Good Golly Miss Molly

[DanDeMan]

Good Evening,

During today’s 7mmBR / TPP HP Hunter load testing an issue that has been lost to the cobwebs of my mind came roaring back.

Since this rifle is not mine, I’m only doing load-testing and some other experiments for an article to be published in the future, I’ve only shot naked bullets, no moly.  There has been quite a controversy about the effects of moly-coated bullets on a number of possible benefits.

I’ve been shooting them for about 9 years and will continue to do so.  The main reason that was discovered way back then was because one could gain about 50 to 75 fps out of minimum case capacity sized cartridges over naked bullets due to reduced friction between bullet and barrel.  Another benefit that this shooter has seen is much quicker clean-up.  Two wet patches and one dry and that is it, no brushing needed as the carbon fouling just does not stick to a bore that shoots only moly-coated bullets.

After 10’s of thousands of rounds through 6mm, 6.5 and 7mm barrels using moly-coated bullets and the above listed cleaning technique (match quality barrels only) it was noticed that whether the barrel was clean or had 500 rounds through it the bullet would go into the group.

Today’s testing highlighted that effect because it does not exist with naked bullets.  And, there is much more carbon fouling in the barrel with naked bullets.  The patches tell the tale as they are much dirtier.

The cobwebs were cleared during the 6-shots used to foul the barrel before load-testing commenced.  The first shot was over 1” higher than the next 3 which were 3/4 “ above the last 2.  That is a vertical dispersion of almost 2 MOA between a clean and fouled barrel.  I have never seen that effect with moly-coated bullets so long as the above list cleaning technique was used.

Those that have derided moly-coated bullets should reflect on this effect and the reduced carbon fouling to decide whether moly-coated bullets are worth the extra effort.

Speaking of extra effort, most moly-coating techniques are less than adequate.  The technique this writer uses is quick and simple and produces well coated bullets that do not leave moly on the hands from handling the bullets.

That moly plated technique is:

Dump 1,000 bullets into a MidWay USA vibrating tumbler.  Add the appropriate amount of moly.  Run for 45 minutes.  Remove bullets and place in RCBS Sidewinder Tumbler filled with corncob media and run for 1 hour.  Sift out the media and you will have 1,000 bullet perfectly plated.

[Jason]

What brand of barrel are you using, what moly are you using, and what is on your "wet" patches? I have avoided moly-coated bullets because of all the extra effort and mess involved, but I have a rifle that I'm about to have rebarreled and have the tumblers to do the coating with. I seriously hate taking up a lot of time cleaning that I could be using for loading or shooting, so I might start using moly bullets because of less mess and effort involved.

As others have already said, thanks a lot for relating all this information (this post and others) to us.

[DanDeMan]

Jason,

A Shilen Match barrel is on the 7mmBR/TPP.

The moly used is from MidWay.  I purchased their Moly kit back when it was on sale years ago.  Don't add anything but bullets and moly to the vibrating tumbler.  And, don't touch the bullets as the oil from your fingers will mess up the plating process.  I gently dump the bullets right out of the box into the tumbler..  The moly plating process used by the commercial bullet manufacturers is horrible.  It flatens the meplats, a very bad thing and leaves a nasty coating of moly on the bullets.  The NECO process should be avoided at all costs.  I known, as it was used for about a year back in the mid-90's.

If done correctly, as per my suggestion, moly plating 1,000 bullets is quick and not a mess to deal with.

[sdwooster]

Dan,

  What is the right amount of moly that you use with 1000 bullets? Your method sounds good and easier than the one i use. Is the sidewinder a must for the corn media? Or can you use a vibrator style?  

                                            Steve

[DanDeMan]

Steve,

How much moly I put into the vibrating tumble depends on how much is at the bottom of the tumbler from the last batch.  After the bullets have vibrated for about 45 minutes they are removed by a large, slotted spoon that allows most of the moly to remain in the bowl.  I've been using the same bowl for about 8 years so there is a nice buildup of moly on the inside of the bowl as well as typically some loose moly on the bottom.  If one is starting with a new bowl I'd add about 1/2 teaspoon of moly per 1,000 sprinkled over the top of bullets.  Since my old bowl is well "seasoned" I add about 1/4 teaspoon.

