Posts Tagged ‘blueprinting’

FN SPR project: Blueprinting

It is time to talk and show some of the work I have done on my third (required) project this semester. The FN Special Purpose Rifle (SPR) is essentially a pre-64 Winchester 70 action. We managed to get a good group deal on these and I ended up buying 2 of these. One (this one) I will keep as a complete rifle as it will be part of my portfolio. At some stage, I will complete the second rifle and sell it. I will chamber this rifle in .243 Winchester and I will make a laminate stock for it.

FN SPR action

Ready to start


As with the Mauser and Remington projects, I start by blueprinting the bolt and receiver. I trued the bolt face first.

Bolt face

I also had to true the bolt lugs. No picture of that but the process is the same as for the Mauser bolt. I then trued the front of the receiver.


The only other step needed on the bolt and receiver was to lap the bolt to make sure there is full contact between the bolt lugs and the receiver. In my next post I will show the process of cutting and chambering the barrel.

Remington 700 project: Bolt blueprinting

Started on my Remington 700 project this week (March 19). I am putting a lot of attention to detail into this one as I am building it for my wife! This is a brand new action from Remington chambered in .223 Remington. I did contemplate doing this in 5.56×45 but we do not have the correct reamer. (I listed the calibers incorrectly before. My mistake, I am blaming it on the fact that I was working on my Winchester 94!) The first picture shows the action and bolt. The bolt is disassembled as I only need the bolt body during the barreling and chambering process. 

This picture shows the barrel blank. I purchased the barrel from Shilen as they give us a really good trade discount as students. The barrel has a number 6 contour (which means it is pretty thick and quite heavy) and made from chrome moly steel. The twist rate for this is 1:9 to allow for the use of a range of bullet weights.


Here is the action without the trigger assembly. You can also see the recoil lug in the background to the left and center of the picture. The recoil lug helps to control recoil once the action is mounted in a stock. On the Remington 700, this is an extra piece. On the Mauser and FN actions, this part is part of the action.

I started doing all the blueprinting work on the bolt and action. This allows for added accuracy. We use a fixture to mount the bolt in the lathe and then center the work piece just behind the lugs of the bolt. You will see the instruments we use to measure a little further down as we also use them for setting up the barrel. What is measured is known as run-out and shows how well the work piece is centered in the lathe. The more accurate the work is set up, the better it will function. I try for zero run-out but it is not always possible. For this bolt I got it to less than 0.0005 inches (12.7 microns or 0.0127 millimeters).

The next step was to “true” up the back of the bolt lugs. Truing the lugs just means we make sure they are the same height and that they are square to the bolt body. The first picture shows the process, the second shows the result.

This process repeats on the front side of the bolt lugs. This is not always needed as it depends on the action. On the Remington 700 it should be done. Again I am showing a during and last picture.


This is almost all the work on the bolt body for now.