I'm looking to plunk down the bucks for a custom barrel to finish off my SPR project.  Since I'm just starting to look at what's available, I was hoping to get some feedback from you guys.

What I do know is:
1) The profile is set, unless you guys know of any deficiencies to the SPR profile.  
2) I need an M4 extension.  It's going into a LMT upper.
3) Standard muzzle thread.
4) Plan to shoot heavy bullets exclusively, so 1:7 or 1:8 twist.
5) It will probably be stainless.  KG coated.

What I haven't decided on is:
1) Barrel brand.  I know names of the top makers, but what makes one better than the other?
2) The chamber.  I plan to handload and accuracy is key, so chamber choice becomes critical.  I pretty much understand the difference between a Nato chamber, a Wylde chamber, and a SAMMI chamber.  Since I plan to handload for this gun or worst case use factory match ammo, I'm leaning toward the SAMMI chamber.  I think I would prefer the shorter leade (throat) to tinker with accuracy.  Am I correct going with this chamber?  Am I only giving up the ability to run Mil ammo?  Does the Wylde chamber give up a little or a lot of flexibility for handloaders?  Do I have a choice as to a custom length leade, or is this set by the chamber reamer that is used?
3) Most barrel profilers, like Compass Lake offer matched bolts.  What makes the bolt matched?  Is it lapped like a custom bolt gun?
4) Are there any other options that i'm not aware of?

Quoted: I'm looking to plunk down the bucks for a custom barrel to finish off my SPR project.  Since I'm just starting to look at what's available, I was hoping to get some feedback from you guys. What I do know is: 1) The profile is set, unless you guys know of any deficiencies to the SPR profile.   2) I need an M4 extension.  It's going into a LMT upper. 3) Standard muzzle thread. 4) Plan to shoot heavy bullets exclusively, so 1:7 or 1:8 twist. 5) It will probably be stainless.  KG coated. What I haven't decided on is: 1) Barrel brand.  I know names of the top makers, but what makes one better than the other? WOA 2) The chamber.  I plan to handload and accuracy is key, so chamber choice becomes critical.  I pretty much understand the difference between a Nato chamber, a Wylde chamber, and a SAMMI chamber.  Since I plan to handload for this gun or worst case use factory match ammo, I'm leaning toward the SAMMI chamber.  I think I would prefer the shorter leade (throat) to tinker with accuracy.  Am I correct going with this chamber?  Am I only giving up the ability to run Mil ammo?  Does the Wylde chamber give up a little or a lot of flexibility for handloaders?  Do I have a choice as to a custom length leade, or is this set by the chamber reamer that is used? WOA SPR barrel uses a match chamber, very condusive to handloading.  My WOA SPR barrel will not feed M855 due to the tight match chamber.  All this info was verified through a discussion with John Holliger of WOA. 3) Most barrel profilers, like Compass Lake offer matched bolts.  What makes the bolt matched?  Is it lapped like a custom bolt gun? From what I understand the "matched bolt" is a marketing gimmick. 4) Are there any other options that i'm not aware of?

For what you want, you are probably going to have to custom order your barrel.  I am not aware of any of the manufacturers that put M4 extensions on their "target" barrels.  Additionally, you are asking for a specific chamber, so you may also be locked into a custom build.

ADCO's got the inside track on some interesting barrels.  A call or email to them may get you what you want.

Quoted: What I haven't decided on is: 1) Barrel brand.  I know names of the top makers, but what makes one better than the other? 2) The chamber.  I plan to handload and accuracy is key, so chamber choice becomes critical.  I pretty much understand the difference between a Nato chamber, a Wylde chamber, and a SAMMI chamber.  Since I plan to handload for this gun or worst case use factory match ammo, I'm leaning toward the SAMMI chamber.  I think I would prefer the shorter leade (throat) to tinker with accuracy.  Am I correct going with this chamber?  Am I only giving up the ability to run Mil ammo?  Does the Wylde chamber give up a little or a lot of flexibility for handloaders?  Do I have a choice as to a custom length leade, or is this set by the chamber reamer that is used? 3) Most barrel profilers, like Compass Lake offer matched bolts.  What makes the bolt matched?  Is it lapped like a custom bolt gun? 4) Are there any other options that i'm not aware of?

1. WOA barrel.

2. Get the Wylde. It is still accurate enough but will ensure functioning that the tight SAAMI chamber may not give you all the time. The SAAMI chamber is fine for a bolt gun, but can give you fits in a gas gun. The leade angle is set with the reamer. You can not give a custom leade angle. Get it from WOA and you will NOT be dissappointed. You will still be able to get excellent accuracy with your handloads.

3. By matched, they really mean headspaced. Lapping the lugs on a AR bolt does nothing for accuracy, it is a gimmick. As long as the bolt is in spec and is properly headspaced, that is all you need.