Posting up some links, charts and pictures to commonly asked questions. Hopefully you will all find this as a good reference to help you understand and visualize the concepts better.
Written and produce by Dieselpower@calguns.net
This is chart that shows the ideal twist rate for different types of projectiles for the .223 remington/5.56x45 NATO. This is just a generalization. Its makes the assumption that all projectiles are of solid lead core construction. Twist rates in reality are directly correlated to bullet length not weight. So bullet's of lesser density, like hollow points or lead free hunting bullets will be longer/bigger than bullets of the same weight but higher density materials (like lead). So please use this this chart just as a general guidline.
One more thing, please do not make the assumption that if the twist rate is ideal for the bullets you are using that you can automatically expect sub moa accuracy. Conversely, do not assume that if your twist rate is less than ideal for the bullets you are using, that you can only expect 8 moa accuracy. Twist rates are just one factor of many that must be considered when trying to predict overall accuracy.
Written and produce by Dieselpower@calguns.net
Here is a diagram detailing the differences in how an absolute (100%) cowitness and lower 1/3 cowitness looks. Please not the right hand column: when your back up iron sights are folded down and out of the way, they look identical. The biggest difference is when you have a fixed front sight, the lower 1/3 will give you a larger sight picture as the front sight sits lower and out of the way.
Pay special attention to the two diagrams on the right. See how they look exactly same. This is the way your sight picture will look 99.9% or the time with either method.
Started by Rob_S, and recommended by Quentin, this is chart detailing specs on various AR15. Please note, this was started by Rob_S, he no longer maintains it, it is not up to date, and I do not know if it is the most recent update.
Just use it as a reference guide. One guiding principle you must understand is that "milspec" is just a certain specification that the military has deemed to be important to them. It doesn't necessarily mean that it is the best, nor does it mean its the worst. I recommend using mil spec as a minimum standard. In other words, get at least mil spec, or get better than mil spec if at all possible.
Another way to look at this list, is to see how and why some ARs are cheaper or more expensive than others, and why some brands are considered higher quality. There is a direct correlation in the amount of time and expense invested in testing to the overall quality of the unit produced. Less testing should always mean the unit can be produced faster and cheaper.
Batch testing- while better than no testing, is often considered just barely better than no testing. Simply because if batch testing turns up a defect, you really don't know what the manufacturer's standards and procedures are to fix that mistake. You also don't know if they batch test 1 out or 10 units, or 1 out of 10,000. If a defect is found do they go back and retest the whole batch for defects or just keep on trucking along. If only manufacturers would be more forth coming with testing procedures......
- Magnetic particle Inspection for internal flaws and defects.
- High Pressure Tested Bolt and over pressure round is fired then the bolt is MPI tested to make sure there no defects.
Extractor spring insert
-The insert (o ring) is design to help the extractor do its job. There is a lot of debate whether its really needed, but imho every little bit helps.
Properly Staked Gas Key
- added insurance to prevent your gas key from coming loose and creating a stoppage. With the proper tools, it would take a manufacturer seconds to do this.
Bolt Carrier Style
. M16 Full Auto carriers are heavier, and have a protective shroud which protects the firing pin as the BCG cycles out of battery and resets the hammer. AR15 semi auto style is light and usually does not have the protective shroud, tho some hybrid carriers do have it. For all intents and purposes a civilian semi auto AR15 will do fine with either type of carrier, tho many people prefer M16 FA for the aforementioned attributes. Use of the M16 FA carrier, cannot and will not make your AR full auto.
Barrel Length and Velocities for 5.56 Nato M193 and M855
A great chart showing the different velocities from different barrel length and types of Nato ammunition. Use it as a general guide, some variables not taken into account are environmental factors (ie altitude and temp etc), mechanical factors (button rifling vs polygonal, semi auto with a gas port, bolt action no gas port) and finally differences in ammo manufacturing.
Basic trajectory curve--Ballistics of the 5.56x45 NATO
This link shows the ballistics of M193 55gr FMJ and M855 62gr FMJ and goes into depth the differences between 25, 36, 50, and 100 yard zeros. It is very well written and objective, and has lots of pretty charts and graphs. This link sends you to M4carbine.net and was written by Molon dated 9/30/10. Please bear in mind that the charts do not take into account for different barrel lengths, ie 14.5, 16, 18 or 20 inches, as the added velocities of the longer barrel lengths will change ballistics and zero distances. This is a heavy read, but very indepth and chock full of valuable information.
Aftermarket Trigger Review #1
A great read, with lots of great information about the people behind all the aftermarket triggers, and the differences between the models. Truly a read for the gun geeks in most of us.
Aftermarket Trigger Review #2
Very nice and objective review of some of the lighter aftermarket triggers available. There a review of a milspec LWRC coated trigger. Most reviewed are 2-4# target/competition type triggers. Pretty pictures, objective review, hard numbers. Very well useful imho.
Tactical Yellow Visor's Rob_S' *Handguard charts
Not complete or comprehensive but a very nice chart to reference different dimensions, weights and prices of various FF handguards. *Lots of work and research went into it!
AR15 various weights
Great thread with various configs and weights.
If anyone else has some suggestions or would like to add stuff to this post, please do so. Or if a mod would like to add this info to my other thread, Please do so at you discretion (I can no longer modify my AR15 primer thread since its been so long.)