Target Sports

HANDLOADING: WEIGHTY MATTERS PART TWO

Created on 26th May 2009

LAURIE HOLLAND continues his look at heavy bullets in 223 Remington

BEFORE LEAVING the issue of matching 0.224" bullets to rifling twist, there are a couple of queries worth addressing. First, how come the Berger 64gn Match and one or two similar weight Sierra semi-pointed soft-points are suitable for one turn in 12" (12T) twist barrels, but the military 62gn (strictly speaking 4g = 61.7gn) FMJBT needs 7T, as in the UK L85A2 and L89A2 (SA80), US M16A2 etc assault rifles? The spin-rate that stabilises a bullet is not determined by the latter's weight, but its length as measured in calibres. The FN SS109 military design is unusually long for its weight due to its internal construction (Figure 1), but doesn't need the 7T specified for the rifles to allow them to fire ammunition loaded with the still-longer FN L110 63.8gn tracer model. The SS109 just works from 10T barrels, but 9T is ideal at 5.56mm MVs. Conversely, Berger and Sierra designed their 64gn HP Match and SMP sporting models with flat bases, keeping them very short for the weight and giving them long bearing surfaces, in order to work well at 3,000fps from a 12T barrel.

We know that 12T rifling stabilises bullet lengths that come with weights up to 55gn, plus the odd special heavier design; 9T handles designs in the 68-75gn weight range (Hornady A-Max excepted); 8T works with 80s, even if VLDs benefit from another half-inch or inch reduction in the twist rate. But how do things work out the other way - short, light bullets in an ‘over-fast' twist barrel? With the exception of some ultra-thin-jacketed varmint bullets, 9T rotational speeds are fine with 52-55 grainers and 8T generally gives excellent results from the 68-75gn group, even if bullets are theoretically being spun over-quickly. However, belting the lightest bullets out of 7T and 8T barrels at standard velocities imposes enormous stresses through excessive rotational speed. 3,300fps gives a bullet just under 200,000 rpm from a 12T barrel, raises that by 50% to 295,520 rpm with 8T and sees in excess of 340,000 rpm - a 72% hike from 7T!

Unless velocities are reduced, some bullets produce erratic performance - they even disintegrate. The more heavily constructed 55gn designs, especially FMJs, will stay in one piece and resist distortion, but accuracy deteriorates when a bullet is spun that much faster than optimal levels. (See table 1 p35)

TR and F/TR

I posed a couple of questions last month: why wasn't the 5.56mm cartridge, now the nation's primary smallarms cartridge, adopted as standard for Target Rifle (TR), as previously happened with the .303" and 7.62mm? Secondly, can .223 Rem handloaded with 80gn bullets compete with .308 Winchester equivalents?

TR uses issued military ammunition in some club and all county and national level competition, the three NRA-approved cartridges being 7.62mm, 5.56mm, and 0.303" with only the first named being made available. Nobody uses the L2A2 5.56mm cartridge, for the excellent reason that it is in no respect competitive compared with the 155gn 7.62mm sniper round (RG ‘Bisley Match' and suchlike). It fails on two counts: ballistics and consistency (accuracy), the latter partly due to its being specified by the MoD as a cheap product that only needs to hit ‘Figure 11'-sized targets.

Unlike 7.62mm, which was initially in the same boat, there has never been a military need to produce a higher-specified (sniper) version. That aside, the SS109 bullet features a unique multi-component internal arrangement that presents considerable difficulties to the ordnance factories in producing high-grade, consistent products. Moreover, even if batches of 62gn 5.56mm and 155gn 7.62mm are matched grouping-wise, the former will still offer inferior external ballistics performance that needs 40%-plus extra wind correction thanks to its lower BC bullet. (This also applies to 69gn handloads, albeit to a reduced extent.)

So forget TR - but how do the civilian versions of the two cartridges compare in handloaded form for club or F/TR-Class competition, the latter restricted to rifles chambered for this pair? Good factory rifles with 24-26" barrels will see 80gn-bullet .223 hold its own accuracy-wise in 200 to 600yd club-level shooting. On paper it gives slightly inferior performance in the wind compared to handloaded .308 with 155-grainers at 500 and 600yd, but I reckon there is nothing between them. On the plus side for .223, it produces less recoil, hence less rifle movement on the bags or bipod. There was a problem with ‘factory-class', with the Tikka T3 Tactical the only out of the box model with an 8T barrel, but I'm delighted to note that the superb single-shot Savage Model 12 LRPV (Long-Range Precision Varmint), with its rigid action, crisp ‘AccuTrigger', and exceptionally heavy 26" barrel, is now available in a 7T version alongside the original 9T. Unfortunately LRPVs are thin on the ground, the importer having expressed doubts about the market for single-shot precision rifles! If you are interested in one, Savage accuracy specialist Stuart Anselm of North West Custom Parts and that long-time supplier of interesting rifles Brian Fox (Fox Firearms) are your best prospects.

