Target Sports

RIFLE REVIEW: BACK TO BLACK

Created on 26th May 2009

Laurie Holland has fun with the SSR-10, a manual version of the classic AR-10 military semi-auto

WHEN SOUTHERN Gun Company owner Bob Clark asked if I'd like to borrow a one-off SSR-10 rifle and do some load development with the .223WSSM cartridge in it, I was ecstatic. I'd previously tried to get Bob to lend me an SSR-10 (or a part, at least) without success - not too surprising as each ‘Speedmaster' is built to individual customer order from a long list of components and options.

The SSR-10 is the UK-legal (ie manual straight-pull) version of the AR-10. What's that? OK, let's take another step back. One of the two great military rifle designs carried over from the last century is the AR15, or M16 in US military-speak. This has proved outstandingly adaptable and efficient in sporting and target shooting. US NRA High Power Service Rifle has more registered competitors than any other fullbore target-shooting discipline worldwide and nearly all use the ‘black rifle' in accurised sub-MOA examples (although these still have to comply with strict NRA rules to ensure strong links to the military M16A2 are maintained). With its modular construction and hundreds of components, manufacturers and gunsmiths across the USA providing specialist parts or complete rifles, you can have one built for any purpose bar big game or benchrest.

Although .223 remains dominant, other cartridges are chambered in these rifles. However, if you want more power and range you're limited by the receiver and magazine lengths. The longest factory cartridges this AR accepts are the .204 Ruger and 6.8mm Remington SPC, both with 2.26" (57.4mm) COLs. Likewise, the fattest designs that can be accommodated with the bolt-head diameter are the 7.62X39mm and its PPC and Grendel offspring, using a 0.440" (11mm) case-head diameter.

7.62mm

Despite, or perhaps because of, the American civilian love-affair with the AR15, there is a growing body of shooters who want self-loaders that handle cartridges in the .308 Winchester class. Several specialist producers cater for them: Springfield Armory, with the M1 Garand (.30-06 and 7.62mm) and a choice of M1A civilian versions of the military M14; DS Arms, which has an impressive range of SA58 (FAL-type) rifles; and no fewer than seven makers offer ‘big AR' rifles although only ArmaLite Inc. of Geneseo, Illinois is able to use the original company name and ‘AR-10' model designation.

What does ‘308-class' mean? Most British examples have been built in 7.62mm for Practical Rifle competitors, or in more tightly chambered .308W match versions, but any .308W length cartridge (2.8" COL) with the 0.473"/12mm case-head diameter (which will feed from a 7.62 magazine) can be accommodated. That means .243 Winchester; .260 and 7m-08 Remington; the Tubb 6XC which starts with a .22-250 Rem case; and the new Hornady-developed 6.5 Creedmoor which provides .260R performance from a shorter case.

Straight-pull

This is all very interesting - but how is it relevant in the UK, given our dear leaders' collective view that we are unstable mental defectives who cannot be trusted with semi-automatic rifles? Well, fortunately the super-flexible AR comes up trumps, being suited to manual operation. Moreover, the accuracy-enhancing bits, fancy/ergonomic furniture and similar that have been developed by AR specialist components suppliers work equally well on our straight-pulls. In short, our custom straight-pull ARs match their gas-operated cousins in every respect bar the obvious one.

While some half-dozen domestic outfits will build a manual version of the smaller model for you, the Southern Gun Company is, as far as I know, the only one which offers the grown-up rifle. Apart from size, there is one significant difference between the two SGC versions: the company uses its in-house-designed and CNC-machined receiver halves in SSR-15s. Ambidextrous operation has been the norm on this model for some years, with a permanently attached short folding FN FAL-type cocking handle sliding in a track in the left upper receiver wall. There's provision to attach a longer and more ergonomically and mechanically efficient handle assembly directly to the bolt-carrier on the other side. The SSR-10 starts with Armalite Inc AR10 receivers. SGC machines a slot for the manual operating arm and handle assembly into one side of the top half, so customers must specify left or right hand-only operation.

AR and SSR-10

As with SGC's SSR-15s, the SSR-10's bolt and its carrier are not bought-in but machined in-house from scratch. Although the SSR-10 keeps the 15's eight-lug bolt configuration and cylindrical carrier, everything is noticeably bigger: length, diameter and weight. Up top a rectangular steel block acts as a guide rib, also providing a sturdy attachment point for the two Allen-headed bolts that secure the operating handle.

