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The benefits of using Bore paste to clean barrels by Speedy Gonzales

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Benchrest Shooting

Benchrest Shooting
by Speedy Gonzalez

Benchrest Shooting is one of the most demanding shooting disciplines in the world when it comes to the quality, craftsmanship and maintenance of the equipment in order to compete on a world class level. One of the most guarded secrets in Benchrest competition to maintain this maximum level of accuracy is the "PROPER" use of "JB Bore Paste".

Ever since it's introduction there have been heated debates into the wee hours of the night about JB Bore Paste, pitting man and beast against each other about it's miraculous cures for severely fouled bores and how others were ready for the scrap yard by merely opening the jar near any barrel in the house. Well Ladies and Gent's it is time to dispel all the myths surrounding this diminutive ivory jar, that has carried many of us benchrest shooters over the threshold into the "Benchrest Hall of Fame".

Before we get into the "PROPER" use of JB Bore Paste lets dissect the process that takes place within the bores of our firearms that cause the degradation to their inherent accuracy.

Upon firing a round down our barrel the greatest culprit is heat. In many modern cartridges the bore temperature reaches or exceeds the melting point of steel for a micro second. This is the reason for the large diameter barrels one typically sees on many firearms built for competition, the greater mass of steel serves as a heat sink to draw the heat away from the bore in a the most expedient manner. Second to heat is pressure. With every round that passes through the bore pressures can rise to nearly 75,000 PSI causing the bore to expand and contract, possibly thousands of times over its lifetime.

These first two mechanical processes are what set the stage up in the bore for all fouling that with begin to manifest itself after microscopic fissures begin to form from the heating and cooling and expansion and contraction that take place with every shot. Remember heat, pressure, & carbon is what forms diamonds and the carbon fouling is about that tough to get out.

The last culprits in our un-holy trinity that lead to fouling our bores are machining defects in the bores themselves. These can be reamer marks left from a poorly chambered barrel leaving the free bore and throat scored and rough, too tight a pilot on a reamer can also severely scratch the tops of the rifling for an inch or so in front of the throat. Tool marks left in the bore from the rifling process also play a role in contributing to fouling and rapid accuracy drop off.

Well just when you thought there is no way things could get worse, HANG ON, THEY DO!!!!

Let's throw all of these nasty things in our blender along with a bit of carbon from the burned powder and primer residue and gilding metal from the jackets of our bullets and maybe even a pinch of lead and plastic to complete our ballistic cock-tail. Yep! Time to re-barrel after the mess we just made....RIGHT!!!!

Wrong! Bwanna, this is where our old buddy JB steps in at the last minute and saves the day, gets the girl and rides off into the setting sun.

That would be great if it were that easy but I am going to continue with our saga just a bit longer, so grab a beer or a whiskey if you need one by now and read on.

The heat & pressure generated in the process of firing that projectile down the barrel begin to fuse the carbon to the metal of the bore, to a greater or lesser degree according to the condition of the bore, then as the projectile passes over this layer of carbon it leaves behind a small copper wash, with each shot this laminating process continues to build until we have a marked decline in the firearms performance. Now, what the typical shooter can see is the copper wash left in the bore after a string or shooting session. This copper fouling is easily addressed by most solvents on the market today, but they only address the copper and whatever loose carbon residue lies in the bore. Under close observation with the Hawkeye bore scopes sold by Brownells it becomes very apparent that only the copper was removed in the cleaning process and that the underlying carbon was not touched at all and is ready to begin its fouling process with the first round passing through this now supposedly clean barrel. With the bore scope one can easily see all of the remaining carbon in the bore. These are noticeably darker streaks in the bore as compared to the surrounding metal. I always recommend the purchase of a bore scope, it is the only way to accurately judge the condition of ones barrels. If you can not afford one individually get together with your shooting buddies and purchase it as "Group Insurance". Sorry couldn't resist that one.

OK, we have finally got to the good part. Finish your drink; roll up your sleeves, because we are going in.

The "PROPER" use of JB Bore Paste 101:

Most methods of cleaning with JB Bore Paste such as a patch over a jag or a patch over a brush address the tops of the rifling and the center of the grooves but leave the area where the groove meets the rifling untouched as observed through a bore scope (Yours is probably on the way by now!). So, how do we get around or overcome this perplexing predicament? I have made you wait long enough so here we go........................................................................................................

Here is a pretty picture of a rifling button. As one can see it has the reverse imprints of the rifling helix ground into it, but most important is its shape. If you look closely it resembles a football with its ends lobbed off, as the rifling button passes through the reamed hole of a barrel blank it completely fills the bore swaging the impression of the rifling as it's pulled or pushed through the barrel. In essence this is what we're going to attempt to accomplish. We want to mimic the rifling button in order to fill 360 degrees of the bore and groove of our barrel in order not to leave a single spot where carbon fouling can hide.


