Miscellaneous Questions #20

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:

Is factory ammunition better than handloads?
What are the dates that the US military ammunition stopped using corrosive primers?
What effect does lubricant in the bore have on bullet impact?
How many spare magazines is enough for my rifle and pistol?
How long will the springs in loaded magazines last?
How much of the target does my front sight cover at a given distance?
Do you have any suggestions for maintaining my AR type rifle?

Q. Is factory ammunition better than handloads?

A. While factory produce ammunition can be very high quality, it is not necessarily the most accurate ammunition for a particular firearm. Factory ammunition is made to give performance within the stated SAAMI specifications for most firearms, but by necessity can not be optimized for every barrel and firearm.   Carefully handloaded ammunition is frequently greatly superior in accuracy to factory loads since it can be tailored to the characteristic of the firearm it is used in.  See the article on Load Development.

Some folks claim that the quality control and reliability of factory ammunition is superior to handloads.  If handloads are carefully made this is not necessarily the case, and bad rounds can be culled during inspection.  Due to the high speed nature of factory production frequently bad rounds get through.  Below are a couple of factory "oops"  from my collection.  In addition, I've seen bulged cases, split cases, torn cases, upside-down primers, and a case without a flash hole.  The moral of the story--check ALL your ammo.

Smashed primer	Deep seated bullet	Upside-down bullet	Missing primer and a metal  flap from flash hole	Buckled case
		Crumpled neck GI Production

Q. What are the dates that US military ammunition stopped using corrosive primers?

A. The following information comes from the NRA.  While shooting corrosive primed ammunition is not a problem if the firearm is properly cleaned (especially the gas system, if any), corrosively primed cases should not be reloaded. "Safe case date" is date at  which all cases with the indicated headstamp can be considered safe for reloading.

Q. What effect does lubricant in the bore have on bullet impact?

A. Some tests run several years ago by a friend of mine showed that the first shot out of a bore with a light coat oil in it generally printed low and to the right from the normal group position from a clean, dry bore.  Using a variety of firearms in .223, .243, 308 Win, and .30-06, errors as much as 9" from the expected impact point at 100 yards  occurred.

However, simply wiping the bore out with several tight fitting dry patches to remove any excess oil before firing put all shots were they were expected to go.

Q. How many spare magazines is enough for my rifle and pistol?

A.  As a noted firearms instructor once said, "You can't have too many magazines."  At a minimum I think you should you should have 4--1 in the gun, 2 reloads, and a spare.  I feel comfortable with 8 magazines for combat arms and 3 for detachable magazine hunting arms, but I confess to having an awful lot of magazines.  While we are on the subject, remember to clean and inspect your magazines regularly and to rotate your loaded ready-magazines.

Q. How long will the springs in loaded magazines last?

A. A lot depends on the quality of the magazine spring so there is no pat answer.  In the early 1980s I was given 3 loaded M1911 magazine full of RA18 rounds.  The magazines were the old style with the cavalry lanyard loop on their base so they were probably as old as the ammunition.  To my amazement all three magazines functioned flawlessly and all 21 rounds of ammo fired.  I've had M1 carbine magazines and M14 magazines that had been left full for years and all worked.  On the other hand I have seen cheap after market magazines fail after being loaded for a year.  I would rotate (and check) magazines every 6 months just to be on the safe side.

Q. How much of the target does my front sight cover at a given distance?

A.   The answer to this is basically the same as calculating sight adjustments. 

S = sight radius in inches (The distance from the rear of the front sight to the rear of the rear sight)
W = width of the front sight blade in inches
D = distance to target IN INCHES
T = target coverage in inches

T = (D * W) / S

As an example, if your front sight is .052" wide and the sight radius is 20" and your target is at 25 yards (25 x 36 = 900")

(900 * .052) / 20 = 2.34"

Q. Do you have any suggestions for maintaining my AR type rifle?

A.  For bore cleaning I follow normal procedures and use Ed's Red as a bore cleaner.  Keep the front sight "up" to prevent cleaner from getting into the gas tube.

Clean the bolt carrier assembly by removing carbon from the bolt cam pin slot, the inside of the bolt carrier (that chrome lined hole where the bolt goes) and the bottom of the bolt carrier itself. You can use a wet pipe cleaner or a worn bore brush to clean the inside of the bolt carrier key. Do not put anything inside of the gas tube- it is unnecessary, and you will only stick debris in there that will cause problems

Attach the chamber brush to your cleaning rod and scrub out the chamber. I generally use a worn brush with a wet patch wrapped around it and insert it in the chamber. Spin it a few times and replace it with a new brush. Spin that and then dry the chamber out. Clean out the locking lugs in the barrel extension with cotton swabs. Clean out the upper receiver and charging handle.

Use a toothbrush to clean the bolt, especially the bolt lugs. 

As for lubrication it has been proven that the AR system runs much better wet then dry, even in dusty climates.  The preferred oils for the AR platform are MC2500 (TW25B oil) or Slip 2000.  For grease (on the hammer and sear points or larger bearing areas like the inside of the upper receiver and charging handle) use TW25B.

Consider that your rifle is an internal combustion engine.  Like an internal combustion engine, it requires lubrication to make it function. However, just don't put lube on, but put it on in the right places.  There are certain wear points in the gun that need attention, and failure to do so can cause a stoppage. A good rule of thumb is to look for shiny marks, which indicate metal to metal contact. If it shines, lubricate it.

Remove the bolt from the bolt carrier. Turn the bolt carrier over and observe the shiny area on the bottom. This is a wear point. The slot that the bolt cam pin rides in is another wear point, as is the chromed hole in the bolt carrier that the bolt rides in. The entire bolt carrier should have a coat of lube, but pay particular attention to any shinny areas. The military also states that a drop of lube down the bolt carrier gas key is required. The bolt itself requires a coating of oil, paying particular attention to the bolt rings and the lugs.  Keep in mind that when firing many rounds a day, the bolt will get blown dry.  Putting a couple of drops in the 2 holes of the bolt carrier during a break in the action will lube the bolt rings and will keep the gun running.

Before reassembling, check the locking lugs on the bolt and the extractor for chips or cracks.  Check your bolt rings for serviceability as follows. Insert the bolt fully into the bolt carrier.  Suspend the assembly (preferably over something soft) by holding just the bolt head. If the carrier falls of the bolt of its own weight the rings are starting to wear and will need replacement shortly.  Repeat the test but hold the assembly by the rear of the carrier.  If the bolt drops out on its own, you need to change the gas rings immediately.  If it passes these tests, you are good to go. You don't have to bet paranoid about misaligning the gas rings. Colt Armorer Instructors state emphatically that the gun will run with one good ring, but misalign the slots anyway--why take a chance.

Lastly, inspect your magazines for damaged or cracked feed lips and disassemble the magazines and clean the interior.  Leave the magazine insides dry.  For best reliability your 30 rd magazines should have the gray or tan Gen III anti-tilt followers although the green followers are useable.

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Disclaimer

As far as I know all the information presented above is correct and I have attempted to insure 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 2010-03-08