Changing out an AR15 BBL

[ShaiVong]

OK. So im so tacicool that I fire a good 500 rounds through my AR15 a day while doing tactical summersaults, cartwheels and tripple cow sows.. Obviously after putting 575,000 rounds through the old AR (codename Uma), its about time for a new barrel.


Alright back to reality. I have a freefloating handguard installed by BM when I got the upper, and it suxx0rs. Its basically a varmenter vented handguard without the vents . Its not on their sight so i have no idea wth they got it from. How hard is it to remove and replace a freefloating guard? I built the lower myself, do you think its possible for me to get the ole clamp adapter and wrench and take this sucker off? I may just replace the front sightpost as well and get a weaver gasblock that i can slap a flipup on, who knows.

So is it doable by a non-gunsmith? Do you just drift out the pins holding on the front post?

Any recomendations for a light FFing front guard with weaver rails?

 

[ShaiVong]

Bump!

 

[Jeff White]

To take the free float handguard off, you have to drift out the gas tube roll pin in the front sight base, then drift out the taper pins. Have new pins on hand to replace them with when you put it back together.

Putting the new gas block on may not be as easy. It's entirely possible the holes in the gas block won't line up with the grooves for the taper pins that are in your barrel. You may have to take the barrel to a gunsmith and have him line everything up and drill new grooves for the taper pins. You should have no problem putting the original front sight base back on.

HTH Jeff

 

[ShaiVong]

Thanks Jeff; most informative!

Is it a huge issue to take a barrel off? I'm afraid I might have to do that to remove/replace the HG. Does it need to be torqued 'just so'?

I really have no idea how these barrels are even held on.. The only one ive replaced is on a 10/22

 

[Jeff White]

ShaiVong,
The barrel screws into the threads on the upper receiver. It's not that big a deal to change them. They need to be torqued three times to 30 inch pounds IIRC. (my TM is in the basement as I type this) That means you torque it to 30 inch pounds, then back it off and repeat, then repeat again. The barrel nut is part of the handguard in freefloat setups. You'll need a receiver vise block to put the upper in while you're removing and reinstalling the barrel.

Jeff

 

[ShaiVong]

Thanks for all the info Jeff; doesn't sound too bad, and the upside is if i can get this to work I can just start building/modifying my OWN uppers!

The first step is always the hardest!

 

[Jeff White]

ShaiVong,

Well don't blame me when ARs start multiplying in the safe because you look in your parts box one day and decide that with the addition of a couple parts there's a new rifle in there .

Id recommend checking out http://groups.msn.com/TheMarylandAR15ShootersSite a lot of good info there, manuals to download etc.

Jeff

 

[444]

You probably don't have a muzzle brake or flash suppressor on a varmint style upper, but if you do, the muzzle brake presents a serious problem that Jeff didn't mention. Per the AWB, a muzzle brake must be permenently installed on the barrel. In order to remove your front sight tower you need to remove the muzzle brake...................................

I am thinking of doing the same project you are talking about. I have a Bushmaster upper that has a 24" barrel with a float tube. The issue I have with it is that it doesn't have a sling swivel stud on the flat tube so that I can attach a bipod. Now this isn't any big deal. I can drill a hole and install it myself. But, I have been considering transforming this upper into an SPR clone. Or something close. I have considered removing the float tube and installing a four rail fore end. An SPR has an 18" barrel and has a unique looking flash suppressor on it. I am not sure if I am going to go that far or not.

 

[444]

If you are interested here is a link to the AR15.com search engine and a number of threads with pictures of SPRs.
http://www.ar15.com/forums/search.html?b=3

Here is the float tube I will probably use:
http://www.mstn.biz/
PRI Carbon Fiber Freefloat Forend

Here is another more concise version of what an SPR is according to a vendor:
http://www.ar15.com/forums/topic.html?b=2&f=134&t=141410

 

[ShaiVong]

I don't get it.. Whats an SPR? The link said something about a good barrel/can combo? What makes it different from other AR's w/o a can?

 

[Jeff White]

SPR=Special Purpose Rifle. The are built at the weapons center in Crane Indiana. It's different from other ARs in that it's purpose built for sniping. Very handy when you need a weapon for a longer range precision fire application but you don't want to burden a team with the logistics of a different caliber system. The SPR is light and versatile enough to fill other roles besides sniping.

Jeff

 

[ShaiVong]

So its just an 18/20" flat top AR? What do they do special to it that makes it a 'sniper' AR? Match barrel? Good trigger?

I already have like a 1/2# trigger on my bushmaster (got their 2 stage trigger.. but it only has one stage , prolly my fault).

Whats with the special SPR barrel profile?

Sorry for all the questions; just trying to understand why its different in function from a regular 'varment' AR

 

[444]

An SPR is very similar to what you are describing, only for military applications. It is designed for more precise shooting at longer range.
The first thing that makes it different from any other M16 issued by the military is that it has a scope on it.
The SPR has an integrated rail system that allows the use of lights, night vision scopes, IR lasers etc.
That last link I posted breaks down exactly what components make up an SPR.
What makes it different from a varmint AR15 is mainly the integrated rail system and the flash suppresor.