I don't think using a vibrating tumbler with corn cob media will work as it is doubtful whether the bullets will move through the media.  My guess is that they will stay at the bottom of the bowl, but give it a go and let us know if it works.  Let it run for an hour.

When the bullets are removed from a RCBS Sidewinder full of corn cob media they are very shiny and there is no moly on the hands when handling the bullets.

The clean barrel test was run again with naked bullets during the last 7mmBR / TPP load-testing session at 100 yards.  Sure enough a 5-shot group produced a vertical line about 1.5" long.  It's the darndest looking target.  A picture will be included in the article for grins and chuckles.  This is the second time the same result has been observed after shooting a 5-shot group out of a clean barrel with naked bullets.

[still_learning]

Hi Dan,
I shoot moly bullets also, but hear conflicting data about cleaning the barrel.  When I Google moly cleaning, I can find some national match shooters claiming they go several hundred rounds between cleaning, others who say you still have to clean as before, or a moly ring in the barrel at various points will cause pressure problems.  Life with a rimfire is simple; you can shoot it until the groups start falling off with no other affect.  I tried this approach to my 6.5 moly and discovered several hundered rounds later that the groups still held and the first shot was on mark.  Now I'm getting concerned about the buildup..I can't see any, but then again I don't really know what I'm looking for either.  Using the Kroil/Butch bore shine approach cleans the bore, but then it takes a session at the range to get the bore seasoned again.  Two questions:  what do you recommend for cleaning frequency, and what about the build up, is it a real problem with several hundered bullets thru the bore?
Thanks,
Michael

[DanDeMan]

Michael,

The “moly ring” is a function of a poor moly-plating process.  These processes typically produce bullets with clumps of moly on them or too heavy of a coating that does not adhere properly and that produces moly buildup in the throat area of the chamber.

A friend decided to try moly-coated bullets a number of years ago.  He was using a process that did not work well.  During his first HP Silhouette match shooting the moly-plated bullets he had serious pressure excursions that finally resulted in his bolt sticking badly.  Once we got his bolt open he and I discussed his load.  When his rounds were looked at the problem was at once obvious.  His bullets had clumps of loose moly on them.  Once the bullets were wiped off and his chamber throat brushed out to remove the moly build-up the pressure problems disappeared.

If one’s bullets are properly moly-plated there is no moly build-up in the barrel.  A proper plating process produces bullets that are shiny, with a thin coating of moly, no loose moly on the bullets whatsoever and the bullets can be handled with no moly coming off on the hands.  Finally, the bullet meplats should NOT be flattened from the plating process.  Flattened meplats cause substantially reduced ballistic coefficient of the bullet, not a good thing.  Oh, and no wax should be used in the process.

As to cleaning the barrel when using PROPERLY moly-plated bullets, two wet patches with any good cleaning solvent like Butch’s Bore Shine followed by a dry patch is all the bore needs.  This simple cleaning process every couple of hundred rounds is sufficient so long as one is using high quality, clean-burning powder.  If low quality powder is used, that deposits large amounts of fouling, then cleaning more often is required.  I use the VVO N100 series powders.  They are the cleanest burning powders I’ve ever used.  That certainly contributes to my rifle’s ability to maintain top accuracy with very infrequent barrel bore cleaning.  Of course we are talking about match quality barrels, not factory barrels.  The chamber and lugs should be cleaned more frequently with special attention focused on keeping the lugs clean and well lubed as well as the primary extractor surface on the bolt handle.

[stsbuyer]

Dan,

I have several hundred of Sierra's 6.5mm 107 and 142 Matchings that have the moly coating. Could I tumble them in a sidewinder to get the better finish that your getting with your method? I have an extra Lyman Turbo tumbler that I could set up just for moly and will do my own from now on. But sure would like to clean the ones I have.

