This is part of a written compilation of a series of accuracy testing with the Thompson Center Compass bolt-action rifle, chambered in .308 Winchester, which will include load development using numerous different components and the installation and glass-bedding of a Boyd’s Prairie Hunter stock. We will establish 3 different loads using different components (each with it’s own post and video), then we will use those loads to get a baseline of accuracy with the stock that comes on the factory rifle. Once we do that, we will test those same 3 loads with the Boyd’s stock installed. Last, we’ll glass-bed the stock and test those same 3 loads again to see how the accuracy changes throughout each step of the process. In theory, we should see a linear increase in accuracy, but this is going to be a way to see first-hand if that will actually hold true.
Today we begin testing of the Thompson Center Compass in .308 Winchester in its factory configuration using the components listed below. Sighters (shots not included in the test groups) are used to confirm relative zero and eliminate cold-bore shot variables, which are heavily debated in some circles to alter initial groups. Groups are fired at 100yards and each group consists of 5 rounds of one powder charge, and the powder charge is incrementally increased by half a grain for each sequential group. Time is also allotted for barrel cool-down between each string of shots/firing. Today is a nice Spring day that didn’t deter us with much wind, so it was prime for a day of load development.
WARNING: The loads shown are for informational purposes only. They are only safe in the rifle shown and may not be safe in yours. Consult appropriate load manuals prior to developing your own handloads. Risencitizen.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.
- Brass- New PPU/PRVI Partizan .308 Winchester
- Bullet- Hornady 168g Z-Max
- Powder- Varget 40g – 44g
- Primer- CCI Large Rifle #200
- Cartridge Overall Length- 2.800″
Loading Process/Case Prep
Loading these rounds was pretty straight forward. Even when using brand new brass, I like to give the cases a good resizing using the RCBS Full Length Die Set (Group A) in .308 Win. Make sure you lubricate your cases well when doing this though because it’s easy to get cases stuck during this process. I used to use the RCBS Case Lube that comes in the squeeze bottle, but I have grown to hate that stuff. Now I use Redding Imperial Sizing Wax or Hornady One-Shot Case Lube most of the time. You can even make your own case lube using 1 part lanolin to 10 parts isopropyl alcohol, which is exactly what the Dillon spray bottle case lube consists of (literally it has two ingredients).
Tumble, Chamfer, and Deburr
After resizing, I like to tumble my brass purely out of habit using a Frankford Arsenal or Hornady Dry Tumbler and Media Sifter. Any tumbler will work, those are just the ones I have. Many of the case lubes listed previously evaporate off most of their material so it isn’t required to tumble them after resizing, but I like to do it anyway. Next, I chamfer and deburr the case mouth (inside and out) using a Lyman hand tool. If I do large quantities of brass, I will use the Lyman Case Prep Express. I also typically clean the primer pocket out of habit, although I don’t really even think it’s necessary, but this brass is brand new so there is nothing to clean.
Priming and Measuring Powder
Now we prime the brass with CCI #200 Rifle Primers. I have been using a RCBS Hand Primer for years (not the universal one), but I have grown fond of the Frankford Arsenal Hand Primer with the adjustable seating depth being a nice touch. After priming, we load up with powder, and Varget is the target for today! Working from 40g to 44g in half grain increments, we load each case using an RCBS Uniflow Powder Measure, RCBS Beam Scale, RCBS Powder Trickler, and RCBS Universal Powder Funnel. Again, use what you want, these are just what I have at my disposal.
Lastly, we need to seat our bullets. These 168g Z-Max bullets came in Midway packaging, but they are Hornady bullets all the same. Since this is just initial testing, we’ll load these to an OAL (Overall Length) of 2.800″. This RCBS Die Set comes with a Bullet Seating Die that contains a built-in crimp if you choose to use it. I have no intention to crimp these, so we’ll just adjust the seating plug to get the depth we want. Once we reach our desired depth, we’ll lock down our die, complete all our rounds, clean up our bench, and go do some shooting!
Shooting groups is the part where I need to get my game face on. Everyone knows that consistency is accuracy, and reloading rounds in a controlled space is pretty well spoken for. However, once you get outside, everything changes. Variables can swing in from every direction (sometimes literally), and the best thing you can do is to just try to shoot on the calmest day you can. So, that’s what we did.
We picked a nice cool Spring afternoon to go do load development. I usually place a Champion Redfield Style Precision Sight-In Target on a piece of anchored cardboard 100 yards away from me in a field, stretch out my Midway Shooting Mat, kick out my bipod legs, toss my ol’ sandbag/sock on mat, pull my Impact Electronic Ear Muffs out of my bag, and get comfortable behind the gun. In reality, I have to get up constantly to check camera equipment batteries and whatnot, but we’ll just pretend that part doesn’t happen.
I usually load up some sighter rounds to confirm zero and eliminate the cold bore variables that people will argue about in the comments if I don’t do it, so I do it. Once the barrel cools down, I shoot the first load, which is the lowest powder charge, feeding from the magazine as I would if I were hunting, then go mark the target for reference later and allow for the gun to cool off before the next group is put on paper. This is how all of the shooting is done to maintain consistency as much as possible.
Unfortunately, we discovered after the test was concluded that our scope was moving forward through the rings, so it was difficult to put any kind of solid conclusion on this test. However, even running into that issue, we still had some decent groups on paper.
Below is a picture of the final target after the shooting is concluded and a video of the shooting (groups are marked MOA but were supposed to be in inches). Each group is measured edge to edge with calipers and the bullet diameter is subtracted to get the final measurement.
- Smallest Group: 1.085″
- Largest Group: 1.955″
- Extreme Spread: 0.870″
- Group Average: 1.600″
Please feel free to comment with any questions, and check out the YouTube channel or Facebook page for more content on this topic and others. Thank you for reading. Stay Risen.
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