Miscellaneous Questions #12

This section contains brief discussions of various ballistics and shooting related topics as requested by correspondents. If you have a question you have been trying to find an answer to (keep 'em ballistics and shooting related--see your minister for the mysteries of life) email me by clicking here and I'll do my best to find the answer for you and if it is of general interest, publish it here. If you can contribute additional input to one of the answers I'd would appreciate hearing from you too.

Check back frequently as new topics are always being added.

On this page:

How does tracer ammunition work?
What is "magnum" ammunition?
What is parallax error?
How do I adjust the eye piece focus of my scope?
Can you recommend any inexpensive target stands for practical shooting practice or matches?
Is there an inexpensive way to make reactive targets?
What is the composition of the various alloys used for casting bullets?

Q. How does tracer ammunition work?

A.   Tracer ammunition uses bullets made with a recess in their base which contains a compound that will create a bright light when ignited by the powder gases when the cartridge is fired.  Tracer ammunition is primarily used in automatic weapons to allow the firer to visually walk his fire into the target and is usually used in a 1 tracer to 4 or 5 ball rounds mixture.

There are three  basic types of tracer ammunition, bright trace, subdued bright trace, and dim trace .  The standard "bright" tracer starts burning at the muzzle, while the subdued bright tracer doesn't burn at full brightness for a hundred or more yards (to help avoid giving away the firer's position), and the dim tracer gives a very dim visible trace that is hard to see with the unaided eye but which is visible with night vision equipment.

In US /NATO practice tracer ammunition is identified by a red (traces from the muzzle), orange tip (delayed trace),  and violet tip (dim tracer visible with NVG equipment) .  

Warning.  While tracer ammunition is not designed specifically to have an incendiary effect, it is capable of starting fires and should only be used under controlled conditions.

Q. What is "magnum" ammunition?

A. Originally the term "magnum" was used by champagne makers to describe a very large bottle of their product.  The term was picked up by some gun makers to denote a cartridge with a large capacity case and greater than "normal" power levels and that practice carried on to today.  The term has become imbued with an almost magical status for some folks-- giving visions of earth shattering power.  In fact there are many non "magnum" cartridges of greater power than some "magnums."

As an example of magnumizing we can look at the .38 Special  / .357 magnum and the .44 Special  / .44 magnum. The cases of both the 357 and .38 Spl, and .44 Spl and .44 Mag are identical between the standard and magnum versions except for the length of the case. (While "magnum performance could be obtained from the standard length case, the case was lengthened to prevent its use in firearms not approved for the extra pressure.)

Q. What is parallax error?

A. Parallax error is an optical aberration of telescopic sights in which the point of impact can vary with eye placement.  It is caused by the fact that the target does not fall on the same optical plane as the reticle. It is of primary concern for very precise shooting, such as shooting for group.  Most fixed focus hunting scopes are focused at about 150 yards so if your target is at a different range you can get parallax error if your eye is not centered in the cone of vision consistently.  

Maximum parallax error occurs when your eye is at the very edge of the exit pupil and for a 4x hunting scope focused for 150 yards the maximum error would be about 1" at at 500 yards if your eye was fully off center--giving the possibility of a 2 inch combined error if your eye placement varied from side to side of the field of vision.  At short distances the 4x scope above would have about 2/10" error (4/10" total combined error) at  100 yards.  Thus parallax error is primarily a worry for shooting groups but not in the field. 

Some scopes have an adjustable objective lens that will allow you to adjust the plane of focus to your target's approximate distance thus minimizing parallax error.  If your scope does not have parallax adjustment it is important to consistently place your eye in relation to the scope. 

Typically, non adjustable scopes are set for the following parallax free ranges.  Consult your owner's manual to verify this data for your scope.

