocity testing and have plans to use a high speed camera for various technical projects.
The Krieger/Criterion barrel factory is a testament to the American spirit of innovation and ingenuity at its best. Although there are high tech machines and computer controlled mills, the real heart of the operation is the experience and expertise of its employees.
Copyright 2007 by Jon Y. Wolfe. All rights reserved.