Most hunters are familiar with the Cooper Firearms of Montana accuracy guarantee on its centerfire rifles: .5-inch, three-shot groups at 100 yards with “hand-loaded match grade ammo.” No doubt such a guarantee helped establish and maintain a reputation for better-than-average accuracy. Just as importantly for the manufacturer, it sells rifles. The test target supplied with the Cooper Model 52 Jackson Hunter .270 Winchester depicted a tiny three-shot group fired with a handload made up of an unspecified charge of IMR-4064 and Sierra 135-grain MatchKings.

I attempted to measure the test target group using a Brown & Sharpe dial caliper. Diligently measuring the group three times, I came up with a different figure in each instance. Admittedly, they were close. Groups measured to three decimal places are frequently listed in articles, so I must assume those measuring them take several readings, then average (subtracting bullet diameter) or employ a “group” measuring device that is used with a dial caliper. Having no such device and returning to the realization that the Cooper was in fact a hunting rifle, the dial caliper was carefully put in its case and replaced with a well-worn 6-inch wooden ruler. The test target group measured exactly .375 inch, outside to outside. Subtract .277 inch from that figure . . . indeed, a very small three-shot group.

The Model 52 Jackson Hunter is a bolt action with a three-round detachable magazine and a floated 24-inch, medium-weight stainless steel barrel. The synthetic stock is a Bell & Carlson with an aluminum bedding block. Fitted with a usable recoil pad, length of pull is 13.75 inches. The trigger is about perfect for a hunting rifle, breaking cleanly at a precise 3 pounds. Some might describe the Cooper 52 as a big or even “clunky” rifle. Advertised bare weight is 7 pounds, 12 ounces; mine scales in at 8 pounds, 12 ounces with a Leupold 2.5-8x 36mm VX-3, unloaded and minus a sling. The 2.5-8x36 is a rather light scope; one of the higher magnification variables that is so popular today would easily push total weight to over 9 pounds. Burdensome? Only the user can make that determination, but there is an advantage to a heavier rifle. Many hunters agree that such a rifle is more tolerant of user shortcomings, making it easier to shoot well, whether from a bench or in the field. Those who practice far less than they should are always ahead using a heavier rifle.

A fair amount of time was spent handloading and shooting the rifle from a benchrest. Firing close to 1,000 rounds, 15 bullets and several powders were used in developing loads shown in the table. Brass was Remington and primers were Federal 210 Match.

The 52 has proven to be quite accurate, noticeably more so than many production guns. Most of the load testing was performed during an unusually hot summer with temperatures approaching 100 degrees by noon, usually accompanied by a breeze. One three-shot group would heat the barrel considerably, resulting in far more time spent waiting for the barrel to cool than actually shooting.

Handloading for the Cooper was straightforward, even unremarkable for the most part. Maximum loads taken from current handloading manuals were, in some instances, a bit hot for the Cooper, but the same could apply to many other rifles. Bullet seating depth was experimented with, and virtually all bullets were seated deeper (though not by much) than had been necessary with other .270 Winchester rifles I have worked with. Experience with the others indicated that many .277- inch bullets could be seated out to full magazine length without the bullets being engraved by the lands when chambered.

Along the same lines, once a starting point was reached, bullet seating depth was not very critical with any of the bullets used, though most loads in the table have bullets seated several thousandths off the lands. I’ve found Barnes bullets normally require more experimentation in this area than most other bullets. Pleasantly, such was not the case this time. While the 130-grain TSX BT (boat-tail) was more accurate than the 140-grain TSX BT, changing the seating depths on either made no discernible difference in accuracy.

With the Cooper, I relied on velocity comparisons (my figures versus those from handloading manuals) as the best, though admittedly rough, indicator of higher-than-normal chamber pressure. Speaking of less-than-foolproof processes, an experienced handloader who is very familiar with a particular rifle can sometimes get a basic feel for safe pressure through “reading” primers. With the Cooper .270, fired Federal 210 Match primers in starting loads usually had the same flattened appearance as those from much heavier loads.

The same goes for bolt lift on fired cases. As with many rifles using custom or semicustom actions, they are often stiff, supposedly because parts tolerances are smaller than in mass-produced guns. In the Model 52, bolt lift on fired cases required virtually the same amount of effort, regardless of the powder charge. That’s not to say a danger point could not be reached where bolt lift would be difficult or impossible.

