The Project – building a TSP X chassis rifle

Daniel O’Dea

Aussies love a DIY project as sometimes just the idea of personal input adds joy over just buying something out of the box, not to mention the pleasure involved in customisation and having a finished project just the way you want it or built to your budget.

In last month’s edition we looked at a new modular rifle chassis designed and manufactured right here in Australia by Southern Cross Small Arms – the TSP X. There are lots of fine off-the-shelf chassis-style rifles these days from almost all the major manufacturers but in reviewing the TSP X chassis I thought it might be good to take a closer look at what you need to put together your own chassis build.

In addressing this project I wanted to keep it both simple and within reach of those on a budget, preferably without the need to employ gunsmithing services or buy a complete donor rifle to start with. As such, I’m looking at this as a basic ‘build’ rather than ‘custom’ rifle project, the main difference in my analogy being in a custom project you might start with an action and raw barrel blank you’ve tuned, profiled, chambered, head-spaced, fitted etc by a qualified gunsmith, while in this example we’re simply taking off-the-shelf components for DIY assembly.

These days, seeing the opportunity modern chassis rifles present, some major manufactures offer barrelled actions as opposed to completed rifles, with just such build projects in mind. Howa are one who offer complete barrel action assemblies of various calibres and profiles at a very reasonable price, and as the TSP X chassis has a Howa-compatible variant I thought this would be a good start.

I was looking to build a medium-weight rifle for medium to long-range work and having used several rifles already in the calibre this was the ideal opportunity to jump on the 6.5 Creedmoor bandwagon and build it in that. Research revealed Howa had exactly what I was after, a Howa 1500 barrelled action in 6.5 Creedmoor with a medium-heavy profiled barrel, heavy enough but not axle shaft diameter.

To make it even better the barrel was threaded for a muzzle brake and the unit came with Howa’s HACT two-stage trigger system, all the bottom metal and an oversized tactical bolt knob. With the TSP X chassis I wouldn’t need the bottom metal (magazine box and floor plate) but some other chassis systems can use these or alternative parts. With the TSP X I’d only need an AI pattern magazine.

The only other parts I’d need would be a rail and rings to mount a scope and looking to take advantage of the long rang capabilities of the 6.5 Creedmoor round, I felt a 20MOA rail would be in order. For those wondering what exactly a 20MOA rail is, it simply means that rather than the scope rail being perfectly flat and parallel to the bore axis, it cants downwards slightly towards the front of the barrel which, in turn, provides more usable elevation (in this case 20MOA) in scope adjustment.

So, if say your scope as standard has 30MOA up and 30MOA down turret adjustment, by using a 20MOA rail you end up with 50MOA adjustment for elevation (up) and 10MOA adjustment for inclination (down) allowing turret adjustment for elevation out to much longer ranges. US manufacturer Warne has a large selection of scope mounting options including their relatively new and well-priced Mountain Tech range of lightweight precision rails and rings. This range includes a 20MOA rail option for Howa 1500 and Weatherby Vanguard variants so that and a set of 30mm rings would do nicely.

The Howa 1500 6.5 Creedmoor barrelled action selected comes threaded ⅝” x 24 to accept a muzzle brake and with any longer-range rifle, anything that mitigates muzzle lift and recoil is an advantage as it’s good to be able to spot your shots through the scope. As such I felt an effective muzzle brake would be in order. ACT-based GC Precision Developments not only make a range of precision long range rifles but suppressors (for LE and Permit) and high efficiency muzzle brakes and I run one of theirs on a Remington 700 in .308 Winchester set up for long-range work. GCPD recently unveiled a newer ‘User Timed’ three chambered muzzle brake I was keen to try so this would be a great opportunity.

A few calls and emails and everything was ordered from the relevant suppliers. Another thing I’d need for the project would be tools, thankfully nothing too exotic just a handful of various sized hex (Allen) keys and a torque wrench, all of which I had. When everything arrived I started the bulid.

