This grew from discussions for sniper rifles for the 21st Century rifle controversy page. The usual approach to making a better sniping rifle is to increase the weight of the round and/or increase its velocity. Large heavy bullets may make sense if your targets are likely to include BTRs, but what about other applications such as the weapon of a police marksman. I decided to try thinking on a different track. Rather than increase power, investigate how the power can be used more efficiently? Various sources have told me that 7mm bullets have very good flight characteristics. The following is a comparison of the 7.62NATO/.308 Win round, the .300 Win Magnum and the 7mm Rem Magnum
Terminal effects. All three rounds have proven effective against humans and larger animals for both head and torso shots.
Recoil
165gr .308
180gr .308
165gr .300 Win Mag
180gr .300 Win Mag
140gr 7mm Rem Mag
17.9ftlbs
18.6ftlbs
25.1ftlbs
26.7ftlbs
19.1ftlbs
Recoil levels of the 7mm Rem Mag are close to that of the .308 or a .30-06
Maximum Point Blank Range (MPBR)
Range at which bullet does not pass more than +3" or –3" from line of sight.
165gr .308
180gr .308
165gr .300 Win Mag
180gr .300 Win Mag
140gr 7mm Rem Mag
264yds
259yds
303yds
303yds
310yds
7mm Rem Mag shoots flatter than a .300 Win mag but has considerably less recoil.
Ballistic coefficient and muzzle velocities.
165gr .308
180gr .308
165gr .300 Win Mag
180gr .300 Win Mag
140gr 7mm Rem Mag
.410
.483
.410
.483
.485
2700 fps
2610 fps
3120fps
3070 fps
3150 fps
The higher the Ballistic coefficient the slower the tendency for the bullet to be slowed by the air. The Ballistic coefficients of the .30 180gr and 7mm 140gr are virtually identical, so all rounds will lose velocity at a similar rate. The 7mm starts off with more velocity, so flight time will be shorter. A shorter flight time reduces the effects of wind and target movement.
Out to at least 300yds the 7mm Rem Mag performs slightly better than the .300 Win Mag while producing only the recoil forces of a .308. I don't have any figures for performance beyond this range, but during the Boer war 7x57mm Mausers were effective at more than 800yds. The 7mm Rem Mag fires an identical round at a higher velocity.
Since I wrote the above section, I've discovered the ballistics calculator at www.realguns.com that is linked to below. The differences in velocity and ballistic coefficient of the 180gr .300 Win Mag and 140gr 7mm Rem Mag do not seem to be significant. Out to 1000yds flight time is the same for both rounds. At 1000yds the .300 has more energy, while the 7mm has dropped less. Both still have more than enough energy to be lethal.
There is no reason why Police forces should be restricted to Military or NATO standard ammo. In fact they are neglecting their primary job of public safety by using such rounds if more effective alternatives are available.
It could be argued that the 7mm Rem Mag has too much range for certain police operations. In such cases the round can be down loaded to produce velocities similar to the 7mm-08. Even such a reduced power round will still shoot better than a .308 :-
7mm-08 140gr at 2860 fps has a MPBR of 285yds 7mm-08 120gr at 3000fps has a MPBR 291yds.
For certain situations heavier, shorter ranged bullets may be needed:-
Sectional Densities
140gr 7mm
165gr .30
180gr .300 Win Mag
200gr .300 Win Mag
175gr 7mm Rem Mag
250gr .338
.248
.262
.271
.317
.310
.313
The 200gr round is the heaviest loading for the .300 commonly available. It will be noted that the 175gr 7mm rounds compares very favorably with both this round and the 250gr .338 Lapua Magnum.
I've used the 7mm Rem Mag. For purposes of illustration. There are other rounds with similar performance:- the 7mm Rem SAUM and 7mm WSM. The 7mm-08 and the .270 Win are both superior to the .308/7.62mm for shorter range shooting.
Results with the Ballistics calculator will be most accurate if the actual, rather than nominal calibres are used. The .223 Rem. actually uses a .224 bullet. The 7mm Rem Mag and 7mm-08 both use .284. The .308. 30-06 and .300 mag uses a .308. The .270 Win uses a .277 (which oddly is closer to 7mm than the "7mm" rounds!) .338 does appear to use .338
FEEDBACK John Nystrom, Police officer and Rifleman reports:-
"The USMC pre-Vietnam was using Remington 721 and Wincester mod. 70 rifles in .30-06 AND .270 WINCESTER for sniper work. .270 Win. is very close to 7mm Mag. velocity with less recoil. My feelings from having shot and owned them was that the .270 was much more comfortable to shoot than the recoil numbers indicated. The .270 also was slightly more accurate for me (I think it was the belted mag case). .280 Remington gives you .270 ballistics with 7mm bullets and no case belt. You may also want to look at 6.5mm bullets. The match rifle shooters I know are switching from .308 to .260 Remington and other 6.5mm cartridges for long range shooting. Very accurate with reduced recoil. Service rifle shooters (who shoot the same course of fire as match rifle shooters) have switched from .308 to m-16/ar-15 clones shooting very heavy bullets through barrels with fast twists. Also, a friend of mine who is a 7mm Mag fanatic says that he prefers to shoot ONLY 175 gr. bullets for everyting for prairie dogs to elk and bears because he has the bullet drops to ranges all memorized and never has to worry about changes in BC."
