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BLMW

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OLDGUNNER
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BLMW

#1 Post by OLDGUNNER » Sat May 05, 2018 11:19 am

BORE LAPPING MY WAY...
I understand why commercial barrel makers may use lead laps but that doesn’t mean that I should. I find that leather has the necessary ‘spring’ action to where I can lap the bore with one lap...a different lap for each grit size of course.

I just relapped a Carcano with these two grits that I had previously lapped with 500. I bought more than a few ‘Life-Times’ supply of this lapping compound for 50 cents at a yard sale.
I glued some leather to a wooden dowel and then filed it down to a firm fit for the bore. So far I have not come across an easier way.
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Re: BLMW

#2 Post by Polock » Mon May 07, 2018 9:02 pm

Interesting--did u see any improvement in accuracy/consistency of groups??
I often wondered if lapping a milsurp bbl (esp. one with pittting/corrosion) was worth the effort, or was just cosmetic.
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Re: BLMW

#3 Post by OLDGUNNER » Tue May 08, 2018 5:07 pm

Well, on that I can’t say...because I have not gotten around to making any good tests for that. I just lap first and see what happens. But I will say that I have not been dissatisfied – I know that this is not saying much. But I do gather that most serious Benchrest Shooters and any serious custom barrel maker do lap their barrels in the area of 500 to 900 or so, Except for some military custom barrels where they may stick to the normal 320 or so grit finish, but that is for a particular reason and that is to be able to use a given ammunition, and save weight, and there are exceptions to that where some specialized groups will use custom ammunition in their custom barrels. The Marines and Army are big into this.

And as in everything, “Everything in life is a compromise.”.....and this included ‘everything’ about a firearm.

As for lapping a corroded or rusty bore I would say is safety factor - to help reduce a chance of over-pressure.

Let my add this - my opinion only....after doing ANY LAPPING TO ANY BARREL, if one is paying attention, they should find that if they will use the same ammunition before and after, their group size should either increase or decrease. If it would stay the same it would just be stroke of luck, or due to some thing that one is not considering.
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Re: BLMW

#4 Post by OLDGUNNER » Tue May 08, 2018 9:58 pm

I sure am not saying look at all of these for some straight scoop. But if one is not familiar with bore lapping they may find some of interest into the subject. At least after reading these one WILL at least have more insight into the subject. Above all, in my opinion, don’t be afraid to DO IT. As I say, every gun that I get deserves a good lapping. But I have not bought any four or five hundred dollar custom barrel. And further more I don’t think that any future purest buyer will be saying, “Oh no, I can’t buy your original gun because the bore has been relapped.”

https://www.bing.com/search?q=military% ... 1BAAE98824

https://www.bing.com/search?q=bore%20la ... 54B421E323
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Re: BLMW

#5 Post by OLDGUNNER » Sun May 13, 2018 3:54 pm

DSC_0046.JPG
Okay, I realize that if one has not done any bore lapping it just may be that they don’t know where to start, if they wish to start. There is of course 1001 different ways to do it.

The commercial barrel makers may use lead laps – that is okay. I just don’t wish to do it this way, I have tried it, and I just think that my way is a lot simpler, for me. This is just one of the ways.

I just bought three more 1/4 inch dowels at Walmart for 27 cent each...I will make three laps, one for 380 grit, one for 500 and one for 800 grit.

This first step of mine is to put all dowels into a small hand drill and file a small bit away for the leather strip that I will use contact cement to attach the leather to the dowel. The reason for the slot is better control of the placement of the leather and to be able to use more of the leather thickness for tension of the leather-to-bore. The reason for the relative short slot is to still have the necessary tension without the undue effort in the lapping – just more stokes to get the job done.

Since I don’t have the necessary expensive equipment to monitor the bore finish as I go along, my second step will be to slug the bore – and I have a variety of magna-viewers and a couple of microscopes - view the slug surface as I go along to determine when to go to the next finer grit.

I believe that the normal ‘Fire Lapping’ leaves too much to chance with less control.