Thanks,

Paul

[DanDeMan]

Dan,

I have several hundred of Sierra's 6.5mm 107 and 142 Matchings that have the moly coating. Could I tumble them in a sidewinder to get the better finish that your getting with your method? I have an extra Lyman Turbo tumbler that I could set up just for moly and will do my own from now on. But sure would like to clean the ones I have.

Thanks,

Paul

Paul,

Sure, just fill the Sidewinder with corncob media, add your moly-coated bullets and let the tumbler run for 45 minutes to 1 hour.

[still_learning]

Thank you Dan.  Your reply helped tie up the loose ends.  If I could ask one followup question, and this is a bit off topic, but this barrel normally shoots in the .5 to .6 range at 100 yds, but when it gets too hot to touch, the groups drop a bit and shrink to the low .3's.  Any idea why they shrink instead of opening up?  Thanks again,
Michael

[DanDeMan]

Thank you Dan.  Your reply helped tie up the loose ends.  If I could ask one followup question, and this is a bit off topic, but this barrel normally shoots in the .5 to .6 range at 100 yds, but when it gets too hot to touch, the groups drop a bit and shrink to the low .3's.  Any idea why they shrink instead of opening up?  Thanks again,
Michael

Michael,

As you and most that read this site know, if a barrel has residual stress in it from the manufacturing process there is a tendency for the bullet's point of impact to shift as the barrel heats up from shooting a number of rounds in a relatively short time frame.

Since you are experiencing the opposite affect you barrel probably does not have residual manufacturing induced stress.

My initial thought is that the MV goes up as your barrel temperature increases from firing a number of rounds.  There are two ways you can test for this.  The first way is to shoot several consecutive 5-shot groups over a chronograph to see if the shrinking group size correlates with increasing MV.  The second way is to add 1/2 grain more powder to your load and see if the group size is smaller than your standard load.

[DanDeMan]

Good Afternoon,

A report just in from Mark Varner that shows a MidWay vibrating tumbler will move moly-coated bullets through the corncob media to polish them.  That means one does not have to purchase an expensive RCBS Sidewinder tumbler for the second step in the moly plating process.  I'd suggest at least 1 hr runtime on the polishing process.

[still_learning]

Thanks Dan.  I just returned from the range.  The last shots were faster.  Also, I tried moly'ing the bullets yesterday.  The bullets were still mostly copper looking, but smooth and slippery. They felt ok, but did not look like grey like the Scenar or AMAX moly bullets.  Is this normal for "home brewed" moly coating, or do I need to add more moly?  Thanks for your time and willingness to share your knowledge.
Michael

[DanDeMan]

Michael,

Your moly-coated bullets should have a consistent, dark gray coating.  Here are three important moly-plating process parameters to monitor:

1. Bullets should not be handled or dirty.  They must be clean and oil free.  Oil from the skin can reduce moly adhesion.  If the bullets are dirty or have been handled they should be degreased using a solvent that leaves no residue and completely dry before plating.

2. Sufficient moly should be used.  This is one case were using too much is OK.  Not using enough will produce plated bullets with insufficient moly on them.  Excess moly remains in the bowl to be used for the next batch of bullets.  One should dedicate a new bowl to the moly plating process and not use it for anything else.  It should be thoroughly cleaned and degreased if it is not new.

3. Run the vibrating tumbler with the bullets and moly for 45 minutes to 1 hr.

[Arizona Jake]

As Dan mentioned, bullet surface cleanliness is of key importance to get good adhesion of moly disulfide.

I dump 500 bullets into a small plastic container, pour a little white vinegar, slosh the bullets around for a few minutes, drain the vinegar and rinse them a few times with tap water. I then dry the bullets on a clean towel and put them out to air dry in the sun (to evaporate any water trappend in the hollow points) for a couple of hours.

Vinegar, being a weak acid, quickly removes any surface contamination and surface oxidation from the bullets. Additionally, it will produce a micro-etch on the surface, enabling better adhesion of molybdenum disulfide.

The bullets then go into the tumbler to be moly-coated. I remove the bullets from the tumbler by hand, using a rubber glove and use a couple of old, discarded towels to remove excess moly.  The bullets end up with a bright, silvery finish.