Tag Archives: reamers

Excerpt from “Gunsmithing Student Handbook Series”

At the time of this writing there are three books in the Gunsmithing Student Handbook Series.  In early 2018 “Chambering Rifles for Accuracy” was released.  In its first week on Amazon.com it was #1 in two categories.  Gordy Gritters, famed benchrest gunsmith & Fred Zeglin well known wildcat and hunting rifle maker joined forces to create this comprehensive title.  It covers the subject of installing and chambering barrels from simple rechamber jobs, to hunting rifles and the last half of the book is all about benchrest quality gunsmithing.

The excerpt here gives you an idea of how careful the authors are to cover details often overlooked in such books.  Enjoy:

Tolerance Stacking; 
                Everything You Need to Know About Pilots?

Chamber reamers come with two styles of pilots, solid or removable bushing (the later sometimes called a floating pilot).  One is evil and one is practically perfection.  But which is which?  I can tell you that in renting tools to gunsmiths I have found the industry is split on this question about 50/50.  In other words, about half demand solid pilot reamers exclusively and the other half will not touch those nasty solid pilots with a ten foot pole.

It is clear that there is a trend toward the removable pilot reamers.  This is because barrel makers are not all holding to the same production standards.  Some have the idea that a tighter bore is better, while other makers hold close to the “standard” bore dimensions.  Example, .308 bores are .300” on the bore and .308” on the groove.  Custom barrel makers have tightened the bore to say .298”  This will required a smaller pilot as the standard pilots are normally .299” with tolerances of + 0 to – .0005”. removable pilot reamer 

Removable pilot reamer.

The reason for the tighter bore?  In short, it is believed that it produces better accuracy.  This is only true as compared to a loose bore that is oversized, i.e. a groove on a 30 caliber of .309 or .310 will produce lower pressures and potentially be less accurate because the bullet is not fully engaged until pressure bumps the bullet up to match the bore.

For a pilot to work correctly it should be .001” smaller than the actual bore dimension.  In other words, it needs to be a close slip fit.  If a pilot is too tight it will bind and likely break the reamer, and possibly damage the bore.  If a pilot is too loose it will promote chatter.  It is possible to run the pilot on a removable pilot reamer closer to the bore diameter (.0005” under bore diameter is ideal), but it must still slip easily in and out to avoid damage to the barrel or the tools.

A little history at this point might be interesting:  Red Elliot was and still is legendary with old timer gunsmiths as the absolute best reamer maker of the last century.  Near as I can tell he was the first to offer removable pilots on his reamers.  Why did he do this?  Well, he found that there were enough different barrel makers in his day that the dimensions of the bore diameter (where the pilot rides) varied a fair amount. 

So, this problem of bore dimensions changing a little is nothing new.  What about SAAMI standards you say?  I will address that in just a moment, for now lets talk about how Red Elliot handled bushing pilots.

I have seen several of Red’s reamers with bushing type pilots, what we sometimes call floating pilots today.  Red held very tight tolerances on his bushings so that it required a little pressure to slide them onto the reamer, held in place by a screw mounted in the end of the reamer the bushing would not turn once the screw was tightened.  This is contrary to the bushing pilots we see commonly used today, where the bushing is a slip fit with about .0005” tolerance internally.  This tolerance is added for manufacturing ease. Tolerance stacking is not usually mentioned in conjunction with floating pilot reamers, but we are going to take a closer look at it here.

Another source of tolerance issues is the fact that the pilot receiver on the reamer must be concentric (round), and in line with the reamer.  If either of these conditions is not correct there will be problems with the reamer cutting oversized or out of alignment with the bore.  Admittedly, this is not much of an issue with today’s cnc machines.  So long as the operator does not make an error, and no chips get caught in the set-up.  One other possible source of trouble would be a warped reamer (not common).

Now for SAAMI, their standards are voluntary, so obviously any barrel maker can decide whether or not to hold solid to the standards.  Industry standard is plus or minus a half thousandth (+ or – 0.0005”) on the bore diameter.  The bore diameter is the smallest diameter of the barrel, also referred to by shooters as “across the lands”.  The same tolerance applies to the groove of the barrel.  I will leave the discussion of groove depth as we are talking about bore diameter as it relates to chambering tools, groove depth does not affect these dimensions.