All ARs work the same way irrespective of maker; whether a 10 or 15, a cylindrical bolt plus carrier assembly slides through the upper receiver directly in line with barrel and buttstock, minimising felt recoil and maximising controllability. The eight-lug bolt locks directly into a ‘barrel extension': a large nut encompassing feed grooves and locking recesses that screws onto the rear of the barrel and also secures that component in the upper receiver housing. After firing the bolt and carrier move backwards. The carrier moves first to unlock the bolt, then the pair travel back as a unit to extract and eject the fired case while compressing a powerful spring held in a tube inside the buttstock. This also cocks/resets the trigger assembly, pushing its hammer back and down. On full travel the bolt is brought to a halt by buffers, then pushed forward by the spring, to strip a new cartridge out of the magazine and re-lock the bolt on chambering it. The bolt-carrier is a heavy steel cylinder with the bolt a neat fit inside its front half. The bolt can move backwards and forwards in its carrier by around half an inch. Moving out turns it anti-clockwise (as seen from the front) through use of a ‘cam-pin' that fits in an angled slot in the carrier to unlock it. As the assembly is forced forwards into battery the bolt lugs enter the locking recesses and hit the rear face of the barrel. The bolt is stopped dead, while the carrier is pushed further forward to turn the bolt and re-lock it.

The difference between straight-pull and gas versions is in what provides the rearward impulse to the bolt-carrier. The manual method is the simpler one, with arm power pulling it back throughout its entire rearward stroke. The original method uses a gas-port drilled half way down the barrel, bleeding some propellant gas off and feeding it to the action through a small diameter steel pipe. When the action is in battery, a tubing stub called the ‘bolt-key' fits into the rear of the gas-pipe and forms a seal. On firing, the bullet passes the port letting high-pressure gas into the pipe. This then feeds through the bolt-key and into a space in the back of the carrier body between the bolt and carrier tails. Since the locking lugs are in front of the locking recesses, the bolt cannot move backwards and stays locked for a few milliseconds while the trapped gas pushes the carrier backwards, unlocking the bolt through the cam-pin operation.

Once the bolt is unlocked and the assembly starts moving back the gas is vented into the receiver, but the heavy carrier has been given enough momentum to travel fully back. The bolt acts like a piston in a car engine using three gas-rings to form a seal. None of this applies to the SSR straight-pulls, which have no gas rings; bolt-key; gas passages/vents in the carrier body; etc.

Manual operation

While our firearms laws deprive us of that certain something in the shooting experience that only a centrefire semi-auto provides, manual operation is not all bad news. The bolt starts to unlock while the bullet is still in the barrel in ‘proper ARs', meaning loads and chamber pressures have to be constrained. Gas operation is violent, hence hard on cases and action components. Accuracy can be affected by the gas-pipe to bolt-key fit and speed of lock-up. Piping gas into the carrier assembly/receiver carries burned powder residues in too. This means carbon has to be regularly scraped out of difficult-to-clean recesses. Reliability improves too as there are no bolt gas-rings to wear out or break.

We can also expect our ARs to be a bit more accurate than equivalent-spec US models. This is good news for the AR10 as ArmaLite claims 1-MOA accuracy for its .308W AR10(T) with semi-heavy barrels. Reviewers report better results around the two-thirds to three-quarters MOA bracket with factory 168gn match cartridges, though. So we should do better still with heavier Krieger match tubes, tighter chambers and manual operation.

.223WSSM

Bob Clark is a fan of .22-calibre cartridges in his ‘Speedmaster' rifles, naturally, but as noted in this month's ‘Handloading Topics' (pages 32-35) there are limits on how far you can push the little .223 Remington design. People have used the .22-250R allied to fast-twist barrels, which gives 80-grainers and even the new 90gn models very useful MVs and external ballistics. There is a still larger capacity factory .22 centrefire in circulation: the .223WSSM (Winchester Super-Short Magnum) which uses an abnormally short, fat case with a similar powder capacity to the .308W to match .220 Swift performance. Designed as a ‘varmint' number, factory ammo gives a 55gn Ballistic Silver Tip 3,850fps, and I've seen reports of impressive velocities with 69gn bullets from match length barrels. Bob thought that an SSR-10 in .223WSSM using a heavy 8T barrel that handles 80gn match bullets would be a "bit of fun" with MVs well over 3,000fps on the cards, but found he hadn't the time to do the load development - which is where I came in.

Actually, this is a dreadful cartridge for the SSR. It's short and fat, so magazine operation is out, and each cartridge has to be partly inserted in the chamber before releasing the bolt catch to avoid misfeeds as the bolt slams closed. Full-house pressures of 65,000psi and a thick, tapered case mean extraction is hard, and there's no primary extraction provided by straight-pulls. The review rifle has the operating handle on the wrong (left) side for a cartridge that has to be single-fed. Being a one-off experimental job, various features (like automatic bolt hold-open engagement and a working ejector) are lacking. Despite all this, and the standard (heavy/rough) military AR trigger-pull, it's still fun to shoot, with only slight recoil in the heavy (13lb) rifle.

Bells and whistles

With precision bolt manufacture and lock, a lot of care taken over headspace dimensions and that great fat stainless lump of barrel up front, it shoots well. Early 100yd five-shot groups with 77gn Sierra MKs came in under the half-inch despite atrocious weather conditions. Ironically, with the intention being to see what velocities we can get out of it, the weather stopped all chronographing.

I'll resume testing and eventually report on this cartridge and its .243 sibling in Handloading Topics. Meanwhile, I've ordered an SSR-10 in .308 with 28" Krieger match barrel and various bells and whistles, and we'll see what it can do in F/TR class shooting.