First AR Assembly... Need Advice.

[Scrod314]

Nice rifle, @Scrod314.
Did the upper assembly come with a Bolt Carrier Group?
I see a shiny copper colored carrier.

Looking forward to a range report!

The upper did not come with the BCG or charging handle. I bought a Toolcraft Nickel Boron BCG and a Radian Raptor charging handle.

 

[browneu]

Congratulations on your first build.

 

[Charlie98]

I bought a Toolcraft Nickel Boron BCG

NiB is manna from Heaven. I sure wish my issue M16's had that... but we have to pinch pennies when we are building for the Government. I probably used more cost in cleaning materials trying to break that carbon up than it would have cost for a NiB carrier...

 

[TonyAngel]

I've been using Manta mlok covers. They have a rubbery texture and do a pretty good job of keeping the heat off of your hand.

 

[N555]

The upper did not come with the BCG or charging handle. I bought a Toolcraft Nickel Boron BCG and a Radian Raptor charging handle.

One small problem with nickel boron bolts. Every NB bolt I have seen fail breaks in half at the cam pin, which puts the gun in club mode. "Inferior" C158 alloy breaks lugs around the extractor and keeps running, gives lots of warning before completely fails.
The rest of the bolt carrier being made from nickel boron is ideal.
Does NB last longer, probably, maybe? but I'll take the longer safer failure mode over the gun no workie failure mode.

 

[David Hoback]

One small problem with nickel boron bolts. Every NB bolt I have seen fail breaks in half at the cam pin, which puts the gun in club mode. "Inferior" C158 alloy breaks lugs around the extractor and keeps running, gives lots of warning before completely fails.
The rest of the bolt carrier being made from nickel boron is ideal.
Does NB last longer, probably, maybe? but I'll take the longer safer failure mode over the gun no workie failure mode.

I’m sorry, but you really don’t have an understanding of what you are saying. For starters, are you referring to the Bolt, or the Carrier? All Carriers are actually made of 8620 Alloy steel. And they are either Phosphate, Nib, Nitride or other surface treatment/plating. C158 is an Low Alloy steel made by Carpenter, & NiB is a simply a plating Alloy substrate which is applied similar to any other plating process; in a Salt bath with electrical current. Just as ALL MilSpec Bolts are Phosphate coated, the steel underneath the NiB plating can still be C158, Or, as most BCG’s today are using 9310. Now 9310 is a Higher Alloy steel, and is a better choice steel in the end. As for all NiB Bolts breaking that you’ve seen, I find that maybe a bit unknowingly disingenuous. Unless you’ve seen a couple break? Then, sure. I can see that. I’ve seen many bolts break. MilSpec C158, 9310 Bolts & even the S7 “SUPER” Bolts by by Sharps. (Seen sever of those have the teeth shear off) However, I’m careful not to be misleading over one or another showing a 100% failure rate, which is kinda what you’re doing there.

 

[N555]

I’m sorry, but you really don’t have an understanding of what you are saying. For starters, are you referring to the Bolt, or the Carrier? All Carriers are actually made of 8620 Alloy steel. And they are either Phosphate, Nib, Nitride or other surface treatment/plating. C158 is an Low Alloy steel made by Carpenter, & NiB is a simply a plating Alloy substrate which is applied similar to any other plating process; in a Salt bath with electrical current. Just as ALL MilSpec Bolts are Phosphate coated, the steel underneath the NiB plating can still be C158, Or, as most BCG’s today are using 9310. Now 9310 is a Higher Alloy steel, and is a better choice steel in the end. As for all NiB Bolts breaking that you’ve seen, I find that maybe a bit unknowingly disingenuous. Unless you’ve seen a couple break? Then, sure. I can see that. I’ve seen many bolts break. MilSpec C158, 9310 Bolts & even the S7 “SUPER” Bolts by by Sharps. (Seen sever of those have the teeth shear off) However, I’m careful not to be misleading over one or another showing a 100% failure rate, which is kinda what you’re doing there.

If it's just a surface treatment then why do they seem to break in half before they break a lug?
The standard bolt will probably last as long as the barrel so no point in spending 3x or more on a super alloy bolt.

 

[Varminterror]

If it's just plating then why do they seem to break in half before they break lugs?