Admittedly barrels considered “match” grade or “air gaged” are supposed to be held to a tolerance of .0003” or less total variance, end to end of the barrel.  This does not indicate the actual bore diameter, we are left to assume that it is the standard diameter for caliber.  In the case of a 30 calibers we would be talking about a .300” bore.  What if the maker decides to simply use a gage that works with the bore diameter they are making, say .2995” and it air gages as above.  You have a match grade barrel but the bore is at the minimum size according to industry standards. 

Are you starting to see how bores can vary and still be within standards?

Of course there are those makers who operate outside the standards and make perfectly good barrels.  The point being; different size pilots will be needed to chamber these barrels as was recognized back in the 1950’s and 60’s by Red Elliot.  It’s pretty obvious by now that removable pilots are necessary tools in dealing with variations in bore dimensions.  It should be clear by now that variations in bore diameter of plus or minus .001” or even more, is not that unusual, even though such dimensions do not follow the voluntary standards set by SAAMI.

Solid pilot reamers offer certain advantages over the floating pilot.  First and most obvious there is no built in tolerance between the bushing and the reamer, because the there is no bushing.fixed pilot

 

 Solid Pilot Reamer

Since most barrel makers today are making barrels by the button rifled method dimensions tend to remain pretty steady for a given maker as buttons last a long time if properly cared for.  So if you deal with the same barrel maker all the time chances are a solid pilot reamer will fit the same from barrel to barrel. 

There are other factors that play into the bore and groove dimensions, but that is for a discussion for another book.

One limitation of a solid pilot reamer is that it cannot be changed to deal with variations in bore diameters.  Of course you can have the pilot ground down if necessary to fit a tight bore, but then you would probably need a second or even a third reamer to deal with various diameter bores. 

Everything in life is a trade-off.  Because of the expense of multiple reamers for the same caliber removable pilots are a cost effective answer to the problem.  $10 for a bushing beats $100 or more for another reamer.  There are shops that stock bushings in 0.0002” steps for the popular calibers.  This allows them to match the bushing to the bore every time.

pilot bushingsPilot bushings can be a big investment.

To make the use of removable pilots efficient and accurate, the gunsmith should invest in a set of pin gauges.  These are precision ground pins that can be used to gauge the bore and insure that the correct bushing is selected.  Using pin gauges allows the gunsmith to know what bore diameter the barrel maker is really supplying.

Now keep in mind the pilot has to slip into the bore, so in mechanical terms the pilot has to be about 0.0004” smaller than the bore to slip in without any interference. In most shops the pilot is figured at 0.001” smaller than the bore and rightly so.  Too tight a fit can gall and or leave marks in the bore or stress the reamer and break it during the reaming process.

What happens if the pilot is too loose?

Ninety-Nine times out of a hundred when a reamer chatters (vibrates) in use, it is because the pilot to bore fit is too loose. 

The lack of support when the pilot is too small allows the reamer to move around in the bore, as the tool tries to bite into the steel it grabs hard and because even tool steel is flexible you get chatter as the tool loads and releases tension.  This is the reason that some gunsmith’s insist on having a set of pilots that cover the possible variations in .0002” (That’s 2/10,000 of an inch.) increments.  Keeping the pilot as close to bore dimensions as possible will help eliminate chatter and promote a more precise chamber. 

If you have a pilot that is a perfect match for the bore but is too loose on the inside where it rides on the reamer then the advantage of a close fitting pilot is negated.  To pull the whole concept together…  If you have a .0002” tolerance on your bushing to barrel fit and the same on the pilot to reamer fit, you end up with .0004” total slop on the pilot. 

I can tell you that most people do not grasp this or understand why these tolerances  matter.  I base that statement on 30 years of talking to gunsmithing customers, and the people who call to rent tools.  The comments that shooters and gunsmiths make during our conversations indicate their level of understanding in a hurry.

