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HomeNewsBarrel Work (Machining / Chambering) – Final Reloader | The Global Today

Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

I lately confirmed find out how to make a inflexible reamer holder in preparation for chambering for my 50 BMG. At this time, we’re highlighting the barrel work. 

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Concerning the Construct

My barreled motion is finished! This hefty setup is already a beast. Even the motion wrench from BAT Machine is of monstrous measurement. 

Coming subsequent is Cerakote, break-in, and additional lengthy pictures! 

50 BMG Challenges

Chambering for 50 BMG offered just a few obstacles. All the pieces is on a mammoth measurement and scale. It’s not a SAAMI cartridge so it requires particular tooling and documentation is missing. I needed to safe C.I.P. specs—the European equal of SAAMI—and work from these.

This required some metric to inch conversions and some choices. This cartridge has a wide range of functions, from machineguns to ELR match taking pictures. I made up my mind this construct is not going to be a match gun, however for versatility and enjoyable. Whereas I wish to adhere to tight specs, I additionally wish to guarantee I can shoot 50 BMG navy ammo together with armor-piercing rounds and tracers. My plan is to observe up with a 375 Cheytac designed particularly for taking pictures at over a mile. 

Equipment and Instruments

For this mammoth job, I turned to my Precision Matthews TL-1660 lathe, the bigger of my two lathes.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

This lathe is a beast! Listed here are a number of the specs for the Precision Matthews TL-1660:

  • Extremely Precision, made in Taiwan
  • 16″ swing, 60″ between facilities capability
  • D1-6 excessive precision spindle
  • English and Metric threading with out gear adjustments
  • One shot lube on the carriage
  • 3-Part 5hp motor

*Notice: for many gunsmiths, the TL-1640 can be an amazing alternative. You seemingly gained’t want 60″ between facilities just like the TL-1660 affords. The TL-1640 can save each area, and important cash on freight! I opted for the bigger lathe as a result of I needed to have a lathe readily available with prolonged capability between facilities.

Triebel Reamers and Gauges

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Triebel 50 BMG End Reamer and Throater

Tooling included my 12mm and 18mm inflexible reamer holders for my Triebel physique and neck and throater reamers in addition to a freebore gauge and go and no-go gauges. 

These holders offered such a inflexible maintain that I really ran the Triebel physique and neck reamer with no pilot bushing.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

This gave further oil move to assist evacuate chips. (I checked runout a number of occasions. It was virtually zero!) I custom-made a bushing for the Triebel throater on the PM-1440GT as a result of the unique bushing mixed with the barrel would have resulted in about 0.002 clearance. I needed tighter tolerances, so I made the {custom} bushing from a brass drift punch.

I even have the outboard spider, which I constructed on the TL-1660. It screws into the within of the two.5” inch spindle. (With the spider put in, the spindle measures roughly 2.3”.) I additionally upgraded the machine with a tailstock DRO, which gives a real-time indication of reaming depth for better precision and confidence. Lastly, I’ve my DIY strain flush system which doesn’t require any modifications to the lathe. This method is particularly essential when engaged on such massive scales. 

To make all of this work, I wanted a barrel extension.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
BAT EX Motion Wrench subsequent to Gen 2 XXX Bastard 50 Cal. Muzzle Brake and Barrel Extension

I began with a billet of aluminum, drilled it out and threaded it 1” x 14 feminine and ⅝” x 24 male, and added wrench flats. This particular tooling offered better stability, permitting the barrel to succeed in by the lengthy spindle out to the spider. It additionally lets you blow compressed air by the barrel to filter chips and oil and serves as a connection level for the strain flush system (⅝” x 24). For better readability, I laser engraved ends with the thread specs. 

One other piece of particular tooling was the chuck bore-out.

This lathe has 2.5” through spindle capability, however the chuck that’s a part of the true bore alignment system solely offered 1.650” thru-chuck capability. This barrel shank is 1.75” in diameter. To repair this concern, I eliminated the chuck jaws and  took a boring bar to bore it out to 2.050”.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

I selected 2.050” as I’ve a buyer job with a 2” diameter barrel, so I needed to accommodate that with some further room. That is about so far as I might bore the chuck out. After I had the chuck aside, I seen some Allan screws holding the chuck collectively. I used to be about to stumble upon the counterbore for the place the heads of each screws go… (Whereas I had the chuck aside, I took the time to scrub it up, take away the manufacturing facility grease, and relubricate it.) 

BAT EX Tenon Specs

As soon as I had all of the tooling and the C.I.P. specs, I turned to the BAT Machine EX tenon print for extra info. BAT Machine provides tenon prints for all their actions.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

For a 50 BMG bolt face, the print specifies a 1.75” minimal shank diameter (what we’ve got) and 1 ½” x 16 threads. A lot of the threading I’ve completed has been 1” x 16 or a 1 1/16 x 18. It is a full 1 ½” — a lot bigger than I’m used to. This print additionally specifies pitch diameter and gives the numbers wanted to calculate go gauge stickout (Headspace – Tenon Size = 0.255). It’s completely essential to have all your numbers appropriate earlier than beginning machine work.