Most current loading manuals show .270 Winchester data fired in barrels ranging in length from 22 to 26 inches, with most at 24 inches. Having previously worked with a 26-inch barreled Ruger No. 1 and a Remington Model 700 with a 22-inch barrel, I was very aware of the differences in attainable muzzle velocities between the lengths. These differences appear to be more pronounced with the .270 than with many other cartridges. Sure, variables can enter in here, like “slow” barrels and “fast” ones, but generally, these are exceptions to the rule. The .270 can almost achieve its velocity potential in a 22-inch barrel. A 24-inch barrel makes it easy.

My own experience with handloading the .270 Winchester has covered years and a variety of bullets, but only three powders that I recall: Hodgdon’s H-4831, Accurate 3100 and IMR-4350. Accurate loads were developed with all the powders, but far more H-4831, both standard and short-cut (SC) versions have been used, simply because it worked so well with virtually any bullet. I spoke with Ty Herring at Barnes Bullets when I began this project. He suggested anyone interested in handloading the .270 Winchester is probably best served by using three powders: Alliant Reloder 19, Hodgdon H-4350 and H-4831. No doubt that’s good advice. I added to that list here, but only slightly, though those three powders were used in the majority of the loads. If most of us were restricted to the three powders, we would find nothing lacking in terms of accuracy and velocity.

The two Hodgdon propellants are Extreme powders that are pretty much unaffected by temperature changes. Reloder 19 is considered to be more temperature sensitive, as is IMR-7828 (regular and the SSC “Super Short Cut” version). So is IMR-4350, but this powder was used only in a couple of loads to see how it compared with H-4350 in terms of charge weight and muzzle velocity. Powder temperature sensitivity has become a popular topic lately. Depending on the source, some aspects have been exaggerated while others may be inconsequential. Even though a powder may provide velocity and chamber pressure gains as temperatures rise, then lose the same as temperatures fall, the difference may not be enough to matter in many hunting situations. This is particularly true if temperatures are not extreme and shooting distances are not long.

Fifteen bullets between 130 and 150 grains were selected. Some may use lighter and heavier bullets in a .270, but the majority of .270 users stick with those in the 130- to 150-grain range. Very light bullets are generally intended for varmint shooting. On the other end, should a bullet heavier than 150 grains be required, many hunters simply go to a more suitable cartridge for the purpose. However, the Nosler .277-inch, 160-grain Partition does have a loyal following, though probably small./

The findings are in the table, but there are several points worthy of mention relative to working up loads and compiling figures. Fourteen of 15 bullets had average group sizes of one inch or less with at least one load. The Speer 130-grain spitzer missed the one-inch mark, but not by much, with a three-group average of 1.17 inches. One of those groups was .375 inch. At the top of the list, the Barnes 130-grain TSX BT averaged .42 inch using Reloder 19. I was surprised to find that the old favorite, H-4831 (the SC version here) was the least accurate powder overall, according to the data. H-4831 trailed behind H-4350 and Reloder 19. Taken in perspective, however, the differences were often small to the point that I would not abandon a supply of H-4831 just to use one of the other powders. A few loads using IMR-4350 were also included for comparison with H-4350. IMR- 7828 SSC made a respectable showing with several loads. This is a very slow powder, slower than H-4831, but still works very well in the .270 Winchester with bullet weights beginning at 130 grains. Hodgdon Powder Company took over the IMR line of powders several years back. Having heard nothing about this powder’s temperature sensitivity, I asked Chris Hodgdon. He said that with the exception of IMR-8208 XBR, the IMR powders are getting better all the time in the area of temperature sensitivity, but that the Hodgdon Extreme line remains at the top of the heap. Nevertheless, IMR-7828 SSC or the regular version is worth a try. Three groups were fired using 56 grains (maximum) and the Hornady 150-grain SST. Average group size was .67 inch, but two of the three groups were .25 inch each. Muzzle velocity was just under 2,900 fps.

I went through no break-in procedure with the Cooper barrel. Four or five rounds were used to get the scope on paper, and I started shooting groups. I cleaned after every 10 to 15 groups (30 to 45 rounds) using Hoppe’s No. 9 and a bronze brush, followed with Wipe Out Accelerator and Patch Out Bore Cleaner. Copper buildup was not a problem with the bore, about what one would expect from any high-quality custom barrel. After several hundred rounds, the barrel was still shooting fine but a bore scope examination revealed a carbon layer. It was treated with a dose of J-B paste, but not quite down to bare metal. Afterward, the barrel did not seem to shoot just right until a few rounds were fired. Apparently, the carbon buildup was insignificant and hurt nothing in terms of accuracy. So much for over-cleaning.