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Testing Parts

Updated: Nov 1, 2019

Three years ago a vendor called me and said "Brandan, I have started making slides and I would love for you to try them out and provide some feedback". Since slides have been a an issue in the industry as long as I have been building guns, I hastily agreed. I checked the dimensions and everything looked fantastic. The machining was clean and accurate; they were nice slides. I bought 10 of them and plugged the new slides into my build schedule along with other parts already purchased or produced in-house. I finally got to point where I was going to use one of these new slides, put it in the vise, made my first cuts. They cut like butter, which was kind of concerning because you get used to the harmonics of certain cutters on certain parts. I took the slide out of the vise and noticed it was shinier in the area the jaws were holding the part. I thought to myself... these are too soft. But I had no way to prove it, I had no hardness tester at the time and did not know anyone local who had one. I called the vendor and presented my findings and he responded that he was sure they were within spec. This led to more confusion as I seriously felt this part was too soft, so I called up my tooling guy and told him to put in an order for a hardness tester. Three days later this tester arrived with a bunch of calibration blocks, holders, and other ancillary items. I get it calibrated, read the instructions, and start testing. At first, I was getting results all over the place which didn't seem right. I finally broke down and contacted a good friend of mine in the manufacturing industry who has a background in metallurgy and heat treating processes and told him what I was experiencing. He laughed and asked if I read the instructions. Of course I read the instructions! So then we got into an in-depth conversation about testing variables and how to eliminate these variables for a better control. This was an enlightening conversation to say the least. Though I had read the instructions, there was just a lot of information that you only get through experience and trial/error, just like anything else we do. So finally to the slides that I thought were soft... I test every one of them with the same controls I have learned and found they were in fact soft; they were 26-28rc, which is typical prehard 4140 stock. This is not spec. But when I called them back and asked them about what I had found, they said that was in fact THEIR spec. Ok, so just like all other specs in the 1911 world, hardness specs are also open to change by whatever vendor is manufacturing the part. I have been testing every part I purchase for my builds since then, and testing all of the raw materials I purchase for the production of my own parts. It is interesting to see the results of some of this testing. When something is too hard or too soft, most vendors will work with you, if not, maybe you should find a new vendor. This leads me to what is happening today.


In the past few days I have been bombarded by calls about KKM barrels from customers and other builders. People know that I use them, like them, but people also know that I test them, just like everything else. In the past three years of testing KKM barrels, I have never found one to be out of spec with regard to hardness or critical dimensions. Most barrels are 44rc, with a couple here and there at 42rc. Had one barrel hit the 40rc mark, one of the new ribbed barrels that came in from another builder for verification. Most of barrels have a upper radial lug recess that is 0.300" from the center of the bore. Most have a muzzle that is 0.580". Most have a lower lug that is 0.120" from the link pin tangent, and lastly, most of their C/P ramps have standing lug that is 0.425" from the link pin tangent. This makes building to print much more predictable, which in the business of building the highest quality 1911s you can, consistency is paramount. I will complain that their chambers are often shallow, and I do not like their feedramp angle and position, but the critical dimensions are spot on. So with that being said, I was kind of shocked to hear the concern about their barrels. I recently got 10 barrels in that I have not tested yet so I stopped what I was doing and started testing. As per directions, you should plug any holes, you should support the part with the holders that come with the tester, the tested area should be flat and smooth, THEN you will have removed the variables which come from testing a tube, which can be affected greatly by deflection and axial compression. All of them were 44rc. I did notice that their bores on 9mm were 0.345"- now, which is a result of switching to a new button, but nothing out of the ordinary with regard to hardness.


So to my customers... I will not speak for every barrel out there, but your barrels are fine. Not only are they within specification of hardness, the upper radial lug recess is 0.300" from the center of the bore and 0.698" in diameter to evenly displace radial lug pressure, the chamber is cut to SAAMI spec for headspace, the hood has a close zero tolerance to the breechface in length with adequate clearance on the sides, the lower lugs are cut to a blueprint dimension with the abutment 0.140" back from the center of the link pin hole, with a 0.100" radius to match the slide stop pin... each link size up changes this 0.140" dimension by only 0.00078", the slide stop pin has a friction fit with the lower lugs, gently squeezing the entire assembly together, and lastly, the standing lug on barrel and the distance from the slide stop pin and the VIS is correctly matched according to the blueprint. Critical dimensions of a barrel and subsequent timing of the entire system are just as important to the longevity of the barrel as the hardness of the barrel.


To my friends in the industry... invest in good testing equipment and learn how to use it. Hardness tester, measuring equipment that can accurately measure in the tenths, gauge pins, specialty gauges, thread go-no go gauges, chamber go-no go gauges, bore gauges. It is a large investment, but in the business of building and selling premium firearms at premium prices, your reputation is worth the investment.



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