And since I have trouble posting more than one photo at a time, I will do just that.
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Re: BLMW

#6 Post by OLDGUNNER » Sun May 13, 2018 10:09 pm

Clarification of grit sizes, The grit size of some, most, lapping and polishing compounds can be misleading, For example the common Clover Compounds, an economical brand, will list theirs at different grit size...but they are not completely dishonest. They do specify these as an ‘AVERAGE’ size. Well, what is most important - the largest grit size in the batch of course...the smaller sizes doesn’t mean much. Some of the sellers will not even say ‘Average’. And as one uses the products they will learn to get-by with these ‘average’ sized products, as most of the brands for sale on the common market are. I have talked to the Clover customer service guys in Canada at least three times...and they just don’t know, won’t tell me, or some combination of these. These customer service guys are just this in name only. One of the Clover guys told me one time that they just buy the Silicon Carbide by the ‘boat load’ from India and package it and ‘sell’ it. They won’t even check it and say what may be the maximum size. This is left up to other companies that sell ‘Laboratory Grade’ compounds, and Laboratory Grades typically mean, “No larger than.” And charge one heck of a mark-up for doing this.

I gather that most users, and yes, barrel makers have just learned to get by with using the cheaper compounds of a given size such as say 800 grit, average, and expect it to be may be ‘no larger than’ maybe 600 grit, or what ever. One would have to measure the grit size themselves to see what they may be using. I have measured different grit sizes but it is just a ‘Ball-Park’ figure. One can buy an ‘Etched Glass’ slide with the Calibrated lines to measure correctly but they are expensive. I can remember when they were 30 $, but now maybe 200 $. I use to have one but have lost it.

But for me now, I’ll just lap until I get no leading of a cast bullet using just free Wheel-Weight alloy...or at least my target is. I never did go for that rig-a-more-row of trying to find a lead alloy for minimum leading. Before I learned to lap, I got by just fine with regular WW alloy and regular lube. I guess the only advantage of bore lapping for me is less barrel cleaning and faster velocity cast bullets. And I still have most a box of 1000 Lyman 30 Cal gas Checks from when they were 4 $.
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Re: BLMW

#7 Post by Polock » Sun May 13, 2018 11:33 pm

I appreciate the "how to" get started with lapping--will put this in my toolbox for future reference.
have a few old milsurp bbos that are pretty rough--
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Re: BLMW

#8 Post by OLDGUNNER » Mon May 14, 2018 12:03 am

https://www.emsdiasum.com/microscopy/pr ... plies.aspx

These are the cheapest lapping and polishing compounds that I have ever seen, and I don’t know why. It must be that the others are just so much more expensive.

For example: The Clover compounds at 33 a pound which is maybe 90% by weight ‘grease’...look here per pound, 100% Silicon Carbide.

And the Aluminum Oxide powder...I get Brownells J-B products are 1040 dollars versus 19 dollars worth here if the 2 ounce jars of the J-B at 13 dollars are 1/10 by weight Aluminum Oxide – I call that one heck of a mark-up...if my math is correct. Even if it isn’t correct, it is still one heck of a mark-up.

Look at all of the case polishing compound one can make with 19 dollars worth of this Al2O3. I have lots of Al2O3. I just mix it with old hand lotion.
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Re: BLMW

#9 Post by OLDGUNNER » Mon May 14, 2018 10:27 am

DSC_0047.JPG
Okay, I just held the leather on with rubber bands until the glue dried and then filed them down for a firm bore fit. They will swell up a bit after applying the lapping compound and I will have to file them down a little more. I'll just glue some wooden handles on and that will be it. The leather doesn't wear out like lead. The leather is springy enough to keep the tension.
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Re: BLMW

#10 Post by OLDGUNNER » Wed May 16, 2018 2:35 pm

https://www.microscopeworld.com/p-2035- ... mwsm2.aspx

This is just FWTW...In case some one wishes to know the size of lapping and polishing compounds this is one of the measuring slides that I have found for sale. I just talked to the guy on the phone and he has them in stock and will take PAYPAL. I HAVE/HAD, one just like this that I bought 40 years ago for 30 $...it’s around here some where, but I just don’t know where. I will just muddle by without another for 185. But....FWTW.
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