does anyone else have a borescope that can ask about?

[savage308]

i have a hawkeye borescope and im seeing some unusual bullet line markings in some of my barrels. its seems almost like the bullets are twisting faster than the barrel rifleing and i know thats not possible or is it?

 

[Mudcat]

Say what?! WHile I have seen some wierd stuff thru the borescope, i cant say I have seen anything such as you describe...that is, if I am envisioning what you are talking about. I have seen a LOT of copper in a bbl before that is costing the lands and into the grooves, but I dont think a bullet can spin faster than the rifling...how could it?

 

[Lapuatom]

I also have a Hawkeye bs but have never saw evidence that a bullet was spinning faster than the rifleing. Seems that if there were a discrepencey,the bullet may slip somewhat through the barrel and acually spin slower than the twist rate. Not really sure if that's even possible.

 

[fdshuster]

savage308: Your posting caught my eye. The answer is yes! I have something very similar to what you describe, as seen with my "Hawkeye". Both barrels are button rifled, the "marks" (for lack of a better word) are on the top of one land only, maybe 1" to 1 1/2" in length and begin on the left (or right side), cross over the top of the land, at a very shallow angle and end on the right side of the top of the land. Over a dozen premium button rifled barrels, by the same manufacturer have no such markings, and none of my cut rifled barrels have them. I too have often wondered what was the cause: could not have been the pilot on the chambering reamer, since they are too far forward. My first thought was it was caused at the end of the button rifling process. Could the button have been pulled out too fast and it "skipped" across the top of one land? All conjecture on my part, I haven't a clue. Someone with a lot more knowlege than I will be needed. Does not seem to effect accuracy: both barrels are consistant sub MOA. An after thought: So we're all on the same page: My mark(s) could be shown in a simple line drawing- two lines running side-by-side/ the lands. Start another line at one of the edges, and as you move forward, make the line cross-over the top surface of the land, having it "end" on the opposite side. Look familiar?

 

[GerryM]

Yes it is possable for a button to skip .
Both by pushing and pulling. Usually these barrels don't get out of the shop.
I don't know what barrel brand it is but the maker should be told.
I'm sure he would like to know about it.
Most of them are really concerned on what leaves the shop.

 

[savage308]

i have the same marks you have just more of them. i really think mine might be from trying to use JB bore paste to
get out stubborn copper becouse i work a smaller size brush with a large tight fitting patch back and forth as i have been told to do on many posts to get the copper out.i have done this on many guns and this is the only one ive seen the marks on.

 

[fdshuster]

savage308: I also use JB ( a lot) to remove carbon fouling, and have never found "new" marks after using the JB. I'm always monitoring my bore conditions, constantly, and I know in both instances, my "marks" were there before the rifle was chambered & fitted. The first marked barrel got by me: I did not notice the mark 'til after it was threaded, chambered & fitted. Barrel is a tack-driver so I was not concerned when I saw the same type of a mark on the second barrel, same maker. Send me a pm if you're interested in swapping maker I.D. I'm very happy with this companies barrels & don't want to cause them any negative feedback.

 

[Klong]

Sounds like tool marks from the rifling process. I have seen heavy tool marks in my Savage 22-250 barrel.

 

[fdshuster]

Klong: I believe what you are describing are the typical reamer & tool marks that are the result of reaming ( making it a true circle) the bore before the button is used to form the lands/grooves. The reamer marks are always 90 degrees (or very close to it) to the direction of the rifling, and are caused by the chips produced by the reamer. If the reaming is done slowly & the chips are kept flushed out, minimal damage. If the barrel maker is in a hurry (low cost factory production barrel), the damage becomes heavier. I have Savage & Remington barrels that are ugly with cross-reamer marks. Cannot speak for Savage308's barrel, but my barrels with the marks are all hand-lapped, premium, $300+ barrels, and none of them, including the 2 with the "marks" have any cross (90 degree) tooling "gouges": If they were there after reaming, they would have been removed by the hand-lapping process. Just took delivery on a new cut-rifled 6mm, 1-14 for my 6ppc, and when it arrived, it was thoroughly borescoped. Completely flawless in every respect. If, after chambering, and before firing I see any of the "marks" type damage, then I will have proof that it was caused by the pilot of the (my new Pacific) chambering reamer. 'Til then I am leaning toward the belief it was caused by the button "skipping" across the land(s).

 

[Klong]

Frank, you could be right. The marks in my barrel were not in the chamber area, but the entire length of the rifled part of the barrel. It could be button skipping. They appeared to be circles left only on the lands and they were very deep or tall. It would take considerable lapping to remove them.

 

[fdshuster]

klong: Yes, the factories are limited to how much time they can put into their barrels (and the whole rifle, for that matter), and still be cost competitive. The premium barrel makers will deep drill the bore, and ream, just as the factories, but they leave more metal in the bore diameter, then hand lap and are able to remove the reamer damage. They then are able to button swage or cut the rifling starting out with a perfectly smooth bore surface. I understand the bore is then given a final hand lapping after the rifling is swagged or cut. All very time consuming and expensive, and let's face it, the "average" once-a-year shooter (maybe 20 rounds?), really does not care about it. Funny thing is, some of my factory barrels are downright ugly, but will still shoot to varmint rifle accuracy requirements and standards, MOA. Those that won't are either sold or re-barreled. So much to learn, but I'm running out of time.