Sniper Golf Est. 1996 by Sniper's Paradise

 

 

TWO .22 RIFLES FOR THE WIND

by Fred Barker

 

For shooting prairie dogs, various ground squirrels and other pests or varmints in calm weather a .22-250, .220 Swift, etc. with 50-55-grain bullets, or a 6mm Whatever with 55-70-grain ones at 3,600 to 4,000 ft/sec works fine, no argument. But for windy conditions---like about one day in three in prairie dog habitat---we need bullets that buck the wind better (or are deflected less by crosswinds as others would phrase it).

Wind deflection of a bullet, as ballisticians discovered long ago, depends directly on the rate at which it loses velocity (due to air drag). French and German military engineers in the late 19th century developed long, pointed bullets that shot much better in wind than the usual short, stubby ones. By the late 1930's all our target shooters had sharp-ogive, boat-tailed bullets for 600 to 1,000-yard matches. But progress for varmint shooters came much slower. In the 1940's and 1950's a few wildcatters were necking down .30-06, 7mm Mauser and other cases to hold either the .228"-diameter, 70-grain bullet made for the .22 Savage or for better-pointed custom bullets of 80 or even 90 grains weight. The .228 Ackley and .224 Clark cases were two examples. Demand was low and die-hard varmint shooters were few. By the 1980's, however, riflemen were generally more knowledgeable, Bill Davis developed his Very Low Drag-profile bullet design, and both custom and factory bullet makers started to produce bullets giving low air drag---or ones having high ballistic coefficients (BC's). And both custom and factory barrel makers included some .22 barrels of 1:8 or 1:9 twist rate that would stabilize 75 and 80-grain bullets, especially for rifles in .223 Remington. Finally some progress, but last year (2002 A.D.) I asked myself what's the best choice of cartridge for serious windy-day varmint shooting (and by "serious" I rule out the factory 1:9-twist rifles in .223 Rem. because their velocities are not high enough for shots much beyond 400 yards)? (Note: in mid-2003 Winchester offered a short, fat .22 case holding about 60 grains of powder called the Winchester Super Short Magnum. I haven't yet shot it and don't know its good and not-so-good points. But I'm sure PS will have an evaluation of it soon.)

We can frame the question with ballistic coefficients (BC's), velocity and recoil. Bullets having BC's in the .250 to .350 range, like the 50-55-grain ones in .22 caliber and the 70-grain 6mm ones, show prominent wind deflection beyond about 400 yards (see table below), even if started at 3,700 to 4,000 ft/sec. Bullets with BC's of about .400 to .525 can't be driven as fast (at least in all but a few very large, barrel-burning cases) as bullets of lesser BC and weight, but at 3,200 to 3,600 ft/sec their wind deflection is about 2/3 or even 1/2 that of the lower BC ones. The competitive 1,000-yard benchrest bullets, having BC's of .560 or so up to more than .75, do show, when driven at 2,900 to 3,200 ft/sec, as little as half the wind deflection of a maximum .22-250/.220 Swift load with 55-grain bullets. Recoil and general handiness in the field, though, become factors to consider with these big-bullet guns. For instance, a 6.5-284 rifle sending a 139-142-grain bullet of BC .565 to .6-plus downrange at about 3,000 ft/sec should weight 14 to 18 pounds for comfortable, all-day shooting. And a 30-40-pound rifle in .338 Lapua or .338-378 Weatherby with a 3-foot barrel sending the 300-grain Sierra match bullet (BC about .768) off at 3,000 ft/sec would be death on prairie dogs in breezy weather, but its shooter would need Governor Schwarzenegger's physique to lug it around.

