Compared: 6.5 Grendel, 6.8 SPC, .300 Blackout and .350 Legend
By Gary Zinn
Here at Guns and Shooting Online we have made something of a cottage industry of evaluating the performance of the recently introduced .350 Legend cartridge, compared with other relevant cartridges. We started with Chuck Hawks giving an overview of the cartridge itself in The Winchester .350 Legend. Then I (with helpful editorial support from Chuck), compared the .30-30 Winchester and the .350 Legend and the .35 Remington and the .350 Legend. The purpose of these comparisons was to make a thorough on-paper evaluation of how the .350 Legend stacks up in performance against two cartridges long proven to be effective and efficient at taking deer and similar game animals.
Next, we compared the .350 Legend .450 Bushmaster and .50 Beowulf. These three are straight wall case designs, sized to function in AR-15 rifle platforms. In the article noted above, Chuck Hawks explained the background and importance of the characteristics of these cartridges, as follows:
"It is my understanding that Michigan, Pennsylvania, Ohio and Indiana have mandated that rifles shooting cartridges of at least .35 caliber with straight wall cases between 1.16 and 1.8 inches in length are now legal for use in what I believe Michigan calls the 'limited firearms deer zone.' (Formerly 'shotguns only,' I believe, for deer hunting.)"
The direct comparison of these three cartridges revealed that they are all capable short to moderate range hunting tools in areas with cartridge size regulations such as these. They can also be useful for hunters who wish to use AR-15 rifles to hunt Class 2 game elsewhere.
This leaves the question of how the .350 Legend cartridge compares with bottle neck AR-15 cartridges that have proven useful for hunting Class 2 animals. This is the subject of this article, to compare the .350 Legend with the 6.5 Grendel, 6.8 Remington SPC and the .300 Blackout.
My choice of the Grendel, SPC, and Blackout for this evaluation is based on the results of an earlier article, Are AR-15 Type Cartridges Good for Hunting Deer?. I found these three cartridges to be the best AR-15 hunting cartridges at the time the article was written. The 7.62x39mm Soviet cartridge was also evaluated, but did not make the cut.
The characteristics compared include velocity and energy, maximum point blank range and far zero, trajectory, sectional density, killing power and recoil. At the end I will summarize results, muse about rifle platforms and make some concluding remarks. Here are the loads I will evaluate and compare.
.350 Legend loads
Winchester Deer Season 150 grain Extreme Point (EP) - BC .223
6.5 Grendel load
Hornady Custom 123 grain SST - BC .510
6.8 Remington SPC load
Hornady Custom 120 grain SST - BC .400
.300 Blackout load
Winchester Deer Season 150 grain Extreme Point (EP) - BC .392
Velocity and Energy
Velocity flattens trajectory and makes hitting easier as the range increases. It is also the most important factor when computing kinetic energy. Energy is a measure of the "work" a bullet can do, which in this case means powering bullet penetration and expansion. Energy is an important component of killing power, as will be discussed below.
Winchester quotes muzzle velocity (MV) values for its .350 Legend loads from both 16 inch and 20 inch rifle barrels. The 16 inch barrel data are used here, for all cartridges, because 16 inches is the most prevalent barrel length for AR-15 rifles.
Here are the velocity in feet-per-second (fps) and energy in foot-pounds (ft. lbs.) figures for our comparison loads at the muzzle, 100, 200 and 250 yards. The loads are listed in descending order of their MV.
6.8 SPC, Hornady 120 grain SST
6.5 Grendel, Hornady123 grain SST
350 Legend, Winchester 150 grain EP
.350 Legend, Winchester 160 grain PHP
.350 Legend, Winchester 180 grain PP
.300 BLK, Winchester 150 grain EP
Already there are indications that the 6.8 SPC and 6.5 Grendel are decent hunting loads, the .300 BLK perhaps not so much. We need more information before drawing firm conclusions about the .350 Legend loads.
+/- 3 inch Maximum Point Blank Range
I am a firm believer in sighting-in hunting rifles and loads for maximum point blank range (MPBR). I feel that a +/- 3-inch MPBR is appropriate for rifles used to hunt Class 2 game, including the cartridges being evaluated here. My argument is that a prudent and responsible hunter should never attempt a shot at a game animal beyond the MPBR of the cartridge/load being used (and closer is always better).
Here are the MPBR yardages. Results are in descending order of MPBR.