UPDATE According to this Game Sourcepage the US Secret Service has seen the merits of the 7mm Rem magnum as a sniping round.
Further Thoughts on Police Precision Rifles (PPRs).
.223 Rem. While I've tried to make the point that police should not restrict themselves to military calibres, there is one chambering that does have a place in a police marksman's gun rack. This is the .223 Rem, aka 5.56x45mm. The .223 has some shortcomings as a combat round, and will hopefully soon be replaced in this role by something like the 6.86mm ARC, 6.5mm SCC or 7mm Whisper. It does, however, have considerable merit as a short to medium range marksman's round. When they were first issued, standard M16A2s were found to shoot tighter groups than the army's sniper rifles. Longer barrels, heavier barrels and free-floating barrels can improve on this further. Buffer technologies produce an Accu-wedge for a few dollars. This improves the fit between the two AR-15 receiver halves and writer Chuck Taylor has claimed this increases accuracy by 35%. AR-15/M16A2 weapons are not the only suitable weapon in this chambering. I've heard it claimed that the unchromed barrels of the AR18 shoot even better than standard AR15s. There are also various bolt-action varmint rifles available in .223. .223 Marksman's rifles are most likely to be used at ranges of less than 400m, although they are capable of accurate fire to much greater ranges. The rifle should have rifling with a 1 in 9" twist to allow use of the full range of 5.56mm rounds. For this application, the heavier bullet weights such as the 77gr and 80gr seem the obvious choice. Chuck Taylor favours a .223 load using the 45gr Barnes XLC, a hollow point round with very good exterior and terminal ballistics. This round has a Ballistic coefficient of 0.203, an actual calibre of .224 and a muzzle velocity of 3480fps. Such a "fast and light" load may be more suitable for use in built up areas Police forces are not subject to the Hague convention, so can legitimately use JHP and JSP rounds. Because of the small calibre of the .223 this should be mandatory. The only justified use of potentially lethal force is to protect human life from an immediate threat. In such a situation such force must be applied as effectively as possible. Other chamberings of centre-fire Varmit rifle are also worth consideration. Weapons designed for this sort of hunting tend to be flat shooting and very accurate. As well as .223, .222, .22-250, .220 Swift and possibly .22 Hornet weapons may prove useful. Many of the loadings in these chamberings use hollow-points intended for small game which may not have sufficient penetration against a human cranium. Since all centre-fire cartridges of nominal .22-.224 calibre are in reality all .224 bullets such as the 45gr Barnes XLC can be used.
.270 Win. Along with the .223 this is likely to be the main workhorse of the marksman's section. The .270 Win fills a similar niche to the .308, but shoots flatter, faster, reaches further, hits harder and kicks less. The .270 would mainly be used for medium to long range shooting. An interesting trend recently is the .270 is being offered in several self-loading weapons, such as the AR-10B. Although an anathema for "traditional" snipers, in a hostage situation a rapid follow up shot may be required.
Extended range. In rural settings or terrain such as golf courses it may be desireable for a weapon with a shorter flight time or more down range energy than the .270 Win. A common choice is the .300 Winchester Magnum, although the 7mm Rem Magnum does offer several advantages. In actuallity the .270 equals the .300 and 7mm in speed out to beyond 1000yds, and still has more than enough energy to be effective
Heavy PPR Most police departments don't have a requirement for the capabilities of .50 BMG rifles, but there are applications for weapons with greater anti-material effects than the chamberings already suggested. For example, there may be a need to disable the engine of a truck or boat. The .338 Lapua Magnum, .338-378 Weatherby and .408 Cheyenne Tactical all may have police applications.
With a 125gr bullet the .300 Whisperâ gives AK47 type ballistics, but is considerably more accurate. 150gr has more down range energy, and is probably a better choice for general use. The heavier bullets are subsonic, which offers numerous tactical options as well as allowing discrete animal control. All bullet weights shoot to 1 MOA or less.
As well as being a good round for a marksman's weapon, the .300 Whisperâ is also available in a AR 15 based SMG. With a 150gr bullet the 10" barrel gives 1200fps. This translates as more than twice the muzzle energy of a 9x19mm SMG, and due to the better ballistics of the rifle bullet the .300 Whisperâ retains more energy down range. The .300 Whisperâ SMG is also quieter than a 9mm.
