Home Forums Hunting & Shooting AR and Tactical Rifles Barrel swap question

Been fooling with this bushmaster, and thinking of replacing 16" factory pencil barrel with 20" faxon gunner profile barrel. I believe this would tighten accuracy, & quiet it down a little. My ? Is with a rifle length gas system would I have to change buffer? Also just recently put a 1 2" mlok freefloat guard on, would it cover the gas block on a 20" barrel ? Would like to make this rifle more accurate & fun to shoot. Any info is appreciated.

Well, after looking again that barrel is out of stock. Other recommendations, & still need answer for above questions.

No on the buffer. The gas depends on if it has a mid or rifle gas tube now. If it has a rifle no change, a mid you just need to change the tube ($10-$15).

It has a carbine length gas tube. If I got a 20" barrel I would need a longer gas tube & a new block for a thicker barrel. Are the buffers the same? Also what are some decent barrels that won't break the bank?

Seems as though most barrels are out of stock right now. Looks like I'll be waiting.

Unless you are going to a 20 inch HBAR varmint barrel without a step down - the gas block journal should be 0.75 at the landing - usually the same as your carbine barrel - unless you have a "true" pencil barrel with the .625 gas journal. A 0.75 won't break the bank - they're very common.

The barrel specs from the manufacturer will tell you what size gas block is needed - unless it’s a marginal manufacturing.

Ballistics Advantage, Rock River, Wilson Combat, White Oak Armament - all should be good out of the box.

You need a roll pin punch for the gas tube pin, and I’d get an extra pin if you have a cluttered work area - it’s tiny.

12 inches of handguard should put you within a 1/4 inch or less, of the backside of the gas block - the gas block will be exposed. but the gas tube should be covered.

It is a true pencil barrel. Most things are sold out, but I ordered a 18" mid length green mountain barrel. It's a medium profile fluted 223 wylde. Is there anything I should know about the barrel swap? Seems pretty straight forward.

There are many threads here on barrel swapping. Use the proper tools, is the main thing. We also recently had a good discussion on bedding barrels to improve accuracy. Some good info in some past threads, if you care to look them up. Your initial plan to go with a 20" barrel was a good one, for the stated reasons in your op. I'd also add that the rifle length gas system and 20" barrel is very soft shooting. The barrel and gas system you ordered isn't going to be as soft or smooth shooting as the 20" rifle length system. Just so you are aware. It sounds like you were wanting to keep noise to a minimum as well. I'd suggest running a good linear compensator, instead of a muzzle brake. It helps with redirecting the sound and concussion.

Your buffer might stay the same between these barrels. It depends partly on how big your gas port is. These can vary depending on manufacturer. Just try the original buffer and then if it doesn't work quite the way you think it should, try different buffers. I realize that can be tricky with the availability of parts right now but that's the route I've taken in the past.
Keep us posted on your progress.

Got the barrel put on a couple of days ago. I made a mistake in earlier post, it's rifle length not mid length. I fired 2 into the ground after installation. Everything went well, got to get to the range later this week. I have high hopes for this Green Mountain barrel. I'll post back with results.

BSA, if the barrel works out well I may get a linear compensator to replace flash hider. Which one do you suggest.

Kaw Valley is a good one. I'd also be tempted to try an Ultradyne. If I could get an ultradyne for my 6x45 (odd ball 9/16x24 threads), I'd be all over it and buying another set of their flip up sights. Some other good, yet inexpensive, linear comps to consider are the XN series that you can find on ebay. I was using one on an 18" barreled rifle and it worked great:


So much in fact that I put one on my 6.5 Creedmoor:


I believe they call it a "sound forwarder" XN 6.5, but is a linear comp. Accuracy is not affected:

and is much quieter than a flash hider or muzzle brake.

I shoot a 20" H-Bar barrel or a carbine barrel and leave all the guts in the tube, the buffer is a medium weight.
With just the barrel & gas tube you might want to try a different weight buffer, but see how it shoots first.
My 20" is quieter to me than my 16" because there is less blast concussion, but you still get some from the open chamber.
E-bay has ton's of barrel devices, I have some short and some long, they make it a little better as far as blast.
I hate brakes because I hunt alot with mine, the open chamber adds noise at the shot, if you shoot a AR and a bolt action side x side
both with a 20" barrel it's quite a difference.

Barrel swaps are easy if you have the tools. It's a 20 minute job with the tools. Without the tools its doubtful it can be done without tearing something up.

kwg

This Green Mountain barrel tightened things up. Me & my dad shot 35 rnds off sandbag @ 200yds. Half were 223 frontier 55gr fmj, other were Winchester green tip 5.56. We were shooting 2" groups with an occasional flier. This is a great improvement over the pencil barrel that came on rifle. Need a rear shooting bag setup to steady things. All in all I'm happy with this barrel. Btw BSA, that's a good looking gun & some nice groups.

I had good luck with a Green Mountain barrel from Keystone. They shoot good!

Some of the guys at my club run them. They seem to do well. Sounds like the op's is off to a good start.