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Old 07-18-2019, 10:50 PM
Oso Polaris Oso Polaris is offline
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Default Need Help - Lapping or Fire Lapping?

I have a rifle that I re-barreled with a Pacnor chrome moly chambered in 20Vtg that just came back from the gunsmith a month ago. Its a beautiful Sako rifle that I had re-blued (barrel and action) as part of the process. Before shooting a new rifle, I always clean the barrel to ensure that there isn't any debris, metal filing, or grease build up. When I ran the 1st patch through it came back coated with rust. I immediately broke out the brass brush and more cleaning patches...it continues to give off rust after 75-100 brush strokes.

With the exception of this one issue, the two rifles that he worked on look fantastic and the work is top notch. Something went wrong during the bluing process inside the bore and the oxidation process was not completely neutralized. Mistakes happen and this isn't about darkening gunsmith's doorstep. I still need to speak with him about possible solutions.

I visited my local gunsmith and we borescoped the barrel. At this point in time there doesn't appear to be any major pitting. Aside from rust issue, we observed some strong tool marks in the barrel. Based on this, I thought that I might consider a more aggressive treatment for the barrel than my initial plan of using bore paste (J-B or Montana X-treme). I was thinking about lapping, not just polishing, the bore to decrease risk of rust in micro-pores causing a fouling issue in future.

Anyone try doing fire lapping? Thoughts or suggestions appreciated. Anyone making .204 cast bullets that I could use to impregnate with lapping abrasive grit (I am guess highly unlikely because would vaporize at normal shooting velocities)?

Thanks

Last edited by Oso Polaris; 07-19-2019 at 12:16 AM.
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Old 07-18-2019, 11:38 PM
TinMan TinMan is offline
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I've had good luck doing the J-B on a jag with a tight patch, without fire lapping. Before doing a fire-lap, I would try do a standard break-in procedure with a shoot one/clean one for several rounds to see if that helps.
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Old 07-19-2019, 01:47 AM
Gary in Illinois Gary in Illinois is offline
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Default Fire lapping

If I were faced with this situation I would follow the normal break-in process first. For me fire lapping would be the last resort to attempt to salvage the barrel. Fire lapping causes the greatest wear nearest the chamber (i.e. the throat) and has less effect the farther the bullet travels down the barrel. Throats wear out fast enough with normal wear from normal use.

FYI, you can impregnate polishing compound into jacketed bullets by applying to two pieces of plate glass and rolling the jacketed bullet between the two glass sheets smeared with the polishing compound.
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Old 07-19-2019, 02:14 AM
SmokinJoe SmokinJoe is offline
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What I would try is a good scrubbing with IOSSO using one of their brushes, short stroke it thru the bore two or three times, then clean out all the gook with your favorite solvent. Bore scope it again and see if it doesn't look pretty OK. As was recommended, go on and break it in after that, then make a decision about anything more aggressive if it doesn't seem to want to shoot well. My guess is that it will be fine after the thorough cleaning and break-in. With CM barrels always be sure to finish your cleaning regimen with a couple drops of oil on a patch run through the bore, those suckers WILL rust.
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Old 07-19-2019, 04:07 AM
Nor Cal Mikie Nor Cal Mikie is offline
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If it was my rifle and I saw rust, I'd be checking it after about 20 rounds. Run a patch or two thru the barrel then get to firing. After that, oil the crap out of it.
Picked up a Remington XP 100 in .221 Fireball at a gun show. Just happened to have a box of ammo with me. Saw rust in the barrel before I bought. Before I got home and about half a box of ammo later, no more rust.
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Old 07-19-2019, 04:12 AM
Johnly Johnly is offline
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The only barrel I fire lapped was a Stainless Remington 700 barrel in 338 WM.
It copper fouled like crazy and the accuracy was marginal at best as a result.
I used lead bullets with the tip smeared with Clover valve grinding compound, a few coarse, followed my higher number of rounds as the grit became finer, cleaning between grit changes.

The results were well beyond I had hoped for, the barrel no longer fouls and it shoots like it thinks its a varmint rifle.
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Old 07-19-2019, 01:37 PM
Bayou City Boy Bayou City Boy is offline
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Fire lapping can and will help to improve some larger caliber barrels with significant land and groove dimensions.

With small caliber barrels, the lands and grooves are much more shallow, and I'd try a lot of things that have been already mentioned before I went to extreme measures.

JMO - BCB
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Old 07-19-2019, 04:12 PM
moorepower moorepower is offline
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Could he have used a Savage barrel by mistake? I would use my favorite bore polish and do some fire forming and then look at it again. IF it still copper fouls heavy, I would call PacNor and have some bore scope photos handy. FYI Savage humor from a multi Savage owner. IF it was heavily pitted, I would have said he just used a Bofors steel barrel
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Old 07-19-2019, 11:33 PM
Oso Polaris Oso Polaris is offline
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Guys,

Thanks for the feedback! I've got new tube of bore paste on its way. I despise rust, but I will go slow.

I'll give an update in a week or two after I have a chance to polish the bore and start a barrel break-in process.

Thanks
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  #10  
Old 07-20-2019, 03:55 AM
Kevin Gullette Kevin Gullette is offline
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Lightbulb Polishing.........

.......a centerfire rifle bore is not a good idea. Lead rimfire bores are a different story.

I'm pretty sure that Shilen laps their centerfire bores with 240 grit laps.

Just a thought.

Kevin
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