In general if the total pilot run-out is under .001” then all will work fine and there should be no worries.  This rule holds true for solid pilot or removable pilot reamers.  Long ago I lost track of how many rechamber and barrel jobs I have done.  I can tell you that

Chambering Rilfes for Accuracy, cover

 it is possible to get an accurate job from either type of reamer.  In fact, if pressed for a choice I would say that solid pilot reamers are more accurate on average.  Especially for inexperienced gunsmiths.

I do not make this statement lightly, as I own hundreds of reamers of both types.  This goes back to the understanding of how the tools relate to the barrel.  To reiterate, the one caveat would be that for best accuracy the pilot of the reamer must meet the tolerances of less than .001” run out verses the bore, for all this to hold true.

There is another major factor in how well a reamer cuts and how accurate the gun will be…  The gunsmith must do a good job on the set up for machining.  If the threads are not true to the bore, or the chamber is crooked or oversized, or the throat of the chamber ends up off center, accuracy will be elusive to say the least.

Use of a floating reamer holder is a great way to insure an accurate chamber.  This tool allows the reamer to follow the hole in the barrel without any side pressure that might be caused by minor misalignment of the tail stock to the bore of the lathe.

Whether you plan to build accurate hunting rifles or top quality competitive benchrest and long range guns this handbook has detail descriptions and plenty of clear photos to make the subject easy to understand.  The other titles in the series deal with headspace, the vital counterpart to chambering, check them out here.  More titles are planned for the series.  These are college level training manuals that a gunsmith at any level of experience will value.

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The Big News for Fred Zeglin, April 2018

How many authors can brag that they held #1 in two categories on Amazon.com?

I don’t know the answer to that, but I am one of them so here I am, bragging.

Last month (April 2018) Gordy Gritters and I (Fred Zeglin) released our new book, “Chambering Rifles for Accuracy”.  This book is the 3rd in the Gunsmithing Student Handbook Series. Obviously the reception of the book and it’s counterparts in the series has been very good.  It’s gratifying to see our work appreciated by so many customers.

On behalf of Gordy and myself.

Thank you for pushing us to #1 on Amazon during the first week of April.

#1 on Amazon

#1 in Two Categories on Amazon!

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28 Nosler Announced at Shot Show 2015

During the first day of SHOT Show 2015 I swung by Nosler’s Booth.  GEDSC DIGITAL CAMERA

And what to my wundering eyes did appear, the 28 Nosler. That’s right Nosler is adding to their line-up.  The 28 and 26 Nosler utilize the same headspace gauges.

Talking to Mike Lake, who did the design work on these cartridges for Nosler, he stated that everything from 26 to 9.3mm have been registered and approved by SAAMI.  For now, Nosler is only bringing the 28 Nosler to market.

When asked why Nosler took all the designs to SAMMI now Mike said, “We were aware of the wildcats that have appeared on the 26 Nosler case.  So, it just made sense for us to get the dimensions for all the calibers completed and registered with SAAMI.”

The 28 Nosler according to Nosler’s new catalog will push a 160 grain bullet at 3300 feet per second (fps).  A 175 grain bullet will launch at 3125 fps.  In case you were wondering that is faster than the 7mm RUM with less powder.  How is that possible?  Pretty simple really, the 7mm RUM is very over bore, in other words it has too much case capacity for the 7mm bore.

Last years introduction of the 26 Nosler was met with great enthusiasm by shooters.  There is every reason to believe that even more shooters will like the 28 Nosler, 7mm cartridges in general are more popular the 6.5mm in the U.S.  Look for this to be a much discussed cartridge in 2015.

I talked to Pacific Tool & Gauge and 4D Reamer Rentals LTD.  PTG says the 28 is in production already and 4D placed an order for it as soon as the cartridge was announced.  4D also ordered reamers for all the Nosler designs registered with SAAMI.

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New Chamber Reamers for 2015

26 Nosler

Popular new Cartridge for 2014.

Shot Show is just a few weeks away, Fred Zeglin of 4D Reamer Rentals LTD heads to Shot each year to make sure he has all the new caliber offerings for his clients.  Last year is was the 26 Nosler and the 25-45 Sharps (SRC).

So far the information leaks about new cartridges for 2015 have been controlled, no sneak peaks at what is coming from the factories.  However, Fred says there are new wildcats getting some attention.

