Of endoscopes, lapping bullets, and accuracy mysteries.

[Ian]

Four things came together finally today: My new .22 caliber Teslong bore scope, my not so new Mossberg MVP tacticool 5.56, a Tubbs .223-caliber full lapping kit (50 bullets), and some free time. My neck is still sore from the biopsy yesterday so the low-recoil rifle got the not for today's project.

I really, really wish I had figured out the camera capture feature of the scope before I started this so I could share the whole process, but I did figure it out after ten each of the first two grits so there's that. Sfarting out, I cleaned with Ed's Red and patches to get the carbon out and have a look. Machine marks galore from the bore being drilled and drag marks from the button very evident the whole length. The throat wasn't pitted or cracked, so that was good. There was zero copper, it took me a full week to get all that out long ago and I haven't shot copper since. There was no trace of powder coating or lead fouling whatsoever, and the last bullets I shot were powder-coated, gas-checked Lyman bullets. Did I mention powder coated bullets are truly awesome?

Ok, here's the "but". The damned thing won't shoot. Best it ever did was close to MOA at 100 yards with careful handloaded jax. I have something over 500 rounds of all sorts of factory, jax handloads, lead-free cast, lubed cast, powder coated cast, everything but paper-patched bullets through it and it averages right at 1.5 MOA for ten shots no matter what. Last time I cleaned it, after doing the unleaded cast bullet tests, I was using tighter patches than normal and noticed the first half of the bore was tighter than the second half, probably due to the flutes of the second half. Anyway, I decided it was time to use the lapping bullets as a last-ditch effort to get this thing to group.

So, after five lappers and a cleaning I scoped it again. Hijo La! Copper EVERYWHERE. That's gonna be a bitch to get out. So five more and a cleaning, starting to notice some smoothing and it is uniform from one end to the other. Going all the way to the muzzle with the camera for the first time....aw chit. Chit chit chit. Here's what I was looking at:



From the other side:



Gee, I wonder why it won't shoot?

Time to pull this thing apart and lose about 1/8" off the crown.

 

[Ian]

I thought this was interesting too, no fouling to speak of in the gap between the muzzle and the muzzle brake. There has been some concern among shooters of suppressed rifles that the back blast might injure the crown or that a muzzle brake with a baffle directly in front of the muzzle might di the same, or at least pack up with trash and cause irregularities in the crown.

Well, I can't say that the deep pitting/corrosion wasn't caused by backblast but I doubt it because most of the crown is sharp. What I can say for sure is that nothing has accumulated between brake and muzzle on THIS rifle:

 

[Gary]

Is that just a poorly made barrel or are those muzzle pics showing gross copper/Lead, ect. implants? Should of waited for the rest of the story.

 

[Ian]

Closer to the chamber we can see more of the heavy copper fouling from 20 lappers. As I mentioned, no before pics, but the drill marks wew all the way across all of the lands and they're more than half gone now, so the laps are doing their job admirably and I still have 30 more of progressively finer grits to shoot. I can already tell a huge difference in bore finish by how much more smoothly a tight patch wetted with Shooter's Choice goes down the barrel. The copper cleaners make the patches grab hard, but much less now.

 

[Ian]

Is that just a poorly made barrel or are those muzzle pics showing gross copper/Lead, ect. implants? Should of waited for the rest of the story.

It appears to be severe corrosion pitting. What from I couldn't say. The shoulder/body junction of the chamber has some too, but nowhere else other than three spots just inside the muzzle. I inspected the crown a few times in the past as I was diagnosing the accuracy issues but didn't ever use enough magnification to notice the pitting.

Edit to add that this barrel, since new, has been horrific in its affinity for grabbing copper. Since new I've tried to break it in with jax several time but I spent more time cleaning than anything else so I gave up trying to smooth it up with ordinary jax. I used Iosso bore paste a few times and it really got things clean and seemed to pull a never-ending amount of black stuff out of the bore...maybe it was the black nitride coating? There doesn't seem to be much there anymore if there ever was any.

 

[Rick]

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.