Rifle scopes - 150 yards
Handgun scopes - 100 yards
Shotgun scopes - 75 yards
Rimfire scopes - 60 yards

Q. How do I adjust the eye piece focus of my scope?

A. The easiest way to do this is to first ensure that your firearm is unloaded and point in at a distant object.  Then briefly look away from the eye piece and then look back through it.  Repeat this process while adjusting the eyepiece until both the reticle and the object appear sharp at the same time.  The reason you have to repeatedly look away from the eye piece is that your eye will try to bring both the reticle and object into focus if you stare through the scope, causing eye strain and contributing to parallax error.

Q. Can you recommend any inexpensive target stands for practical shooting practice or matches.

A. The cheapest way to acquire free-standing target stands is to make them.  Many years ago John Martyn, of the New Jersey Combat Pistol League a club that I founded and ran, came up with inexpensive targets stands that were literally stapled together  from 1" x 2" furring strips, cardboard pieces, and scrap lumber.  They were used with cardboard IPSC targets or paper targets on a cardboard backer.  We turned these out in great quantities for our 60 member club and they were also used by several other clubs with great success.  

The original bases were nailed  together and used formed  metal strapping to hold the uprights, but this modification using wood channels works better and is cheaper.  If a frame's uprights got shot up they were cut into spare cross pieces.  Several of our members picked up left over furring strips from construction sites and you can probably scrounge some up for free too, although they are very inexpensive to buy.  Try bargaining with a lumber yard for left-overs or damaged ones.  Corrugated cardboard boxes are everywhere for the asking and the pieces can be cut to size on a circular or band saw.  We kept a box of "parts" handy for fast repair during matches.

Tools needed Staple gun (T50 type) with 1/2" or 7/16" staples 1" nails 2" nails or drive screws Electric drill with drive bit if needed. For each target holder you will need 2 - 8-foot 1" x 2" furring strips 2 - 4" x 18" pieces of corrugated cardboard 2 - 4" x 4" pieces of corrugated cardboard cut into 2 triangles each For each target foot (2 per holder) you will need (exact dimensions are not required) 2 - 24" to 30" pieces of 1" x 3", 1" x 4", or 2" x 4" 4 - ¼" x 4½" x 7" scrap plywood or wall paneling 2 - 1" x 2" x 7" furring strip scraps (from target frame wood) 2 - 10-24 "T" nuts and 2 - 10-24 x 2" screws (optional)

You can alter the width of the target holder cross pieces to make a holder for typical bullseye and sighting in targets instead of silhouettes. 

Target Holder Directions

1. Cut the 8' furring strips into two 72" pieces and two 16 3/8" strips.  Save the short 8" scraps for use on the feet.
2. Place a 16 3/8" piece between the top of two 72" furring strips and secure with a single staple at each joint.
3. Square up the frame and  staple a triangular piece of cardboard at each corner with 2 or 3 staples on each edge.
4. Measure 48" down from the top and secure a 16 3/8" piece between the two 72" furring strips with a single staple at  each joint.
5. Staple a 4" x 18" piece of cardboard across the strip with the bottom edge of the cardboard on the strip.  Use 2 or 3 staples on each short side and 4 or 5 on the long edge. (Stapling the bottom edge of the cardboard to the cross strip will make a handy pocket for holding patching tape or pencils.) 
6. Flip the frame over and staple all the joints with a single staple at each joint and then staple the cardboard pieces on the frame like you just did on the other side.

Stapling detail	Corner brace	Corner brace	Horizontal tray

Target Feet Directions

You can get away using only one foot per target but two are better.  In windy conditions you can hold the feet in place with rocks, sand bags, or whatever.

