AR: Bolt Carrier Group coating/cleaning question.

[kymasabe]

Long story short, I ended up with two BCG's for my new build and am trying to decide which to use.
1. Palmetto State Armory, Phosphate coating, chrome lined, Carpenter 158, MPI and high pressure tested
2. Toolcraft, Black Nitrite, 9310 steel, MPI, lifetime no-questions-asked warranty.

I don't know enough about either coating to know which will carbon less and be easier to clean.
And, I don't know enough about either BCG to know which one is more reliable and a better product.

[Tacticool1976]

the Black Nitride will be a bit slicker that the phosphate...

use the Toolcraft bcg as your main and keep the PSA as your backup..

i myself run a Failzero nickelboron bcg and love it, i also have a Spikes Tactical phosphate as a backup and the original BCG that came with the rifle as another backup..

[LBussy]

In my experience, the BCG is one of the easier parts to clean. It's not like trying to clean the damned chamber. THAT design ... I'd love to punch Stoner in the throat for that one. If I had a dollar for every hour I spent trying to clean that area ....

I agree with @Tacticool1976, the Nitride should be slicker. I don't think it will actually make much difference in practice however. If it were me I'd build another one and use the bolt in that.

[kymasabe]

Originally Posted by LBussy

I agree with @Tacticool1976, the Nitride should be slicker. I don't think it will actually make much difference in practice however. If it were me I'd build another one and use the bolt in that.

Well, since I have now have a spare BCG and charging handle, was thinking of using the Toolcraft in the AR I'm building and possibly using the PSA in a .300 Blackout future build. Or, as you guys suggested, keep as a spare.
And Tacticool1976, I agree on Nickel Boron. I had an Aim Surplus EXO nickel boron BCG in my last build, loved that thing, but wasn't in the budget this time.

[marine6680]

I'm not a fan of the coatings... I had a few nickel boron ones, every one caused timing issues.

I prefer the 158 carpenter steel bolts, the 9310 bolts are said to be better by some, but it's actually a bit give and take, in that it has a couple properties that are better, but others that are worse.

The nitride might be easier to clean than phosphate... I have not tried one. I am wary about timing issues cropping up with them as well. They may be fine though.


As far as cleaning... I have toned down the level of detail I pay when cleaning... The AR simply doesn't need to be spotless to work.

[LBussy]

Originally Posted by marine6680

As far as cleaning... I have toned down the level of detail I pay when cleaning... The AR simply doesn't need to be spotless to work.

Is there a therapy group for that? Because it's been a LONG time and I get itchy when my weapons are not "arms room clean."

[marine6680]

Lots of will power... That's about all that can get you through...

Otlr you can remind yourself that regular cleaning to that degree is likely bad for the gun...

[LBussy]

Originally Posted by marine6680

Lots of will power... That's about all that can get you through...

Otlr you can remind yourself that regular cleaning to that degree is likely bad for the gun...

I've just gotten to the point where I can let them go till the next day.

One step at a time, it's a process, etc.

[Mobuck]

The BCG on my Adam Arms piston upper appears to be Melonite coating. Takes almost no cleaning beyond wiping down. Of course, I don't rattle bang bang and seldom fire more than 10-20 shots per session during zero check and a bit of varmint control. The carbine gets cleaned once a year.

[stagpanther]

As a personal preference--I almost always go with an NIB BCG with an enhanced bolt--but that probably makes little difference in a "conventional" 5.56 build. My opinion is that the importance of precision of alignment of the BCG to the centerline of the receiver and barrel extension/ bore as well as tuning of the gas system far outweighs what the BCG is actually made of.

[MagnumWill]

Get a piston upper if cleaning is your primary #1.

Honestly, either BCG will work just fine. I have 3 PSA bolts and a BCM and they all work equally. I kind of exclude my PWS as it’s kind of it’s own animal, but I can put 100 rounds through the PWS and it literally looks like I haven’t fired it, it’s so clean.

[mellow_c]

Marine,

What kind of timing issues did you have with nickel plated bcgs? What sort of gas system, buffer weight were you using? I've never heard of timing issues due to a bcg having a slicker coating. I'd like to know what you've experienced so i know what to look out for just in case.

[stagpanther]

Marine,

What kind of timing issues did you have with nickel plated bcgs? What sort of gas system, buffer weight were you using? I've never heard of timing issues due to a bcg having a slicker coating. I'd like to know what you've experienced so i know what to look out for just in case.

I'm sorta stumped on that one too.

[marine6680]

Early unlocking... Mid length gas system, buffers from H to H3... Buffer helped but never eliminated the problem.

Followed the BCG every time... Checked in multipul rifles, ones I knew worked fine.

Happened three times with 2 different brands. Raineir and PSA. Tried buying one twice, and the third time it came with the upper... All ended up returned for standard BCGs.

[stagpanther]

Early unlocking... Mid length gas system, buffers from H to H3... Buffer helped but never eliminated the problem.

How does a carrier being coated with NB cause early unlocking (usually the bolt lugs themselves are not coated)? I'm asking with genuinely curiousity and respect--not being argumentative.

[JeepHammer]

I always wondered why both upper & BCG were coated, one without reguard to the other.
The two coatings often don't get along with the other many times...

I don't know how other builders do things, but I lap the upper to both size, and smooth.
Anodizing often leave a rather rough surface, and since it's a corrosion finish, it intrudes into the bore of the upper. I remove that intrusion, lapping makes the upper much smoother reducing friction and allowing lubrication to work more effectively.

I 'Blue' BCG and work it in the upper to determine where friction points are.
This allows me to give tight spots extra attention, polishing spots that grind the hardest.

