The death of a good barrel from Bartlein point of view

[Tim L]

Can someone come up with a theory as to how something blasting down the barrel can damage the lands but not the troughs?

Unless we can get round that, I find it hard to accept this was caused in that manner.

Interesting to see that the damage runs longitudinal with the barrel (it was hard to determine that in the other photos) so again, how does something being blasted down the barrel resist the effects of the rifling, which will make anything going down the barrel want to spin with the rifling?

[Tim N]

For the novice detective can someone explain how the grooves are formed in a bartlain barrel?
The second photo seems to show a "grain" in the grooves running parallel to the damage on the lands.
Which for me could mean the gouges were there prior to the rifling process, then compressed flat during that process?
May also explain how the gouges finish so neatly each side of the lands.

[DaveMc]

Thanks Peter for putting in the work on this.

We have actually seen the results of redding beads blasted down the barrel in an earlier post http://ozfclass.com/phpBB2/viewtopic.ph ... ght=#37467 and the effect is quite different. I really don't think this is the case anymore. I originally thought it could have been the ss media but I can't see this anymore either. The consistent way they run through the lands is not what you would expect. Rods travelling down the barrel would not "track" like this (They would bounce off the lands not into them) and perfectly end on all the time. The direction of the tracks seem to bend up and over the lands. Generally following groove direction then catching and changing direction to bore direction.

Put all this in context with the grooves and lands being significantly eroded (in order of 1+ thou from Franks measurements) as well.



Put all that together............


Tim N - This was explained earlier in the piece and is "almost definitely" not a manufacturing issue - I would put my house on it.

[Tim L]

That could be a bit of a gamble Dave. The only way I can see there being gouges on the lands and not in the grooves is if they were there in the bore but cut out when the grooves went in. Maybe not visible but there waiting to happen through a flaw in the material.

I really cannot see how this can occur AFTER the rifling is put in. ANYTHING going down that barrel is going to want to stay in the bottom of the groove, that's just physics. If you want it to skip across the top of the lands it's going to take some external force to do it.

[DaveMc]

Simply Tim, (but I have the advantage of being able to see the real thing)The bottom of the grooves appear worn as well 1+ thou taken from them as well. Plus the gouges go up the side of the lands (as mentioned earlier - if it was cut in original bore before rifling cut then this would not happen) whatever is making the tracks over the lands is also affecting the bottom of the grooves but not "tracking" there - just eroding in a significant manner. As it hits the lands the eroding substance wants to track - or follow the same groove. All grooves are of similar diameter and formed by small cylindrical objects.....

Also this got worse and worse with time and originally was a cracker.....Tony's other barrel is showing same symptoms but in an earlier onset and has less rounds down the barrel. Hardness testing has found barrel to be in the correct state...

We are narrowing in on it - but lets see if any new suggestions come forward from these observations.

[DenisA]

In respect to the grooves on the lands, what about the possibility of the end of the twisted core of the brush scraping the lands. It could be a poorly manufactured bulky end or a slight bend in the brush.

Is the cleaning rod definitely rotating in the handle with the rifling?

It'd be interesting to get the brush in the bore of the second barrel and poke the bore scope up the muzzle end to how much clearance there is.

Doesn't explain the all over excessive wear, but just a thought.

[DaveMc]

ANYTHING going down that barrel is going to want to stay in the bottom of the groove, that's just physics. If you want it to skip across the top of the lands it's going to take some external force to do it.

Yes - that is simple physics. - look closely, the gouges seem to "want to" track in bottom of rifling as their direction at bottom of slope is almost parallel with rifling but get dragged up slope and then when they hit the top of land they track straight down the bore (cleaning rod pressure direction?).
Not all follow this exactly but a great percentage do.


Denis - Yes this is a valid suggestion but doesn't explain the general wear - they could however be two separate events. One from overuse of paste, the other from a dag of hard materieal or other hanging off end of cleaning rod (ferrule) or brush/jag. I went over this with Tony and he is fairly confident none of that occurred and it is hard to imagine how this created fairly evenly spaced gouges over the lands but possible......

[AlanF]

If some stainless steel pins were left in a case, and they went to bottom of the case before or during the powder filling, then perhaps they would not all be ejected behind the projectile, with some left in the bore to be pushed ahead of the NEXT projectile, when the main damage would be done. Would be interesting to see where the damage starts at the chamber end. If the gouging starts at various distances from the chamber for different "clock positions", it would support this theory.

[DaveMc]

Alan - If left in the barrel they would all start on the bottom at various lengths down the barrel. And no doubt get wedged between projectile and wall and then travel down barrel in direction of rifling or straight along bottom of barrel in front of projectile (which I can't imagine would happen)- similar to the damage done by the balls in other thread - I was thinking something like you suggested earlier but just can't see/imagine it in the real thing. These gouges are all the way down the barrel and all the way around. At this stage I personally can only imagine something in the cleaning process.......driven by a cleaning rod that wants to travel with bore direction but a force applied in the direction of the rifling by the grooves.

[AlanF]

Dave - are you saying the gouging definitely all starts at the throat? As far as pins settling near the bottom of the bore, agreed, but if this occurs over the first 9 inches, then maybe the pins could be picked up on different lands due to the twist of the rifling?

[DaveMc]

I don't have all the barrel here Alan but from my understanding they are yes. But more importantly I can't see how the pins would get pushed "across" the lands if it was picked up by the projectile. They would surely wedge between projectile and wall and then get pushed along in front of projectile and spin with rifling - I can't see how they would climb over rifling and I can't see that you wouldn't get gouges in bottom of grooves like the balls did.

