Gas-port regulating gas-block insert install and DIY manufacture.

[markm]

When terms similar to "snappy" are used, what is that in reference to?

Felt Recoil Impulse. We've shot enough combinations to make a rough, yet subjective call. I can surely feel when a combo barely has enough ass to cycle properly/lock back, etc.

[MistWolf]

A sample of one: I compared how my 10.5" shorty ran with a conventional carrier versus the LMT e-carrier. I found that the conventional carrier needed the SLR gas block to be opened up one more click to lock back than the e-carrier did

[markm]

Makes sense with what we saw with the 10.5 lmt. I would have expected it to be pushing towards the sluggish side. I wonder what Pappa's 10.5 lmt would do with a standard carrier.

[jerrysimons]

Round two 718 Inconel

My carbide bits came in, the countersink was special order and took longer. I am pretty happy with the results. It occurred to me that the flat head sot on the concept version serves only to install the insert into the gas-block and that there was other ways to accomplish this without the machining required that I don't have the machine to do. I used a round taper file to grab and hold the insert while threading it into the gas-block, the groves grab tight when tightening. To loosen, since they spiral righthanded, you have to press harder but it also works to get it out.

I ordered a bigger TiN coated carbide end-mill but after someone posted above about being surprised my first uncoated one got dull from one Inconel insert I tried it again. Sure enough it worked fine. I had read Inconel sucks to machine because it work hardens (best at slow speeds with minimal passes) but I didn't realize that is what happened with the first Insert I shortened. Once it cut down a little ways and the surface smoothed out I had to put more pressure on the lever to get it to cut till eventually it was harder than I though it should be and I just assumed the bit was dull. Well the same thing happened with this second insert. The uncoated carbide end-mill works fine.

The 100* 3/16" AlTiN coated carbide countersink worked well to make an index point for the drill bit and provide a little gas inlet.

McMasterCarr didn't have a 1.65mm/.065" carbide drill bit between wire gague sizes 51/.067" and 52/.0635" so I got a .065" carbide reamer to use in conjunction with the .0635" carbide jobber.

[elephantrider]

Wow, looks solid. I wonder if that will even wear at all.

[markm]

The would outlast the barrel. The plain old modified set screws are a small fraction of the strength of that, and they show no wear so far. Again... port erosion is inside the bore. The top of the port on a barrel doesn't erode the way the bore end of the port does.

[MistWolf]

That looks good, Jerry. Nice work!

[tom12.7]

The port erosion is definitely more dramatic inside the barrel bore, but erosion does still occur beyond that. There are many combinations that run into circumstances involving cyclic rate increases during the lifespan of the barrel due to the erosion. The condition is normally worse with the common carbine length gas system, but can be worse in other longer gas length combinations with some lighter bullets and slower powder combinations. There's some higher mileage examples that show erosion in the gas block and portions of the gas tube.
The concept of an external to the barrel orifice that compliments a proper base barrel port is solid for combinations that would otherwise not maintain a more preferred cyclic range span over the course of barrel life. Sure, a lower erosion resistant orifice system could help, but a higher erosion resistant system would be more preferable if tasked to properly compliment the base porting during the complete possible lifespan of use.

[pezboy]

Say you have two identical barrels, one with a port oversized a certain amount and the other oversized twice as much as the first. Would they both require the same diameter hole in the insert or would the barrel with the larger gas port need a smaller hole?

[elephantrider]

Say you have two identical barrels, one with a port oversized a certain amount and the other oversized twice as much as the first. Would they both require the same diameter hole in the insert or would the barrel with the larger gas port need a smaller hole?

According to Clint (BRT) the inserts tend to perform like the size gas port for which they are drilled. As in, a 0.076" insert, acts like a 0.076" port regardless of the size port that it is going over. So they should require the same size insert.