Jim Borden, the very knowledgeable owner of Borden Accuracy, provided an interesting historical insight about barrel fitting and the term “blueprinting”. Jim has posted on his Borden Accuracy Facebook page an explanation of the term “blueprinting” as it originally was used with respect to barrel/shoulder/lug fitting.
Barrel/Shoulder Fit and Blue-Printing
Jim told us: “Something often overlooked on barrel installation is the shoulder fit. Many are so overly obsessed with doing a crank-on fit of threads that the shoulder contact is overlooked. Full, solid barrel shoulder to recoil lug or action face is critical to optimum accuracy and precision.
Many years ago part of the ‘blueprinting’ of an action was the use of Prussian blue to ‘blueprint’ lug fit, thread fit, and barrel shoulder fit. It was a colloquial expression that had nothing to do referring to a blueprint or drawing of the action.” Bet you didn’t know that!
About the photo below, Jim noted: “the fuzzy look on the threads is a liberal coating of Never-Seez thread lubricant.”
Look carefully to see the Prussian Blue applied to the barrel shoulder, plus Never Seez on threads.
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Are you seeing unpredictable changes in Point of Impact on your target? Think you may have a scope issue? Well maybe not — when was the last time you checked your BARREL?
Yes scopes do fail, and scope bases/rings do get loose. But sometimes problems with erratic POI shifts are caused by a LOOSE BARREL. This issue came up a while back in our Shooter’s Forum. One member complained that his zero was shifting from day to day — by as much as two inches at 100 yards. He was convinced he had a scope problem, based on erratic POI:
“I think my scope loses 1 to 3 MOA per day. When I shot my rifle Monday it was dead on. On Tuesday it was 1″ low. Then on Wednesday it was 1 or 2″ lower. I don’t get it. — the elevation knob never touched. Scope will track and return to zero that day perfect. Yes EVERYTHING has been checked, nothing loose. What is the chance the erector tube spring has gone south? For the record this is a Vortex GE. Never had a bad scope, but this has me wondering”. — LB
On Forum member told LB to send the scope right back to the manufacturer. Two other members suggested mounting the scope on a different rifle to test. Good advice. That’s generally a smart strategy before you conclude a scope has gone bad…
Could Problem Be the Scope Base?
Two Forum members, ExPiper and Dickn52, suggested checking the scope base, recounting their past experiences with troublesome bases. This was intelligent — anyone with a POI problem should check all the optics attachments:
“Went crazy one day chasing my impacts on a 100-yard target. Shots would group fine for three then go nuts for 4-5. I cranked and un-cranked for about an hour. Then I reached up and the base wobbled on the rifle. Removed scope, tightened base screws and back in business.” — Dickn52
“Years ago I had a problem [where] shots were climbing with almost every shot. I was blaming the scope. However, when removing the scope I noticed that the 20 MOA base was cracked and getting wider with every shot. Needless to say I replaced the base and the problem was solved. — ExPiper
Eureka Moment — The problem was the BARREL, not the Scope
There were many helpful suggestions, but member PirateAmmo steered LB to the real problem — a loose BARREL: “We had a problem on a home-built AR-platform rifle once, barrel was loose a tad…”
Member Snert chimed in: “Yep — I had a PPC that suddenly went 19″ low. Picked up gun off bench by barrel and felt a wiggle. I tightened the barrel and the POI went 19 inches up”.
Problem Solved — Barrel Tightened up and POI Back to Normal
The gentleman with the POI problem took the advice of PirateAmmo and checked his barrel. BINGO! Low and behold, the barrel WAS loose.
LB posted: “Barrel loose by about 2%, checked it twice before and didn’t find it the first two times”.
After LB re-tightened his barrel, his rifle started shooting normally again. No more shooting low by 1-2 inches. Problem solved. The fix didn’t cost a penny and now LB doesn’t have to send a perfectly good optic back to the manufacturer.
Lesson learned? Check ALL the variables before you assume a scope has gone bad. Along with the barrel, also check your action screw tension, and of course the scope base and rings.
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Are you seeing unpredictable changes in Point of Impact on your target? Think you may have a scope issue? Well maybe not — when was the last time you checked your BARREL?