So after looking over the wide variety of possible cases and running many trajectory-wind deflection print-outs on Sierra's Infinity ballistic program I chose two rifles---one using a factory case and the other a wildcat. These are a .220 Swift with custom barrel of 1:9 twist and a larger case, the 6.5X55 Swedish Mauser case necked down to .22 caliber. This larger case is one of the "50-grains-of-powder" .22 cases, along with necked down .243 Win, 6mm Rem, 7mm Mauser and similar-sized cases that hold about that much slow-burning powder under a 75 or 80-grain bullet. I chose the 6.5X55 case because I had a good supply of the strong and closely-dimensioned Lapua cases. If starting from scratch I probably would have chosen the 6mm Rem. case because it's easier to neck down and has a longer neck than the .243 derivatives. Also, a larger case like the .22-.30-06 and holding about 60 grains of powder would be a barrel-burner (the 50-grain cases are rough enough on barrels). This Swift with a 1:9 twist, rather than the standard 1:14 one, I call the ".220 SwiftQT", with "QT" for quick twist. The .22-6.5X55 label is unwieldy, so this wildcat is named the ".22 SwedeQT".

The table below gives wind deflections from Sierra's Infinity program of the .220 SwiftQT and .22 SwedeQT using Hornady's 75-grain A-Max bullet, in comparison with a 55-grain Nosler Ballistic Tip bullet loaded at 3,800 ft/sec in a standard .220 Swift and a 142-grain Sierra MatchKing driven 3,000 ft/sec from a 6.5X284 or similar case. These bullets are arbitrarily chosen: similar ones from other manufacturers give similar wind drift. Shooting conditions for the figures in the table are like those in some of the prairie dog country of the western USA: 80 o F, 15% relative humidity, 4,000 feet elevation and wind blowing 10mph at 3 or 9 o'clock . We should note that the BC's used in the program are mostly approximate: i.e., they generally decrease slightly as the bullet's velocity decreases down range (Sierra is the only manufacturer giving a set of BC's for each bullet for several steps in velocity). Determination of BC's by different manufacturers also may be done under slightly different conditions. We also note here something familiar to 100-200-yard bench shooters: wind deflection of a bullet gives gyroscopically induced vertical components roughly 30-40% of the horizontal drift (see Vaughn's Rifle Accuracy Facts, P.S. Inc, and McCoy's Modern Exterior Ballistics, Schiffer Pub., Ltd.). These vertical components are substantial for long range shooting.

Cartridge Bullet, wt., BC Muzzle Vel. Wind Deflection, inches 400 yds. 600 yds. 800 yds. .220 Swift (1:14 twist) 55 Nosler, .265 3,800 12.7 31.6 63.1 .220 SwiftQT 75 Horn. .44 3,250 8.7 20.9 39.7 .22 SwedeQT 75 Horn. .44 3,500 7.9 18.9 35.8 6.5X284 142 Sierra .595 3,000 7.1 16.8 31.5 Table showing horizontal wind deflections, calculated by the Sierra Infinity program, for environmental conditions see text..

These windage figures speak for themselves. The .220 Swift driving a 55-grain bullet at 3,800 ft/sec certainly is an excellent varmint cartridge, but as shooters have said over the years, "it doesn't buck the wind much". Though a 75-grain .22-caliber bullet may start out 300 to 550 ft/sec slower than the 55-grain bullet its wind drift is about 1/3 less. Drift of the larger 6.5mm bullet, though having a high BC, only beats the 75-grain .22 bullet by 10-15%. Even at 1,000 yards the .22 SwedeQT load gives only 8" more drift than the 6.5X284 (60" vs 52"), which is something to note. For prairie dogs at extreme ranges, 1,500 yards to 2 miles, of course one does need a serious, heavy-class 1,000-yard bench gun (or something similar), pushing bullets of very high BC at 3,000 to 3,500 ft/sec. But for shots in wind at 500 to 700 yards, where hits are due more to good equipment than to statistics or probability, I'll use a .22QT cartridge.