6mm Creedmoor has already been added to 4D’s list of reamers you can rent.  It looks like wildcats on the 26 Nosler case are what will be hot in 2015.  Those calibers will include:

  •  25 Nosler
  • 27 Nosler
  • 28 Nosler
  • 30 Nosler
  • 33 Nosler
  • 35 Nosler
  • 375 Nosler
  • 416 Nosler

All of these wildcats based on the 26 Nosler case will use the same headspace gauges, they are simply necked up, or in the case of the 25 necked down versions of the parent case.

6mm Grendel and 6.8mm Grendel are making waves too.  Both of these are based on the popular 6.5 Grendel.  If you’re a bolt action fan these cartridge are available in a configuration better suited to a bolt gun as the BPC (Borden Palmisano Cartridge) series, all using the same gauges.

Look for 4D Reamer Rentals to add all these reamers and more in 2015.

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New Approach to Firearms Education

Flathead Valley Community College will launch a new two-semester evening Firearms Technologies Certificate starting this fall.  The 27-credit program will feature curriculum developed to support the growing firearms industry in the Flathead Valley in Montana as well as across the country.

One of only a few colleges in the nation to offer firearms related programs. FVCC has taken a unique approach, developing the program as an enhancement to its existing industrial machine technology program introduced last year under the Department of Labor “Amplifying Montana’s Advanced Manufacturing and Innovation Industry” grant (#TC-23760-12-60-A-30).  This approach will make FVCC the only school that focuses on manufacture of firearms and related parts.

The new program will provide students the opportunity to incorporate advanced machining skills with an understanding of firearms operational systems. Courses are tailored to emphasize the manufacturing of firearm components.

Fred Zeglin, curriculum coordinator for the program, developed the courses under the guidance and input from local firearms manufacturers.  “Manufacturers say they are seeking trained machinists who understand firearms.  Classes have been designed to build understanding of a wide variety of firearms and the way that they function.” said Zeglin.

Emphasis will be placed upon the completion of several gunsmithing projects involving blueprints and schematics using a combination of both hand and machine tools. This program will provide a clear understanding of firearms design and function, enabling graduates to assist with design implementation or tolerance issues in manufacturing environments.

The program will be held in the evenings with labs during the daytime on Friday and Saturday. Course topics will include firearms introduction and safety; manual mill and lathe systems; bench metal techniques; firearms theory and firearms repair; machine tools for gunsmiths; and precision rifle building.  This selection of courses are designed to increase the marketable skills of the students in the manufacturing realm.

The program will be marketed nationwide bringing focus to the local industry.  Prospective students must apply both to the program and for admission to FVCC. Program applications are due August 1 at 4 p.m. Applications are available online at http://www.fvcc.edu/firearms or in the Admissions Office in Blake Hall on the FVCC Kalispell campus. For more information, contact Jori Bullemer at 756-3905 or jbullemer@fvcc.edu or Will Richards at 756-4862 or wrichards@fvcc.edu.

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25-45 SRC (Sharps Rifle Co.) SHOT Show 2014

Found this little goodie at Media Day for Shot Show.  You might imagine seeing the Sharps name that has always been associated with single shots and then seeing nothing but AR-15 rifles in the booth.  I took a double take…  which is probably what they were hoping for all the writers that visited the event.25-45 SRC ammo

Having been in the gun business for so many years I have seen the rebirth of many company names.  Some have been successful and others have quickly died away.  No telling what will happen with this new company.  Sharps Rifle Company (SRC) is one of several brands, (five at present) under the one roof.

Turns out the item of interest was the 25-45 SRC cartridge.  This is the most recent iteration of a wildcat most commonly known as a 25/223 Remington.  Another well known variation came out in 1987 as the 25 TCU (Thompson Center Ugalde).  The TCU version was designed for metalic silhouette competition.  Of course that cartridge was intended for use in a 14″ barrel from a Contender pistol.  While they are not interchangeable the two cartridges are very similar.  Ahh, what’s old is new again.  I sense a theme here.