1) JB Bore Paste

2) Bore Guide: Use a proper bore guide as described in my earlier cleaning article. If you don't have one yet stop right here and call Brownells or Sinclair Int. before we scrap our barrel. A properly fitting bore guide is like buying life insurance for you favorite barrel.

3) Cleaning Rod: A good coated one piece rod with a ball bearing handle such as a Dewey work great. Do not use a stainless or jointed rod! These will cause severe damage to your bore and shorten barrel life.

4) Brass Jag: There are many jags on the market; most are designed only to push the patch through the bore. The best jag for the task at hand is the PARKER-HALE style pictured below. It will securely hold the patch during the process and allow us to generate the proper shape to accomplish our task. John Dewey sells such a jag for his rods and come standard with the Parker-Hale rods.

5) Patches: High quality square cotton patches are a must in order to accomplish this procedure correctly. The largest patch that will enter the bore is best. I bit of trimming with scissors is often required to obtain the best patch to bore fit.

6) Solvent: A good bore solvent such as Butches "Bore Shine" or Speedy's Formula shown below.

7) Bore Seasoning: Colloidal Graphite in a suspension media or LOCK-EEZ purchased from Brownells or most NAPA Auto parts.

STEP 1: As discussed the first order of business is to generate a form that closely mimics a rifling button enabling us to more effectively and efficiently clean our firearms barrels allowing them to perform to their maximum accuracy potential. See picture below.

The generation of this patch /mandrel profile is quite easy and you will wonder why no one ever showed you this method before.

First we coat the upper 1/3 of the patch with JB Bore Paste as shown below. This is going to act as our adhesive to hold our first fold together. Don't spare the JB otherwise things start to come unraveled later. Lay your Parker-Hale style jag about 1/4 the way over from the left side of the patch as demonstrated below. Now fold the patch down over the jag and you will see how the JB keeps everything in place as we proceed.

Now that we have completed our first fold we must again liberally coat the remainder of the back of the patch with JB. This second coating will further aid in the binding of the patch and also act as a reserve for JB as we clean the barrel. The JB will bleed through the holes in the cotton mesh once pressure from compression of the patch takes place as it is gently pushed through the bore.
We are now ready to begin the wrapping process required to mimic the rifling button. Take you rod with the patch attached as shown in your RIGHT hand with the patch facing left like a small flag. See attached two photos below
Now with your left hand, start to wrap the patch in a clockwise rotation around and behind the jag. In about 3/4s of a turn start to pull the patch slightly downwards as you continue to wrap it around the jag making sure that it is a nice smooth wrap with minimal wrinkles. This will leave a bulbous nose at the tip of your jag and a tapered helix below where the patch terminates. See examples below.
Your patch and jag should now resemble the photo below.
We have one last coat of JB Bore Paste to add to the outside of our wrapped patch. This should be applied liberally once again and worked into the fibers of the cotton enabling them to perform their task with the least amount of work. Once full coated your completed wrapped patch and jag combo should look like the examples below.

At this point we are ready to properly begin the process of cleaning out barrel with JB Bore Paste.

You should begin by running a patch of solvent through the bore so as not to push the JB Bore Paste through a dry bore.

Insert your bore guide and slowly push the wrapped jag through it until you feel it the jag and patch contact the throat of the barrel. Since right hand twist rifling is typical on most rifle barrels, grasp the cleaning rod body firmly and turn it to the right as you apply forward pressure to the rod. This will cause the JB Bore Paste wrapped patch and jag to engage the rifling and follow the helix of the bore. Once engaged stop and mark your rod with a silver Sharpie pen or a small band of masking tape in order for you to visually see where the patch is engaging the rifling, so as not to pull it out beyond that point.

Very slowly and carefully begin to push the rod in and out working only the first 8 to 10 inches of the barrel for 15 to 30 strokes depending on the condition of the barrel. (This is where that bore scope comes in handy). These 8 to 10 inches are typically where the greatest amount of fouling takes place.

Once we have worked the rearmost portion of the barrel we will begin to increase the length of our stroke about 1/2 to 3/4s of with every stroke from starting from our witness mark on the rod. When we finally reach the muzzle, we will push out the patch very carefully and unwrap it from the jag. Then slowly withdraw the jag being careful not to ding up the crown with the serrations on the Parker-Hale type jag. The picture below demonstrates exactly how well the patch wrapped jag conforms the barrels rifling as it can be easily seen on the patch.