Muzzle-Finish Barrel Work

I began with the muzzle-end of the barrel, mounting the barrel within the lathe and doing a pre-dial to get it to about 0.001 of runout. I parted off an inch utilizing an particularly inflexible chopping software.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

This was particularly easy due to the scale of the TL-1660. Bigger lathes have fewer issues with chatter and breaking parting instruments. After parting, I did a ultimate dial on the muzzle finish, turned the tenon, threaded the tenon and reduce the crown.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Turning the Muzzle Tenon Down
The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Threading the Muzzle Tenon
The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Slicing the Crown

For this I used some nice gear from Simtek Boring Bars, really useful by Bruce Thom at BAT Machine and associates over at Salmon River Options

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
50 BMG Barrel in Precision Matthews PM-1660 Lathe after Threading the Muzzle

Breech-Finish Barrel Work

After flipping across the barrel within the lathe, it was time to get to work on the breech. I cut up this into three elements for simplicity. Half I included dialing within the barrel, going through the breech-end, turning the OD, chopping the thread reduction, going through the shoulder and turning the 1 ½” x 16 threads.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Going through the Tenon on the Breech Finish
The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Threading the Barrel on the Breech Finish

It’s the identical course of as every other barrel, however with much more materials. The OD of the tenon work turned out nicely.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Checking Pitch Diameter Whereas Threading

Half II, chopping the chamber, marked the most important chamber I’ve ever reduce. I needed to be actually certain of my set-up, barrel dial-in and method, lest better threat of breaking the reamer. 

I started with a 0.100” plunge, contemplating how the most important a part of the shoulder on the pinnacle and neck reamer enters the opening we drilled and bored true. Bulk elimination began with a drill bit whereas effective tuning was left to a boring bar.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Bulk Chamber Reduce on Breech Finish

I zeroed the tailstock DRO proper the place the reamer began to enter the opening on the higher a part of the shoulder. This gives a reaming depth primarily based on the shoulder. (You could find this distance on the C.I.P. specs.) After this preliminary plunge, I checked runout with a dial check indicator— 0. This was an particularly good signal contemplating I eliminated the pilot bushing on the reamer. I then ran three completely different passes, stopping to verify for runout periodically.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Reaming the Barrel

Listening to the software work is particularly satisfying. It’s easy, with none chatter. Sometimes, I’d place my fingers on the inflexible reamer holder to really feel for further motion or vibrations—I felt none. 

With a lot materials to take away, strain flush got here particularly in useful. 

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

When it was time for ultimate headspace checks, I screwed on the motion and used the go and no-go gauges. The go and no-go gauges are about 0.006 aside—fairly tight for a 50 BMG.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

I received the headspace the place I needed it and went the additional mile, tightening the motion onto the barrel whereas it was nonetheless held within the lathe. That is to make sure that when the threads compressed, I might nonetheless be inside the desired specs.

The throater reamer took heart stage in Half III of the breech-end work.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Slicing the Throat

Having a separate throater reamer permits for better customization primarily based on what ammunition you propose to shoot by the gun. I started with a 0.100” reduce and measured the stickout with the freebore gauge.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Utilizing Gauge to Measure Stickout

I ran subsequent passes and squirted chopping oil onto the reamer with out strain flush. With so little materials to take away, strain flush wasn’t needed. I additionally chambered the ball ammo to verify stickout and verified with a Sharpied ogive of the bullet.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Navy Surplus 50 BMG Ball Powder, Bullet, and Ammo subsequent to six.5 Creedmoor Spherical

This course of concerned plenty of checks. My freebore gauge is a minimal freebore gauge. I went simply past this with the throater to accommodate the specified bullet leap for the 50 BMG ball ammo. (This ammo is outdated—manufactured in 1952!) 

As a part of this course of, I pulled one of many bullets from the ball ammo. I needed to go to the milling machine, use a ½” collet, tighten it down and use a vise and shellholder to take away the bullet. Whereas trying on the particular person elements is cool, I might verify headspace with an unfired case.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today
Checking Headspace with 50 BMG Case

Missing a lot of my loading supplies (Hornady 50 BMG brass, and so forth.), I turned to Bruce and Daryle Thom from BAT Machine, Dave Manson, and others I belief for suggestions on find out how to greatest optimize the barrel. 

To complete up, I reduce the chamber transition, polished the within of the chamber with some roughly 250 grit sandpaper on a dowel, and did some laser engraving.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

After I laser engrave barrel particulars, I wish to screw the motion on and plan for acceptable clocking. 

Conclusion

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

I invested over two to a few occasions as a lot time on this chambering job as I do on extra conventional chambering jobs. It was an extremely beneficial studying course of and resulted in some particular tooling. Having a lathe opens up worlds of alternative for gunsmithing in addition to custom-making no matter elements/instruments you want. This got here particularly in useful for this job, as evidenced by the {custom} throater bushing and metric inflexible reamer holders. 

Subsequent is a full Cerkaote job (chassis + barreled motion) and bedding and ultimate meeting. When all collectively, I’ve some navy ball ammunition to run by the gun and have plans to work up a load with Hornady A-Max 50 caliber match bullets.

The Global Today Barrel Work (Machining / Chambering) – Final Reloader | The Global Today

Get the Gear

BAT EX Action

Accurate Rifle Systems ELR Chassis

Accuracy Solutions BipodeXt

Triebel Reamers and Gauges

Brownells Barrel Vise

APA Gen 2 XXX Bastard brake

SSG True Bore Alignment System (TBAS)

Precision Matthews TL-1660 Lathe

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Thanks,
Gavin Gear


#Barrel #Work #Machining #Chambering #Final #Reloader

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