Having an ongoing problem with a Vepr 7.62x39 (chrome lined bore) where, starting from a clean bore (using Patch Out), accuracy is consistent at @ 1" MOA for the first dozen shots or so and then it quickly degrades to all over the place. Powder fouling seems excessive. I am assuming there must be some burrs or rough spots inside the bore that are causing this (not temperature related).

I used a Tornado steel bore brush (loops not bristles) and finished with JB Bore Compound on occasion, which has helped maintain @ 1" to 2" groups for 60 or so shots. But this seems like a temporary fix, as after the next regular cleaning with Patch Out, it went back to the same pattern of the first dozen or so shots grouping well, and then rapidly degrading accuracy.

I guess I could use the Tornado brush and JB Compound every time I clean the bore. Maybe this is the only way to effectively scrub the fouling out of this barrel, and maybe eventually it would smooth out the rough spots in the bore -- or maybe not since the chrome lining is so hard.

However, to speed things up or permanently smooth out the rough spots, I was wondering if anyone had used any other method to lap or fire lap the chrome lined bore (where you shoot weak-loaded bullets covered in an abrasive compound down the bore to smooth it out)?

Thanks!

http://www.davidtubb.com/final-finish-bullet-kits

I would use the Tornado brush sparingly if at all. You may be "roughing up" bore each use of said brush. How many rounds through the rifle? What ammo? Final Finish on a gas operated AK may not be the best idea either. I might just keep using JB or run 500 or a 1k of steel jacketed and see if the barrel smoothes out. Try a different ammo maybe. No real help, just thinking out loud.

Take your "tornado" brush and throw it away: anything but a brass brush in a firearm bore is harm-full.

Try another brand of ammo!

What problem?
You have one-of-kind, super-duper 1 MOA Vepr that is more accurate than any chrome barreled AR.

I would drop that type of bore-brush, just use like a Hoppes bore-snake with brass bristles instead. Also make sure you use good lubricant inside the bore, just a decent amount of lube equally spread inside the breach/bore, don't get too excessive.

I tend to use a little CLP dabbed onto the bore-snake just in-front of the 'brush' part, then run it through the bore: breach -> muzzle

Yeah, but it only shoots that way for the first dozen rounds.

Actually, the Tornado brush has been the only thing that's helped it sustain accuracy beyond a dozen rounds or so (to 60 or more). This is not a stainless bristle brush (which can scratch the bore and have largely disappeared from the market) but a series of loops:

http://www.hoppes.com/cleaning-accessories/tornado-brushes

When I did not use the Tornado, it went back to the pattern of 3 or 4 good groups and then rapidly degrading accuracy (from excessive powder fouling I would assume). I'm guessing there are tool marks in the throat causing this.

Anyway, it's a hard chromed bore designed to take thousands of rounds of bi-metal (steel) jacketed bullets. Although it seems to get out stubborn fouling, the Tornado brush doesn't seem to be a permanent solution,

The question is, has anyone used any fire lapping bullets in a chrome lined barrel, like Tubbs, Neco, Bear Tooth, etc.?

Thanks!

No. Fire-lapping a chrome bore seems to be an oxymoron.

The Tubb system has worked wonders for some but with a chrome lined barrel id give them a call first.
I only say that because I personally have no clue.

How many rounds total through this rifle, and what ammunition are you shooting?

I always thought fire lapping for anything other than benchrest or similar guns was a waste of barrel?

I've heard the first dozen or so shots should be to "Foul" your bore when its been cleaned that much before even making precision shots, then it normally shoots good (rather than the first shots shooting the best.)

I use just a Bore snake, although I use it dry after I'm done shooting while the Barrel is still hot!! Then I put some CLP on the tail and run it through and couple times for storage, and then run it through a few days later to get some of the broken down carbon.

Its crazy how it dissolves carbon being I run it through every few months of not shooting to put some fresh lube in the bore and some carbon will come out.

Hopefully it is not harmful to run DRY "Boresnakes" through the bore, being they go in at an angle and there's not really a Bore Guide. I do that when the Bore is either fouled, or lubed normally though but I have done it plenty of times when dry. Mainly using it to lube the Bore but the lube is on the tail, so the bristles are dry. I've done it on New AK's to lube the bore for storage, so the bristles are normally dry and the tail has CLP which hopefully isn't bad for it.

I've just recently started lubing the bristles but just hoping I haven't damaged any of my Arsenal Bores by running a "Dry Boresnake" through it, rather than a Rod and Patch.

Being a novice before, I accidentally put a 223/556 AR chamber brush into the chamber to where the long steel bristles where inside of the AK chamber (they are meant the scrub the area in an AR between the feed ramp and the chamber), and the tapered bronze part meant for an AR chamber actually went into the throat and bore of my AK, hopefully the tip of it didn't mess up the rifling in the "Throat" being the bronze tip of the brush had some nicks on it... I used needle nose pliers to turn it it was so tight and the brass bristles and permanently flat now it was so tight. I wont be surprised if it shoots like shit. Hopefully the Chrome lining is super hard!!