Now let me describe the two .22QT rifles. These are built (relatively inexpensively) on "historical" actions---an FN Mauser of 1898 design and a Winchester push-feed M70 one finalized in 1937 except for the push-feed bolt head and breeching of 1964-1968. Yet each shoots sub-1/2-moa groups. Their barrels, though, are not historical but of current first-rate custom manufacture. They're from Pac-Nor ( PS advertizer), are 5-groove, 1:9 twist, straight-tapered to 0.750" at the muzzle and hand-lapped to qualify as "match grade". Chris Dichter of Pac-Nor says that they were rifled with the same button (and I note here that Chris makes his own buttons and has more than 500 on the shelf!). These barrels, however, are not made of the usual #416 stainless steel, but are of the classic #4140 chrome-moly that has been used by many barrel makers for the last 50 years or so. After my article in PS a couple of years ago on a problem with some stainless steel barrels I have to put my money where my mouth is and use a few match-grade ones of chrome-moly steel. These two from Pac-Nor shoot as clean as good stainless barrels: the first cleaning patch wet with Marvel or Kroil penetrating oil goes down the barrel smoothly---no dragging on any sort of fouling. They were lathe-polished and I blued them with Oxpho (strange name!) from Brownells, so they look rather good.

The .220 SwiftQT's FN Mauser action is of early 1950's manufacture, so its wing safety is on the left side of the bolt sleeve and works well next to a scope. Precision gunsmith Ralph Burge, who also shoots 1,000-yard benchrest, fitted and chambered the barrel. Ralph (who formerly made custom rifles and advertised in PS but who is not taking new work now) was trained partly at the Trinidad gunsmith school and partly by Mssrs. Sinclair, Atkinson and other expert smiths. Ralph is able to do the classic work of truing and squaring the receiver ring, forward part of the bolt and rear of the barrel, and of fitting and chambering the barrel so that the chamber and throat are in line with the center line of the barrel. On looking into the throat and especially at the beveled land surfaces (or call it the origin of rifling) with a borescope I see that each bevel is the same size and starts from the same imaginary circle just forward of the chamber. If the reamer is the slightest bit cocked these surfaces will be a little further up the barrel on one side than the other, which probably happens not uncommonly with many smiths less expert than Ralph. A bullet forced into a cocked throat will have its long axis pushed a little bit out-of-line from the bore center line---giving in-bore yaw and a slight movement of the bullet as it exits the barrel that degrades accuracy (see the expert discussion of this in McCoy's book). Ralph cut the neck diameter of the chamber at 0.256", so I turn the cases to 0.015" with a K&M tool for 0.002" diametral clearance. I made up dummy rounds for Ralph with the bullet shank-boat-tail junction about 1/16" forward of the neck-shoulder junction of the case; these were used to set the throat length and avoid the dreaded doughnut problem. So this old action, even though having lots of clearance of the rear end of the bolt and the bolt raceway is so snugly and accurately set up at the front end that it shoots very well.

The FN's stock is of European beech with beavertail forend, of a pattern much like the old Winchester M70 Marksman stocks. The receiver ring, rearmost inch of the barrel, tang and part of the bridge are epoxy bedded. Two small shelves of epoxy were set in the stock under the bridge. These, I suspect, aid accuracy because the Mauser tang, as many have noted over the years, is relatively weak.The receiver rails between bridge and ring do not contact the stock. A Timney trigger replaces the military-type one, With a Redfield 8-32X scope the rifle weighs 12 1/2 pounds.

The only published load data I've found for the Swift with 75 and 80-grain bullets is in Sierra's manual (now into Edition V). It lists 5 powders giving 3,200 ft/sec with Sierra's 80-grain bullet from a 26" barrel. I've tried Norma's MRP, Alliant Re22, Accurate 3100 and MagPro, and VihtaVuori N165. All except MagPro start to give stiff bolt lift at about 3,225-3,275 ft/sec with 75-grain bullets and at about 3,125-3,175 ft/sec with the 80-grain Nosler bullet. Enough MagPro can be put into the cases (of Winchester manufacture) to give 3,400 ft/sec for the 75-grain bullets, but bolt lift is stiff and these are proof loads. So my working loads give 3,250 ft/sec to the 75-grain bullets and 3,200 ft/sec to the 80-grain Nosler (the only bullet of that weight I've tried so far). Load development has been with three-shot strings---I don't call them "groups", because I'd rather shoot out the barrel at prairie dogs and this not being a target rifle 5 or 10-shot groups are not that important. But, regardless, three shots mostly go into 3/16" to 1/4", so the gun shoots very well.