 

[Ole_270]

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.

Yep, rifles that were favorites can drop in the pecking order the first time you stick that thing down the tube. Then you start thinking of ways to remedy the situation whatever it is, some of those remedies can get expensive.
Prime example, my early Ruger M77 Tang Safety 250-3000. Scope showed heavy firecracking for several inches ahead of the bore. Sometimes it would take 3 days of various solvents including overnight foam soaks to clean the copper out. Bright idea? The dry paper patch routine worked so well on the M99 250-3000, lets do it here. Now after 20 or so patched bullets, checking with the scope about midway through, the bore is decently smooth. Cleans as easy as anything I've ever owned. Had to lengthen the oal .07 to get it to shoot decently though. What was easily a MOA rifle is now closer to 1 1/4 at best, with flyers that ruin those groups. When they're that rough, taking the tops off all the bad spots sure moves a lot of metal. Wonder how long it would of lasted as bad as it was getting?

 

[Ian]

Ta-DAAAA!!! Faced off .090" from muzzle and barrel shoulder:



A shot of the re-faced crown with the brake reinstalled:



Pardon the patch lint, but the crown be mo'betta now. Tomorrow I'll continue firelapping and see where that goes. Got the bore soaking in copper solvent now.

 

[Cherokee]

Interesting to how it turn out.

 

[Ian]

It probably won't help this rifle considering none of the other major issues that I've found and fixed so far made any difference. we'll see.

 

[fiver]

I wouldn't even sweat those chatter marks.

my 7-57 ICL has chatter marks I can see without my glasses on.
it'll still put 5 under 3/4" easily,,, it'd do better but it puts the first 2 together, then drops the POI down about 3/8-1/2" and slightly left, the next 3 cluster together right about there.

 

[freebullet]

About what I'd expect from Mossberg. It's deer kill pattern accurate out the box, you wanted more?

 

[Bret4207]

So that's what production button rifling gets you eh? Sheesh! I'd say copper is fairly easy to get out compared to that mess Ian.

 

[fiver]

I think more like button rifling and soft steel combined can be the issue more than just the rifling process itself.
if you think about it, it's a fairly low dollar gun that has to make some percentage of profit.
basically if they pass proof testing and can get a shell from the magazine into the chamber your meeting the criteria of a rifle.
if they only last a few thousand rounds [shrug] so what? the customer will just buy a new one in a few years.

the life expectancy of most guns made today is maxed out at 5,000 rounds.
some won't even do 20% of that before they shoot loose or start eroding many of the parts they need to function correctly,,, and they are not 300$ wal-mart wonder rifles.[smithcoughandcoughwessoncough]

 

[S Mac]

Don't forget, how many gun buyers shoot as much as most of us? I think for many, four of five boxes of ammo would last their lifetime.

 

[Ian]

It's a $600 rifle, not a $299.87 rack special. Supposedly Lilja made the barrels for Mossberg but if they did it was on a low-ball contract.

Here's a $90 (full retail) profiled blank by Green Mountain that I used to rebarrel my Savage 1899.



Here's a 1966 model 336 Marlin .30-30 with Microgroove rifling after I firelapped it. The Marlin button was unique in that it swaged almost all of the radial gun-drill marks away. This is why we see .303" bores in them, the whole surface is swaged, not just the grooves.



So tell me again how a barrel for a cheap rifle can't be good?

 

[S Mac]

Boy, that borescope is indeed revealing.

 

[Ian]

Not bad for $49 shipped. Of course it takes a $1000 smart phone or computer to operate it.

 

[Ian]

The crown job may have helped. These were all shot at only 75 yards, but after I put the rifle back together and swapped the Vortex scope back on (had been using a loaner target scope trying to diagnose the crappy groups) i made one shot to get in paper, adjusted it slightly, and shot nine. No aim point, just used the middle of the page because I wasn't supposed to be shooting for groups with these lappers, but now I wish I had posted a sticker. Best group this rifle has ever shot to date.

 

[Bill]

Wow! Just think, if you had been aiming at a dot.

Bill