Anyway to look into the throat with a gun microscope or anything a Smith may have? I cant see in detail enough with my bore light.

Not sure what to tell you, guess I'm just listing some things I've done that weren't too smart.

I've contacted Tubb and Neco but have gotten no response from them. According to Tubb's website it's "okay" to use their fire lapping kits on a chromed AR15 barrel.

There are probably about 300 rounds through this gun. Mainly I have been using Hornady SST to sight in, which is my go to defense and hunting round. Function has been flawless as it digests any Com Bloc ammo it is fed. However, I can't get the same level of accuracy from the Russian ammo as I can with the first few shots of SST.

I don't expect an AK to be a tack driver, but it should at least be consistent, even if accuracy is mediocre. This one is frustrating because it has pretty good accuracy for the first dozen or so shots and then it's all over the place, so it's not consistent enough to trust as a SD rifle. Something is definitely not right. Unfortunately, nobody in my neck of the woods has a bore scope so that I might actually see what the problem is.

Anyway, with no first hand info forthcoming about fire lapping, I'm tempted to just shoot the shit out of it with Russian bi-metal ammo and hope that smooths out whatever burrs or inconsistencies there might be in the bore. I would be happy with consistent accuracy, good to mediocre as long as it's consistent. Otherwise, I may be replacing the barrel.

What is " ... all over the place. "?

How many shots in a string ? How fast are you shooting?

Do you allow the barrel to cool during shot strings? If so, does accuracy improve when you do so?

Do you allow the barrel to cool between shot strings? If so, does accuracy improve when you do so?

its not uncommon for a point of impact to change slightly after the barrel heats up. Next time you go to the range make a note of the point of impact after each shot and observe when point of impact starts changing.

Groups will go from @ 1-2" for the first dozen shots and then rapidly degrade to 8" or more.

It's not heat related, as once the accuracy degrades I can wait a week take it out to shoot and it's still all over the place. Once the bore is cleaned, accuracy returns. Also, Vepr barrels are pretty stout
and heat resistant.

Excessive powder fouling seems to be the culprit.

This is how I would lap that barrel. Like others said, watch barrel temp. Check your handguard fitment.

That seems impossible to be caused by fouling. I'll bet something is loose, and when you clean the rifle it gets tightened back up. Fouling would show a gradual decrease in accuracy, not 12 MOA shots (what 1 MOA ammo are you using?) and then suddenly 8 MOA groups from there on out.

 

What optics are you using, and how are they mounted?

Try a different US made brand of cartridges.
If different cartridges don't change anything try a quick clean every 10 shots. No need to get the bore completely clean. You just want to see if removing some powder fouling increases the number of shots before accuracy degrades.

If neither of those have an effect something else is going on.

when you're cleaning it,  do you remove and clean the gas tube? does it become loose during shooting sessions?

I would do as others have suggested and put 500rd of bimetal through it over the course of a couple range sessions. now your barrel is lapped.

What I mean is that the first dozen or so shots (after I've fired 2-3 initial bore fouling shots out of a clean barrel) will stay @ 1"-2" consistently. After that they'll go to 3" and keep expanding with successive groups until they'd be as much as 8" after 50-60 shots. At first I thought the scope (a Leupold) had gone to hell, but the scope turned out to be fine after factory inspection.

Nothing is loose and it is not temperature related. Groups alway tighten up after the bore is cleaned. Powder fouling seems excessive though.  This is using a decent Nikon 3x9 off a Lead Sled. This is using Hornady SST factory ammo. Copper jacket, not bi-metal.

Anyway, finally heard back from Tubb and they recommended using their .303 British finishing kit (.311" diameter). However, I don't reload and don't know anyone who does for 7.62x39, so i'll just shoot the hell out of it with bi-metal Russian bullets and hope for the best. Time marches on.

Searching the web, one guy claimed some pretty spectacular results using the Tubb system on a 20" bbl. Polytech Hunter (338ken). Three Silver Bear SPs in one hole @ 100 yards -- I'd take that any day::

http://68forums.com/forums/archive/index.php/t-25972.html?s=784dcf221e778e8a2a91d2f240640946

http://i945.photobucket.com/albums/ad293/338ken/AK-HunterGroup.jpg


Considering the number of 7.62x39 rifles out there with rough factory barrels, this caliber would be a good candidate for a Tubb Final Finish loaded ammo kit.

I heard back again from Tubb who said I should use their .303 Final Finish bullets (same .311" diameter as the 7.62x39), but should only use the last 3 compounds in a chrome lined bore.

They also suggested that I call Arizona Ammunition to load the bullets in 7.62x39, which I did and ordered the Final Finish loaded ammunition kit for $89.00 plus shipping. They also load for the Neco fire lapping kit and do various other services and custom ammo loading:

http://www.arizonaammunition.net/services/barrel-treatment-systems

Any Updates??

Still waiting for the cartridges to arrive.