Winchester touts the .350 Legend as "designed for deer hunting out to 250 yards." The MPBR numbers say that this is a substantial over-reach, for all the Legend loads, which have MPBRs between 185 and 204 yards. Among the cartridges compared, only the 6.5 Grendel and 6.8 SPC loads approach being 250 yard cartridges.
Trajectory matters, because the flatter a bullet flies the easier it is to hit a target down range. Bullet placement is the most important factor in achieving quick, humane kills, so anything that makes hitting easier is desirable.
Here are the 100, 200 and 250 yard trajectory figures in inches, for each load, sighted-in for a +/- 3 inch MPBR, computed for a scope mounted 1.5 inches over the bore. Trajectories are rounded to one decimal place; yardage is noted in parentheses. Results are in descending order of MPBR yardage.
These data further document what the MPBR data indicate: the 6.5 Grendel and 6.8 SPC are about 240 yard cartridges, while two of the three Legend loads, along with the .300 BLK, fail to reach a useful range of 200 yards.
Note that all five loads, sighted-in for +/- 3 inch MPBR, shoot right at three inches high at 100 yards, which is how these cartridges should be zeroed. This is typical of medium velocity cartridges in general.
Sectional density (SD) is the ratio of a bullet's weight in pounds to the square of its diameter in inches. SD affects penetration, as all other factors being equal (bullet construction, for example) the bullet with the highest sectional density will penetrate deepest. Obviously, to kill cleanly, any hunting bullet must penetrate into the animal's vitals, so hunting bullet SD is important. For Class 2 game, a SD of .200 has long been considered about the minimum acceptable for medium range rifle cartridges. Here are the SD numbers for our comparison bullets, in descending order.
A longer, smaller diameter projectile penetrates better than a shorter, fatter projectile of the same weight and construction, which only makes sense. The abiding problem with medium and large bore bullets is that they must be quite heavy to have high sectional densities. This is why the .264", .277" and .308" bullets have SDs noticeably higher than the relatively light for caliber .357" bullets.
The 180 grain .350 Legend load just makes the minimum SD .200 rule of thumb, while the lower SDs of the 160 and 150 grain .357" bullets does not bode well for them penetrating deeply on heavy bodied animals. This may not be a great concern on deer and similar sized thin skinned game that do not require a lot of penetration if only broadside lung shots are taken, because these large diameter bullets are going to deliver a lot of shock energy to the target, even if they do not always penetrate well. The killing power analysis, below, sheds more light on this.
Killing power is the most difficult factor to estimate, as there is no definitive scientific formula to apply. Various systems have been created to estimate the killing power of rifle cartridges, with varying results in terms of accuracy. Unfortunately, many such systems have no correlation with reality at all.
One of the best, in terms of positive correlation with reality, has proven to be the G&S Online Rifle Cartridge Killing Power Formula. Not only is it generally consistent with results in the field, it can be used to compare any load at any range and includes the factors of energy at impact (which includes velocity), SD and cross-sectional area in an easy to use formula to arrive at a Killing Power Score (KPS) for a given load at a given distance, via the formula:
KPS at "y" yards (you pick the yardage) = (impact energy at y yards) x (sectional density) x (cross-section area), or simply: KPS @ y = E @ y x SD x A
Cross-section areas of relevant bullet diameters are .0547 sq. in. (.264"), .0603 sq. in. (.277"), .0745 sq. in. (.308"), .1001 sq. in. (.357").
Note that this is a comparative system. We estimate that a rifle cartridge should generate a KPS of at least 12.5 at the range the bullet impacts to be a viable hunting cartridge for common Class 2 game, up to roughly 150 - 175 pounds (e.g., deer and pronghorn), while a KPS of 15.0 gives a margin of killing power for larger Class 2 game (up to 300 pounds).
I calculated the killing power of these loads at 100 yards, as most whitetail deer, blacktail deer and feral hogs are killed at 100 yards, or less. KPS values at the five yard increment closest to each load MPBR are included, to document the power of the loads near the longest range at which a responsible hunter should use them. Loads are listed in descending order of 100 yard KPS values.
If I had to choose one of these loads as an all purpose tool for hunting common Class 2 game, it would be the 6.5 Grendel, which combines adequate power, the longest range in the group and good bullet sectional density. If I wanted the most powerful cartridge of the lot, I would choose the 180 grain .350 Legend load, although it has the shortest MPBR. I believe this load will prove to be the most effective of the initial Legend hunting loads, mainly because it has the highest bullet sectional density.