Yes scopes do fail, and scope bases/rings do get loose. But sometimes problems with erratic POI shifts are caused by a LOOSE BARREL. This issue came up recently in our Shooter’s Forum. One member complained that his zero was shifting from day to day — by as much as two inches at 100 yards. He was convinced he had a scope problem, based on erratic POI:
“I think my scope loses 1 to 3 MOA per day. When I shot my rifle Monday it was dead on. On Tuesday it was 1″ low. Then on Wednesday it was 1 or 2″ lower. I don’t get it. — the elevation knob never touched. Scope will track and return to zero that day perfect. Yes EVERYTHING has been checked, nothing loose. What is the chance the erector tube spring has gone south? For the record this is a Vortex GE. Never had a bad scope, but this has me wondering”. — LB
On Forum member told LB to send the scope right back to the manufacturer. Two other members suggested mounting the scope on a different rifle to test. Good advice. That’s generally a smart strategy before you conclude a scope has gone bad…
Could Problem Be the Scope Base?
Two Forum members, ExPiper and Dickn52, suggested checking the scope base, recounting their past experiences with troublesome bases. This was intelligent — anyone with a POI problem should check all the optics attachments:
“Went crazy one day chasing my impacts on a 100-yard target. Shots would group fine for three then go nuts for 4-5. I cranked and un-cranked for about an hour. Then I reached up and the base wobbled on the rifle. Removed scope, tightened base screws and back in business.” — Dickn52
“Years ago I had a problem [where] shots were climbing with almost every shot. I was blaming the scope. However, when removing the scope I noticed that the 20 MOA base was cracked and getting wider with every shot. Needless to say I replaced the base and the problem was solved. — ExPiper
Eureka Moment — The problem was the BARREL, not the Scope
There were many helpful suggestions, but member PirateAmmo steered LB to the real problem — a loose BARREL: “We had a problem on a home-built AR-platform rifle once, barrel was loose a tad…”
Member Snert chimed in: “Yep — I had a PPC that suddenly went 19″ low. Picked up gun off bench by barrel and felt a wiggle. I tightened the barrel and the POI went 19 inches up”.
Problem Solved — Barrel Tightened up and POI Back to Normal
The gentleman with the POI problem took the advice of PirateAmmo and checked his barrel. BINGO! Low and behold, the barrel WAS loose.
LB posted: “Barrel loose by about 2%, checked it twice before and didn’t find it the first two times”.
After LB re-tightened his barrel, his rifle started shooting normally again. No more shooting low by 1-2 inches. Problem solved. The fix didn’t cost a penny and now LB doesn’t have to send a perfectly good optic back to the manufacturer.
Lesson learned? Check ALL the variables before you assume a scope has gone bad. Along with the barrel, also check your action screw tension, and of course the scope base and rings.
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Jim Borden, the very knowledgeable owner of Borden Accuracy, provided an interesting historical insight about barrel fitting and the term “blueprinting”. Jim recently posted on the Borden Accuracy Facebook page an explanation of the term “blueprinting” as it originally was used with respect to barrel/shoulder/lug fitting.
Barrel/Shoulder Fit and Blue-Printing
Jim told us: “Something often overlooked on barrel installation is the shoulder fit. Many are so overly obsessed with doing a crank-on fit of threads that the shoulder contact is overlooked. Full, solid barrel shoulder to recoil lug or action face is critical to optimum accuracy and precision.
Many years ago part of the ‘blueprinting’ of an action was the use of Prussian blue to ‘blueprint’ lug fit, thread fit, and barrel shoulder fit. It was a colloquial expression that had nothing to do referring to a blueprint or drawing of the action.” Bet you didn’t know that!
About the photo below, Jim noted: “the fuzzy look on the threads is a liberal coating of Never-Seez thread lubricant.”
Look carefully to see the Prussian Blue applied to the barrel shoulder, plus Never Seez on threads.
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This barrel’s shoulder was 0.025″ off the action because Red Locktite had been used on the threads.
Gunsmith Thomas ‘Speedy’ Gonzales offered this interesting report about how NOT to headspace a barrel. Hopefully you never discover something like this…
“A good friend and customer sent this rig in for repair after FedEx damaged the rifle during inbound transport from another smith. After repairing the stock and rebedding it, I decided to re-polish the barrel to make the repair perfect. Well this just added insult to injury as the barrel did not want to come off. After a few choice words, the barrel finally broke free only to reveal something very disturbing. It seems the barrel had been ‘headspaced’ by using RED Loctite to hold it in place.” [Editor: That’s definitely NOT how barrels should be fitted.]
Speedy was not happy: “I hope the smith that did this sees the photos and realized what jeopardy he put my customer in or anyone who shot the rifle for that matter. When cleaned up, the shoulder on the barrel was over 0.0250″ (25 thousandths) away from the face of the receiver.” [Editor: That’s a lot in this business]. Check out the images below to see how much the barrel rotated further inward when cleaned up. The barrel spun in nearly another eighth-turn or more. Not good.
