From note pad to concept Part 1

 

I have often been excused of glacial movement in everything I do. So true to character it took 43 years of pushing a boulder uphill to finally evolve enough and design a bolt action receiver that would be a cut above what I'd been using most of my career.

I knew what I wanted from the basic skeleton. I pushed around some rough sketches in my mind and when time permitted I began working on some prototypes parts. All this R&D was pretty random at first. Without trying to reinvent the basic bolt action design my goal was to incorporate subtle features I liked about a number of receivers such as the Brno ZG-47, Winchester Model 70, and even some of the DNA from the Remington 700. 

All of these previous receivers were being made with the current technology of their time but one thing was for sure there were no 5 and 7 axis mills and lathes available in the earlier eras. 

Bret Wursten and I trolling ideas

In this fantasy atmosphere I wondered what it would be like not to be constrained within a budget that cut corners where you actually needed those damned corners. I've been reattaching those corners for decades, Working within this imagined "no bottom line" framework some ideas began to come together. 

For the next couple years every operation I preformed on the lathe or mill I imagined how I could eliminate these modifications or corrections if they were already built into a new platform. 

Bret Wursten, the owner of Central Valley Machine would prod me ever so often and ask me when I wanted to put these ideas into motion? Then one day while we sat on a ridge line glassing for mule deer he poked me with a stick and said the following "Starting next week I want you to give me a half a day per week with our Solid Works Engineers and put whatever concepts you have rattling around in that thick skull of yours at least into a digital file". I'd run out of excuses. 

We didn't miss very many of those meetings over the next 10 months. I would arrive with a few notes, maybe a sketch drawn on a napkin and we'd go to work. James would be called in to assisted when we needed to know how or if we were going to be even able to hold and machine a certain part. The weeks rolled by. Neal would drive the mouse I would look at the image and say, "We need more Cow Bell right there"

                                                                                                                                  

Neal sent these images over before the machine work was to begin and made following comment. "Enclosed are some of the figures you've been carrying around in your head for quite a few years". 

It took a Texan to state the obvious

The year was 2011 and I was standing in front of an interested crowd giving a power point presentation in a Country Club just outside of San Antonio Texas. I was doing my best to visually show those assembled the steps required to modify, blue print the receiver, then fit and chamber a barrel. The next images showed me modifying the underside of a current production Model 70 receiver to except one of my floor-plate, bow and magazine assemblies. Then I did my best to described the art of surface grinding the receiver to install a set of my scope mounts. Fitting the stock came next and then going over the final finish work to turn the project into a finished Legend rifle. 

When the presentation drew to a close I asked if there were any questions from the audience. A gentleman in what looked to be his early seventies rose to his feet and asked me the following “ Son, if it takes that much work to make a Model 70 into what a Model 70 should be, why in the hell don’t you build your own action ? ” 

I can't remember what response I gave, I’m sure it was vague at best. He was polite sat back down and listen to me field other questions for another 45 minutes. As everyone stood up to go he walked up to me and said “Young fella you ought to think about what I said” he then shook my hand, winked, bid me safe travels home and walked off. You gotta love Texas. 

To this day I do remember I didn't sleep much that night nor was I smugly content on the flight home. The gentleman did have a point. 

Through a series of similar events I was eventually recruited to design a receiver for the CorBon Bullet Company. The CAD design and manufacturing of this receiver was done by Central Valley Machine. I flew in Steve Wickert who's background is pretty deep in this area for some consulting advice to round out the brain pool. While most of my "blue prints" both mental and physical were drawn on napkins the CVM team looked at the process as standard machine work and not as a black art. 

Soon we had a handful of prototype receivers and waited for approval of the overall design. Then the anticipated go-ahead to start the 1st run of production. One receiver went to the Shot Show early that year and another one of these receivers was auctioned off at the 2012 SCI Convention in Las Vegas. During that convention a the steady stream of interested parties came by my booth to ask me about the CorBon Model-1 receiver. My impression was the bullet company was sitting on a winner. 

Sadly some ideas never make it off the cutting room floor or the launch pad. Over the next two and half years I received a lot of phone calls from those interested in purchasing this receiver and I dutifully referred them to the Bullet Company as directed. Production never began. 

