Will the new M4 bolt work on a regular AR? I have the A2 HBAR?

All the parts are interchangeable between a M4 and an A2.

Except the rear sight assembly - M4's, with their shorter barrels, have different elevation wheels to allow for more/faster bullet drop.

A2 rear sight wheel is marked 8/3
M4 rear sight wheel is marked 6/3 Z

What is the "NEW" M4 bolt you are referring to???   This is news to me.  I thought ALL AR/M16/M4 bolts were exactly the same.  I'm not referring to the carrier here.  I do know that the GI extractor spring has more compression strength, but wasn't aware of any other changes.  Enlighten me please.  

Same as any other AR-M16 bolt, only difference is Colt puts a black insert to the extractor spring.

That is not the only difference.  It has a heavier extractor spring.

Which is only to identify the heavier spring. It is otherwise the same as the blue one[:D].

Based on some notes from others, it would appear that Colt has just switched over to the heavier spring in all their production, including civilian market ARs.  Anyone with an AR can duplicate the new spring by getting some heavy duty ones from Wolff Gunsprings.

This is what the add said at e-bay where I got this for 108.00 plus shipping.

One brand new complete DPMS AR15 / M4 Bolt Carrier assembly. It is USGI Milspec and complete with firing pin, ready to drop in. Features a chrome lined carrier for easy cleaning & reliable operation plus upgraded to the latest design extra power extractor spring with M4 black insert. This is the latest Mil spec for more reliable extraction. The carrier key screws are stacked on in 3 spots, so they will not loosen during firing, for increased safety and reliability.

I heard that the colt bolts or extactor assemblies are different  for the 14.5 m4 barrels is that true,

Thanks

Bill

As noted above, only the extractor spring, and the black insert to identify it, are different from the earlier models.  Everything else is the same,

There is an aftermaket, semi experimental, bolt/carrier assy being introduced to the market currently, but it's not mil spec, and in my opinion too damn expensive to be worth bothering with.  Most of us aren't planning on firing 10,000 rounds on full auto in the next year and the stock bolt, with the heavier extractor spring, is going to do just fine. The one in my SP1 carbine has, for over 25 years now[:D]

My Bushy carbine came with a blue ring/lighter spring. Had some failure to extracts during initial break-in. Changed to Wolff heavy springs, now it works perfectly.

A current RRA carier assembly, purchased from Pete had the black ring/heavier spring.

Also of note the RRA carrier is the "enhanced design" that has more meat around the firing pin hole.

genius91

Sorry, but that's wrong.

Both the 8/3 and 6/3 elevation wheels move the rear sight the exact same amount for the same elevation - in this case .071" for 600m.  Don't believe me?  Measure it for yourself.

The main reason for the difference is there just isn't enough room under a carry handle for a rear sight base with .152" of vertical travel.  So Colt made the thread twice the pitch, so now you only get 600m for one whole revolution, instead of exactly 1/2 turn on the 8/3 wheel.  It was a good trade off 'cuz they really doun't expect troops to take 800m shots with a carbine anyway.

Careful, though, you'll run into problems if you decide to use a 6/3 rear sight in a fixed handle upper because the base sights about .070" lower than an 8/3.  The rear sight "shelf" on a carry handle is taller than a standard receiver.  So if you're building an M4gery on a fixed handle upper receiver, just use an 8/3 rear and everything will work just fine.

Lol my Match Target Comp HBAR with a 20" barrel came with a removeable sight that only goes up to like 600,  which is an M-4 sight I think.  Can the Wheel be replaced for the 800 thingy or does that not work because of space issues?