This is just some cautionary advice for anyone new to the ar platform who are looking to buy their first rifle. (factory build). I am rather new to the “black rifles” myself, and without proper research, I bought a new Bushmaster xm-15 m4a3 patrolman carbine last month for 899.99. While I was initially quite happy with my purchase, it didn’t take long before some research made me see the error in my decision. I bought the bushy for a defensive rifle I could trust my life with. Not just for plinking. Now while the bushmaster has ran flawlessly through about 600 rds, I’d be hesitant to depend on it. The gas key is properly staked, but the BCG is the cut out ar-15 style carrier, and the buffer is a light buffer. It has the blue extractor insert. Also, the castle nut is not staked, rather held on with blue loctite. You can easily feel the violent cycling due to the light BCG and buffer. While all of these issues can be remedied, that would mean sinking more money into this rifle, leaving me with simply a glorified Bushmaster. as it sits, rather than spending 900 on this, I would’ve been just as well off buying a 600.00 Del-Ton. For this reason, I went today and picked up my brand new Colt le6920 Socom. This rifle will be ready for any situation presented to it instead of just hoping my Bushmaster will be. So before you go sink your hard earned dollars on a “plinkster”, please take heed when you hear the term “Buy once, Cry once”. Unfortunately It took me buying twice. 
Fix the bushmaster with an H buffer. If it runs, it runs.
well you could have easily staked the nut with a ball peen and punch… Did you sell the bushy? Should have bought a Colt from the start lol. I know… research,…
It’s yours. Assuming that it is feeding and cycling properly I would add an H or possibly H2 buffer. I would get a new quality bolt and stake the castle nut/endplate.
Too bad there’s no fix for that out of spec chamber.
No. I still have the bushy and I plan on keeping it. All in all its a nice rifle, but my intentions were to buy a “go to” gun, and in my opinion, the bushy is not one. sure I could stake the castle nut, put in a new bcm BCG, and a new h buffer, but then I will be close in price to what I spent on the Socom which I picked up for 1400.00. Ill just use the bushmaster for plinking and may even take it to a class this summer to see if it holds up. had I known what I should’ve been looking for in my 1st purchase, it wouldn’t have been a bushmaster…“you live…and you learn”.
If it’s out of spec it’s going to be too tight and it can always be reamed out to proper size.
OP if I were you I’d either drop a little money on the Bushy and bring it up to speed or sell it. I doubt you’d take much of a loss on it.
Good buy on the Colt, with how cheap they are its tough to recommend anything else unless someone is looking for something very specific or high end IMO. Thing is though also I think people get a bit too caught up on some thing. Reading these forums, looking at the “tiers”, hearing all the stuff people say. Fact is that Bushy will probably run fine for years, with a little work probably even better. Heh look at it this way now you got 2 ARs and 2 ARs is always better than one.
I’d wager in the near(ish) future he could sell it for a profit to someone NOT from M4C
so what has actually been found wrong with this particular Bushmaster? Nothing mentioned makes me think it wouldnt be a reliable firearm. contrary to what the internet says, an unstaked castle nut will not cause your house to burn down.
Over gassed, not built correctly, parts not meeting the TDP (which the baseline standard for a fighting gun), etc, etc.
C4
So he determined all that about this gun he owns? FWIW, Daniel Defense guns are notoriously overgassed.
We have no idea what the OP figured out. We have known this for years based off of us taking them apart and or fixing them. DD really aren’t over gassed (in all barrel lengths). Even if a DD barrel is over gassed, it would be slight compared to a BM barrel. For instance, the GP size on a 16" carbine length gas system is .063. A BM will be in the .078 range.
C4
Good luck to you. Keep 'em both. Use them, abuse them, shoot the snot out of them and see what makes them tick.
ill give the OP $400 for his bushmaster, sight unseen, if he would like to be rid of his very unreliable rifle.
As stated, I am keeping the bushy. I plan on breaking the hell out of it so I can see first hand how much abuse all these commercial parts can take. once broken, I’ll upgrade the bcg, buffer, buffer tube so I can call it a fighting rifle that I trust with my life. while I am breaking my bushy, my “battle ready out of the box” Colt will be lying in wait. And I’ll put faith in that. If you have a bushy that you choose to fully depend on, thats your choice. These are all my own opinions.
I’m glad to hear it. I wish you great luck with whatever battles come your way
You’re smart for keeping a completely functional rifle, instead of selling it for a loss. Now is a terrible time to sell because the market is flooded.
You are putting too much stock in what you read online though. If any one of those 600 previous rounds (not a lot, but 600 more than the Colt you are praising) had been shot in self-defense, it would of been successful if you had done you’re part. In real world shooting, it isn’t what you shoot, it’s what you hit.
It’s the hit and miss nature of bushy and other lower quality AR’s. Yes, you can make them good, but why not just buy good, or better right out of the box for a little more or sometimes same price??
Point is, even if a rifle runs, with these improperly spec’d parts, trouble can rear it’s ugly head when you least want it to.
^^ this.