Run several wet patches slowly through the bore to remove all of the JB Bore Paste inspect with your bore scope (I am sure you got one by now) and re-clean according to my regular cleaning regimen (see below).

Make sure that you run a chamber swab into the chamber insuring that you have remove all JB Bore Paste from that area. A patch wrapped around the front of the swab will usually be a visual reference that there is no remaining JB in the chamber.

Though not a big fan of Moly (That's another story) after all this cleaning the barrel should be "SEASONED" or made ready to shoot in a method to keep fouling down to a minimum once we put it back in service. What I have done was A trick I learned from my mentor Pat McMillan and that was to coat the bore with LOCK-EEZ (Lock-Eez is graphite suspended in a carrier that evaporates very quickly leaving only the graphite behind.) It is applied in the exact same manner as we cleaned the barrel with JB Bore Paste working it into the first 8 to 10 inches at first then slowly working it into the entire length of the barrel. Once you have worked it into the bore you are ready to go out into the range or field with the assurance that you have prepped you barrel for whatever its intended purpose is.

We hope this is of benefit to those who wish to do thing properly and wish to maintain the maximum performance of their firearms.

Good shooting & keep'em in the X-Ring,
Speedy Gonzalez

Topic starter Posted : 09/08/2021 12:29 PM
Newt, Phil Stewart, lawrence katz and 13 people liked
Hunter MemberPress

Great article.  I ordered some last week along with the osso brushes, and patch-out.

Posted : 09/08/2021 2:15 PM
Sniperish Moderator

Very good read

Posted : 09/08/2021 6:58 PM
Spotter MemberPress

Great article.  Thanks for sharing.  I learned the hard way what carbon can do to a barrel.  I have never used J-B paste, but I am now a firm believer in Iosso bore past and a bore scope.  I wouldn't clean any of my rifles without them.  Thanks again for sharing good information.



Posted : 09/08/2021 7:10 PM
Enthusiast MemberPress

Since the enlargement of the Jag will occur once the patch has been wrapped, would you use a smaller Jag than the bore diameter? Use a 6mm Jag for the 6.5mm caliber bore?

Posted : 10/25/2021 7:13 PM
Member Admin
Posted by: @jeff-wright

Since the enlargement of the Jag will occur once the patch has been wrapped, would you use a smaller Jag than the bore diameter? Use a 6mm Jag for the 6.5mm caliber bore?

Yes, you may need a smaller jag. 

Topic starter Posted : 10/26/2021 5:50 PM
EdLoc liked
Out of primers Customer

Good read! Fixing to order some  today

Posted : 11/05/2021 2:20 PM
Out of primers Customer

Well Eric you’ve been doing a great job!  You have revealed to me even more ways to separate me from my money. The EC Tuner which I literally just got in the mail today and now I discover how badly I need a borescope, different jags and JB.

Awesome. Thanks.
I think. 🤔😎

Posted : 11/06/2021 11:14 AM
Enthusiast MemberPress

Is there any point to the pellets that Brownell sells that are used in conjunction with JB Bore Paste and Kroil?  The pellets that go over a different style jag in combinationwith a patch.  I'm asking because before I read this article I had already purchased the setup sold by Brownell for JB Bore Paste.

Posted : 12/20/2021 10:34 AM
 Lawrence Katz
(@Lawrence Katz)

I have been using the pellets for years in all calibers. Naturally you need to purchase the correct jag and preferably one that holds two pellets. I also use them with JB and Kroil. I seem to have a problem with regular patches that are cut too large so I avoid doing so.

Posted : 12/20/2021 1:47 PM
Out of primers MemberPress

Very informative. Thanks 

Posted : 12/25/2021 6:47 AM
Spotter MemberPress

Are there any tricks to using JB or Iosso in semi-autos, where the gas hole is present? I am concerned with getting the paste in the hole on my AR and M14. Thanks 

Posted : 01/17/2022 4:35 AM
Enthusiast MemberPress
Posted by: @fatelvis

Are there any tricks to using JB or Iosso in semi-autos, where the gas hole is present? I am concerned with getting the paste in the hole on my AR and M14. Thanks 

That is a very good question. That would be for DI only, correct?  

Posted : 01/17/2022 3:26 PM
Spotter MemberPress
  1. @americanpatriot 

    Yes, I am referring to a DI rifle.

Posted : 01/17/2022 3:56 PM
Enthusiast MemberPress


I use a duster to spray air back through the gas tube into the bore. I patch out the remaining paste. Haven’t had any issues so far.

Posted : 01/20/2022 3:50 PM

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