F/TR competition is different, with League rounds shot over 800-1,100yd stages and likely to see custom-built or rebarrelled rifles. Despite incredulity from some, 223/80 at 2,700-2,800fps hits the target at 1,000 yards, groups rather well and sees bullets remain stable despite being subsonic (as are bullets from most .308W loads at this range). With its greater powder capacity, larger choice of bullet weights and designs suitable for long-range applications, .308 Winchester can be better optimised for this task. In particular, users can fit longer (30"-32") barrels to gain an extra 200fps, with 155gn bullets taking them to 3,000fps, or produce useful velocities from 175s and 190s. Barrel lengths above 26" provide poorer returns from .223 load combinations, maybe only another 50fps with 80gn bullets. Another issue that comes into play is MV spread, it being important to produce loads that keep this in the 20s or less to produce consistent elevation on the target. While good .308 handloads achieve this standard without difficulty .223 struggles, with 30-40fps a relatively good result.

However, not everything is doom and gloom: when we get around to loads and results you'll see a combination that gave the 80gn SMK an extra 100 fps in my 26" barrel rifle, taking it to 2,900fps at acceptable pressures and with a reasonable MV spread and 0.5-MOA accuracy. It uses a slower burning powder than those normally employed in the cartridge, so might give worthwhile velocity gains from a longer barrel. In any event, Table 2 lists calculated 1,000 yards retained velocities and wind drift, but I would recommend treating these figures with some scepticism - ballistics tables are notoriously inaccurate for this pair of cartridges at this range as effective BCs often drop markedly as bullets approach the speed of sound (1,120fps). Many factors, such as spin-rate, can also affect the actual ballistic performance.

Brass

There is a large choice of cases, both military and commercial, but of those I've encountered I'd only recommend a couple: Winchester and recent Lapua production. If buying the latter, make sure the box is marked ‘Match' as this version has much thinner walls and greater internal capacity than the older type. Some military examples are heavily built, restricting capacity. MEN examples have 6% less room inside than Winchesters, which affects pressures and performance. This is relevant for two reasons. Firstly, as the .223 is not over-endowed with powder capacity and performance we want as much of both as we can get. Secondly, the smaller the capacity the faster pressures rise - so much so that one has to reduce maximum charges by up to 1.5gn for some makes to avoid excessive pressures (Table 3). Case capacity is an issue when handloading any bullet, but it becomes more critical as weight increases - so one must not use top loads quoted for 80gn bullets in a ‘roomy' case with any old brass, especially that previously fired without a known history. If you're offered fired military RG L2A2 brass, be wary. This is a high pressure version of the cartridge that can see excessive case expansion - even case-head distortion - if fired in a loose chamber and full-length sizing won't correct this.

Winchester brass is much cheaper than Lapua, but needs more work using swaged concave-floor primer pockets and punched flash-holes. These often leave brass spikes sticking up inside the case, which affects primer flame distribution and powder ignition consistency. I de-burr all cases and ‘uniform' primer pockets - the former is a quick easy job, the latter a chore. In my experience most cases are pretty consistent out of the packet for weight and neck-thickness, but you'll likely find a few fall at the extreme ends of the weight distribution curve - they can be anything up to a couple of grains either side of the majority. For match and long-range shooting it's worth weighing new cases and culling the aberrant few percent, putting them aside for practice rounds. The remainder should fall within a 1.5gn weight range. The Lapua version is consistent out of the box, nearly everything being within a 1.0gn weight range. With machined primer pockets and drilled flash-holes there is rarely any work required here - the occasional small burr is left inside the case around the flash-hole, so it is still worthwhile running the flash-hole reamer through new cases (just give each a single turn using gentle pressure). All cases need the inside edge of the case-mouth chamfered before the first load, and a shallow-angle ‘VLD' tool is advisable with long boattail bullets.

How long do they last? Unless you hammer them pressure-wise you get 10 loadings out of Winchester brass, although the occasional neck split might appear after half a dozen. There's not a lot of ‘meat' in the case-head around the primer pocket in this slim case, and primer fit often becomes noticeably looser on the seventh or eighth loading. If you achieve nine or 10 loads you'll also likely notice neck-tension variations during the bullet seating operation due to inconsistent work-hardening. The moral is to measure, batch and prepare new cases; keep them segregated throughout; note the number of times loaded; and restrict match use to five cycles. I scrap Winchester batches after 10 firings even if they still seem OK. I don't know yet how long my Lapua Match cases will last (in either match-trim or absolute life) as my most-used batch has only been fired half a dozen times. Primer pockets are still as tight as they were when new, and the word is that they will achieve 12 loadings - maybe more.

A final word on case capacity. If a thick-wall/low capacity example gives full pressure with less powder, isn't that a good thing? In this situation it's not, as MV doesn't depend on peak pressure - rather the total amount of energy applied while the bullet is in the barrel. Ultimately, more powder provides more energy and hence more MV. (However, if the application requires a light, low-velocity load, one could choose the heaviest/smallest capacity case available to increase the fill-ratio or load-density with the
reduced size of the charge.)

