I picked up one of these rifles in 300AAC and I decided to turn it into a fun project. The goal will be to tweak and customize this rifle and turn it into a lightweight bush rifle for carrying around the Texas hill country.
The rifle needs to shoot both supers and subs, be quick to sight, and most importantly be easy to carry over a shoulder. If you’ve spent any time in the hill country you’ll know that more often than not you run across critters that are within 100 yards of where you are (if you’re quiet enough), even deer. If I plan my project right it’ll be set up to be zeroed for supers @ 150 yards and subs @ 50 and 100 yards. I’m just pulling those numbers out of a hat right now because they sound good. We’ll see what happens when the time comes to set up sights.
There are probably better calibers for this kind of work, everyone has different tastes in that regard. I hold a special place in my heart for the good ole 30-30. I do like 300 Blackout though, I like shooting subsonic and these are readily available off the shelf which is a lot easier than working up a subsonic load in a 30-30 (not that I haven’t done exactly that on occasion).
I also set a goal of trying to stay as close as possible to the original American rifle parts as I could. I don’t mind changing parts here and there but to me swapping out the entire stock or replacing the bolt really makes it a completely different rifle. It’d be a lot easier to do that and really sport this gun up but where’s the fun in that?
If you know 300AAC, you know that it was originally designed with short barrels in mind. Thank’s to some really outdated and stupid laws, your average rifle comes with a 16 inch barrel.
Step 1 with this project was to fix that. After breaking the gun down all the way, I mounted the barrel up in the lathe and cut a healthy 5 inches off the end. Some off the cuff math tells me that this will leave a little over 10.5 inches of barrel which will hopefully clear the stock with enough room to toss a suppressor on when the mood strikes me.
There’s plenty of material midway down the barrel to comfortably turn threads back on the new stump. After cutting 5/8×24 threads with a bit of a land and re-crowning the end, we’re left with a much more manageable barrel for the caliber not to mention the gun just lost a whole bunch of weight. It’s important to note that you need to set the barrel up aligned to the bore, not the outside of the barrel. This particular barrel took about 3 thousandths of cutting before the outside was cutting cleanly. That kind of delta can mess up a good suppressor in a hurry when you add in tolerances for threads and a mount.
Don’t worry about the messy barrel. There’s lots to do yet and refinishing will be the final step so I’m not worried about cleaning things up just yet.
Barrel threading runs around $120. Another 5 grand to go and that lathe will have paid for itself!
I’m a big fan of QD sling mounts. The stock mounts work fine, don’t get me wrong, it’s just a personal preference. Luckily the American stock lends itself well to conversion to a QD setup.
There are lots of QD base options out there but I just happened to have a couple extra of the little QD cups that come with the MagPul AR15 stocks. With a little tweaking it’s a perfect fit.
First step is to drill out the existing sling mount stud to a 1/2 inch hole. Remove the existing stud first, of course.
Drilling into the existing mount hole is perfect, it leaves the support ribs intact and the base for the mounting screw is right where you need it. The screw hole needs to be opened up just a tad bigger than 5/16 but both of these holes are easily drilled with standard bits.
With the hole drilled, the MagPul QD mount taps in perfectly. The retaining screw needs to be trimmed down so the end of the screw is flush with the inside of the QD mount but that’s an easy task.
As always, use a little locktite on the screw to keep it from backing out when you’re tugging on that sling trying to push your way through those nasty cedar trees.
On the outside of the stock, just the right amout of QD cup is exposed.
Yea, I got a little sloppy with the initial drilling of the hole. I ran this one free hand instead of using my drill press vise. Oh well.
Drop a sling ring into the mount and the front sling mount upgrade is complete.
The Feed System
I know, I said I like to stay as close to factory as possible. Except when it comes to mag setup. I’m willing to set aside my morals and change that up.
I’ve done several bottom metal conversions, some came out nicer than others, but either way I much prefer the easier access release that’s typical with swapping out the bottom metal as well as being able to use more manageable magazines. The factory mag on the 300AAC rifles has gone through a few revisions to address feeding issues so I’m bypassing that issue completely by changing the mag system out for a different setup.
In this case I went with a CDI Precision American bottom for the ranch rifle, and let CDI do the inletting. They’ve got the template and do it for free when you buy the metal, so for just shipping it saves a lot of time.
The new metal is a snug fit, which is good, and requires the mag release to be fitted once the metal is installed. We’ll have to wait for that part until the receiver is finished, fitted with the barrel and re-installed in the stock.
Test fitting the parts shows the new mag setup. Aside from holding more rounds, I like the traditional mag appearance.
Next up is milling the receiver for the express multi-tab sight. Yes, I’m aborting the rail system and scope and going with something simple and fixed. This is going to be a brush gun used for short range. We’ll be skipping the scopes on this gun.
There’s a base for these, but I want to keep the sights as low as possible to the rifle to minimize protrusions so I’ll be milling out a dovetail slot directly in the receiver for the sights.
While we’re at it, this is the right mounting to take care of the NFA engraving required by our ATF overlords. I’ll knock out the engraving and the dovetail slot while the receiver is here, and then refinish the cuts. The stock rail screw holes need to be soldered shut, smoothed, and refinished as well.
With the receiver mounted in the CNC machine, an end mill cuts a nice square platform that forms the basis for the sight mount. Once the bulk of the material has been cleared out of the way a standard 60 degree bit is used to make the dovetails for the sight.
Just like the average action movie, we’re skipping several hours of milling, test fits, and cleanup, and jumping ahead a bit. The basic cut is done, and the express blade sight pressed into the slot. We’ll fill in the old rail mount screw holes later.
A quick view down the top of the receiver showing the blade sight test fit and also the flat milled into the top for the NFA engraving. The end result will be cerakoted, but I dabbed a bit of cold blue on it to prevent any corrosion or rust while I work on other things. You’ve read this page in a few minutes, but in reality I’ve been doing little bits at a time and already have a couple months into this.
At the front of the shortened barrel I’ve drilled/tapped a hole for the sight base screw and also soldered the base to the barrel. This will be the last modification to the barrel/receiver combo (except for some ramp polishing) so it’s been degreased and blasted in preparation for cerakoting. I hadn’t noticed the two small score lines, not sure where they came from. Oh well, it adds character. That’s my story and I’m sticking to it.