Posts Tagged ‘FN’

FN SPR: Barrel completion

In this post I will complete the work I did on this project for my second semester. The last step is to cut the barrel to size and crown it. The crown of the barrel is very important for the accuracy of the rifle. It must be cut square to the bore. If the crown is not square to the bore or damaged, the gases that propel the bullet will push it slightly of course.

First the easy part. I marked and cut the barrel to length using a hacksaw.

Ready to cut

Rough cut done

After this I installed the barrel in a four jaw chuck on the lathe and set it up.

Setup for crowning

Once I completed the setup, the cutting started. First I did a smooth cut square to the bore.

High speed!

I then used the compound of the lathe to cut an 11° crown. On the Remington project a square crown was acceptable as I installed a muzzle brake. For the FN I chose the 11º crown. While there is some debate about which type of crown is better, I just chose to do a few different types.


This concludes the work for my second semester on the FN project. Thank you for following along!

FN SPR: Barrel

I took a short break from updating the blog since it is the only break I will get before my summer semester. I have not been idle and took a few short courses during the break. But now we need to look at the FN project again.


The setup work on the barrel is a repeat of everything that I did for the Mauser and Remington projects. After centering the barrel in the lathe, I cut the tenon and threaded the barrel to fit the receiver. The next step was to cut the cone for the bolt.

Cutting the cone

Cone complete

With the cone completed, I cut the chamber in the barrel. This rifle is chambered for .243 Winchester.  I tightened the action onto the barrel and it is now ready for test fire.

It fits!

Bolt open


Bolt closed

Time to do the test fire!

Test fire 1

Test fire 2

I am pleased with the test fire results. Case expansion on this rifle was 0.0005″ (12.7 microns/0.0127 mm). The final step of the barrel process is to cut the groove for the extractor. I marked the location of the barrel relative to the action, removed the barrel and set the barrel in a mill to cut the extractor slot.

Starting the extractor cut


During the cut

After I completed the cut, I re-assembled the action and barrel and verified the headspace and made sure the extractor works.

All lined up!

The only work left for the barrel is to do the crown. I will cover that in the next post on this project. As always, thank you for reading.


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.