Size

Handloading the .223 is quite straightforward, with a good choice of makes and types of die. Neck-sizing usually suffices for turn-bolt rifles and reduces workload - especially with the Lee Collet model, which doesn't need the case to be lubed. It's essential to full-length (FL) resize cases for AR15-type straight-pulls to ensure trouble-free operation, and one has to keep a close eye on headspace. When FL-sizing for a conventional bolt-action setting the die is simple: back it off slightly from full shellholder contact, then screw it back a quarter-turn at a time until cases just chamber freely, with no resistance felt in bolt handle movement. You cannot ‘feel' this ideal set-up with a straight-pull, but you still need to know the case shoulders have been set back enough to guarantee the locking lugs are fully engaged. (Partial bolt locking can give rise to a dangerous situation, although AR15s should stop the firing pin making contact with the primer unless 100% lock-up has been achieved. However, many American High Power competitors had .308W M1A/M14 rifles self-destruct because of this problem, and not only with handloads!) On the other hand one doesn't want excessive headspace, as this reduces accuracy and case-life. Case-to-chamber longitudinal clearance in the order of one to two thousandth of an inch is ideal. The only sure way of obtaining this is to measure fired cases with a case headspace gauge from Hornady or RCBS (the Precision-Mic) and adjust the sizer die to suit. I've found that both RCBS and Hornady New Dimension dies give the ideal setting for my rifle's minimum-headspace ‘match chamber' when at the default setting - die body against the shellholder with the press-handle fully down - but you cannot assume that always applies. Forster makes ‘National Match' versions of its .223R and .308W dies for ammunition to be used in AR and M1A type match rifles. These set the shoulders back slightly more than normal, and with the die adjusted at the default setting they let the handloader fine-tune the die position and consequent headspace.

Little effort is required to FL-size the .223 case, especially if it's been fired in a tight match chamber. It is important to be consistent in lubricating cases and subsequent press operation, moving the press-handle at the same speed with each case (especially when loading for straight-pulls). Inconsistency can produce varying case-shoulder positions and hence headspace. I use Imperial sizer wax (now branded as a Redding product), which works with the slightest of coatings on this little case and can be applied thinly and consistently, rolling the case between the thumb and forefinger.

If you FL-size cases then stretch is an issue with this markedly tapered design and thin walls, even if you remove the expander ball from the sizer die and use a mandrel instead as a separate operation. It's vital to measure case-length after sizing, not in the as-fired state, as the process often adds four or even five thousandths of an inch with Winchester cases. Maximum length is 1.76", with the trim-to value 10 thou' less at 1.75", so trimming is required every two or three loadings with this rate of growth. Neck-sizing reduces growth, so trimming may only be needed once during cases' life.

Mention of a mandrel or separate expander die raises the issue of case-neck tension on the bullet. With large variations in the neck-wall thickness of makes of .223 cases, and the likely use of the cartridge in semi-auto rifles in many countries, manufacturers produce dies that size necks down substantially, usually leaving the neck undersize after expansion for a tight bullet fit. This shortens case life, with substantial neck dimension changes during sizing, expansion, bullet-seating and firing rapidly work-hardening the walls. Since this usually happens at different rates for cases even in one batch it affects accuracy after some loadings. Many handloaders like a tight bullet fit and get worried if seating seems to require hardly any effort on the press-handle, but there is evidence that the lightest possible neck-tension on the bullet improves accuracy. This isn't really on for AR-type straight-pulls, which hammer the cartridge into the chamber under spring-pressure and may even work like an inertia bullet-puller with bullets under light tension. These can move forward in the neck, perhaps even moving out of it completely if there is enough freebore, when the fast-moving cartridge is abruptly stopped by the front of the chamber. With the bullet stuck in the rifling this is most undesirable, especially if one has to unload the rifle! If loading for a conventional bolt-action rifle keep neck-tension light and reduce sizing to the minimum, using a Redding neck-bushing die or a conventional Forster sizer with a custom neck section diameter (around £10 over the normal price).

Next month I'll finish off this report on the cartridge, moving onto primers and ascertaining the correct cartridge length (COL). It's vital to get this right with long, heavy 80gn bullets. If you read American sources orientated towards NRA High Power Service Rifle using 20" barrel AR15s in semi-auto mode, there are only a handful of powders worthy of consideration - Alliant Reloder 15, Hodgdon VarGet and Vihtavuori N140/540. I'll look at whether that applies here, reporting on 11 powders from half a dozen makers matched to five bullets. With 6,000 rounds through the SSR-15's barrel by the time I finished this round of tests, I'll also report on whether it still shoots well and the amount of throat erosion that has occurred from new as measured with an 80gn Sierra Match King bullet touching the rifling.