.300 BLK 10” minor function issues

[LockedBreech]

I had a friend who ordered several boutique AR type rifles and managed to have problems with a few, all the while our 90+ issued Bushmaster rifles were perking along just fine.

Just assembling parts that work isn’t like LEGOs and there are reasons every new factory firearm even Glocks should be vetted/broken in with a couple hundred rounds prior to being stamped “Good To Go (until it ain’t)” in your mental gun inventory. Try that extra bcg with a different coating or just get the one you have in the gun worn in.

I assume you don’t just capitulate when another attorney files a counter offer, consider yourself in negotiations with your new toy. It’s a relatively cheap educational opportunity that if nothing else will make you appreciate that DD rifle even more.

The law analogy made me laugh. Advice taken and I’m in good spirits about the learning opportunity.

You can bet my next buy is gonna be a prebuilt though.


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[mmc45414]

I’m not trying to be a dick either but I’ve said 3 or 4 times now I have an off the shelf Daniel Defense for serious work. This was an attempt at building something from scratch to try to avoid the exorbitant cost of a good pistol AR from a reputable maker. I was foolish enough to think I could part out a home-defense-quality rig which is clearly not so, but I never actually put this rifle into serious use.

I get where you are coming from, I do not think you are foolish, I have followed a similar path and have been generally successful, but there was a little bit of a learning curve.
I do not think my rifles are "as good as" a highly regarded brand that should be expected to be turn key, but I didn't trust them to be.
I think a common problem is buying assembled uppers. So much of what is most likely to be wrong with a rifle's function is in the upper and BCG, and I do not think many of the second and third tier brands are meticulously assembled by knowledgeable experts, they are screwed together by people that need a job and got hired and shown what to do. IMO a person's probability for sucess would be better if you started with parts rather than an assembled upper. Another factor is the rifles probably get test fired, assembled uppers probably just get shipped (maybe some at the LaRue, BCM such level test fire uppers).

Might be cheaper than troubleshooting it.

I do not think so, I think you are going to find something wrong with the upper/BCG, and I think once you start looking it will be obvious.
As I mentioned, something is wrong enough that it is causing a big ass spring pushing a pound of BCG/Buffer to STOP, I do not think it will be hard to find out by analyzing the functions of the various components. Or, something is not blowing it back far enough, and with 55k PSI blowing on it, if it is not blowing back until the buffer stops it there is going to be something wrong with the plumbing.

I think the troubleshooting process might need to step back and look at how it is functioning before shooting more.
- There could be a flaw in the chamber, do cartridges drop in and back out without resistance?
- There could be a problem with the bolt or barrel extension, or a tolerance problem between them. I would slowly push the bolt into battery and feel for any resistance, perhaps compare the feel to your DD upper and BCG.
- I would take the handguard off and look at the gas block, I think this is something that is crucial and often haphazardly assembled. If it is a low profile gas block and the barrel isn't dimpled, the location was probably just eyeballed and could be an easy fix, just like in that thread I linked earlier.
- How old is the spring? Maybe it has lost the mojo and has enough left to run the broken in DD upper, but should still be due for replacement.
- You just went to a new BCG, and it could have some kind of manufacturing flaw. Obviously the carrier key needs to not just be staked, but needs to be tight in the first place, if it is loose and staked staking doesn't matter. Maybe there is a flaw with the extractor or spring.

Anyway, my take is that all of the top tier brands (I have some of their parts) can be trusted to be reliable without any/much prove out, an assembled upper from a second tier manufacturer probably not.

[LockedBreech]

Thanks for taking the time to write that mmc. The spring is brand new but from a PSA lower, so checking the spring is definitely the first thing I'm going to do. Easy first step.

I don't think it's gonna be that though, I think you're right about the bolt/chamber. I spent some time riding the bolt slowly home last night and there's definitely something giving it friction / stopping it in the last 5-10% of travel. Going to take a really close look (light, magnifying lens, all that) at the chamber and bolt tonight and see if I see anything obviously wonky, using my worn in, reliable DD as a control group.

[mmc45414]

I spent some time riding the bolt slowly home last night and there's definitely something giving it friction / stopping it in the last 5-10% of travel

I might take it apart and push it home manually, it will normally have some resistance at the point when the bolt hits the breech and then starts to turn, but it should be easy to push it closed with your finger pressure.

[JCN]

Thanks for taking the time to write that mmc. The spring is brand new but from a PSA lower, so checking the spring is definitely the first thing I'm going to do. Easy first step.

I don't think it's gonna be that though, I think you're right about the bolt/chamber. I spent some time riding the bolt slowly home last night and there's definitely something giving it friction / stopping it in the last 5-10% of travel. Going to take a really close look (light, magnifying lens, all that) at the chamber and bolt tonight and see if I see anything obviously wonky, using my worn in, reliable DD as a control group.

As kind of a combination follow up of previous posts, if you hand cycle the bolt when dry (wipe off lube) a bunch of times you’ll see where the shiny spots are and help wear them in.

That’s what I was getting at for mating parts together that might have a little interference / tolerance stacking when new.

Hand cycling a new gun action is something I usually do before starting to shoot it.

I want extensive trigger time with anything I would consider for home defense anyway.

That usually starts with dry fire in the basement.

[SecondsCount]

As kind of a combination follow up of previous posts, if you hand cycle the bolt when dry (wipe off lube) a bunch of times you’ll see where the shiny spots are and help wear them in.

That’s what I was getting at for mating parts together that might have a little interference / tolerance stacking when new.

Hand cycling a new gun action is something I usually do before starting to shoot it.

I want extensive trigger time with anything I would consider for home defense anyway.

That usually starts with dry fire in the basement.

Check the gas key to gas tube interface.

[LockedBreech]

I'll see if I can't get some pics up later.

[mmc45414]

Check the gas key to gas tube interface.

Very good point, would also be a byproduct of gas block misalignment.

[SecondsCount]

There is the SAAMI standard for chamber dimensions, pressure etc.

True, but I was thinking along the lines of the TDP. The SAAMI standards have some wide chamber tolerances.