By Gary Sciuchetti

From the American Rifleman, September 1989, page 42

Here is the complete text of the article I referred to.  There are numerous diagrams to make his points clear, which I didn't scan.  I'll add that of the 48 loads he tested, the BEST (least deflected) was the .223 Remington with FMJ bullets; the WORST (most deflected) were .45-70, 12-gauge sluge, .264 Win Mag with a soft-point bullet, and .44 Magnum.  The .30-06 was #5 on the list.  Virtually all the calibers normally touted in gun rags as "brush busters" were WAY down on the list, well below #30 or so.  Of the top 10, 7 were FMJ's, which indicates that deformation is one of the most important factors.
 
Incidentally, this article also invalidates one of the myths that is a particular pet peeve of mine: the idea of the "tumbling bullet" in the .223.  The .223 load that worked best of all in these tests was the old M155 Ball round I used in Vietnam.  If you ask 100 Vietnam veterans what they know about this round, 99 of them will tell you "...it was so deadly because it tumbled and caused worse wounds," which is utter and complete bullshit.  The M155 round was as stable in flight and on target as anything else the military has ever used, and based on this test, more than most catrdiges.  Oh...#3 on the list was .30 Carbine, also with an FMJ.  Two of the other top 10 were Silvertips.

Every shooter has read about and discussed brush-busting cartridges.  Volumes have been written about brush busters, and some better ammunition manufacturers have suggested certain cartridge and bullet styles penetrate brush.  Authorities have echoed the common belief that large calibers with heavy, round-nose bullets punch through brush with little or no deflection.  There is also a common belief that smaller calibers with high-speed pointed bullets either blow up or are deflected at absurd angles.

Tests which appear limited in scope have been conducted that conclude one type of cartridge or bullet penetrates brush better than another.  Usually these tests compare only two or three cartridges.  Perhaps the experimenters lacked the time or opportunity to conduct a more in-depth study.

Ultimately, I decided to conduct tests to determine how much deflection a small branch would have on a bullet's flight.  To enable the reader to understand the tests, they are described in detail.  The intent here is not to attack or discredit any cartridge or bullet by presenting it as a poor performer in brush.  The overall comparison of cartridges and bullets is for the reader's study and conclusions.  My observations and conclusions are noted in case you wish to use them as a guide.

A deflecting medium needed to be established that simulated a given size tree branch.  This medium had to give consistent resistance to all cartridges tested to provide for meaningful comparison.  Simply shooting into a cluster of branches and relying on chance that the same number of limbs would be intersected by the bullet is not reproducible or practical.

A definite aiming point had to be established so the exact path of the bullet could be followed and measured.  Therefore, the target could not be hidden by the simulated brush.  Sheets of paper, sometimes called witness sheets, had to be as large as possible and located at various distances behind the simulated brush so downrange deflection could be measured.  Witness sheets had to offer minimal resistance so they would not add measurably to bullet deflection.  Each shot was measured and recorded.

The test was conducted with factory ammunition to eliminate variables and opinions associated with handloading.  Included in the test were most popular American cartridges from .22 to .45 cal., plus 12-ga. shotgun slugs.  These cartridges included many popular bullet styles and weights.

The major challenge in setting up the test was to find a material simulating brush in resistance and having consistent deflecting properties.  Previous tests have never accomplished this essential requirement.  Some researchers tied bundles of twigs together and relied on chance that the same number of twigs would be encountered by the bullet with each shot.  Other tests have been conducted using carefully spaced dowels. The dowels may appear to simulate brush, but insuring the angle of intersection with the curved surface of the dowel would necessitate precise and consistent bullet placement.  This degree of accuracy would be difficult, if not impossible, to attain consistently.

Since exact repeated bullet placement did not appear possible, it was decided to try a sheet of plywood set at an angle.  Plywood is multidirectional in grain, has a density similar to brush, and it could be cut from a single sheet.  Plywood sheeting 1/2"-thick set at 45° provides about 0.7" of theoretical resistance.  By setting the plywood 45° to the path of the bullet, the effect of glancing or pulling on the bullet could be simulated on a repeated basis.  The next step was to confirm the plywood theory.

Half-inch plywood set at a 45° angle has the same "ballistic limit" as a 1" branch.  (The ballistic limit is the amount of resistance that an object provides to a projectile which will absorb all or nearly all of its energy.  Ideally a bullet will exit the medium and fall out the back side).  With a little experimenting, it was determined that the ballistic limit of the ply-wood equaled the CCI .22 Long Mini Cap shot from a 6" barrel revolver.