  • 65 Grain Rapid Expansion Varmint is advertised at 3300 feet per second from a 20″ barrel.
  • 87 Grain soft point or FMJ loads are advertised at 3000 feet per second also from a 20″ barrel.

Of course, headstamped brass and commercially loaded ammo is always a selling point and SRC is offering just that.  For more information on the brands and products associated with SRC click here.

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Savage Offers New Model Axis II XP, Shot Show 2014

Axis XP

This new variation on the Axis XP features the AccuTrigger, which is adjustable from 2.5 to 6 pounds.  The rifle will come with a Weaver Kaspa scope mounted and bore sighted.  This is a 3-9×40 variable scope.

Barrels are 22 inches, matte blue on all metal surfaces.  The stock is a black molded synthetic.  A detachable five rounds magazine rounds out the package.  Eight calibers from 223 to 30-06 are offered.  MSRP is only $415

Axis barrels can be changed out just like the popular Savage 110 type barrels.  In fact our friends at 4D Reamer Rentals LTD. tell us that the barrels are interchangeable.  4D offers Savage pre-fit barrels in more calibers than any other maker we have found. So you can swap the barrel on one of these rifles and have the caliber of your dreams.

Rumor has it that 4D will be introducing a new barrel nut wrench, at the SHOT Show, for Savage smooth barrel nuts, like those found on the Axis series of rifles.

Finally, Savage is offering Youth models on the new Axis II XP series.  These rifles will have a 20″ barrel chambered for 243 Winchester.  Two camo patterns will be offered:  A woodland pattern and the very popular “Muddy Girl”.

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Savage Barrel Nut Wrench, New for SHOT Show 2014

4D Savage barrel nut wrench

Savage offers smooth barrel nuts on many of their bolt guns.  Until now, no commercial wrench for removing or installing these barrel nuts when headspacing a pre-fit barrel existed.  4D Reamer Rentals LTD has designed this new wrench for use with the smooth type barrel nuts found on many Savage rifles.  The wrench will not work with splined type nuts.

These smooth barrel nuts are commonly available in the market place and provide a nicer finished look without the splines cut into them.  These smooth nuts will work on all Savage 110 action variations, including Axis™ and Stevens™. 

Made from aircraft grade aluminum this wrench can be used for both Large (fat magnum) and Small (standard) thread barrel nuts.  

The finish on the production wrenches will be either painted or anodized, depending upon the buyers preference.  Graphic dipped models, as pictured here, would be for special presentation pr personalized gifts.

Dealer pricing available.
Savage Barrel Nut Wrench by 4D MSRP $49.95

Rental from 4-dproducts.com will be $15  they are carrying the smooth barrel nuts too.

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Tricks the Pros Use When Rechambering a Barrel.

Chamber with ejector removed.

Many a chamber reamer has been damaged or broken when a novice gunsmith tried to rechamber a barrel with an extractor or ejector cut.  In this post I will explain how to get a high quality job without danger of damaging the reamer.

At right is the breech end of an NEF barrel that is about to be rechambered.  The mistake that is commonly made is to try to insert the chamber reamer into this existing chamber without preparing the chamber area.  Reamers are not made to work on an interrupted cut such as an extractor cut.  Trying to use a conventional drill bit will not work in this situation either, it will simply do a lot of damage and make a mess of the job.

There are two easy ways to handle this problem and end up with a nice clean chamber.

  1. Use a piloted counterbore to cut a recess that will accept the chamber reamer, eliminating the extractor cut.  The problem with this method is that you would need a specialty tool for every shoulder diameter that you might decide to rechamber for.
  2. Place the barrel in the lathe and use a boring bar or a simple boring tool ground for the purpose.  This method has the advantage of working on any cartridge combination that you might encounter.

Measure the bore to work with the reamer.

Bore out the area of the extractor cut to a dimension very close that of the shoulder diameter of the reamer you will be using.  The idea again is to prevent the reamer from cutting an interrupted cut.  As the shoulder of the reamer engages the chamber it will then cut uniformly and without chatter.  If you attempt to cut the chamber without performing this preparation each flute of the reamer will bang against the extractor cut as it comes around.  In most cases this will at a minimum damage the reamer, worst case it will brake the reamer.

hand ground boring tool.

