If the goal for your reloads is precision without a compromise in function, the Bushing Bump Die from Forster is worth a look! Normally you’d have to choose between full-length sizing and neck-only sizing with the drawbacks inherent in each type of sizing. With the Forster Bushing Bump Die you get precise control over neck tension with familiar bushings *and* the ability to bump the shoulder without disrupting the fire-formed case body. Interested? Check out this video!
Setting up the Bushing Bump Die
There are two major factors that will affect die setup with the Forster Bushing Bump Die: Die height for shoulder bump, and bushing diameter for neck tension. The first thing to do is measure bullet diameter and case neck thickness to determine the optimal bushing diameter. I would suggest using a micrometer for bullet diameter (or use published bullet diameter), and to use a ball micrometer (like the RCBS unit) for case neck thickness.
Once you have these numbers, it’s easy to calculate optimal bushing size, which is a factor of:
- Bushing diameter (inches, as calculated) = BD
- Bullet diameter (inches, as measured) = D
- Average case neck thickness (inches, as measured) = T
- Bullet tension press fit = BT = 0.001″
- Brass spring back factor = SBF = 0.001″
The formula is: BD = D + 2 x T – BT – SBF
Simplified, this becomes: BD = D + 2 x T – 0.002″
When I measured my case neck thickness, I came up with 0.014″, and bullet diameter was measured at 0.264″ as expected for the 6.5mm caliber. Here’s my “working out of the math”:
So we have 0.264″+ 0.028″ -0.002″ = 0.290″ bushing. That wasn’t too hard! The pre-selected bushings that came with my 6.5 Creedmoor die were 0.288″, 0.290″, and 0.292″ – so this selection was *perfect* – I can go up or down by 0.002″ as factors change without needing to order additional bushings- awesome.
iGaging EZ Data Micrometer showing bullet diameter
Installing the bushing is simple:
- Remove the decapping spindle
- Remove bushing (if installed)
- Drop in bushing chamfered end first
- Tighten decapping spindle until it bottoms out against bushing
- Back decapping spindle out 1/8 turn
- Tighten spindle lock ring
You can then install the die in your press, and lower the die until it contacts the shell holder. Lube the case neck of a case, then size it- now you’re ready to measure the shoulder bump. I use the Hornady headspace gauge kit which work quite well for these types of measurements. If your shoulder bump (0.001″ – 0.002″ for a precision bolt gun) is not where you want it to be, you can raise and lower the die slightly to “fine-tune” the value you are looking for.
iGaging Origincal 0-6″ digital caliper with Hornady Headspace Guage kit
The Forster Bushing Bump Die is a great tool to have for precision reloading. Combined with a full-length die, you can adapt to most common loading scenarios for a precision rifle. And that’s what reloading is about isn’t it? Saving money, having fun, and getting the results *you* want with your firearms. If you need precision and flexibility, check it out! You can find the Forster Bushing Bump Die at Midsouth Shooters Supply HERE.