GM-M29 barrel

[Leonidas24]

Yes.

Things like the BRT gas tube are great to fix something you already have, or maybe tune a slightly large port. But I don’t think there’s much point in getting a barrel that is substantially off where it should be.

That's worth a discussion in itself. Some would consider .076 to be substantially off where it should be (on an 11.5) and numerous reputable manufacturers (BCM and Sionics to name two) have used that gas port size in the last 10 years. Even more so I've come to the conclusion that the relatively standard size of .076 to be too large for a 16" mid-length. I have an earlier produced Centurion 16" LW that is .080 from FN and currently have it reduced down to .071 using a BRT gas block insert. With the Vltor A5H2 and standard rifle spring it runs everything from Wolf steel up to AE 5.56 with no issues in heat or cold. Now that could largely be attributed to the A5 being so forgiving, but even so a previous Sionics 16" mid I had ran like a top with PMC and an H3 buffer which originally got me thinking about what an ideal port size really should be. Colt reduced their port sizes considerably from industry "standard" by using a .071 on the 6960.

ETA: Where do we draw the line before requiring an adjustable gas block or BRT gas tube become necessary? A considerable number of barrels on the market still seem to be made in concurrence with the lowest common denominator.

[JediGuy]

Ballistic Advantage proved that there can be a balance between mass production and appropriate gas. Other niche manufacturers like BRT and Triarc take this a step further, and you pay for their product.

I am curious about the contention on this board recently that minimum gas shouldn’t be less than required to cycle the bolt while the rifle is pointed straight down.

[Steve-0-]

Ballistic Advantage proved that there can be a balance between mass production and appropriate gas. Other niche manufacturers like BRT and Triarc take this a step further, and you pay for their product.

I am curious about the contention on this board recently that minimum gas shouldn’t be less than required to cycle the bolt while the rifle is pointed straight down.

I will tell you, even .003 more gas makes a difference in a carbine thats either dirty or being fired from an un-shouldered position. Buffer and spring weight play into this as well.

[1168]

GM answered my email yesterday. I’ve been debating sharing this because you bastards are going to buy them up. GM-M29 .059” GM-M19 .076”.

[DG23]

GM answered my email yesterday. I’ve been debating sharing this because you bastards are going to buy them up. GM-M29 .059” GM-M19 .076”.

Not me.

Did all my spare / new barrel buying long before the prices went stupid and it will be a metric shit ton of rounds downrange before I am in need of or wanting anything else...

[JediGuy]

No pencil? No want. I’ll only want a heavier barrel if I can find grandpa’s RDIAS.

[vicious_cb]

GM answered my email yesterday. I’ve been debating sharing this because you bastards are going to buy them up. GM-M29 .059” GM-M19 .076”.

That sounds a bit too small for a 14.5" carbine. Maybe he meant 0.069"? If you do pick up this barrel can you pin gage to confirm?

[1168]

No pencil? No want. I’ll only want a heavier barrel if I can find grandpa’s RDIAS.

They do make those, if thats your thing. One of them is quite appealing.

That sounds a bit too small for a 14.5" carbine. Maybe he meant 0.069"? If you do pick up this barrel can you pin gage to confirm?

If I buy it, I definitely will measure it.