Strange borescope images from my Marlin?

[Vettepilot]

It does look like a non-reamed, drilled hole often does.

It will be interesting to see if it shoots. If not, then back to plinking and "kid duty". I don't remember it being noticeably inaccurate in that use before, so we shall see...

Vettepilot

[uscra112]

Seems like the micro rifling button chattered,, and got worse as it went.
If it was from the bore reaming before the rifling,, how did exactly matching corresponding chatter end up in the grooves ?

Because the button ironed the reamer marks in there.

Gone are the days when Marlin broached its' barrels. I use old Model 60 barrels to rebarrel boys' rifles from time to time. Never have seen one like that! If I were the mfg. engineer in charge at the time, I'd commit seppuku from the shame.

[KVO]

"Ironed into the grooves by the button" absolutely correct. You'll see the same thing occasionally even on high end button rifled barrels (not nearly to this extent though). I've seen this phenomenon on Liljas and Shilens. Heck I have an Obermeyer that still has a couple of minute reamer marks that weren't cleaned up on finish lapping but still shoots lights out. I'm not downplaying that your particular barrel IS extremely rough, but may still be capable of what you ask of it. A borescope can be a great barrel sales tool but doesn't tell the whole story.. I've also borescoped several dozen premium grade rimfire barrels from ALL the makers that looked absolutely perfect- and ended up in the tomato stake/ 10/22 pile because they were duds in the accuracy department as tested from a dedicated test fixture bolted onto a concrete block shooting Anschutz round and 20 series (square) actions.

[uscra112]

As a colleague once said of another hi tech bit of instrumentation:

"This thing shows us things we didn't know we didn't want to know."

[Vettepilot]

Yep. The borescope is a perfect example of "A double-edged sword." It will definitely show you things you should know.... and things you don't WANT to know. (And just might have been better off not knowing.)

Mine has already been very educational, and saved me some grief though, I must say. Cool tool for sure!

Vettepilot

[john.k]

When the cheap flex lead cameras first came out ,there was a constant stream of complaints from new rifle buyers that the chamber on their gun wasnt concentric with the bore ......this is very easily seen as the conical lead looks quite obviously cockeyed.......The reply was the warranty didnt cover design features ,and provided the rifle shot to industry standard accuracy limits ,no return ,no refund.....(limit for a 223 was something like 4 moa)

[beemer]

I had my bore scope out today and decided to look at my Marlin 39AS. The bore was like yours, maybe not quite as bad but not by much. It has always been a accurate rifle, one of my favorites. Also took a look at a Sears 22 made by Hi-Standard, the same thing.

Shoot and enjoy !

Dave

[Vettepilot]

Interesting. Thanks for the info!

Worked on the trigger a little last night. It attacked me! (Hammer spring popped out and smacked me on the forehead!) ;~)

Will probably finish it today, but I'm not sure when I'll get a chance to shoot it.

Vettepilot

[Vettepilot]

Maybe those grooves are there to catch and hold some lubricant off the bullets.

Ha!

Vettepilot

[starnbar]

Not to hijack the thread if you need a good endoscope check these people out endoacustica they have some high quality stuff not made in China

[EDG]

I was a manufacturing engineer for a long time.
What you are seeing with the bore scope are typical reamer tool marks from the button rifling process. I have at least 2 Marlin barrels with that "finish". One is a Western Field branded .30-30 and the other is a .375 Marlin. Both bores grow copper fur when jacketed bullets are fired.
Shooting jacketed bullets and cleaning the fouling out will result in ironing out the rough edges.

[Vettepilot]

Ok, thank you. It's a .22 rimfire, so no jacketed bullets, but the marks appear worn down somewhat anyway. (The gun is 35 years old.)

However, if what you say is the case, how is it that marks appear in the grooves in places, directly mating/corresponding with marks on the lands? (reference the first photo closely.)

Vettepilot

[Petander]

Both bores grow copper fur when jacketed bullets are fired.

I once helped a friend regulate a nice 8 mm Merkel double rifle. He was selling it for a very reasonable price. The gun was "growing fur" inside the barrel. Even though it was shooting okay, KNOWING AND SEEING INSIDE bothered me so much I let it go... I still regret letting it slip.

...these scopes really are double-sided swords.

[Static line]

I have that same Teslong bore scope. Great scope for sure. I deleted most of my bore scope pictures from a Marlin 44 magnum that showed a few rough tooling marks. This picture is from the bore of my Ruger 77/44. Notice the flaw. Mind you, you are probably seeing anything in your bore at 15 times more power then your eye would pick up so really, in most cases, nothing to worry about.