AR15: Straight Pins Inferior to Tapered?

[WheelGunRealGun]

I just found out that the LMT SPM 16 uses straight pins for the front sight base rather than the mil-spec tapered pins. Why does LMT do this, and is it inferior to taper pins? Are they more likely to come loose? LMT seems like a highly regarded mil-spec company, and I'm surprised that they aren't using mil-spec taper pins.

The straight taper pins, semi-auto BCG, carbine buffer, and lack of parkerization under the FSB make me wonder if LMT is cutting corners too much.

[pete2]

Is mil-spec actually supposed to be better quality? Bought from the lowest bidder=better?

[WheelGunRealGun]

Mil spec isn’t always better, but in this case I’m talking about dimensionally mil-spec rather than materials and such. I can’t imagine why straight pins would be more durable and reliable than taper pins, but I’m hoping someone might be able to shed some light.

[imashooter]

Inferior? Not if the work is precisely machined.

[kymasabe]

My experience is...I've seen tapered pins on phosphate and parkerized barrels, and straight pins on nitride/melonite/qpq barrels. Either one works just fine. For a better explanation why, call the fine folks at Adco Firearms, as they do gunsmithing and use each of those pins in specific applications.
https://adcofirearms.com/shop/gunsmithing/fsb-install/

[WheelGunRealGun]

My experience is...I've seen tapered pins on phosphate and parkerized barrels, and straight pins on nitride/melonite/qpq barrels. Either one works just fine. For a better explanation why, call the fine folks at Adco Firearms, as they do gunsmithing and use each of those pins in specific applications.

Does being phosphated/parkerized count as a "coated/hardened" barrel? I'm still not quite clear on why one is better than the other in certain applications other than perhaps ease of installment.

[FrankenMauser]

Taper pins can squeeze the bore and create tight spots. That, alone, can put them in the 'inferior' category.
Properly sized and installed straight pins cannot.

Both types, however, can have tight spots created by the drilling process, if excessive pressure and a dull tool are used.


Lack of parkerizing under the FSB is to get a better gas seal.



"Mil-spec" to those that have served in the military, means:
At one time it met some kind of military standard - even if only being the right color or coming in the correct type of packaging.
It was made by the lowest bidder.
The product occasionally meets minimum standards.
...That's about it.

If you want to see what the world of "mil-spec" is all about, start using things like mil-spec toilet paper, mil-spec powdered eggs, mil-spec socks, and mil-spec hamburger (labeled very prominently as "not safe for human consumption").
Your opinion of the marketing label, "Mil-spec" is likely to change very quickly.

[M1Rifle30-06]

Taper pins can squeeze the bore and create tight spots. That, alone, can put them in the 'inferior' category.
Properly sized and installed straight pins cannot.

Both types, however, can have tight spots created by the drilling process, if excessive pressure and a dull tool are used.


Lack of parkerizing under the FSB is to get a better gas seal.



"Mil-spec" to those that have served in the military, means:
At one time it met some kind of military standard - even if only being the right color or coming in the correct type of packaging.
It was made by the lowest bidder.
The product occasionally meets minimum standards.
...That's about it.

If you want to see what the world of "mil-spec" is all about, start using things like mil-spec toilet paper, mil-spec powdered eggs, mil-spec socks, and mil-spec hamburger (labeled very prominently as "not safe for human consumption").
Your opinion of the marketing label, "Mil-spec" is likely to change very quickly.

Interesting. Never heard of lack of parkerizing under the FSB to be to create a better gas seal. I always assumed it was for convenience of manufacture, along with the straight pins, but if LMT does it because they consider it superior through their testing, that's a different story.

What do you mean by "tight spots"? I assume that the taper pins cause the FSB to pull down on the barrel? What kind of problems can this cause, and why has the military stuck with it?

Good point about those examples of "mil spec" items. I certainly don't want mil spec toilet paper. I imagine it'd be like John Wayne: rough, tough, and doesn't take crap.

[kymasabe]

Originally Posted by WheelGunRealGun

Does being phosphated/parkerized count as a "coated/hardened" barrel? I'm still not quite clear on why one is better than the other in certain applications other than perhaps ease of installment.

No. Phosphate and parkerized barrels are easy to dimple or drill. Nitrided, melonite and qpq barrels are much harder.