As for BCG, I check each for fit.
Your gas key is supposed to butt up against the gas tube, not bend the tube or leave a gap.

When the BCG is properly made, and the bolt 'Tail' is fitted together correctly, the firing pin can be fitted where it DOES NOT dimple the primer as the bolt closes.
I cringe every time I see an AR dimple the round it chambers!

As for cleaning, bottle brushes! Tubing brushes work also.

In the military, we used a shot of 'Pam' (cooking spray) in the upper above the end of the gas tube, and on the bolt tail/BCG bore. It made cleaning MUCH easier.

A shot of ZEP 45 or Kroil in the chamber nut lugs makes them a TON easier to clean.
I mop mine with Kroil and run, works really well.

Brownells has some great NYLON chamber/lug brushes, nylon never scratches or gets matted down like bronze or steel brushes do.

It's not common at all, but the best way to keep carbon from 'welding' itself to parts is simply polish the metal. The slicker it is, the easier carbon & crud is to get off.
Most people don't want to pull the barrel, then the chamber nut to polish, but it does help with solid, CONSISTANT lockup & cleaning.

[marine6680]

All the coated BCGs I usually see, have both the carrier and bolt coated.

The only thing I can hypothesize is that the coating does reduce friction, enough that it reduces lock time. The carrier speed is increased a bit and the bolt opens easier.

I don't know for sure, but every one has had the same problem. Signs of the bolt unlocking while there is still pressure in the chamber.


Meanwhile, I will just keep my parts fairly stock/normal... I'm not looking to shave off a tenth or a few hundredths off my group size. So no lapping and grinding and polishing in my future.

I have a rifle capable of sub moa with good ammo, which is plenty for me, and a couple that can do moa with good ammo, and 1.5 with decent quality stuff. Which fits the roles they are built for.

[stagpanther]

Hmmm about half my builds use NIB BCGs--though the bolts themselves are generally enhanced hardened steel so the lugs and face are generally not simply NIB coated. I've never noticed any reliability/timing issues compared to other types of BCGs--lock up timing I've generally found to be much more an issue of barrel gas system configuration--or simply how well the components are aligned. But I could be missing it without noticing it.

[mellow_c]

marine,

Now I've got to ask... what signs should one look for to tell if a bolt is unlocking early?

[marine6680]

Ejector swipes on the case head usually.

That is an indication that the bolt is rotating while there is still pressure in the chamber, forcing the case head against the bolt face and against the chamber walls. The case is held tight against the chamber and will not move... When the bolt tries to rotate against a static case head that is pressed against the bolt face from the chamber pressure, the ejector channel causes a deformation in a swiping pattern.

If you don't reload you are likely to never notice it happening... And it isn't necessary a big problem. It can be a reliability issue though. Being that the whole unlocking and extraction process is working harder than. It needs to. Putting excessive stress on components.

Another reason I recommend midlength over carbine length gas systems.

[stagpanther]

I don't know how other builders do things, but I lap the upper to both size, and smooth.
Anodizing often leave a rather rough surface, and since it's a corrosion finish, it intrudes into the bore of the upper. I remove that intrusion, lapping makes the upper much smoother reducing friction and allowing lubrication to work more effectively.

I too have found uneven finishes can affect the true of the receiver's bore--one violator being cerrakoted receivers where the paint coats the inside of the receiver (sometimes can throw functionality of other parts as well).

[JeepHammer]

There is 'Good Enough', which is fine if that's what you are after.

Sub-MOA takes the same care, fit & finish on an AR as it does on a bolt rifle.
The myth a semi-auto doesn't need a bolt face square & true with the barrel is simply wrong.
The myth a multi-lug rotating AR bolt doesn't need to lock up squarely on the chamber lugs is also a myth.
Same rules apply.

In a lot of cases, polished surfaces, particularly carbon steel parts, clean MUCH easier when polished.
About all metals clean easier simply because places the crud can get ahold of are reduced.

There is interference, parts making contact that shouldn't, or parts making contact with excessive pressure causing premature wear.
Sizing the upper properly for the BCG takes 5 minutes and makes a bunch of difference.

As for 'Lock Time', that is time between trigger releasing hammer & ignition of primer.
Hammer swing time, firing pin movement time, etc.
Lock time is hard to reduce in an AR, some folks use titanium firing pins, lighter hammers, etc, but it really doesn't effect actual lock time very much.

Lubricants, coatings, etc might DECREASE 'Cycle' time, the time it takes to extract, eject, cycle the bolt to the rear, pick up the next round, chamber that round & lock the bolt into battery...
Again, I'm skeptical since a SLOW Cycle makes for a much smoother cycling.

Just like every adjustable gas system maker tells you, only open the gas port enough to cycle the bolt, slowing the cycle time, which is still much faster than any normal person can get on target again.
I can't see any advantage in speeding up the cycle time on a semi-auto (unless you are some 1 in 10 million freak that can beat the disconnect in reaction time).

Before you can let off the trigger to release the disconnect, and pull the trigger again, the bolt has had plenty of time to cycle, so I don't see an advantage in speeding up the cycle time, I've never met one of the 1 in 10 million either, and I build race guns fairly regularly...

What I do is first & foremost, make sure things fit like they are supposed to.
Then I reduce excessive friction to REDUCE WEAR.
Reduced wear means the firearm functions correctly much longer.
I like reliability, reduced wear provides reliability.

It's like rounding over sharp edges on feed ramps, rounded & polished means the rounds feed more reliability, and the ramp edges don't carve up your bullets on the way to the chamber.
Now, if you like carved up, odd shaped bullets, by all means, use the roughest, sharpest, most poorly machined feed ramps you can find, it's fine with me if that's what you are looking for...