I’m gonna say you have a small sample set, and your observation has been pure coincidence among statistical certainties.

I’ve certainly seen more broken lugs than broken bolt bodies - which always happens at the cam pin hole, but both failure modes do happen.

Breaking at the cam pin hole is common enough that some companies have come up with closed wall bolts with a cam pin “pocket” rather than a hole.





MAYBE… Maybe… one reason you see more NiB bolts break at the cam pin hole would be the fact 1) bolts break with use, and 2) many NiB bolts are JP enhanced bolts which have improved lug/head geometry to avoid bolt lug failures. So inevitably, they’ll fail at the cam pin hole rather than the lugs.

 

[N555]

I’m gonna say you have a small sample set, and your observation has been pure coincidence among statistical certainties.

I’ve certainly seen more broken lugs than broken bolt bodies - which always happens at the cam pin hole, but both failure modes do happen.

Breaking at the cam pin hole is common enough that some companies have come up with closed wall bolts with a cam pin “pocket” rather than a hole.

View attachment 1102462

View attachment 1102463 View attachment 1102464 View attachment 1102465 View attachment 1102466

MAYBE… Maybe… one reason you see more NiB bolts break at the cam pin hole would be the fact 1) bolts break with use, and 2) many NiB bolts are JP enhanced bolts which have improved lug/head geometry to avoid bolt lug failures. So inevitably, they’ll fail at the cam pin hole rather than the lugs.

For $125 I'm buying at least 1 of those.
I always wondered why the cam pin had to go all the way through the bolt after I learned of them breaking in half. I guess it doesn't.

 

[brass shower]

@N555 by any chance were those broken bolts being used on a piston/op rod gas system? Those are notoriously harder on bolts than a regular direct impingement system.

 

[N555]

@N555 by any chance were those broken bolts being used on a piston/op rod gas system? Those are notoriously harder on bolts than a regular direct impingement system.

I didn't ask and that's a good point. I know someone with and ever growing collection of them.

 

[David Hoback]

If it's just a surface treatment then why do they seem to break in half before they break a lug?
The standard bolt will probably last as long as the barrel so no point in spending 3x or more on a super alloy bolt.

It’s not a question of “if”. I told you exactly what is was. Feel free to research it and you see. Understand, I’m not defending the NiB in these cases. If you have a friend who has aquired many AR’s with with NiB bolts, sure, they very well could have broken. My point is, that is the weakest point on a an AR bolt. Regardless of steel, and/or coating/plating. As you can see in the pics below, standard MilSpec Bolts in 158 or 9310 steel with Phosphate & even Nitride treatment suffer the same issue. It’s not a material or coating or treatment issue… It’s simply an AR15/10 issue as by the cam pin is the weak point of the bolt.

 

[Scrod314]

These pictures are disturbing. Does that cause a kaboom?

 

[David Hoback]

These pictures are disturbing. Does that cause a kaboom?

No, the rifle simply becomes inoperable.

 

[citizenconn]

Good luck with the project. If I can share a little advice from many, many AR builds:

Get a good stock of back-up parts: field repair kits with extra springs, pins, detents, safeties, etc.; extra bolt(s) and preferably extra bolt carrier; extra buffer springs and buffers of various weights. Get a few brands of magazines to see what works best with your AR.

Having extra springs, detents, etc. beats crawling around looking for the one that just shot across the room/shooting bench while you were assembling or repairing issues. Extra bolt/carrier and buffers make it much easier to diagnose feeding/cycling problems. Carrying these things as well as a basic set of assembly/disassembly tools in your range bag can rescue a range trip.

I'd have to take off both my gloves and shoes to count the number of times I've donated parts/time to help someone at the range get their AR back up and running because they didn't have the parts or knowledge to diagnose and repair it.

 

[AK Hunter]

Congratulations on your build. Since you know how easy it is now, do you plain to build more?

 

[Uffdaphil]

My experience with the small plastic/polymer Mlok rail covers is that the base that holds them in place got brittle after a while. Heat/age? I don’t remember which brand so don’t want to bad mouth an innocent. These were from early days so newer plastics may be fine. I stick with soft Ergo types or hard G10 panels these days and ladders for quad rails.

 

[Scrod314]

No, the rifle simply becomes inoperable.

