cam pin wear

[Disciple]

I have an H&M Blacknitride+™ treated cam pin as a spare. I did not intend to use it with a phosphate carrier as I presume that would transfer wear to the track. Perhaps I should not use it with a nitride carrier either? Is the nitride case hardening shallow enough to allow the load distribution you describe?

[lysander]

Agree, they are soft(not hardened) . . .

Rockwell C45 to 48 ain't exactly soft.

[Disciple]

Rockwell C45 to 48 ain't exactly soft.

Is that a case hardness? Do you have an opinion on the use of a nitride treated cam pin with either a nitride carrier, or mil-spec phosphate? How hard is the cam track on a mil-spec carrier?

[constructor]

Rockwell C45 to 48 ain't exactly soft.

Softer than 60 isn't it?

Here's some for you, try these out and let the rest of us know how things go.

deltateamtactical.com
H&M Nitride Heavy Duty
AR-15 M4 M16 Mil-Spec Cam Pin

Mil-Spec Cam Pin Genuine AR-15/M16 parts made to military specifications by a government contractor.

Nitride finished Rockwell Hardness is 80-85 where QPQ nitride Increases exterior hardness To above chrome

Specs So 3x harder than regular finished cam pins.

These often replaced parts should be replaced or inspected every 5000 rounds

Nitride Cam pin life is 10,000+ rounds 2x that of Phosphate

[Wow]

Isn't the cam pin being "softer" a good thing? That way it it will fail before it start wedging the bolt apart?

[constructor]

Isn't the cam pin being "softer" a good thing? That way it it will fail before it start wedging the bolt apart?

yes......

[lysander]

Is that a case hardness?

No, it is through-hard.

Do you have an opinion on the use of a nitride treated cam pin with either a nitride carrier, or mil-spec phosphate?

Generally, one part should be harder than the other, but if they are equal it's not a big problem it just introduces some uncertainty as to which parts wears faster.

How hard is the cam track on a mil-spec carrier?

It is roughly Rockwell C58 to 63. Nitriding yields similar hardness, that is pretty much limited by the fact it is an steel alloy.

[Pasta123]

Hi Lysander,

Speaking of cam pin wear, is the wear on the upper receiver an issue overtime on the AR-15?

Just recently I saw a detailed video about the QBZ-191, basically a Chinese piston AR knock off, where they build another lever around to address the cam pin wear (increase longevity) on the upper receiver.

Sounds like over-engineering to me but I'd like to know your experience with the AR.

Screenshot 2023-07-24 at 14.21.27.png

[lysander]

If you put some oil on the left side of the cam pin head every 1,000 rounds or so, you shouldn't have a problem.

Putting mechanism to lock the bolt forward has been around on many designs since the early 1910s, currently, H&K has been doing it on their designs quite a bit.

Just remember - "More parts = more potential parts to break"

And M16/M4 upper can go at least 36,000 rounds* and not show problematic wear in this area, if properly lubricated.


*Probably more, but, I can't say more, as no test I know of has gone longer than 36,000 round per single weapon.

[Pasta123]

If you put some oil on the left side of the cam pin head every 1,000 rounds or so, you shouldn't have a problem.

Putting mechanism to lock the bolt forward has been around on many designs since the early 1910s, currently, H&K has been doing it on their designs quite a bit.

Just remember - "More parts = more potential parts to break"

And M16/M4 upper can go at least 36,000 rounds* and not show problematic wear in this area, if properly lubricated.


*Probably more, but, I can't say more, as no test I know of has gone longer than 36,000 round per single weapon.

So it's a trade-off. Either have a required maintenance, or more moving parts. Whatever fits depends on your needs.


There are other things that's interesting:
1. They have completely redesign the retaining pin mechanism and get rid of that "flimsy cotter pin". I think it states in the patent where the cotter pin is only good at a certain spot, or it'll risk falling out, and looking to combine the best of both worlds. Is it true?

Screenshot 2023-07-25 at 15.37.01.png

2. Not only it's a dual-spring extractor, they're also oblique to it to reduce horizontal movement. Is this what people called "extractor vibration"?
3. it's a four lug design with a fixed ejector.



#1 and #2 sounds skeptical to me, and for #3 I'd think it depends on more factors than just four lugs.
What's your take?