Sadly the Model-1 stuttered, stalled and eventually died a quiet death. No one ever heard the tree fall.

Remember that one receiver that was auctioned at the 2012 SCI Convention ? It was purchased by one of my clients that was then sold to another one of my clients. The new owner wanted a 375 H&H and below is how it all turned out. This first attempted at a receiver for both myself and Central Valley Machine laid too rest the the reservations any of us had. The barreled action fed like a shark from the 1st dummy rounds that entered the magazine and all the combined metal work operated as designed. The accuracy with this Model-1 was simply outstanding. You could load a tuna can over a case filled with charcoal briquettes and  it would shoot at the 1/2"or under mark, this barrel will literally shoot anything. I give Kudos to both Krieger and William Hambly Clark Jr as this was the first barrel I ever fit using his # 4 technique as described in his book Centerfire Rifle Accuracy. 

Despite the untimely death of the project it was evident what we had was a solid platform to begin with, All the ducks were lined up at CVM, but still, I held the reins tight.

One thing was sure the fire had been lit, all thanks to a Texan that had a lot more common sense than I did.  Make an action indeed, the nerve of that guy.

Converting a Pre-64 30-06 to 300 H&H Part 3

OK now lets tie all this together. The first thing to do is file the different flat widths we've cut into that wasp waist shape between each feed rail. Had we been using a CNC we could have programed this step hit the RUN button and watched these mirrored contours take shape. 

Instead we must make the modification blend by hand. This is best done with 6" to 8" medium cut mill files followed up with a # 4 cut file blending our stepped cuts together in an uninterrupted transition from front to rear. Since we made these mill cuts into the rails with use of the digital readout, both the depth and length these two apposing sides should blend out in almost a mirror image. The upper and lower edge of each rail must also be filed with a slight corner breaking radius. The transition along both rails should feel smooth and interrupted. The plan is to just blend these milled flats not hog out more rail width than is necessary.

Then starting with 180 grit W&D paper both rails should be polished top and bottom, front to rear. This sand paper work should be continued up through 320 grit. Keep the radius theme on both sides of the rails

Next you need to file an angular ejection bevel on the underside right leading edge of the rear bridge as we have left a very sharp corner that will catch on every cases being ejected. In addition any sharp corners generated by and end mill need to be chamfered with a file and then paper. 

You need to address the side walls and radius of the feed well. This operation is best done with mold making stones and stoning fluid. These rapid break-down stones will take on the contoured surface you're working with and starting with approximately 180 grit and progressing up to a 300 then a 400 grit stone the sides of the feed well should soon shine like a new dime. 

You must remove the sharp corner at the rear of the feed well wall that we've generated by widening the feed well. 1st with a pillar file, then a stone and finally with paper we need to turn that sharp corner into parabola shape. Failure to do so will cause the belts on the case to hang up on that sharp corner. 

Next we begin blending the 90 degree shelf above the leading edge of the magazine box ID we have established by cutting the feed well forward with the existing angle of the 30/06 bullet ramp. Some would suggest making this new angle straight from the top of the mag box to the rear edge of the flat behind the lower recoil lug seat, you could. However if you blend the standing material into the established bullet ramp angle with again a parabola shape you will in fact be leaving much more steel in the ramp area than Winchester ever left behind on factory 300 H&H receiver. This leaves the lower lug area with significantly more material and removes the knife edge effect at the top of the bullet ramp found all too often on a factory 300 or 375 H&H receiver. Another advantage of this extended parabola shaped ramp also puts the bullet nose in contact with the ramp sooner allowing the bullet nose to begin its rise towards the chamber as well as rolling the base of the case into the bolt face and under the extractor sooner. Remember the beaten to death term "controlled round feed" in my experience the sooner this control starts as the bolt is pushed forward the better the entire concept design becomes.

When converting any Standard action to a Magnum you need to make up a complement of dummy rounds to cycle through the receiver to fine tune the effort. I choose to use round nose bullets on this project as if you can get these to feed perfectly every other semi or Spitzer bullets will feed but not necessarily vice versa.

