AR Disease Strikes Again Part II

[44caliberkid]

Sorry Stag, need to borrow your title. My son was thinking of buying a 350 Legend for deer season, but I told him to hold off. I had a budget 450 Bushmaster barrel and an Anderson upper with a big ejection port for the 45's. Scrounging through my parts I found a Double Star full float handguard and barrel nut and a Magpul AR-15 rifle stock that uses an A1 or A2 tube. Found a tube, buffer and spring of unknown origin and my collection of lower parts. I had a Brownells carrier but had to order a bolt, from AR15Discounts I think. Had a Rise Armament trigger on hand but ordered a muzzel device from Next Level Armament.
I put the stock, upper, lower and handguard together and did my own winter camo paint job then assembled the rest of the gun. I have put together a lot of AR's, in .223, 6.5 Grendel, 6.8 SPC, and 458 Socom. I have never had one fail to operate from the get go, except my 6.8, which everyone said needed a 100 rounds to break in, and magically, at the 100 round mark it fed, fired and cycled everything from all magazines. So I take out the new 450 BM, loaded a round in the mag, it chambered, I fired it, no ejection. I opened up the Odin Works adjustable block to 100%. Still no ejection. Back to the bench, I checked gas block alignment and flow. I tried a carbine lower that works with every upper I put it on, still not cycling. So I start reading the internet. 450's are tough to cycle they say, need a bigger gas port hole. Mine measures .077 or .078. A trip to Brownells and I came back with drill bits from .082 to .093. Started drilling bigger holes and test firing. It looks like the bolt doesn't even move. I switched to a good non-adjustable block at one point in case the Odin Works one was the culprit. While working, I notice the buffer recoil spring seems pretty stiff, I'm using a rifle buffer. I find a new DMPS rifle buffer spring and swap that out too. Definitely a lower power spring than what I had. Finally after going to the largest drill size (carbine length gas), I go to range, load a round, fire and the empty pops out. Hallelujah! Loaded up two rounds, it fires, ejects, loads perfectly. Increased to 3 rounds and start getting the scope on target. My son still needs to zero it to his eyes, but my last five shots at 50 yards, with Hornady Black were all touching, looked like the cylinder of a 5 shot revolver with a tiny patch of untouched paper in the middle. More than adequate. We're saving the brass for reloading. Shot 29 rounds in all. Tried to upload some pics but it says my file sizes are too large and I'm computer illiterate.

[44caliberkid]

Ah ha! Figured it out. (Pics)

[stagpanther]

Them big bores can shoot one hole groups and still be over MOA. I had no issues at all with my 458 socom build but I found it made a difference using really good barrel, bolt and receiver parts.

[44caliberkid]

My grandson used the 450 I built to pop a big Iowa doe tonight. Hornady Black at 150 yards went clear through. Big exit wound.

[stagpanther]

Nice--I bet grandpa gets some choice backstop cutlets.