Why haven't coated bullets become more popular?

[Maple57]

Back in the day I was running 75 grain moly coated bullets in my 223 for F Class... At the same time and at the same range, Maynard was running them as well for TR... before we knew any better.

One day I got curious about it and did an in depth chronograph review of moly vs un-coated.

What I found was contrary to all marketing propaganda in favor of moly.

Moly is a lubricant... or claimed to be a lubricant... so if true, then velocity should increase with moly... not decrease.

What I found was a consistent decrease in muzzle velocity... so if moly is a lubricant, it is obviously less effective in that role than copper.

Second problem is that moly is Hydroscopic... meaning it attracts water.... so how many guys want their barrels coated with something that promotes rust?

Thirdly... Velocity spreads were far worse with moly coated than plain copper.

So... ya... I still have about 500 rounds of 20 year old .224 Hornady 75 grain moly coated Amax if anyone is interested.

 

[maynard]

No, moly will decrease the pressure required to move the bullet down the barrel decreasing friction therefore decreasing velocity. Where Gary's bullets coated with HBN and loaded with 47.0 gr of varget were not super sonic at 900m. The same uncoated bullet with 1 gr less powder were supersonic. Very plain to see uncoated bullets have more velocity. This was only brought to light because of the use of electronic targets that need super sonic bullets to pass through the target.
As the sport evolves and increased use of e-targets become the norm, what happens if a shooter shows up with an accurate load that is just under super sonic at 900m or 1000 yards. Pretty tough to test when your only practice time at that distance is the match.

 

[diopter]

X2. Electronic targets use normally three sound sensors around target frame to triangulate the sound of the bullet passing between them. There should also sound sensor at firing point to the firing of the shot. If shot fired but no reading at target frame then it's a miss. or crossfire.

 

[maynard]

Actually it is a 5 microphone system. The two mounted one in front of the other on the bottom left of the target also act as a chrony to give you a velocity at the target. If a bullet passes between the target frames a red arrow will be displayed indicating what side of the target the bullet passed. There will be lots of growing pains and rules may have to change a bit as we move more and more to e-targets.

 

[scout]

Moly is a lubricant... or claimed to be a lubricant... so if true, then velocity should increase with moly... not decrease.

What I found was a consistent decrease in muzzle velocity... so if moly is a lubricant, it is obviously less effective in that role than copper.

Second problem is that moly is Hydroscopic... meaning it attracts water.... so how many guys want their barrels coated with something that promotes rust?

Moly is a lubricant, but does not last the length of the barrel on a bullet. Rather, it reduces the engagement friction of the bullet into the lands. The reduction in friction is a reduction in pressure ... which is a reduction in velocity. The advantage to coating bullets is that the velocity can be recovered by adding more powder and still having a lower chamber pressure at the same velocity.

On the hydroscopic front - SS barrels on the prairies are pretty safe form rust, so I've never been concerned about barrel corrosion and moly. But shooting in high humidity conditions such as rain or pulling cold ammo out of the truck to start a match tends to attract moisture to the bullets, which increases the friction coefficient ... and primers start getting popped. I've switched to hBN.

 

[maynard]

If you put enough rounds down the barrel you will get moly all the way to the muzzle.lol Real PITA to get out when switching back to bare bullets. Let's just say it is a multi-day cleaning adventure using Kroil, JB bore paste, foaming bore cleaner and a big bag of patches.

 

[scout]

If you put enough rounds down the barrel you will get moly all the way to the muzzle.lol Real PITA to get out when switching back to bare bullets. Let's just say it is a multi-day cleaning adventure using Kroil, JB bore paste, foaming bore cleaner and a big bag of patches.

Been there, done that ... lol ... and hBN seems to be tougher to scrub out than moly. I can understand that bare might be better for TR when you have to deal with issue ammo at the international matches.

Going back to the original post, I'd say that coating bullets is going out of favour due to the time involved to coat the bullets (plus initial expense if you go the NECO process), some consideration of the negative perceptions around barrel corrosion, and you can still get good results with naked bullets. All said, if I didn't have to deal with rain in match conditions, I'd have stayed with moly.