Sometimes the Mini Cap would go completely through, sometimes it would stop inside, and sometimes the Mini Cap would stop with the bullet protruding through the back side.  The equivalent resistance offered by brush was established by shooting a branch in different places until the thickness of the branch would barely stop the bullet.  This was done with a green willow branch, a small fir tree and the low dead limbs of a pine tree.  Green limbs from 1" to 1-1/8" diameter and hard dead limbs of 7/8" to 1" diameter equaled the ballistic limit of 1/2" plywood at 45°.  The purpose of setting the plywood at 45° was to find out what effect, if any, the angle of incidence and departure would have upon the bullet when the simulated brush was intersected at other than a right angle.

To verify the similarity of deflection of 1/2" plywood to be the same as a 1" diameter green willow branch when shot with a high-power rifle, the author substituted a 1" green willow branch for the 1/2" plywood and re-shot test No. 2A (the .243Win, with the l00-gr. soft-point bullet).  The retest was labeled test No. WB (see large table).

When the branch verification test was conducted, the two shots hit the branch off-center and gave interesting results.  The bullets hit the branch about 1/4" from the edge.  This produced a V-like notch across the branch.  One side of the bullet encountered virtually no resistance, while the other side had approximately 7/8" resistance.  Contrary to what one would expect, these bullets were deflected the least.  Each shot missed the baseline shot (fired through witness paper) by 1/2" at 50 yds.  (40 yds. behind the branch).  This indicates hitting a branch off-center does not cause significant deflection.  Because these two shots hit off-center, they were not counted and two more shots were added to produce a five-shot group.  The five shots that hit the center of the 1" branch gave the most deflection-averaging l0-1/8" at 50 yds.

Compare test 2A and WB in the accompanying table.  The outcome of this test showed that a direct hit on a 1" branch gave identical resistance to a bullet as 1/2" plywood set at 45°.  To recapitulate, plywood offered the same resistance as a l"-diameter branch, and it was a more uniform testing medium than attempting to punch a l"-diameter branch consistently.  The exercise with the .243 also indicates bullet deflection is more a function of bullet deformation than the angle of incidence or departure of the deflecting medium.

Using a horizontal line through the baseline shots on the target, it was found 53% of the deflected bullets hit above this line.  This would indicate the 45° angle to the plywood does not have a significant glancing or breakthrough effect on the bullet, (i.e. fewer than 50% of the bullets, after hitting the downward 45° sloped plywood struck below the aiming point at 50 yds.).  This testing demonstrated to my satisfaction that angled 1/2" plywood provided the essential deflecting properties of brush, confirming its superiority to previously used test media.

The actual test procedure consisted of setting up five targets aligned with each other and spaced 10 yds. apart (see test set-up drawing).  The targets were single sheets of 31-1/2"x42" paper attached to a frame made of 2"x2" wood.  To minimize the resistance to the bullet by the targets, the paper had no backing.  To find out what effect five sheets of paper had on the bullet, five shots were fired from a .30-'06 through the targets with no ply-wood in place.  The group measured 7/8" on the 50-yd. target.  One could conclude the total inaccuracies of the shooter, rifle, ammunition and paper interference is less than 1" at 50 yds.

The first target, at 10 yds. from the muzzle, had an aiming point which when shot placed the bullet in approximately the middle of each sheet of the five witness sheets if undeflected.  All shots were fired from a V-rest on a shooting bench.  The first shot, termed the baseline shot, was fired through all sheets.  The baseline shot established the path of the bullet if no interference, except the paper, was encountered.  The baseline shot was marked on each target by circling and crossing the bullet hole with a black felt marker.  After marking the baseline shot, a piece of 1/2" plywood was placed at 45° to horizontal approximately 6" behind the first target.

Using the original aiming point, the second shot went through the hole of the baseline shot (within 1/8") but intersected the plywood.  The plywood was moved between each shot so the next bullet did not travel through an existing bullet hole.  Five shots were fired through the ply-wood and each shot was color-coded as it passed through witness sheets.  The witness sheets downrange of the plywood were checked for deflection by measuring from the center of the baseline hole to the center of each additional bullet hole.  The maximum deflection was noted.  The mean or average deflection was determined by totaling the measurements of all shots and dividing by five.  By averaging five shots to find the mean, the dimensions normalize any variations in the plywood (knots, voids, etc.) and give a good comparison between cartridges.  When measuring the amount of deflection caused by the plywood, all dimensions were rounded to the nearest 1/8".

Economics restricted the cartridges and calibers to those presented in this article.  No endorsement or criticism of brand name or caliber is intended.  Test cartridges were numbered from the smallest to the largest caliber.  As additional cartridges were added to the tests, they were given numbers with letters that kept them in the same caliber sequence.

Forty-eight different factory-loaded cartridges were tested in the common calibers from .223 Rem. to .458 Win. Mag. for a total of 288 shots evaluated.  This does not count accuracy testing, retests, ballistic limit experiments and actual branch deflection tests.  The table shows the mean and maximum deflection for each five-shot group.  Study the table and draw your own conclusions.