Inoperable beyond repair, or just time for new bolt and/or bcg?

 

[Charlie98]

Good luck with the project. If I can share a little advice from many, many AR builds:

Get a good stock of back-up parts: field repair kits with extra springs, pins, detents, safeties, etc.; extra bolt(s) and preferably extra bolt carrier; extra buffer springs and buffers of various weights. Get a few brands of magazines to see what works best with your AR.

Having extra springs, detents, etc. beats crawling around looking for the one that just shot across the room/shooting bench while you were assembling or repairing issues. Extra bolt/carrier and buffers make it much easier to diagnose feeding/cycling problems. Carrying these things as well as a basic set of assembly/disassembly tools in your range bag can rescue a range trip.

I'd have to take off both my gloves and shoes to count the number of times I've donated parts/time to help someone at the range get their AR back up and running because they didn't have the parts or knowledge to diagnose and repair it.

Shooting an M16, albiet in a very limited scope, while in the Army, I never had a part fail... so I sort of fell into the idea that they were indestructible. Shoot... after the beating my M16A1 took in Basic, and still shot Expert... who am I to complain? But that changed after I started building them, and reading some threads over on ARF. After that, I saw The Light, and proceeded to get a stock of basic parts and part kits. My range tool box is full of AR replacement parts, and the tools to do basic repairs. An even then. We were out of town, on a big shoot planned for in advance... my buddy's AR sheared 3 lugs, deadlining the rifle until we got back to TX and got a new bolt. My tool box now has a BCG, too.

 

[Charlie98]

Inoperable beyond repair, or just time for new bolt and/or bcg?

No, you just have to drop everything, disassemble it to get the closed bolt out of the barrel recess, dig all the chunks of broken metal out of the trigger group, and new parts installed.

 

[N555]

Inoperable beyond repair, or just time for new bolt and/or bcg?

And check head spacing.
You can also do that before you need it. Keep a known to be properly head spaced bolt with your spare parts kit.
Any off the shelf bolt should head space properly if the chamber was cut correctly. But that assumption contains too many ifs and shoulds for my liking.

 

[David Hoback]

Inoperable beyond repair, or just time for new bolt and/or bcg?

New bolt, and back in business!

 

[David Hoback]

Shooting an M16, albiet in a very limited scope, while in the Army, I never had a part fail... so I sort of fell into the idea that they were indestructible. Shoot... after the beating my M16A1 took in Basic, and still shot Expert... who am I to complain? But that changed after I started building them, and reading some threads over on ARF. After that, I saw The Light, and proceeded to get a stock of basic parts and part kits. My range tool box is full of AR replacement parts, and the tools to do basic repairs. An even then. We were out of town, on a big shoot planned for in advance... my buddy's AR sheared 3 lugs, deadlining the rifle until we got back to TX and got a new bolt. My tool box now has a BCG, too.

My father always said the same. He served as a Marine, and was in Vietnam ‘69-‘70. His Battalion was among the last to be swapped out of their M14’s and he said how at first he was incredibly skeptical. The “Mattel Toy” they called it… “what is this little thing gonna do!”, he would tell me. Then he said all those feelings of doubt left on their first fire fight! By this time the issues from the beginning were long gone. My father’s M16 never failed him a single time, and he was a big fan. Although be never owned another. He didn’t own any guns from his time in Service, until I built him a 1911 for Father’s Day in 2009 I think it was. He had some good stories. Miss you pop.

 

[BushMaster-15]

I suspect sustained rate of fire continually overheating is the Main cause of Bolt failures . NO matter the finish run a little lube and don't go Rambo with an AR and it will hold up just fine . I'm still running some original 90's Bushmasters that actually make small groups and have yet to have a malfunction . So it's kind of like Yeah it can happen but often ? , NO Not IMO .

 

[TonyAngel]

As said, get spare parts. A whole new bolt is a good place to start. I just wait for Toolcraft BCGs to go on sale for $99 and I grab one every now and then. Also don't buy small parts from discounters. Stuff like gas rings, cam pins, extractor springs, etc. I get mine from either Bravo Company or Forward Controls Design. I usually go through my bolt every 5K rounds or so and change everything whether it needs it or not. I'm not big on cleaning so I just do it when it's convenient rather than waiting till I have to do it when it isn't so convenient.