Loooooong story follows. Hopefully this can help out some other noobs like me.

I purchased my S&W M&P 10 a few years back to have an AR platform with a longer reach than my Colt AR-15 LE6920.

I read and watched several reviews for the rifle then went ahead with the purchase. Out of the box, the rifle operated smoothly and as I expected. Zero complaints.

I knew when I purchased the rifle I would be making modifications, some performance and some aesthetic and that the modifications would occur in stages over time.

The first "mod" was adding a Nikon P-308 scope. Simple and it worked.

Next, I replaced the trigger with a Geissele given the heavy pull of the OEM trigger and my desire to eventually shoot at distance. I was concerned that without a trigger swap, I would shoot less consistently at distance and I really enjoyed the Geissele I put on my Colt so it also created a consistent pull across both rifles.

The mod was a little bit more complex but still nothing difficult. Now it was time to to start messing with other things.

I read about concerns with the handguards attached to such a thin barrel as found on the M&P 10 and that too much pressure against the handguards or barrel could effect shot placement.

So I decide I wanted to install a free float handguard which would require swapping out the gas tube and block. This is when my problems started.

The install seemed to go fine but when I took the rifle to the range, I immediately encountered failures to eject and failures to feed.

I made several attempts to adjust the position of the (non-adjustable) gas block and alignment of the gas tube all to no avail.

I then went to a local gunsmith (our options where I live are minimal) to let him work some magic. I picked up the rifle after a week and was told he fired the 20 rounds I left with him with no problems.

SWEET!! I took the rifle to the range and immediately had failures to eject and failures to feed. My heart sunk. I considered that maybe it was because he fired it in a climate-controlled range and I fired it hot and humid weather. All I knew was I wasn't about to return the rifle to a gunsmith that told me he solved my problem when he didn't.

I was now in a bind in my mind. I didn't trust the gunsmith and I couldn't return the rifle to S&W since I modified the gas system. My research told me my next options were extreme (in my eyes) and irreversible. I wasn't sure that I wanted to commit.

I essentially settled on doing nothing for 18 months and every time I thought about the rifle, I was disappointed with it and my decision to mess with the gas system.

Despite that, I wouldn't sell the rifle as is (I don't like selling things that are broke), so I determined it was time to take take more drastic steps to make the rifle function. If all else failed, I'd research replacing the barrel.

This involved enlarging the gas port and purchasing an adjustable gas block. I bought some nitride(?) drill bits from Harbor Freight (no judging) and confirmed that sizing up the gas port would require a 5/64" bit given a 1/16" bit was too small.

On the gas block front, adjustable gas blocks were hard to find due to most being out of stock. I was able to finally locate an SLR Rifleworks adjustable gas block and went with it. Unfortunately this gas block would not be able to be adjusted with my current handguard on but that was a minor inconvenience. I also ordered a jig to align the gas block which was a great decision and made the gas port/gas block alignment simple.

So I got after it. I said screw it and drilled into my barrel, both to open the gas port and to dimple the barrel to align the gas block. I was amazed at how easily the drill bit went through the barrel. I used a cheap drill press and set it to not drill too deep

I was rather anxious with what I had done but first opportunity I got, I took the rifle to the range. It took maybe five minutes to adjust the gas port to the right setting.

I had the gas block set to half-open/half-closed and it fired a single round, ejected the round, and locked back on the now empty mag. It kicked pretty hard.

I closed the gas block a little more and rinse and repeated several times firing a single round from a magazine with only one round loaded.

I did this until the bolt did not lock back on the empty mag. I then opened the gas block two positions and left it there.

I then fired 5 different kinds of rounds both 7.62 and .308 and various grains.

IT RAN LIKE A CHAMP!!

I am now a happy camper and no longer regret the mods I made. It was a bit scary drilling the barrel having never done such a thing before but the process has increased my confidence in what I can do with my rifles.

Hope this info is helpful to anyone having similar problems.

Time to work on shooting this thing at range.