The .22 SwedeQT's Winchester M70 push-feed action was barreled to a 6mm case a few years ago by benchrest gunsmith Dan Dowling, who squared the action, bolt face, etc., so when the Pac-Nor barrel was installed by Greg Tannel (Gre-Tan Rifles, see PS ad) he did no further action work (although I probably should have had him reduce the tip diameter of the firing pin and bush the bolt face for it---a job he regularly does on other rifles). Greg used a custom Clymer reamer having straight flutes. (Note: Clymer now is able to furnish smooth-cutting spiral-fluted reamers.) My bore scope shows that the throat cut by Greg, who dedicates one of his lathes for chambering jobs only, is visually perfect (like the one cut by Ralph for the .220 SwiftQT).

Though the M70 synthetic stock contains an aluminum bedding block I rebedded the receiver ring, rearmost inch of the barrel and the tang. I also reworked the factory trigger to about a 2-pound pull (OK for prairie dogs). This rifle with an old Burris 12X silhouette scope on top weighs about 11 3/4 pounds, but for next season I'll put on a Nikon or Burris 6.5-20X or 6X24x scope with mil-dot reticle and use Burris Pos-Align inserts in their Signature rings on steel Weaver-type bases.

Working up loads for the .22 SwedeQT is easy---simply start with about 48 grains of slow powder like Norma MRP-2 or Accurate MagPro and go up to near-max ones using perhaps 49 to 51 grains. The 80-grain Nosler match bullet (again, the only 80-grainer tried so far), however, takes 1 grain less than 75-grain ones. I've shot the 75-grain JLK and 80-grain Nosler more than any of the other brands, but all shoot very well. MRP-2 under the Nosler bullet to date has given slightly the best accuracy (yes, I did shoot some 5-shot "groups" with this rifle), but finding a load slightly more accurate than another is not important in a prairie dog rifle---I already know that it's a sub-1/4-moa gun. The wind and distance will be much more important in blowing up PD's. A 6.5X55 full-length sizing die acts as a body die for this case, and I neck-size and seat bullets with a Redding die set for the .22-250 Ackley Improved (the outer edge of the .22 SwedeQT's 25 o shoulder just misses the inside surfaces of the two Redding dies. So I didn't have to order any custom dies for the Swede case.

Shooting this gun is fun , but forming cases is work . Lapua's 6.5X55 case is tough and its neck is relatively thick (0.0l55"-0.0165") so I first turn them down to about 0.0145", then anneal, neck down in a .243 Win.neck, further neck down in the .22-250 Ackley die, and then turn and anneal again.

Thus a rifle chambered for the factory .220 Swift case with a custom 1:9 twist barrel works very well as a windy-day varmint gun---far better than a standard 1:14-twist Swift. But for slightly better wind bucking and flatter trajectory one of the "50-grains-of-powder" .22 cases is almost as good as any rifle of larger caliber. The .220 SwiftQT, of course, will take factory ammo in a pinch, and that quick twist gives a 50 or 55-grain bullet so much rotation that a well-hit prairie dog goes down cartwheeling (clockwise, of course, from a right-hand-twist barrel)! Like many another prairie dog shooter, I do enjoy using a .223 Rem. or standard .22-250 or Swift for day-to-day 300 to 500-yard shooting. But for slightly longer ranges and in the wind one of the QT rifles goes onto the bags. (And we'll soon know what Winchester's .22 WSSM is all about.)

Note: Norma's excellent MRP and MRP-2 powders apparently are not available at some gun shops. Graf & Sons of Mexico, MO (800-531-2666) has them.