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Are you seeing unpredictable changes in Point of Impact on your target? Think you may have a scope issue? Well maybe not — when was the last time you checked your BARREL?
Yes scopes do fail, and scope bases/rings do get loose. But sometimes problems with erratic POI shifts are caused by a LOOSE BARREL. This issue came up recently in our Shooter’s Forum. One member complained that his zero was shifting from day to day — by as much as two inches at 100 yards. He was convinced he had a scope problem, based on erratic POI:
“I think my scope loses 1 to 3 MOA per day. When I shot my rifle Monday it was dead on. On Tuesday it was 1″ low. Then on Wednesday it was 1 or 2″ lower. I don’t get it. — the elevation knob never touched. Scope will track and return to zero that day perfect. Yes EVERYTHING has been checked, nothing loose. What is the chance the erector tube spring has gone south? For the record this is a Vortex GE. Never had a bad scope, but this has me wondering”. — LB
On Forum member told LB to send the scope right back to the manufacturer. Two other members suggested mounting the scope on a different rifle to test. Good advice. That’s generally a smart strategy before you conclude a scope has gone bad…
Could Problem Be the Scope Base?
Two Forum members, ExPiper and Dickn52, suggested checking the scope base, recounting their past experiences with troublesome bases. This was intelligent — anyone with a POI problem should check all the optics attachments:
“Went crazy one day chasing my impacts on a 100-yard target. Shots would group fine for three then go nuts for 4-5. I cranked and un-cranked for about an hour. Then I reached up and the base wobbled on the rifle. Removed scope, tightened base screws and back in business.” — Dickn52
“Years ago I had a problem [where] shots were climbing with almost every shot. I was blaming the scope. However, when removing the scope I noticed that the 20 MOA base was cracked and getting wider with every shot. Needless to say I replaced the base and the problem was solved. — ExPiper
Eureka Moment — The problem was the BARREL, not the Scope
There were many helpful suggestions, but member PirateAmmo steered LB to the real problem — a loose BARREL: “We had a problem on a home-built AR-platform rifle once, barrel was loose a tad…”
Member Snert chimed in: “Yep — I had a PPC that suddenly went 19″ low. Picked up gun off bench by barrel and felt a wiggle. I tightened the barrel and the POI went 19 inches up”.
Problem Solved — Barrel Tightened up and POI Back to Normal
The gentleman with the POI problem took the advice of PirateAmmo and checked his barrel. BINGO! Low and behold, the barrel WAS loose.
LB posted: “Barrel loose by about 2%, checked it twice before and didn’t find it the first two times”.
After LB re-tightened his barrel, his rifle started shooting normally again. No more shooting low by 1-2 inches. Problem solved. The fix didn’t cost a penny and now LB doesn’t have to send a perfectly good optic back to the manufacturer.
Lesson learned? Check ALL the variables before you assume a scope has gone bad. Along with the barrel, also check your action screw tension, and of course the scope base and rings.
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There is a new book, Chambering Rifles for Accuracy, that will benefit folks who want to understand the chambering process, and potentially learn to chamber a barrel on their own. We caution, however — you really need a skilled, hands-on mentor for this this task. For someone without a lot of machining experience, chambering can be tricky, and working with lathes can be dangerous to say the least.*
With those cautions stated, this book will help any gun-owner understand how chambering is done, and what to look for when assessing chambering work by commercial gunsmiths. Chambering Rifles for Accuracy is co-authored by Gordy Gritters and Fred Zeglin. The methods detailed in this book can be used equally well by gunsmiths in a professional shop, and by skilled, well-trained hobbyists working in a home workshop. The book costs $49.95 from Amazon.
Gordy Gritters is a highly-respected gunsmith and gunsmithing instructor. Gordy has built many match-winning competition rifles so he knows his stuff. Fred is a gunsmith, gunsmithing instructor, author, and is the owner of 4-D Reamer Rentals, so he is very knowledgeable on the use and care of reamers. Fred has extensive experience building high-accuracy hunting rifles.
Fred wrote the first half of the book, which covers what is needed to prepare for and chamber high-accuracy hunting barrels. Zeglin lists all the tools needed such as reamers, micrometer reamer stops, headspace gauges, and more.