The remaining four loads have the common limitation of not carrying general Class 2 game power (KPS 15 or greater) all the way to their MPBR distances, though all are powerful enough (KPS greater than 12.5) for medium size, thin skinned game, such as deer. The 6.8 SPC is the best of these loads, with performance so close to that of the 6.5 Grendel that if a hunter has either one, then he/she does not need the other. The main difference is that the Grendel carries more killing power to MPBR distance than does the SPC.
The loads that impress me least are the 150 and 160 grain .350 Legend loads, mainly because of the low sectional densities of the light for caliber bullets. In addition, the .300 BLK load has the limitations of being the least powerful load overall and having the next to shortest MPBR.
Our KPS parameters and results assume vital area hits, of course. A game animal hit somewhere other than in the vitals is not likely to go down cleanly, no matter the size, weight and impact energy of the bullet. This is why I preach the "never take a shot beyond MPBR, and closer is always better" doctrine. Shorter range shots improve the likelihood of placing a bullet in the right place.
Evaluating recoil of the .350 Legend is shaky right now, because there is no body of reloading data that can be consulted to get load powder charges, a necessary variable in recoil calculations. Winchester has published some vague promotional material with numbers that suggest that the .350 Legend generates about 12 percent lower recoil than a .30-30. The loads being compared are not clearly specified, which is why I say the information is vague.
I came up with a tentative recoil estimate that may or may not be accurate for the .350 Legend, 180 grain load, but it is the best I can do right now without verified powder charge data for the new cartridge. My guesstimate is that this load will generate about 9.0 ft. lbs. of recoil in an eight pound rifle. I would expect recoil of the 150 and 160 grain loads to be slightly less, because of the lighter weight bullets.
By comparison, my best estimates of recoil in the other calibers and loads are 7.9 ft. lbs. for the 6.5 Grendel, 7.5 ft. lbs. for the 6.8 SPC and 7.0 ft. lbs. for the .300 BLK (all in 8 pound rifles). The bottom line is all of these hunting cartridges and loads are easy on the shoulder, so that recoil is not a significant deciding factor among them.
Additional Thoughts and Conclusions
All in all, the .350 Legend holds its own against the comparison cartridges. Therefore, it has potential as an effective hunting cartridge, especially when fed 180 grain bullets that have adequate sectional density for deer and hog hunting. The Legend looks like a prayer answered for those who hunt in areas where rifles are restricted to short, straight-walled cartridges.
This leads to the issue of rifle platforms for the cartridge. Winchester has announced that the Winchester XPR bolt action rifle will be chambered in .350 Legend. CMMG has announced an AR15 carbine (with a 16 inch barrel) in the cartridge, plus 5 and 10 round magazines. Winchester notes, "several other firearm manufacturers are gearing up" to produce rifles chambered in .350 Legend.
Producing bolt action rifles in .350 Legend should be a snap. Any short-action platform that handles the .223 Remington can be easily reworked to handle the .350 Legend cartridge. Ditto for AR15 platforms, whether complete rifles or uppers.
For old school deer hunters (like me) the lever action is perhaps the best all-around platform for a hunting cartridge. I say this even though I have carried compact, short-action bolt rifles on the majority of my deer hunts. Lever action rifles, such as the Winchester Model 94, Marlin Model 336 and Henry Lever Action .30-30, carry and mount well and cycle fast when more than a single shot is needed.
A well designed bolt rifle also carries and mounts satisfactorily, but cycles slower than a lever gun. Meanwhile, my limited experience with AR15s in the field is that they are unwieldy to carry and awkward to mount, but that may be just me.
Unfortunately, the traditional lever rifle designs, with rear-locking bolts, cannot handle the .350 Legend cartridge, for the simple but critical reason that its MAP is 55,000 psi, well above what rear-locking lever designs can handle. This high-intensity MAP is no problem with bolt action and AR designs, but a lever rifle chambered in .350 Legend must have a front-locking bolt, such as the Browning BLR and Henry Long Ranger designs.
The .350 Legend may prosper as a medium bore deer hunting cartridge, not only in restricted cartridge areas, but in general. AR15 fanciers, long saddled with marginal deer cartridges, are likely to jump all over the cartridge.
Copyright 2019 by Gary Zinn and/or chuckhawks.com. All rights reserved.