Of endoscopes, lapping bullets, and accuracy mysteries.

Bret4207

At the casting bench in the sky. RIP Bret.
Definitely shows promise. I have heard of guys shooting groups while lapping that were the best the rifle ever shot before or after lapping. Doesn't make sense, but that's their story.
 

Tomme boy

Well-Known Member
WOW! I remember when you got this and said the bore was rough. But man I thought my Savage 223 was bad!!!!!! I'm scared to get one of these scopes now.
 

Ian

Notorious member
Rick has been saying that about bore scopes on these boards for over a decade. Sometimes you need to know, though.
 
F

freebullet

Guest
Nice work, Ian.

Now it's a $1500 rifle if Mossy had to do what you did.o_O
 

Bret4207

At the casting bench in the sky. RIP Bret.
Agree on the friction Ian. Better powder burn or something. Too many people reported it not to consider it a possibility.
 

Ian

Notorious member
More Mossberg pics after another decoppering. This is after the first three sets of ten, coarsest grits. The final two sets are just polishing rounds, so what has been lapped here (less than 50% of the bore surface) is what I'll be left with. Not overly impressed because the cast bullets will be touching the whole thing. Good news is it looks just the same from throat to crown.

2020-02-24-22-03-00.jpg
 

Ian

Notorious member
Now for the other project I've been working on, the M4 barrel by AR Stoner, $70 on sale IIRC. This thing is horrid, linear scars across the lands, huge swell at the grenade launcher wasp waist, tight spot behind the gas block, pits, scars, and a throat so tight that 5.56 primers fall out in the action. It's clearly marked "5.56 NATO" which is pure balderdash.

Anyway, I shot a series of soft lead, 320-grit impregnated bullets through it with a pinch of Titegroup, about 20 rounds. Then I ran some more 5.56 through it to see if the throat moved enough to not blow out the primer pockets, but no improvement there and it coppered to buggary. A week of cleaning and here's where I am, still like an anaconda full of baboons but somewhat better. This is why soft lead is the thing to use for uniforming barrels for shooting cast bullets, this shot near the throat:

2020-02-24-22-04-18.jpg

Farther down, the tight spot just before the gas block, note how almost the whole surface has been cut by the laps:

2020-02-24-22-04-35.jpg

Farther down we have more normal bore size (same as the first and last few inches) and then this bulge at the wasp-waist in the profile, note how it has barely been touched by the laps:

2020-02-24-22-05-52.jpg

Pretty neat, huh? I mean aside from the obviously horrid bore. If I didn't have a $50 suppressor-mount brake pinned and welded to it and a $130 JP adjustable front sight gas block captured on it I would just trash the thing and buy a better one, but I might be able to save it. Maybe. It shot 10 into 8" at 100 with ball ammo after this round of lapping....

Resized_20200223_200432.jpg
 

Ian

Notorious member
Oh, almost forgot, there are a few spots like this throughout, remember what Rick said?

2020-02-24-22-05-02.jpg
 
F

freebullet

Guest
That's a heck of a tool.

Looks like they used a home tap & die set to thread the bore before rifling. Dual rifling? Interesting approach.

70 for barrel, time, components ect makes the 150-200 for a dpms hbar that shoots 40gr fbhp into small groups seem cheaper. I don't want to know what's in them because they shoot good as me.

I sold one pretty similar. No time for that much correction on the maybe. Will be interesting if you can salvage.
 

Bret4207

At the casting bench in the sky. RIP Bret.
So we're looking into a mirror when we see these pics, right? Amazing. It would be interesting to run that thing down a really nice barrel that was also button rifled to compare the look of it. I wonder if these are low bid, quick and dirty jobs?
 

S Mac

Sept. 10, 2021 Steve left us. You are missed.
I'm guessing you roll the lap bullets between two plates to impregnate the compound?
 

Brad

Benevolent Overlord and site owner
Staff member
With lead bullets, yes. A couple of steel plates work well. Want the grit embedded into the driving bands.
 

fiver

Well-Known Member
yeah a mirror at an angle.
on the above pic the barrel is to the left.
then you can see the housing [where the fuzzy bits are] then the mirror 'in focus' showing the barrels surface.

maybe you guys will believe me now when I describe a barrel as being ''cut on a pipe machine''
those are the bad ones, these are just 'meh' on the low end.
 

358156 hp

At large, whereabouts unknown.
That's bad. It looks like a freshly dozed fire road. I see your son can't bear to look at it either.

Great lookin' kid by the way.
 

L Ross

Well-Known Member
First thing I learned with a borescope is that if you don't really, really, truly, honestly want to know what's in your bore do not get a borescope. Borescopes don't lie and they don't feel in the slightest bit bad telling you.
I have a 03 Springfield Sporter, a 200 dollar pawn shop find. A couple of years ago 6 different shooters used it to hit 60 buffalo silhouette targets in a row, plus 5 out of 6 sitting cat tie breaker targets, at 210 yards. We were shooting Lee 312-155-2R bullets with 16.5 gr. of IMR-4227 seated on the ground with a set of cross sticks. When the awards were passed out the rifle was awarded 1st, 2nd, and 3rd place and we all had a good laugh. Sadly, C.R. Milazzo, (of M-K II AR-15 trigger fame), had a damned borescope with him. My shooting buddies, (and with friends like that, blah, blah), wanted me to have Charlie scope it. I resisted in vain and eventually the colonoscopy was performed. Yikes!!!!! If you have ever seen the bottom of a sun baked mud puddle, that, is what the throat of this poor rifle looks like. Cracked and crazed and scorched and hazed and all manner of nasty. I can count on holding 3" or smaller groups at my 210 rail, but now it's kinda like seeing the hint of an adam's apple on a cute girl's neck, in the bar, at an angle, at midnight. You know what I mean?
 
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