My experience Barrel Lapping and what I’d do differently next time

[Bernie7]

Hello Friends,

I just wanted to share my experience performing a barrel lap on my Western Airguns Rattler .357.

Equipment used:

• Tipton Ultra Gun Vise
• J Dewey .30 Nylon coated 36” rod
• J Dewey .30 cotton bore mops (lap compound)
• J Dewey .357/9mm bore tips (cleaning)
• Dewey Universal Patch Loop
• LGBA - Converts .30 & .35 cal. Rods to accept 8/32 brushes
• No name cotton swabs
• Wooden dowel from Ace hardware
• JB non embedding bore compound
• JB bore bright
• Frog Lube Super Degreaser (Solvent)
• Frog Lube Paste (CLP)

I had removed my barrel and placed it in the vise. Cleaned it extremely well with patches using frog lube degreaser. Having only shot it once : ( and it being a PCP it didn’t need penetrating oil. I mention this because in all the tutorials I watched it appears Kroil is routinely used..

I was in a bit of a tough situation though. The moderator was attached with blue loctite and I live in a small apartment in the city with no good ventilation and nearly no workspace. I decided I’d leave it on instead of busting out a blow torch. This proved to be fine, although likely a foolish decision simply due to making things more complicated than they needed to be and overestimating the hassle/difficulty in removing it. Once it was sufficiently clean, I measured a piece of dowel so that when everything was positioned against the wall it would extend through the suppressor and slightly into the barrel to prevent the brush from accidentally exiting the barrel and damaging the crown.

I measured the total distance to the end of the dowel which came to 27”. I took some painters tape and marked 9” and 18” on the Dewey rod.

I started by applying a heavy dose of JB bore compound onto a .30 mop and proceeded to perform 33 back and forth strokes to the 9” marker watching to ensure the rod was rotating with the rifling and attempting to keep it somewhat centered. There was some resistance, but not a lot.

Almost immediately the bore mop darkened. I continued until I reached 33 strokes, at which point I applied more jb’s to the mop, removed the 9” indicator and performed another 33 strokes, this time extending to the 18” indicator. I removed the mop completely half way through, and rotated it 180 degrees before reinserting it knowing my Dewey rod had a slight bend. Upon completion, I applied more compound, removed the 18” painters tape marker on the rod and performed another 33 strokes, this time just going from breach all the way to the end where I hit the dowel.

I then performed standard cleaning alternating with dry patches and degreaser patches until they came out clear. I took a video with a borescope to document the change after each step of the process.

Next up was the bore bright. This time I decided (due to it being less abrasive), I was going to do full length passes for every stroke. I set it up, same as before with the dowel blocking me from accidentally exiting the barrelI and damaging the crown. I did 60 strokes and then just like before, cleaned the barrel, alternating wet and dry.

I immediately noticed a difference where the patches moved much more smoothly through nearly the entire barrel until they approached the crown where I hadn’t done any polishing.

Again, I took a video to document the change.

Finally I applied Frog Lube paste to the inside of the barrel. Somewhat interestingly, even though I’d thought I cleaned the barrel really well already, it appeared there was still dirt and grime that was only removed when using the paste.

I cleaned until dry and again took a video.

Here’s what I would’ve changed:

1. I would’ve purchased bore mops that were specifically designed for 9mm/.357. Unless I’m missing something, the lapping occurs roughly in the same way filing a piece of wood or metal works. It abrades the surface using progressively finer grit to smooth the surface. But in order to do this, pressure must be applied. Simply because a smaller bore mop could be used to clean, doesn’t make it a good tool to lap. High pressure is likely needed to improve results so I would’ve gone with a larger diameter mop. It also probably does a poor job of getting to polish the grooves.
2. I would scrap the x strokes to this point of the barrel, then y to this point, z to this point and just do full length strokes. I fail to see why (if performed correctly) doing less near the crown would somehow produce better results.
3. Check out the videos/pics to see the results : )

Thanks for your time friends! Happy to hear anyone else’s thoughts/experiences as I’m about to perform this process again on two of my Leshiy 2 barrels.


Prior to the process:

Post Process:

After an application of Frog Lube:

 

[nervoustrig]

Looks good! And great job documenting it, sharing your goals and reasons for approaching things the way you did, the borescope photos,...everything.

Can see a clear improvement to the surface quality of the bore. It should reward you with far more shots in between cleanings.

 

[Bernie7]

Thank you @nervoustrig ! You might not remember but it was you who gave me a lot of advice about a year ago but due to work and starting a serious relationship I had stepped away from the hobby. Looking to get back and try to contribute to the community when able

 

[TimeRabbit]

Hi Bernie7 , Thanks for putting in the work and sharing I am looking forward to hearing your thoughts on the benefits of your project.

I have been thinking about tackling this same project and a recrown. I was wondering with a recrown after the polishing would I be prudent to polish all the way to the end of the barrel slightly past the crown or should I still stop the mop before it exits the barrel.

 

[Bernie7]

@TimeRabbit Unfortunately I don’t have experience recrowning but from some surface level reading I personally wouldn’t perform that process unless I had a proper drill press/mill. Seems like for a pb handgun where accuracy can be off by a quarter inch at 25 yards and not really affect the primary objective it would be fine but if you’re shooting bench rest or hunting/pest removal where shot placement could be the difference between an ethical shoot or an animal suffering I’d want to be really sure I can hit a perfect 90* angle down to a hundredth or thousandth of a degree.

That being said, if you are going to be recrowning or you’re starting with a blank I’d absolutely lap the entire length of the bore. In fact one of my concerns that I didn’t really write about was if the mop had an uneven distribution of fibers side to side (as opposed to front to back), and the polishing was being performed unevenly near the muzzle end of the barrel, would it cause instability to the projectile due to friction being unevenly applied inside the barrel, especially right as it was exiting the barrel?