Wear in an M4?

[Heavy Metal]

The two most common failures on the upper are the wearing of the charging handle release notch and the wear of the dust cover notch.

[TurretGunner]

I can't believe I.G. hasn't mentioned the one thing that will cause a rifle to be worn out. Because it has the serial number on it, the lower receiver "is" the rifle. Any other parts could be replaced as needed. As far as a lower wearing out, I was a unit armorer in the early '80s and saw 5 rifles that were coded out for the same reason, excessive wear on the pin holes in the lower. They all displayed the same symptoms "fails function check". On semi they would fire when you pulled the trigger (and hold it), cycled the bolt and would fire again when you released the bolt. When taken to General Support and checked with the pin gauge, the holes were enlarged. All five rifles were Hydramatic manufactured rifles and my speculation would be that they used a softer alloy of aluminum than Colt or H & R did. All were M16A1s manufactured in the early '70s, so they were about 12-15 years old at the time.

I had a hydramatic A2 overstamp in basic and that thing was a rattle box piece of shit. The upper and lower had so much play I tried to tell the DS I need a new rifle. After eating the dirt for evey questioning about something "I dont have a ****ing clue" about, I went on to shoot expert with that POS. Brings back some great and suck fest memories.

Since H&R and GM made rifles, were they disclosed the TDP? :/

[Iraqgunz]

I didn't mention it simply because they do not wear out very often. Also, no one here with a few exceptions has the proper gage to check the trigger and hammer pin holes, or knows how to do it.

Also, let's look at simple economics.

Take a lower receiver that costs 100.00. Now let's assume that you have another 80.00 in lower parts installed. That's a total investment of 180.00.

I have said rifle for 8 years and the lower magically gets messed up and needs replacement.

8 years= 96 months. 100.00 lower/96 months= 1.04 a month. So getting spun up over a lower or any other part of the weapon makes no real sense.

In my military time I have seen hundreds of lower receivers that had thousands and thousands of rounds on them and they were stull functioning years later.

I can't believe I.G. hasn't mentioned the one thing that will cause a rifle to be worn out. Because it has the serial number on it, the lower receiver "is" the rifle. Any other parts could be replaced as needed. As far as a lower wearing out, I was a unit armorer in the early '80s and saw 5 rifles that were coded out for the same reason, excessive wear on the pin holes in the lower. They all displayed the same symptoms "fails function check". On semi they would fire when you pulled the trigger (and hold it), cycled the bolt and would fire again when you released the bolt. When taken to General Support and checked with the pin gauge, the holes were enlarged. All five rifles were Hydramatic manufactured rifles and my speculation would be that they used a softer alloy of aluminum than Colt or H & R did. All were M16A1s manufactured in the early '70s, so they were about 12-15 years old at the time.

[urbankaos04]

We don't use a "go" or "no go" gage. We use a "field" gage. Throat erosion is measured with a bore erosion gage.

So a field gage is different than a bore erosion gage? I've never used any gages, so I have no clue, as you can tell, as to the differences.

[markm]

So a field gage is different than a bore erosion gage? I've never used any gages, so I have no clue, as you can tell, as to the differences.

Yeah. The throat erosion guages usually have a funny looking handle on them. They're measuring something different than headspace.

[urbankaos04]

Yeah. The throat erosion guages usually have a funny looking handle on them. They're measuring something different than headspace.

Thank you for the response, much appreciated. And, so, for the record, a field gage should be used when trying to determine if a used rifle/carbine has excessive headspace when wanting to use a new BCG?

[Cagemonkey]

Was wondering how one measures gas port erosion/rounding off? How do armorers know when to upgrade the buffers from H1 to H2 and H3 to reduce the cyclic rate and increase bolt lock time? Can 2nd echelon armorers perform this task at their maintenance level?

[TurretGunner]

Was wondering how one measures gas port erosion/rounding off? How do armorers know when to upgrade the buffers from H1 to H2 and H3 to reduce the cyclic rate and increase bolt lock time? Can 2nd echelon armorers perform this task at their maintenance level?

No one does that shit in the army. Well maybe the state/brigade armorers or level 3 shops. They dont **** around with different buffers. They check chamber/barrel/throat and if they pass then it goes back to unit. The only time they mess with anything else is if there is malfunctioning.

The AR-15 is really a simple system and only needs to be tweaked when your using non standard parts (short gas systems,ect) and using quality parts. No one in the army cares about cyclic rate on a M16 or an M4 beacuse we don't use them outside of a small portion of JSOC. If it shoots and feeds well, then its a go.

[Tweak]

And, so, for the record, a field gage should be used when trying to determine if a used rifle/carbine has excessive headspace when wanting to use a new BCG?

If you change the bolt you're safest checking the GO dimension and, at least the FIELD. If the barrel was properly headspaced you'll rarely find a bolt that will make it sub-GO later on but it's best to check.

If it's a new build you should check the GO and, at least the FIELD.

You'll have to know beforehand whether you want the chamber to be headspaced to the military or civilian spec, the former can be more reliable, the latter more accurate.

[Iraqgunz]

When a weapon is gaged it gets recorded. Chances are before your port has eroded enough to cause issues, the headspace or bore erosion will already be an issue and stuff will start getting replaced.

No one dicks around with buffers or spring unless defective.

Was wondering how one measures gas port erosion/rounding off? How do armorers know when to upgrade the buffers from H1 to H2 and H3 to reduce the cyclic rate and increase bolt lock time? Can 2nd echelon armorers perform this task at their maintenance level?