My observations and conclusions are summarized here:

1. The lighter weight bullets deflected less than heavy bullets of similar con-struction for nearly every cartridge tested.  By comparing test Nos. 22, 23 and 24 with the .300 Win. Mag., you can see how deflection increased with the increase in bullet weight.  This same pattern is evident when comparing 2 and 2A; 4 and 5; 6 and 6A; 7 and 8A; 10 and 11; 13, 18 and 21; 26 and 26A, 30 and 30A.  Possible reasons are:

a.    Heavy bullets are longer and slower; therefore they require more twist to stabilize.  If stability is marginal to begin with, a slight impact will cause the bullet to tumble.
b.    Heavy bullets usually have rounder noses with more lead exposed.  The jackets are usually thinner at the front so they will expand at lower velocities, thus they deform more easily than pointed bullets.  Deformed bullets de-flect more than undeformed bullets.

3. Pointed bullets appear to deflect less than round-nose bullets.  Compare the deflection of two bullets of the same internal construction, the same weight and the same velocity.  Refer to the .30-'06 180-gr. Rem, pointed Core-Lokt (test No. 17) and the round-nose Core-Lokt (test No. 18).  The best four out of five round-nose bullets were deflected more than the average of the five pointed bullets.  The least deflected soft-point bullet was the 7 mm Rem. Mag. 150-gr. bullet.

Periodically, someone will discuss the correlations between the spinning of a top and the gyroscopic stability of a bullet.  When they make the comparison to the deflection of a pointed bullet, the implications are that the point will get deflected away from its mass or base which in turn will cause it to tumble.  If one were to carry this reasoning a little further, one would have to make the reasonable assumption that a branch would have a greater torque on the round nose because resistance to the outer edges of the round-nose bullet is further from the centerline or axis of the bullet.  Reasoning could be used to summarize the results but not to predict the results.

The only way to find out about deflection is to conduct some conclusive tests.  Observations 2 and 3 are examples of contradictions to popular or common belief.  The popular belief may have evolved from a ballistics expert's opinion that seemed logical when presented in a positive way and may have been convincing enough to be accepted as factual.  Acceptance without question or testing probably gave these misconceptions the seal of approval for other authorities to use and hence became popular belief.

4. Bullet deflection seems to be primarily function of bullet construction and stability.  Bullets advertised as having heavy jackets for slow expansion and deep penetration tend to minimize deformation and therefore deflection.  Non-expanding or full-metal-jacket bullets are deflected the least.  Bullets designed for rapid expansion usually fragmented and have excessive deflection.  The .375 H&H and the .458 Win. Mag. did well on deflection because the bullets have heavy jackets designed for deep penetration on tough animals.  Small branches have a minimal effect on deforming the bullet.

These tests used simulated l"-diameter branches. One might reason less deflection would be expected if the branches were smaller.  If the branches were larger, more deflection could be expected.  Perhaps future tests can verify this, as well as the effects of multiple branches.  In any case, the closer the animal is to the twig or branch, the less likely deflection will cause a miss.  In all probability, if the hunter aims at the shoulders of a broadside deer and hits a small branch 10 to 20 yds. short of the deer, he probably wouldn't hit where he aimed but wouldn't likely miss the deer.  When a deer is 50 yds. or more away, a limb sometimes can be too close to the muzzle for the shooter to see, since the scope is usually 1-1/2" above the bore.  In that case, the angle of deflection can easily cause a miss or a poor hit.  Do not conclude that deflecting a bullet necessarily makes it less lethal.  A tumbling bullet may cause a more lethal wound than a stable bullet.  If you discover a splintered branch or twig between where you shot and where the deer was, don't give up the search for the animal too soon.

Guns shooting large caliber, heavy, slow bullets may be desirable for their knockdown effect, minimal blood clotting (hydrostatic tissue destruction) or for an easy blood trail to follow.  They are referred to as short-range guns because their trajectory and time in flight prevent good placement at long ranges.  Short ranges usually mean the hunter must get close to the animal because brush provides concealment until a hunter is close.  Short-range guns usually get referred to as brush guns.

This is where terminology and reasonable assumption unite to make a false assumption.  With the term "brush gun" the reasonable assumption is that it will not be deflected by brush.  The foregoing tests dispel this assumption.  If at all possible the hunter should avoid putting the bullet through brush or limbs.  Limbs will alter the course of the bullet to some degree, and the results equate to poorly placed shots.  Limbs will reduce a bullet's velocity and therefore its remaining energy when striking the game.  If your hunting conditions are such that you find it necessary to shoot through brush, the test results suggest careful bullet selection can give you more acceptable performance.

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