At right is a simple hand ground lathe bit that will work for this job.  The under side of the tool must be relieved so that it can clearance the inside of the chamber area.  This is a finesse job, only remove as much as you need to get the reamer in full contact with the barrel.

What it looks like when bored correctly.

Here is the chamber area after the boring work is done and before the reamer has been used.  Note that we did not cut away any unnecessary material, only that which will make the reamer cut properly.

Chatter is a common complaint when rechambering a barrel.  The pilot is often either not engaged in the bore of the barrel or it does not fit the barrel properly.  Proper pilot diameter is .0005″ to .001″ smaller than the bore diameter (across the lands).  This allows for a slip fit to the bore.  An undersized pilot will promote chatter.

Finished chamber

A simple way to stop chatter that will not damage the tool is to wrap the reamer with a strip of wax paper.  The wax paper acts as a dampener against the chatter which is caused by vibration.  Do use cutting oil as normal when using the wax paper.

The chamber below completely cleaned up the old rim cut from the rimmed cartridge.  Of course the extractor would have to be modified for the rimless case.

Side note:  Reamers for straight wall cases like black powder and pistol type cartridges are prone to damage from the problems addressed in this post.  In addition they are prone to damage near the rim cutter when chips become trapped in the extractor cut.  So if your working with such reamers take extra care to keep chips cleared, especially when nearing the last few cuts.

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A Couple of Lessons on Chamber Reamers

Forced pilot is damaged

Chamber reamers are pretty complex tools that incorporate all the features of the chamber into one form cutting tool.

At right is pictured the tip of a chamber reamer.  You can see from left to right the shoulder, neck, throat, and pilot.  Note that the pilot appears to be short for the reamer.  It was not short when the pilot bushing was new.

A novice used this tool, the bushing was too tight a fit for the bore.  Proper fit is .0005″ to .001″ under the bore diameter.  That makes for a nice slip fit of the bushing to the bore of the barrel.  The pilot bushing rides on the lands of the barrel.

How do I know the bushing was too tight for the bore?

Evidence of poor pilot fit.

Simple, the bushing was forced back onto the cutting edge hard enough that the throat actually cut the back of the pilot.  Note in the picture at left, the same busing off the reamer.  You can see where the tool cut the bushing.  This portion of the reamer is not very sharp as it was never intended to cut anything.  So that is how I know this bushing was forced into a tight bore.

The primary reason for using removable pilot bushings is so that you can match the pilot to the bore of your barrel.  No need to force things.

You know this guy has no idea how a reamer works…

GEDSC DIGITAL CAMERA

The reamer at right was “sharpened” by a “gunsmith”.  The large flat running down the center of the picture has two grinds.  The fat grind closer to the top of the picture us a relief grind, meaning it will never touch the barrel, it is clearance ground to make sure that chips will not get caught behind the cutting edge.

The narrow grind just below the relief grind is where the actual cutting edge is located.  This grind is also relief ground just slightly.  Only the very edge where the grind meets the flute is actually touching the barrel during chambering.  If you stone on the outside grinds of the reamer the dimensions change very quickly because the geometry of the cutting edge and the clearance grind.  Never stone on the outside edge unless you have been trained to do so.

If you look inside the flute on top of the cutting edge where the chips gather during cutting that is the area that you can stone without changing the dimensions of the reamer (in the picture here that would be visible above the grinds we just discussed, of course each flute is one cutting edge).  Again, because of the geometry of the reamer stoning on this inside edge changes dimensions such a tiny amount that it should not create any problems with chamber size if you don’t get carried away.  Normally all that is needed is the cleaning of metal built up on the cutting edge, no real stoning of the reamer itself.

When I look at the picture of the reamer above, I laugh because you can see where the “gunsmith” stoned on the relief grind.  Since this part of the reamer never touches the barrel at anytime it is clear that this guy had no idea how the tool works.  If you don’t know how a tool works, it’s a safe bet you have no business trying to sharpen it.  Send it to the reamer maker if your not sure, its cheaper that an angry customer.

Want to learn more on the subject of headspace, chambering and firearms?  Here are some books that will cut right to the chase.

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