At this stage I choose whatever brass is available or the brass the client wants to use to properly fit the extractor hook to the those cases. 

       Say what ?????????

As an example the extractor groove diameter on a cross section of six different manufactured 300 Winchester cases I measure a while ago showed a + and - .020 variation in the six brands of brass. 

Without plowing up too much old ground I have mentioned this in other post in the past. The fit of the claw extractor is critical to actually give you controlled round feed. Go back and re-read that last sentence. Now read it again. 

A milling machine vise and a simple indicator is the best fixture to use for determining the proper extractor tension 

Depending on the extractor, zero, some or a lot of material will need to be removed from the extractor for this operation. Starting with a Standard bolt face extractor will take more time to fit than an extractor already converted for a a magnum bolt face. But starting with a standard allows more control over the final results. The actual shape of the finished extractor hook depends largely on the gunsmith and the number of these he has taken the time to actually look at the contours and geometry of one that really works well verses a dud. 

The fit of the extractor hook to the chosen manufacture case should allow the extractor spring away from the bolt body .004 to .006 when the case is rolled and centered into the bolt face in the chambered position in my opinion. 

                       Note: This is a pic of a Left Hand G series bolt and a properly fitted extractor 

In short if the extractor is too tight it will inhibit and retard the process as the case tries to roll into bolt face coming out of the magazine box. To loose a fit and the case will not be captured and controlled by the extractor hook and fall away from the bolt face if the bolts forward or rearward movement is stopped for any manner. This loose round or spent case will drop into the open gap between the rails. Can you say "Jam" "I knew you could boys and girls" 

A finished right hand extractor, filed, polished, blued and installed. Note the shape

So with the now extractor fit we need to alter the length of the Bolt Stop. The amount to remove will vary. I like to have the leading edge of the extractor hook buried just behind the back end of the magazine box opening. I alter the bolt stops length with a carbide cutter in the mill making sure the face of the shortened stop is perpendicular to centerline of the action, this part was designed to fit flush or evenly on the back of the left recoil lug when the two surfaces come in contact. 

The ejector blade is done in a similar manner BUT the angle of the ejector sticking out of the fully retracted bolt face needs to be considered. I want a minimum .110 of ejector blade sticking out of the bolt face with the blade parallel to the bolt face when fully when retracted. That's why we alter the Bolt Stop 1st. 

Now we address the follower, the 30-06 follower is not going to work as it's now to narrow to use in the 300/375 magazine box. A Pre-64 300/375 H&H OEM follower might work but much of this depends on the shape and width of the parabola you cut into your rails or if you chickened out and elected to leave the rails straight per the factory Winchester theme. Likely the OEM 300/375 follower is going to slip up through the new rail contour with the wasp waist and not hold the last round in the magazine under the rail properly. So what follower do we use ? That is a damn good question. 

NECG offers a 98 375 H&H length and width follower, Swift/Blackburn sometimes has them in stock, if Jim Wisner has any on hand I'd recommend his hands down. A 375 G Series Model 70 follower might work but frankly I've never tried one. 

No luck finding one ? If you've gotten this far then making a follower shouldn't be beyond your capabilities and given the choice I'd make it with similar geometry to a Mauser 98 follower instead of the Pre-64 Winchester follower. Having made more than my share of these over the years just plan on most of a day making and polishing the follower from a block of steel. When I've read online that someone felt scalped by paying more than $50 for a follower I know this cry baby has never had to make one.

Note: The follower on the left and is chrome-moly 300/375 Echols Classic/Legend follower. The center follower again made in this shop is for a 300/375 magazine and the material is 7075 Aluminum that will be hard anodized when completed. The other follower on the right is a steel 300/375 follower made by Winchester. 

7075 Aluminum what the f_____?

The original 300/375 OEM Winchester magazine box is very thin and subject to a lot of abuse resulting in major dents appearing in the both the front and rear walls of the magazine box in recoil if the rifle is fired a lot. The owner of this rifle shoots quite a bit so the 7075 was chosen as the follower material. It will also have a 3/16" Delrin bumper placed in the leading and rear edge surface of the follower to further negate any mag box deformation caused in recoil. Slight modifications can be made to the follower if necessary to tweak the functional movement of last round coming out of the magazine. Holding the last round under the feed rail and then releasing the last round in the magazine is one of two functions of the follower, so you better get it right. You will need to have the fixtures or a means to hold the follower to make as well as tweak one, kind of chicken before the egg situation. 

