Strange borescope images from my Marlin?

[Vettepilot]

Hi, hope I am posting this in the right place...

I recently bought a borescope. Cool toy!! Anyway, I have searched all over, and not found any examples of bore-scoping that can help explain what these images of mine show. It is a 1984 Marlin Model 995 .22 rimfire. I bought it used; it was about 3 or 4 years old when I bought it.

So I borescoped it with my new toy, and found the posted images. The marks in the rifling are in both the lands and the grooves, and extend from the beginning of the rifling, all the way to the muzzle. I am somewhat new to gun smithing (and borescoping), but I cannot imagine what made these marks, grooves perpendicular to the rifling, and all the way to the muzzle. The marks seem to show wear; as though they were there from the factory and have worn down from shooting use. What could have caused this, and will it affect accuracy???The last two pics show the muzzle end, which as you can see looks terrible, so I went ahead and cut 1/2" off the muzzle and did a new 7 degree crown with a protection relief.

This has always been used to shoot cans and bottles, and to let the kids use, so I can't say exactly how the accuracy has been. But I was hoping to use it to hone my accuracy skills, shooting groups. What do you all think?

Thanks!
Vettepilot

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[recumbent]

How does it shoot?

[Martin Luber]

Tool chatter during rifling...stick slip. My guess

[Mk42gunner]

My guess is those are marks left by the last reamer pass before it was button rifled.

I've never looked at a small arms barrel with a borescope. The only time I have ever personally looked at a borescope image was when we had SIMA borescope our 5"/54's.

Robert

[MostlyLeverGuns]

I have a couple Marlin's that show reamer marks after the Micro Groove rifling button passed thru. It is just a rough reaming job before rifling. Fire polishing helps smooth it. Accuracy can be excellent with jacketed and cast. Jacketed will copper foul very quickly but kept clean, accuracy can be good. Cast boolits work just fine in these rough barrels. Both of mine are Marlin 336C's - .35 Rem. You will see a lot of reamer marks in the grooves of older factory barrels but the Micro Groove Marlins also show up on the lands.

[Win94ae]

Very cool! Thanks for showing us!

[beemer]

I recently bought a Teslong bore scope, it is a nice toy. Some of those nice bright bores can look different under bright lights and magnification. I have milsurps that look better than some new factory rifles. It is not unusual to see reamer marks in an accurate barrel. Marlin 22's usually shoot very well.

It is fun to look but the bottom line is how it shoots. I once had a Swede with a visibly pitted bore but strong rifling that outshot my other one with a nice bore.

Dave

[EMC45]

Looks like the reamer picked up a chip.

[Harter66]

I agree with tool marks .
I would shoot it for real and see how bad it is . If it's minute of pop can at 50 yd it's probably good enough for the kids to lay waste to armies of cans .

I think I would defer from fire lapping as with a rim fire there's no adjustment to fit the bore . Maybe if you're really set on a repair effort a brass jag could be reduced to bore dia and used to lap just the top of the lands for improvement .

[JRD]

Others have given this advice already. It's how the barrel shoots that matters. Don't get hung up on remnant tool marks left from the manufacturing process. Most barrels aren't as smooth as we envision or as you would think just looking down the bore by eye. Getting a bore scope is kind of like getting a peak into the kitchen and learning how the sausage is made. It may not be pretty but so long as it shoots (or tastes) good...

If you are intimately familiar with barrel manufacturing, (granted most people are not), you can play detective with a bore scope and examine tool marks to infer what manufacturing process was used to rifle the bore. Cut rifling, button rifling, hammer forged, and ECR all have unique patterns of tool marks. All that matters from a practical standpoint is how a barrel shoots, but if you are an engineer or forensic examiner type the toolmarks can be quite interesting.

To the original poster. Your rifle will shoot just fine. Enjoy shooting it.

[yovinny]

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 ?

[Cap'n Morgan]

It looks like broach or button chatter. Both rifling metodes use a single pull or push through operation.

[GregLaROCHE]

Tool chatter when made. Not much to be done now. Hopefully it shoots decent.

[starnbar]

Hey if it shoots ok forget about it/////////////////////////////////////////

[Vettepilot]

Ok, thanks for the responses. As mentioned, the marks show some wear; they've been polished down by the passage of god knows how many projectiles. It might shoot ok, especially since I've done a nice crown job on it. I will go ahead and do my trigger job on it, then see how it shoots. I was thinking of treating it to a new Boyd's stock, but I think I'll wait now, and see how it shoots first!! Since it's a .22, it will be all lead boolits; which is good as I don't think j-bullets would play well with those grooves.

It's a somewhat interesting gun. It's a Model 995, which study has revealed is supposedly a kind of upgraded Model 795. It does have nicer sights than the 795, a wood stock, etc. But curiously, it does not have the Micro-Groove rifling.

Thanks again,
Vettepilot

[Vettepilot]

To those interested, the pics are from the 50 dollar Teslong Borescope, and I didn't even fine tune the focus nor the light setting for the pics; just snapped them. I'm VERY happy with it. Best gun accessory buy ever!!

I found apps, and an adapter cable for my particular phone and tablet and it works perfectly on them as well as my laptop. You can bet it will be with me if I go to buy any used guns!!

Vettepilot

[Vettepilot]

Here's the crown job.



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Hmmm.... strange but I can't get the pic with the lathe spider I made to post right side up!

Vettepilot

[yovinny]

LOL,,, I've had that issue more then once !! Bet you had your phone upside down... ;)

[Vettepilot]

No. The pic is upright on my computers; it just posts here upside down. I tried uploading it twice. Same thing both times.

Vettepilot

[john.k]

Id suggest the marks arent reamer ,but rather drilling without any reaming ,one operation cut out to lower production cost.......funny thing is I get all kinds of advertising material from deep drilling manufacturers claiming their drilled holes have x microinches finish,reaming not necessary....Id say Marlin pushed their drilling feed rate beyond the limit ,to increase production .......Not all the evils at Marlin come from the Remington takeover ,it seems.

[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]

269828
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.