Gordy wrote the second half of the book, which goes beyond basic chambering. Gordy covers setting up a lathe for chambering barrels through the headstock, various dialing-in methods commonly used, how to deal with curvature in rifle bores, and how to deal with reamer chatter (especially prevalent in 5R-type barrels). Then Gordy covers the entire dialing-in/threading/fitting/chambering/crowning process used to build a benchrest-quality rifle. Gordy also explaines how to ream custom chamber necks, and how to throat the chamber for specific bullets or for a specific purpose.
Gordy Gritters also created an excellent DVD, “Chambering a Championship Match Barrel”. No other chambering video shows the entire chambering process step-by-step with the advanced, precision techniques used by master gunsmiths. Gordy has built several rifles that hold world records and have won National Championships. This is a professional 90-minute production from Grizzly Industrial. You can purchase this $69.95 DVD from Gordy’s website or from Grizzly Industrial.
*This Editor’s own uncle suffered a severe arm injury while working with a lathe. He was not an amateur — he had done lathe and mill work for over 40 years. But a shirt-sleeve caught in the spinning chuck. The results were horrific.
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This barrel’s shoulder was 0.025″ off the action because Red Locktite had been used on the threads.
Gunsmith Thomas ‘Speedy’ Gonzales offered this interesting report about how NOT to headspace a barrel. Hopefully you never discover something like this…
“A good friend and customer sent this rig in for repair after FedEx damaged the rifle during inbound transport from another smith. After repairing the stock and rebedding it, I decided to re-polish the barrel to make the repair perfect. Well this just added insult to injury as the barrel did not want to come off. After a few choice words, the barrel finally broke free only to reveal something very disturbing. It seems the barrel had been ‘headspaced’ by using RED Loctite to hold it in place.” [Editor: That’s definitely NOT how barrels should be fitted.]
Speedy was not happy: “I hope the smith that did this sees the photos and realized what jeopardy he put my customer in or anyone who shot the rifle for that matter. When cleaned up, the shoulder on the barrel was over 0.0250″ (25 thousandths) away from the face of the receiver.” [Editor: That’s a lot in this business]. Check out the images below to see how much the barrel rotated further inward when cleaned up. The barrel spun in nearly another eighth-turn or more. Not good.
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This illustration shows headspace measurement for the popular .308 Winchester cartridge, which headspaces on the shoulder. Image copyright 2015 Ultimate Reloader.
In this Brownells Tech Tip, Brownells gun tech Steve Ostrem explains what headspace is and why it’s one of the most critical measurements for nearly all firearms. Even if you’re an experienced rifle shooter, it’s worth watching this video to refresh your understanding of headspace measurements, and the correct use of “GO” and “NO-GO” gauges.
Headspace Definition
In firearms, headspace is the distance measured from the part of the chamber that stops forward motion of the cartridge (the datum reference) to the face of the bolt. Used as a verb, headspace refers to the interference created between this part of the chamber and the feature of the cartridge that achieves the correct positioning. Different cartridges have their datum lines in different positions in relation to the cartridge. For example, 5.56x45mm NATO ammunition headspaces off the shoulder of the cartridge, whereas .303 British headspaces off the forward rim of the cartridge.
If the headspace is too short, ammunition that is in specification may not chamber correctly. If headspace is too large, the ammunition may not fit as intended or designed and the cartridge case may rupture, possibly damaging the firearm and injuring the shooter. (Source: Wikipedia)
Headspace Gauges
Headspace is measured with a set of two headspace gauges: a “Go” gauge, and a “No-Go” gauge. Headspace gauges resemble the cartridges for the chambers they are designed to headspace, and are typically made of heat-treated tool steel. Both a “Go” and a “No-Go” gauge are required for a gunsmith to headspace a firearm properly. A third gauge, the “Field” gauge, is used (as the name implies) in the field to indicate the absolute maximum safe headspace. This gauge is used because, over time, the bolt and receiver will wear, the bolt and lugs compress, and the receiver may stretch, all causing the headspace to gradually increase from the “factory specs” measured by the “Go” and “No-Go” gauges. A bolt that closes on “No-Go” but not on “Field” is close to being unsafe to fire, and may malfunction on cartridges that are slightly out of spec. (Source: Wikipedia)
To learn more, read Brownell’s longer article Headspace Gauges and How to Use Them. Among other things, this explains the relative lengths of “Go”, “No-Go”, and “Field” gauges. The “Field” is actually the longest: “The GO gauge corresponds to the SAAMI (Sporting Arms & Ammunition Manufacturer’s Institute) minimum chamber length, while the FIELD gauge usually matches the maximum chamber depth, or slightly less. NO-GO gauges are an intermediate length between minimum and maximum, that, technically, is a voluntary dimension. A firearm that closes on a NO-GO gauge and does not close on a FIELD gauge may not give good accuracy and may have very short cartridge case life from the ammunition re-loader’s standpoint.”