1. Trim the short furring strip scraps to 7". Sandwich two 7" pieces of furring strip between the two pieces of 4½ x 7 plywood, leaving space between them so a third piece can slide down between them with about 1/16" - 3/32" clearance. You may want to place a cardboard shim on the two 7" strips to provide some side-to-side clearance for firing strips as their thickness can vary.
2. Secure the plywood to the furring strips with a couple of 1" nails on both sides.  If you are the worrying type squirt a bit of carpenters glue on the pieces before nailing together. Note:  If your furring strips are very variable in thickness you might need to pick thick pieces or shim things a bit to allow the target frames to slide into the holder all of the time.
3. Center this assembly on the  24" 1 x 3" base strip and secure from the 1 x 3 side with a couple of 2" nails or drive screws into the furring strip on each side of the holder.  You may want to drill a pilot hole to keep from splitting the wood if using drive screw.
4. Insert the target frames into the feet and go shooting.  We found that 3/8" staples worked best for stapling targets to the frames as they held securely but were easy to remove.

Foot detail	Securing screw T nut

You can, if you'd like, drill a hole through the  horizontal piece of the foot into the vertical channel and insert a small (10-24) T-nut so you can secure the uprights in the holder with a short screw for easy moving about the range without the feet falling off.

And speaking of the old New Jersey Combat Pistol League....  If you are a patch holder I'd love to hear from you and reminisce about the "good old days" before the "gamesmen" appeared.

Q. Is there an inexpensive way to make reactive targets

A. I've come up with a method that seems to work well.  I used the target stands described above with some simple modifications, but you could use whatever you have on hand with a little imagination..   In addition to the stand you'll need cardboard targets, about 2' of heavy string, some small spring binder clips, a small nail, balloons, light string, and tape.  

Frame Modification
Secure the piece of cord across the stand about 32" below the top of the stand either with staples or whatever.  Leave some slack in this string.  Drive small nails into the rear center of the top cross bar of the frame and the sides (at the top of the "A" zone and the head zone), letting them stick out enough to tie string to.

Target Modifications
Inflate some balloons.  Use ones about 4" in diameter for a head shot and either 6 to 8 inches in diameter or a long balloon about 4" by 10" for the "A" zone.  For a COM reactor tape the large balloon to the rear side of the center of the target's "A" zone.  For a head shot target tape the 4" balloon behind the head zone.  

Using two binder clips clip the lower edge of the target around the string on the frame.  Then attach the string to the nail on one side of the frame's cross piece, run it between the balloon and the target, allowing the target to angle forward a little bit, and tie to the nail on the other side of the frame.  Go shoot.  When the balloon is popped the target will pivot forward and the target will fall.  (Depending on conditions you may want to cut the bottom corners of the target at an angle to allow the bottom to pivot inside of the target frame as it falls.  

It has been suggested to use a strip of cardboard instead of the string between the balloon and target to prevent the target from falling if the string were accidentally hit outside of the balloon area.

Another option is to just suspend the target from the top of the frame with the balloon/string without fastening to the cord on the frame (only works in non-windy conditions).  When the balloon pops the target will drop.  You could add some kind of a simple flange to keep the target from flopping in the breeze that would still allow the target to drop.  

I have also seen a setup where a rectangular box or a cardboard tube is attached to the back of the target and the inflated balloon inserted (or inflated inside) the container.  The target is suspended from the frame by a string tied to the balloon.  When the balloon is popped the target just drops.

Use your imagination.  If you come up with a better or easier idea email me and  let me know  by clicking here.

String and binder clip	Balloon with string between it and target	Target lean to ensure fall

Q. What is the composition of the various alloys used for casting bullets?

A. The table below gives the approximate composition of various common alloys and their Brinell hardness.  Note that more tan about 4% tin has little effect on hardening.  Tin's primary use is to improved the flow of the alloy so that the alloy completely fills the mold and gives sharp edges.

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Disclaimer

As far as I know all the information presented above is correct and I have attempted to ensure that it is. However, I am not responsible for any errors, omissions, or damages resulting from the use or misuse of this information, nor for you doing something stupid with it. (Don't you hate these disclaimers? So do I, but there are people out there who refuse to be responsible for their own actions and who will sue anybody to make a buck.)

Updated 2008-07-29