Author Topic: Lapping the bore  (Read 12493 times)

Offline flintsghost

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Lapping the bore
« on: May 03, 2011, 03:15:10 PM »
I had read with some interest that some members who had fired and cleaned their pistols had noticed darkening around the edges of the lands and grooves of their bores that did not seem to want to come out with normal cleaning.

One thing that I had done in the past was to use a product called "JB Bore Cleaner" to restore older rifle barrels that looked like they had seen better years.  I had found in the past that this paste bore cleaner, which is intended to removed built up jacket fouling in a bore, has restored accuracy and seem to polish older rifle bores.  It is not intended to nor will it remove pits.   However it is an extremely fine abrasive paste compound and does obviously lap barrels when used.    

Lapping a bore is the final stage used by barrel makers who use the hook cutter method, i.e. Obermeyer, Chanlyn, Koozer and others, to give a final polish to the bore to remove any roughness or tool marks prior to sending a blank out.   In the case of both my own and my son's R9S's I did lap the bore with JB bore cleaner for about 10 minutes each prior to initial firing and did the same again after first range use.   Based on the accuracy of these two I would say it worked.

To lap a barrel it is suggested that one uses a vise with leather padding around the barrel.  I apply a liberal amount of paste to a Q tip and spread it inside the bore.  I also apply paste to a large patch and using a rod with a jag tip, push the patch into the barrel.  I put my finger over the muzzle end and that allows me to stop the patch before it exits the bore.   I work it back and forth for about 5 minutes and then remove it, respread any paste that has accumulated at the edges and add a bit of oil to the patch.  Then reinsert and polish briskly for another 5 minutes.   Then done and clean all residue off and keep patching it till a patch comes out perfectly clean.

An alternative and more correct manner would be to insert an old rod with a jag from the chamber end and hold the barrel vertically in a vice.  Using a patch around the rear of the jag to prevent anything from going by pour a small amount of molten lead into the barrel and allow it to cool forming a perfect lap on the end of the rod.   When it has cooled hard, pull it out and coat it with the bore cleaner and lap as before.  It will be a perfectly form lap to the lands and grooves and thus would be more efficient than a patch made lap.   The heated lead won't hurt the barrel at all as a bullet fired would develop higher temperatures, but it will form perfectly to the lands and grooves.

It works and for anyone who has had accuracy problems or believes that the barrel is a bit rough, this method with remove the roughness, eliminate the dark edges of the lands and groove and will also enhance accuracy.   The lead is soft and will not wear the barrel.  It will only help the lapping compound get where it needs to be to enhance the lands and grooves.
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Offline MRC

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Re: Lapping the bore
« Reply #1 on: May 03, 2011, 05:13:55 PM »
I am one of several members who have R9's with tool chatter marks the whole length of the bore.  Both of the R9's I have owned have had this.  I sent pictures  to Rohrbaugh of the first one and was told by Eric through Maria that this is normal for their "Old World Broached Rifling Method" and if the pistol functioned why would I care.  That pistol did not function and after I got mad they bought it back.

The second R9 is rough, but not nearly as bad.  I asked Eric about lapping the barrel and he said by the time the barrel was smoothed up, it would be out of spec and worthless.

flintsghost - If you would PM me your e-mail address, I would like to send you the pictures of the bore for your comments.  I would like to see if you think it is acceptable.

Offline flintsghost

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Re: Lapping the bore
« Reply #2 on: May 03, 2011, 09:17:11 PM »
Got the pictures and for the record, I don't think that it would be acceptable to me.   Good luck
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Offline MRC

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Re: Lapping the bore
« Reply #3 on: May 03, 2011, 09:22:44 PM »
Thanks

Offline sslater

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Re: Lapping the bore
« Reply #4 on: June 09, 2011, 12:05:47 AM »
The barrel on my very early R9 looks like the descriptions in this thread, and it bothered me, too.
Then I came across an article in an old issue of one of the popular gun magazines. (I'd write the name and date if I could find the darned thing again - way, way too many gun magazines in this house!)  The author is an old-timer tech editor who had just bought a Hawkeye Bore Scope and used it to compare rifling in a bunch of rifles he had on hand.  He looked at button rifling, single point hook (cut) rifling, etc.

I remember thinking my Rohrbaugh barrel looked just like the cut rifling photos in the article.  So the marks are not chatter, but witness marks from a single point cutting tool.  The Rohrbaugh comment about old-world broached rifling is a bit confusing.  I'd expect broach marks to be lengthwise....

