AR Barrel Length Questions

[Perplexed]

I'm looking at building an AR pistol, and was considering combinations of barrel lengths, free-float HG lengths, and muzzle devices. When an AR barrel is described as being, say, 10.5" in length - does that include the threaded portion? If so, does that mean an attached muzzle device with a length of X inches would add that much to the overall length, minus the length of the threaded portion of the barrel? I'd be looking to have the HG extend to about the rear edge of the muzzle device, so knowing where the seam between the barrel and the muzzle device is would be handy. Of course, I could assemble the barrel and MD, and measure for an appropriate HG, but what's the fun in that?

 

[GunSlingingPlatypus]

Your muzzle device must be permanently attached to the barrel in oder to add to the overall length of the barrel. The length of the barrel is from the bolt face (while closed) to the very end of the barrel.

 

[Perplexed]

I understand the legalities involved in considering the MD as part of the OAL of the barrel; I was asking more about the practical aspects of the threaded portion of the barrel affecting the placement of the MD. As in, how far back will the MD sit on the barrel once it's threaded onto the latter? 1/4 inch? 1/2 inch? And at what point above the barrel will a free-float HG be mounted? Bottom line, how far forward will, say, a 9" HG extend over a 10.5" barrel - will it actually stop 1.5" from the end of the barrel, in which case the MD might thread back to about 1" from the forward edge of the HG? Or is this a case of which manufacturers are involved, with some variation in the lengths and spatial relationships of the barrel / MD / HG, (i.e., depends on who you ask?)

 

[NikatKimber]

The measured length of the barrel starts from the the bolt face, to the end of the barrel - or permanently attached devices. So it doesn't necessarily start at the same point as the handguard, and yes it includes the threads.

 

[uncle money bags]

Length of flash MD includes the reflected portion with threads.

 

[Perplexed]

Length of flash MD includes the reflected portion with threads.

So a MD with a crush washer would thread approximately 0.6" onto the muzzle, if I read the diagram correctly. That helps when aiming for as narrow a gap as possible between the front edge of the hand guard and the rear edge of the MD, without the HG extending around the MD. Thanks!

 

[Super Dave]

What long ass muzzle device are you gonna use, or is this a pistol/SBR upper? Pics or it didn't happen!

Edit: re read it.

What ninja hand guard are you gonna use? Pics statement still applies. Do it.

 

[Perplexed]

What ninja hand guard are you gonna use? Pics statement still applies. Do it.

Probably a Samson Evolution or other similar HG with only a top rail, and I'm looking hard at the Ferfrans CRD. Pics will be a while, as I can't find this MD anywhere for a decent price. "Out of stock."

 

[Super Dave]

So something like this little honey:

 

[Gabriel42]

7" HG with 7.5" barrel:
[Broken External Image]