TESTED: 4D Reamer Rentals (Counterbore Lathe Job)

Have you ever had a one-off job that involved a special tool? How about when that tool can take months to get? That’s where tool rental RULES. And for gunsmithing tools (namely reamers) there’s a solution for that: it’s 4D Reamer Rentals at 4drentals.com! In this story, I used 4D Reamer Rentals for a one-off 30 caliber counterbore job. And it worked out great!

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About 4D Reamer Rentals

4D Reamer Rentals is run by Fred Zeglin, master gunsmith and gunsmithing instructor.

From the 4D Reamer Rentals Website:

YOUR EXCLUSIVE SOURCE FOR CHAMBER REAMERS AND GUNSMITHING TOOL RENTALS!
We have over 1600 chamber reamer rentals in stock and ready to ship. We also rent headspace gauges and many other gunsmithing tools. Our tools are well maintained and inspected before and after each rental to assure you receive the highest quality gunsmithing tools. Our staff has over 35 years of professional gunsmithing experience, setting us apart from the competition.

To locate items that interest you click on the headings in the menu at the top of the page. When you find a Chamber Reamer or Gunsmithing tool that suits your needs, just click directly on the listing. Or search by keyword in the window above.

Headspace gauges are rented by selecting the combination of reamers and/or gauges you need from the dropdown list in the red box that reads “Add Reamers/Gauges” when you’re looking at a specific caliber reamer. We aim to keep it simple.

All rentals are for seven (7) days in your hands. With shipping time, tools are expected back in our facility in seventeen (17) calendar days. If you request overnight shipping, the tools should be back in 14 calendar days.

My Trial: 30 Cal Neck-Only Reamer

Above: 300 PRC barrel in Precision Matthews PM-1440GT Lathe with True Bore Alignment System

One of the 300 PRC rifles I recently built had an issue I wanted to experiment with: when you turn down a muzzle for threading, it can relieve stresses imparted by the button rifling process. The rifle in question was threaded 5/8″ 24- and when I slugged the barrel, I determined that the muzzle end had opened up ever so slightly. This exact issue was covered in Gordy Gritters’ week long precision rifle building class which I took in 2019. So I decided to try one of the fixes that Gordy had outlined: counterboring the muzzle to a point beyond the threaded area. The goal is to have the bullet fully supported until it exits the rifled portion of the barrel- the counterbore should do the trick!

The counterboring job went off without a hitch. The barrel with indicated with a True Bore Alignment System setup from Straight Shot Gunsmithing, and a simple clamp-and-indicator setup was used to monitor depth (depth not critical for this job). With my borescope, I observed a very clean internal “crown” (counterbore transition).

And the results at the range look quite promising! Here’s the first 3-shot group I shot after this job:

And here’s the beauty of the 4D Reamer Rental process, it’s this simple:

  1. Browse the tool categories at 4D Reamer Rentals
  2. Pick the tools you want, add to cart, check out
  3. Use the tools
  4. Mail the tools back

That’s it- couldn’t be easier!

Try 4D Reamer Rentals

If you need a tool for an upcoming gunsmithing job, give 4D Reamer Rentals a Try!

You’ll also want to check out Fred’s gunsmithing books:

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Thanks,
Gavin

One thought on “TESTED: 4D Reamer Rentals (Counterbore Lathe Job)”

  1. Gavin:

    Enjoyed this video and would like to see more of the true bore setup. If you have time, please post a picture of the ‘internal crown.’ Having never used a neck reamer, I am wondering if it leaves a sharp 90 degree angle on the lands.

    After discovering this issue and fixing it, what would you do differently next time? Said another way, what advice would you have if working with a premium barrel and premium components but you know you want shoot suppressed? Is there a larger thread that is less likely or unlikely to relieve stress on the muzzle? This would necessitate a non-standard suppressor or an adapter.

    Thank you!

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