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The Basics, Starting Out
Question: Reamer Dimensions vs Chamber Dimensions vs Case Dimensions
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<blockquote data-quote="VinceMule" data-source="post: 3044662" data-attributes="member: 122164"><p>A. Reamer makers have .0005 tollerance on a print vs actual grind dimension. This can be + or -, so you have to do some measuring when you get the barrel back from the gunsmith. Making a chamber cast with Cerrosafe tells all.</p><p></p><p>Also, chambering techniques vary which will have a great influence on how close to reamer spec the chamber is cut.</p><p></p><p>Reamers wear with use. Naturally, the reamer can get smaller as cutting flutes wear. Again, chambering techniques have a GREAT influence on reamer wear. Various cutting fluids vary dramatically in how they reduce friction/heat.</p><p></p><p>Speedy told me that a guy that taper bores his chambers will get 150+ chambers on a reamer due to only cutting .007 per side with the reamer. </p><p></p><p>Your question, "Does a typical reamer actually need to be slightly larger or smaller than the finished hole diameter?" I hope the above answers your question. I order reamers to the dimensions that I want from JGS and Manson with great success.</p><p></p><p>B. Chamber lengths are determined by the gauge that the gunsmith uses to set the headspace. There is the Go, No Go, and Field. There is somewhere around .003-.004 difference between the Go Gauge and the No go gauge. This could explain some of the chamber lengths.</p><p></p><p>It is interesting to determine the "spread" in headspace lengths of 100 new pieces of brass which is simple to do with an oversize ogive gauge. I have had gunsmiths use the new brass to set the headspace of my rifle, but I did determine the longest and shortest headspace lengths. When you are using the shortest Headspace length to eliminate any case stretching, you may have to bump the shoulder on the longest or have a very stiff bolt close when fire forming on your first firing. You could ask the gunsmith for a headspace length where the bolt barely closes on the Go gauge to eliminate case stretch. Some gunsmiths will accommodate you and some absolutely will not.</p><p></p><p>New brass dimensions can vary greatly from manufacturer to manufacturer. I have found that Winchester has the smallest dimensions in the Web while European-made brass can be much larger, and neck thickness is all over the map also.</p></blockquote><p></p>
[QUOTE="VinceMule, post: 3044662, member: 122164"] A. Reamer makers have .0005 tollerance on a print vs actual grind dimension. This can be + or -, so you have to do some measuring when you get the barrel back from the gunsmith. Making a chamber cast with Cerrosafe tells all. Also, chambering techniques vary which will have a great influence on how close to reamer spec the chamber is cut. Reamers wear with use. Naturally, the reamer can get smaller as cutting flutes wear. Again, chambering techniques have a GREAT influence on reamer wear. Various cutting fluids vary dramatically in how they reduce friction/heat. Speedy told me that a guy that taper bores his chambers will get 150+ chambers on a reamer due to only cutting .007 per side with the reamer. Your question, "Does a typical reamer actually need to be slightly larger or smaller than the finished hole diameter?" I hope the above answers your question. I order reamers to the dimensions that I want from JGS and Manson with great success. B. Chamber lengths are determined by the gauge that the gunsmith uses to set the headspace. There is the Go, No Go, and Field. There is somewhere around .003-.004 difference between the Go Gauge and the No go gauge. This could explain some of the chamber lengths. It is interesting to determine the "spread" in headspace lengths of 100 new pieces of brass which is simple to do with an oversize ogive gauge. I have had gunsmiths use the new brass to set the headspace of my rifle, but I did determine the longest and shortest headspace lengths. When you are using the shortest Headspace length to eliminate any case stretching, you may have to bump the shoulder on the longest or have a very stiff bolt close when fire forming on your first firing. You could ask the gunsmith for a headspace length where the bolt barely closes on the Go gauge to eliminate case stretch. Some gunsmiths will accommodate you and some absolutely will not. New brass dimensions can vary greatly from manufacturer to manufacturer. I have found that Winchester has the smallest dimensions in the Web while European-made brass can be much larger, and neck thickness is all over the map also. [/QUOTE]
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Question: Reamer Dimensions vs Chamber Dimensions vs Case Dimensions
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