As I recall (and I sure wish I could find that magazine again!), the author commented that his field experience indicated all types of rifling could yield good field accuracy, but cut rifling seemed to have a slight edge.

flintsghost's JB Borepaste lapping method sounds like the way to go if I ever get tired of compulsively scrubbing the bore of my R9 after every range session of 13 to 20 rounds.   ;D

Offline MRC

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Re: Lapping the bore
« Reply #5 on: June 09, 2011, 09:25:07 AM »
JB's is a great product and I use it in cleaning nearly all my guns.  It is a very mild and "non-embedding" abrasive.  I spent a lot of years in the benchrest and long range precision rifle game and that is where I got to using it.  I have lapped rifle barrels and the lapping compound you use is a lot more abrasive than JB's.  JB's is closer to toothpaste than the lapping compounds I have used.

I sent pictures of my barrel to flintsghost and he agreed that there is not enough JB's in the world to smooth up that barrel.  His opinion was the rifling was broached with a very dull tool or there was something wrong with the machinery.  Why Eric Rohrbaugh would deem this barrel "good enough" is beyond me.

I like the R9 alot, but two things bother me;

   -Their use of barrels anyone else would reject
   -The undersized grip screws which require factory returns to fix.

« Last Edit: June 09, 2011, 09:25:42 AM by MRC »

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Re: Lapping the bore
« Reply #6 on: June 09, 2011, 12:52:43 PM »

Change out the factory screws with John's excellent screws and your outlook will become more positive. The barrel thing must have come about in recent years because I don't notice it on a 2004 model. I use JB also.

Offline MRC

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Re: Lapping the bore
« Reply #7 on: June 09, 2011, 01:39:13 PM »
I switched to John's screws when I put the VZ grips on.  I hope that solved that problem.

I have  or had 2 R9's with serial #4XXX range and both have barrels that Kel tec would junk.

Spending a lot of time with benchrest rifles I learned that most things on a gun can be fixed.  Be it trigger, stock, scope, or bedding, they all can be repaired.  If the barrel is bad, throw it away as there is no fixing it.  A gun is only as good as it's barrel.

Joe_from_NY

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Re: Lapping the bore
« Reply #8 on: June 09, 2011, 06:01:04 PM »
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Got the pictures and for the record, I don't think that it would be acceptable to me.   Good luck

How about posting a sample of the photos for the rest of us to compare ours to?

Offline Reinz

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Re: Lapping the bore
« Reply #9 on: June 09, 2011, 06:03:23 PM »
I bet the Brothers will just love that.  :'(
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Joe_from_NY

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Re: Lapping the bore
« Reply #10 on: June 09, 2011, 06:10:35 PM »
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I bet the Brothers will just love that.  :'(

On the Seecamp forum, we routinely post photos of any mechanical anomalies encountered with our guns, and the owner of the company seems to appreciate it, as he comes on and addresses it and we all can give our experiences and opinions. Most of the time it is minor and inconsequential, and it is good that the gun owner's concern was put to rest.
« Last Edit: June 09, 2011, 10:57:30 PM by Joe_from_NY »

Joe_from_NY

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Re: Lapping the bore
« Reply #11 on: June 09, 2011, 06:17:08 PM »
does anyone know the user names that the brothers use on this forum?

Offline Reinz

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Re: Lapping the bore
« Reply #12 on: June 09, 2011, 06:29:38 PM »
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On the Seecamp forum, we routinely post photos of any mechanical anomalies encountered with our guns, and the owner of the company seems to appreciate it, as he comes on and addresses it and we all can give our experiences and opinions. Most of the time it is minor and inconsequential, and it is good that an owner's concern was put to rest.


Yeah, but they have already dismissed the barrel issue.
« Last Edit: June 09, 2011, 06:30:07 PM by Reinz »
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Offline Reinz

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Re: Lapping the bore
« Reply #13 on: June 09, 2011, 06:30:41 PM »
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does anyone know the user names that the brothers use on this forum?


I could be mistaken, but I believe that they are just lurkers.
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Joe_from_NY

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Re: Lapping the bore
« Reply #14 on: June 09, 2011, 06:32:03 PM »
Quote


Yeah, but they have already dismissed the barrel issue.


Even so, there are alot of knowledgeable guys on this board who have many years of experience who might be able to give their opinion on the issue.
« Last Edit: June 09, 2011, 06:32:44 PM by Joe_from_NY »