Unboxing the Howa barrelled action the first job was to remove the bottom metal – magazine floor plate, internal box and spring – which as mentioned was superfluous. Next step was to unpack the TSP X chassis which comes with a detailed schematic diagram and step-by-step instructions along with all bolts and components. Starting on the assembly the outlined steps were as follow:

Step 1: In using a Howa action you must remove it from the stock and bottom metal (based on working from a donor rifle) and as I’d started with a barrelled action and had already removed the bottom metal, I was ahead of the game.

Step 2: Invert the action and position the TSP X chassis inlet, confirm alignment then inset the provided front and rear action screws and tighten. Suggested torque setting for Howa actions is 65in/lbs which happens to be the fixed torque setting on my Warne TW65 torque wrench, so I used that.

Step 3: Assemble and secure the butt stock to the TSP X chassis inlet and once the minor stock components are assembled (cheekrest etc) simply line up the recess and lug of the two assemblies and insert and tighten the single M8 x25mm bolt.

Step 4: Attach the fore-end which, like the stock, is a simple matter of lining up and bolting the assemblies together, in this case with two M6 20mm bolts. However, there’s another minor step in the case of the Howa action which is inserting the recoil lug set screw and giving that a tweak to lock up the bedding.

Step 5: Position and secure both the magazine and grip adapters that bolt to the chassis inlet via another handful of bolts, the grip adapter with a single M6 35mm bolt from the top just behind the receiver tang and two small M4 x 10 each side of the magazine release, and the magazine adapter with another two 20mm bolts. The grip itself being a standard MSR/AR Milspec uses a single ¼ 28 UNF threaded bolt as opposed to all the other metric bolts in the build.

The instructions include torque settings for all bolts while a medium strength thread locking agent such as Loctite 243 is recommended and was used in this instance. I’d note the assembly does vary slightly for the TSP X chassis depending on action type but, as with this one, all are pretty simple to put together.

To complete the build I installed the Warne 20MOA Mountain Tech rail to the Howa receiver using the Torx T-15 socket caped screws provided with a dab of Loctite and torqued down with my Warne TW1 25in/lb wrench. The Mountain Tech 30mm rings were then fitted and an on-loan Zeiss 5-30×50 V6 scope mounted.

Last thing to do was remove the muzzle thread cap and install the GCPD high efficiency muzzle brake. Unlike units which have to be timed (lined up) using a crush washer this unit comes with its own locking ring (jam nut). To install you screw the jam nut to the muzzle thread until it contacts the end face, then with anti-seize grease applied to muzzle thread screw the muzzle brake itself on until it contacts the nut.

Back it off to line up horizontally and while holding it in place use the supplied spanner to tension the jam nut, locking the muzzle brake into position. Not much force is needed and this system allows for quick removal if required for fitment of other accessories such as suppressors where allowed under permit.

I’d successfully completed my own chassis build, turning a bunch of precision parts into a functional modern-day chassis rifle. As a proud creator naturally, I couldn’t wait to get to the range and start running it in and working up some loads. Early days so far, but all looks promising with some starting loads providing sub-MOA groups and I look forward to wringing the best out of it.

In summary, building the rifle on Southern Cross Small Arms’ TSP X chassis was a simple and enjoyable process, fairly intuitive, instructions easy to follow and all with basic knowledge and tools. To state the obvious, always ensure any firearm or action is completely unloaded with bolt removed before starting such a build and, equally importantly, ensure any upgrades or modifications fall within state regulatory requirements.

Build components

Barreled action: Howa 1500, Medium profile in 6.5 Creedmoor with HACT trigger system and Tactical bolt knob

Chassis: Southern Cross Small Arms, TSP X Howa Short Action Chassis

Magazine: AI Pattern Accurate Mag (note: genuine AI mags recommended)

Muzzle Brake: GCPD high efficiency ‘User Timed’ three chambered

Scope Rail: Warne Mountain Tech 20MOA Howa Short Action 1913 rail

Scope Rings: Warne Mountain Tech 30mm lightweight low-precision rings

Scope: Zeiss V6 5-30×50

Tools used by author

Hex keys: 2.5mm, 3mm, 4mm, 5mm, 6mm, 3/16″; torque wrench; Warne TW1 and TW65 scope mount torque wrenches; Loctite 243 thread locker; Tipton gun vice.

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