With the barrel installed we now begin checking the progress of what we've done by cycling one, then two, then three and then all four of the dummy rounds through the receiver.  What we're doing now is likely removing steel from the area in the newly established bullet ramp to allow the rounds to slide easily up the bullet ramp. I want to monitor the contact point on the bullet ramp with Red or Black Sharpie and remove with a Crossing or Pippin file the required amount to do so. Great" you say "How much is required ?". The simple answer is, you file and blend the outer edges of the bullet ramp until the bullets contact the ramp on either side of the ramp when driven forward with the bolt. Each side of the ramp should require the same amount material removed when the final shape is established. 

The larger the bullet diameter or the further away the bullet nose is from the centerline of the action the more material will need to be removed. This can take 5 minutes to a number of hours depending on the case and cartridge design. When you feel you have the best shape working for you then you can use a Foredom hand tool with the proper sized cartridge rolls and or the rapid break down stones to go over and remove the file marks and then I paper polish entire bullet ramp. You want that bullet ramp smooth as a Beagle's ear. 

You need to also make sure that the rear of the receiver above the magazine box has a smooth transition above the box opening with no, zero, nada lip over hanging the box for the case rim to catch on. These two surfaces should be flush. The rear of the feed rails should also have a radius that is filed and then polished so as you load the magazine the cartridge rims won't catch on a sharp corner anywhere at the rear of the mag box and receiver. We good ?

Strip all the parts and clean all bits of steel and polishing grit out of the receiver, ejector and stop bolt area with a good solvent and compressed air. Wipe it all dry but do not oil it.

Now is the time to cycle the bolt at normal speed and then very aggressively with a dummy round in the chamber and a full magazine to look for any problems. There will be a few and most will stem from sharp edged corners you neglected. Now lightly oil the rails, bolt body, raceway, etc and try it again. 

When this conversion is 100% complete you will have a Pre-64 300 H&H that Winchester would have been proud of and possibly would have done if given a little more slack in their leash. 

This is not the time to call your favorite smith and ask for the exact same conversion without being willing to go the distance to pay for the effort. The smith will have the better part of two solid days in this endeavor and we haven't even re-addressed the one original scope base hole in the rear bridge being removed. That's for another Blog post I'm afraid. 

The 1st of these conversions will seem a bit daunting, after the 3rd you'll be wondering why you hadn't done this long ago.

Converting a Pre-64 30-06 to 300 H&H Part 2

A majority of machine work has now been completed to the magazine cavity and feed well but the rail width modification is still required.  The OD of the belted case as well as the shoulder OD is larger than the 270/30-06 class of cases so additional room through the rails must be made to accommodate for these larger case diameters. 

It is the height of the case that protrudes above the rails and allows the lower edge of the bolt face to engage the protruding case and then allow the bolt to shove it towards the chamber. The case must stick up through the rails ENOUGH as its pushed forward or the bolt face will override the case head and cause a jam. Most 270/30-06 Model actions are approximately .545 to .550 in width from one feed lip or rail to the other side at the very rear of the feed well opening directly above the magazine box and then widens to .600 to .610 directly above the bottom of the bullet ramp. This geometry has work since the 1st Pre-64 stepped off the bus so it's hard to argue that it isn't adequate, is it prefect? well...............

All the next cuts will be made from the center-line of the receiver so you must establish the best means to do so. Again the fixture I use allows me to do this very easily. Finding the center-line I start off and finish using only a 3/32" carbide end mill. I widen the existing width at the rear of the rail from the original .545  to .610. Taking a photo of this operation is difficult at best due to the close proximity of the mills spindle being so close underside of the action. 

With the help of the DRO I will now cut stepped flats into the rails in incremental lengths from the rear forward and later on file and blend these transitions. If you had a CNC you could write a program to do this parabola shape, push start and step back. 