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This illustration shows headspace measurement for the popular .308 Winchester cartridge, which headspaces on the shoulder. Image copyright 2015 Ultimate Reloader.
In this Brownells Tech Tip, Brownells gun tech Steve Ostrem explains what headspace is and why it’s one of the most critical measurements for nearly all firearms. Even if you’re an experienced rifle shooter, it’s worth watching this video to refresh your understanding of headspace measurements, and the correct use of “GO” and “NO-GO” gauges.
Headspace Definition
In firearms, headspace is the distance measured from the part of the chamber that stops forward motion of the cartridge (the datum reference) to the face of the bolt. Used as a verb, headspace refers to the interference created between this part of the chamber and the feature of the cartridge that achieves the correct positioning. Different cartridges have their datum lines in different positions in relation to the cartridge. For example, 5.56x45mm NATO ammunition headspaces off the shoulder of the cartridge, whereas .303 British headspaces off the forward rim of the cartridge.
If the headspace is too short, ammunition that is in specification may not chamber correctly. If headspace is too large, the ammunition may not fit as intended or designed and the cartridge case may rupture, possibly damaging the firearm and injuring the shooter. (Source: Wikipedia)
Headspace Gauges
Headspace is measured with a set of two headspace gauges: a “Go” gauge, and a “No-Go” gauge. Headspace gauges resemble the cartridges for the chambers they are designed to headspace, and are typically made of heat-treated tool steel. Both a “Go” and a “No-Go” gauge are required for a gunsmith to headspace a firearm properly. A third gauge, the “Field” gauge, is used (as the name implies) in the field to indicate the absolute maximum safe headspace. This gauge is used because, over time, the bolt and receiver will wear, the bolt and lugs compress, and the receiver may stretch, all causing the headspace to gradually increase from the “factory specs” measured by the “Go” and “No-Go” gauges. A bolt that closes on “No-Go” but not on “Field” is close to being unsafe to fire, and may malfunction on cartridges that are slightly out of spec. (Source: Wikipedia)
To learn more, read Brownell’s longer article Headspace Gauges and How to Use Them. Among other things, this explains the relative lengths of “Go”, “No-Go”, and “Field” gauges. The “Field” is actually the longest: “The GO gauge corresponds to the SAAMI (Sporting Arms & Ammunition Manufacturer’s Institute) minimum chamber length, while the FIELD gauge usually matches the maximum chamber depth, or slightly less. NO-GO gauges are an intermediate length between minimum and maximum, that, technically, is a voluntary dimension. A firearm that closes on a NO-GO gauge and does not close on a FIELD gauge may not give good accuracy and may have very short cartridge case life from the ammunition re-loader’s standpoint.”
On German Salazar’s Rifleman’s Journal website, you’ll find an excellent 5-Part Series on barrel chambering. The Series, entitled The Voyeur’s Guide to Barrel Chambering, is not intended to be a “how-to” instructional treatise for gunsmiths. Instead, German’s 5-Part Guide is aimed at the end user — the shooter. German explains: “This Series isn’t intended for anyone who owns a lathe; instead it is for those of us who send an action off to get a new barrel installed. Those who have the equipment know what to do and how to do it and I have nothing to teach them. On the other hand, if you’ve ever wondered just what goes into barrel fitting, this is it.” PART I | PART II | PART III | PART IV | PART V
With well-written text and dozens of very high-quality images, German takes you through the chambering, threading, shoulder-fitting, and crowning processes from start to finish. The idea is to give the “barrel consumer” a clear idea of the processes involved when a barrel blank is converted into functional form, complete with chamber, threaded tenon, fitted breech, and crown.
We highly recommend German’s 5-Part Voyeur’s Guide to Barrel Chambering. German, with the aid of John Lowther (who ran the machines), did a great job. The series has already drawn much attention from our Forum members, along with praise. After reading the articles, John C. from Australia wrote: “Your Chambering articles… really are excellent [and] informative for those of us too scared to watch our gunsmith chamber one of our barrels lest we distract him at a crucial moment!”
We know you’ll learn something from reading through German’s 5-Part Series. And if you see a photo on German’s website that intrigues you, simply click on it to see a larger, higher-resolution version. All the images in the Voyeur Series on RiflemansJournal.com can be zoomed to larger formats.
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Barrel/Shoulder Fit and Blue-Printing
Headspace Gauges
On German Salazar’s 