[GregW]

Stainless steel barrel billets sometimes have what is known in the industry as "stringers". These are longitudinal faults which do not follow the rifling. I haven't seen any for many years though. They are usually invisible until filled with carbon and then appear to the naked eye. They are generally deemed to be "cosmetic" and do not affect accuracy. One in particular had fired 3,000 rounds before the owner noticed. The barrel had performed very well up until then and continued to perform for many rounds after.

Greg Warrian.

[Frank Green]

AlanF and DaveMc, Thanks for all the help and comments!

AlanF thanks for posting the pictures and taking the time to cut the barrel sections etc...


To reply to a couple of comments about possible cleaning/cleaning rod damage. This has some merit/possibility.

We get comments/questions from customers from time to time that the cleaning rod/handle is not rotating when pushing it down the bore with the 5R style rifling. This happens more with this style of rifling then with Whitworth/English/Conventional type rifling. This is because of the angle on the sides of the lands. That angle will cause a loose fitting brush/patch etc...to slip vs. the conventional style. The conventional style rifling will hold onto the brush/patch better and the rod will rotate nicely with the rifling.

If something happened during the cleaning process this would explain why the gouges kinda seem to track with the twist of the rifling but not completely.

Again though besides the gouges I cannot explain how the bore and groove sizes got bigger/changed as well. Also the finish in the grooves is different. Compared to a new barrel or a barrel that has been fired and no cleaning damage etc....the grooves look like they've been chrome plated they are so shiny.

Later, Frank
Bartlein Barrels

[Frank Green]

Simply Tim, (but I have the advantage of being able to see the real thing)The bottom of the grooves appear worn as well 1+ thou taken from them as well. Plus the gouges go up the side of the lands (as mentioned earlier - if it was cut in original bore before rifling cut then this would not happen) whatever is making the tracks over the lands is also affecting the bottom of the grooves but not "tracking" there - just eroding in a significant manner. As it hits the lands the eroding substance wants to track - or follow the same groove. All grooves are of similar diameter and formed by small cylindrical objects.....

Also this got worse and worse with time and originally was a cracker.....Tony's other barrel is showing same symptoms but in an earlier onset and has less rounds down the barrel. Hardness testing has found barrel to be in the correct state...

We are narrowing in on it - but lets see if any new suggestions come forward from these observations.

TimL, To go over what DaveMc said and what I posted earlier.....these are the things I cannot explain. Lets break down the damage to the different areas and will go over the manufacturing process.

We do single point cut rifling.

The barrel is drilled approx. .008" undersize. No where close to bore size. So no way this can damage anything to the bore or grooves. This is ruled out.

The barrel gets reamed. Approx. .0002" to .0003" under finish bore size. The reamer basically is only touching the tops of the lands (this is the actual bore). If the reamer has any damage or lets say it's dragging chips or roping etc....again it will only effect the tops of the lands (the bore). If the reaming operation was the cause this won't explain the gouges on the sides of the lands. So I rule this out as well.

Prelapping the barrel after reaming and getting the barrel ready for rifling. Again this only touches the bore/tops of the lands. So I rule this out.

Rifling.....the rifling head basically for a lack of a better description will ride the tops of the lands (the bore). I have seen damage to the heads wreck/damage a barrel during the rifling process but because the rifling head rides on the tops of the lands it will only cause damage to the bore. It doesn't touch the sides of the lands. So I have to rule this out as it doesn't explain the gouges on the sides of the lands. Also each groove is approx. .0035" to .004" deep (depending on caliber). The rifling head cannot get no where near the sides of the lands or the grooves. So where do the gouges come from on the sides and this also doesn't explain the larger groove size and some minor gouges in the grooves.

The hook tool that cuts the grooves and the sides of the lands only touches the groove during rifling. If the tool tearing/causing skidders etc..it would only effect the grooves and the sides of the lands. It won't leave the gouges on the tops of the lands/bore. So I rule this out as the cause.

Finish lapping causing damage after rifling? It would be possible but the only way I see it leaving gouges like this is if metal chips were left in the bore of the barrel and the chips got cast into the lead lap somehow I guess? But I say no. The barrel is cleaned out with solvent after rifling and inspected for size before it's pulled from the rifling machine etc...The barrel gets finish lapped and visually inspected after lapping as well. If there were metal chips of some sort in the lead lap I guarantee the amount of resistance and the feel it would case you would know something is wrong right away.

and....

with the bore and groove size based on the cut off piece Tony sent us being a .001" or more bigger I cannot explain how this happened as well.

To many things work against one another and rule out it was done when the barrel was made. I just went and randomly pulled another 7mm barrel we just finished this morning and bore scoped it and again I cannot find anything. Believe me if it was something we did I want to find the cause of it so it never happens again but I'm totally baffled.

Later, Frank
Bartlein Barrels

[AlanF]

...AlanF thanks for posting the pictures and taking the time to cut the barrel sections etc...

I posted the pictures Frank, but Peter Smith, one of our foremost experts on these things, did all the work and authored the report.

BTW I hope you know that regardless of what people suspect has happened with this barrel, there are many of us very keen to have Bartleins available here in Australia. My Bartlein which was bought in the same order as the problem one, has just helped me to win the F-Open class in our premier event the National Queens Prize. It has now done 1200 rounds, and by the condition of the throat, has plenty more to come.

Alan