You can just make out the stepped width progressional flats cut into the rails 

Cutting the width and or SHAPE of the rails becomes a matter of interpretation and just how anal retentive you choose to be and still live with yourself. I would say that every Pre-64 70 I have ever worked on left the factory with the rails being straight in nature and wider across the front of the rails above the feed ramp. What I prefer to do today is the widen the rails in the partial parabolic fashion. Tom Burgess referred to this as a candle flame shape. Wider in the mid section of the rails than in the front and in the rear sections, How much you say ? at the widest point .620 to.625 seems to work out pretty well for me for the 300 H&H. When the parabola cuts are blended you also need to file or stone a radial profile to the top and bottom side of each rail. Failure to so will cause the brass to hang up as each case if rising out of the feed well and mag box. Time spent polishing the blended rails will pay off 

 

The ejection port is next and again carbide is your only reasonable option. I make a pass or two usually removing .006 to .010 of steel to clean up the leading edge of the ejection port and back of the front ring. I then begin opening up the ejection port to the rear. 

The number 3 scope base screw hole will always be cut away in this operation so you'd better have plans for repositioning that screw hole and what rear scope base you will ultimately use after this conversion.

How far you go to the rear is up for considerable debate and much of the next series of cuts will depend on your extractors length. The Standard OEM Pre-64 extractor is approximately 4.420 in over length. Some gun smith's will insist that the tail end of the extractor MUST be tucked under the right side of the rear bridge with the bolt turned down into full battery so the extractor's tail has no possible way of becoming jammed in ejection port. If you follow this as a rule then you can really only open up the ejection port to approx. 3.400. 

So if this is a concern you can modify the rear bridge as shown below, similar to the original factory receivers leaving a standing wall and blending an angular cut from the 3.600 opening you've established from the center line of the action out to the edge of the standing wall. 

This Pre-64 30-06 length action below has been chambered and set up for a 7mm Mashburn with an extended throat and uses up most the 3.600 real-estate in over all loaded length. To keep the 4.420 OEM extractor tail under the rear bridge I needed leave some standing wall as shown at the arrow. The OAL of the new opening is 3.600 but the port length is still 3.400. This still requires snaking the rounds in though the ejection port and under the scope mounts. While this takes some finesse and practice for rapid loading the extractor stays contained 100% of the in time in or out of battery. I've done many conversions in this manner especially when chambered for heavy calibers and are iron sight dedicated rifles. 

Then along came the Willams Firearms Company and their version of a M-70 retro fit extractors. The beauty of this Williams extractor is some of these were machined with an extra .130 in extractor length. I can't remember what date these came to my attention but I've used a dozen or so of these and still have a few squirreled away. This now gives us another option if you have one of these longer Williams units. To my knowledge Willams has ceased production and these are no longer available. 

Jim Wisner from time to time will make a run of an even longer extractor 4.900 as seen below for both right and left handed current production model 70 actions and these are also of excellent quality.

Williams Long Extractor 

Wisner Long Magnum M-70 

  

Provided you have on hand 0ne of the Williams longer than normal Extractors you can now open the ejection port to 3.600 completely. "But," you say "the tail will not be buried under the rear bridge !!!! " Well Yes and No as you lift the bolt out of the battery position and the bolt body rotates up the extraction cam the rearward movement in rotation places the LONGER Williams extractor tail under the rear bridge well before the bolt has completed its rotation.

To confuse the issue even more below is a standard Pre-64 action and OEM follower that is chambered for 280 Remington that has the ejection port opened up the 3.416. Note the tail of the extractor showing with the bolt in full closed battery and then the tail tucked under the rear bridge as the bolt is opened. The result is a longer loading port and a captured extractor tail. 

The wonder of it all !

A lot depends in any conversion or modification on the the materials at ones disposal. You will see similar adaptations of this on many of the Magnum length actions chambered for long cartridges. Note the visible exposed tail on this extractor fit to this H&W magnum 98 action, lift the bolt and the tail end slips under the rear bridge before the bolt rotates completely up the extraction cam, no fuss-no muss.

Time for lunch