Rimfire Bore Erosion

[Outback]

Pete,

With the AN2000 rifle it is a easy task to reset a barrel - with a cone chamber it is a good idea to rotate the rifle barrel after around 2000 rounds to get more even wear on the lands - remember the worn edged bottom land in around 8 inches is at the top where there is little wear - the top land does the same in reverse - this means the lead's groove meets a changing land as it proceeds down the barrel - there would have to be some instability involved here and maybe setting up particular vibrations that may distort the lead
The finer and more even the barrel residue is, the greater chance you have of achieving a more consistent higher score - it is an experimental game to achieve this - the ability to do a barrel change in around 5 minutes with the AN2000, lends itself to the rifle where you can gain practical knowledge on different set ups
Over the years, taking notes from this forum and building rifles, has lead to gaining some valuable knowlege and competition success

Outback

[Outback]

Tim

The rifle referred to is the Swiss rifle - Bleiker - Small front locking bolt - pin at 6 - part of the chamber is set into the action (it is still a normal type chamber, just there are 2 parts to it) - this results in a small expansion area as the primer end is a little larger in diameter - just pick up a spent case from the latest model, "Challenger" - in finals in Olympic SmallBore, these are the leading rifles at present - and yes this rifle has a finer residue and spread more evenly

Outback

[Tom C.]

thanks for stopping in ob have a good evening.

[Old Gunner]

Originally Posted by Pete Wass

some folks who shoot CF rifles set their barrels back after a few hundred rounds to have a sharp throat most of the time. Do RF folks do this as well?

Yes at least they used to do so.
Some older single shot target pistols didn't have a throat, the bullets were pushed in to engrave to the rifling before firing. When people run across these old pistols they think they are .22 short chambers.

Atomized glass if imbedded in the bullet acts as a fine lapping compound, to polish the bore like a slow fire lapping process rather that eat away at it visibly as the gas driven particles do at the throat.

PS
Most old centerfire rifles and Shotguns I've examined showed more pitting on the upper surface of the bore. I'd figured this was due to gravity pulling oils away from the top while on a rack for years at a time.

[crb]

Originally Posted by tim

Gerry gave you your answer. That hard crystaline particulate lays in the warm lube and gets "ironed" in repeatetly.

So you are saying that the gun is making it's own lapping compound but this lapping compound is selective and only works on the bottom of the bore ? Even though the lap [ aka the bullet ] makes a full revolution in the bbl this selective compound only etches the bottom 2/3 of the bore.

That has not been my experience with lapping a large number of poppet valves. You can put one small spot of compound on a valve and lap the seat and when you clean the lapping compound off the parts you will have a nice lapped surface for the full 360 degrees.

[Old Gunner]

One factor to consider, that was noted in tank main guns and anti-tank guns more than guns fired at a high angle. Guns fired at near parallel to the ground showed greater erosion on the lower surface of the bore due to gravity acting to pull downwards on even a spining projectile.
These were much heavier projectiles of course, but less dense than a solid lead bullet, at least till metals heavier than lead came into use for projectiles.

[tim]

Originally Posted by Outback

Tim

The rifle referred to is the Swiss rifle - Bleiker - Small front locking bolt - pin at 6 - part of the chamber is set into the action (it is still a normal type chamber, just there are 2 parts to it) - this results in a small expansion area as the primer end is a little larger in diameter - just pick up a spent case from the latest model, "Challenger" - in finals in Olympic SmallBore, these are the leading rifles at present - and yes this rifle has a finer residue and spread more evenly

Outback

Thanks. There have been a few conversations about the Bleiker as to BR applications but so far none[ that I know of] have been used to build a rifle. I believe the barreled actions can be bought utilizing the Lilja but don't know if bare actions can be purchased. I do know that thy are quite costly. I understand the triggers are just beautiful. Is there any chance you can ever post an image of the bolt face or any part of the "floating" chamber ?

[JJ-IA]

Originally Posted by crb

So you are saying that the gun is making it's own lapping compound but this lapping compound is selective and only works on the bottom of the bore ? Even though the lap [ aka the bullet ] makes a full revolution in the bbl this selective compound only etches the bottom 2/3 of the bore.

That has not been my experience with lapping a large number of poppet valves. You can put one small spot of compound on a valve and lap the seat and when you clean the lapping compound off the parts you will have a nice lapped surface for the full 360 degrees.

IMO
It’s because your only applying the grit (compound) on the bottom of the bore, it does the most damage while embedding into the lap (bullet). Say it takes an inch to embed, there isn’t much twist in an inch.

Lapping valves is a poor example unless your shooting steel bullets with non embedding lapping compound for powder. But I always used several dabs and rotated the valve with little pressure to distribute the compound before going to town with it.
Lapping barrels is a better example, and the cut-off mark some distance before the muzzle where the compound is embedding into the soft lead lap.

One other note.
Shooting a bullet after running a loose patch through a barrel doesn’t leave much of a smudge on the target, the second shot leaves a smudge all the way around the hole, evenly.
If the crud is blown out ahead of the bullet, why is the smudge even and darker?

[Old Gunner]

I ran across an except from a book on forensics and crime scene investigation.
The subject was how to quickly ID whether a hole in wood work was a bullet hole or an old nail hole .
Bullets even the smoothest FMJ pick up and carry lead to be scrapped off on the edges of a hole in wood or wall paper.
Even FMJ bullets leave atomized lead in the bore due to powder gas erosion of the exposed base.
Same would apply to any thick fouling, and .22 rimfires seem to smoke up a bore quickly.

[Carp]

It’s because your only applying the grit (compound) on the bottom of the bore, it does the most damage while embedding into the lap (bullet). Say it takes an inch to embed, there isn’t much twist in an inch.

Lapping valves is a poor example unless your shooting steel bullets with non embedding lapping compound for powder. But I always used several dabs and rotated the valve with little pressure to distribute the compound before going to town with it.
Lapping barrels is a better example, and the cut-off mark some distance before the muzzle where the compound is embedding into the soft lead lap.

One other note.
Shooting a bullet after running a loose patch through a barrel doesn’t leave much of a smudge on the target, the second shot leaves a smudge all the way around the hole, evenly.
If the crud is blown out ahead of the bullet, why is the smudge even and darker?


You are right that the barrel doesn't twist much in an inch. I will say however that the smudge has to do with the leading part of the driving band on a RF bullet to "catch" some of the debris and carry it through the barrel and leave the smudge on the target. I had my barrel set back and re-chambered some 3/8" +- this year to limp by the rest of the season. The "wash-out" that was visible by the naked eye was at 6:00. It was obvious and detrimental to accuracy. The barrel setback and rechambering gave more life to the barrel (better scores and placement in matches) but is temporary. The gun still doesn't shoot like it did when the barrel was newer (bought it used). Gravity leaves the debris in the 6:00 position and air pressures push some (how much?) out the barrel ahead of the bullet and the rest of the stuff just simply slowly laps the barrel until it isn't competitive anymore. I have no data on the number of rounds it takes. I noticed a loss in accuracy a year + ago and started refining the problem. It will be a new barrel this winter. Hope This helps with all who have been seeing loss of accuracy.

Carp

[Outback]

Tim
Photo of Bleiker "Challenger" Bolt with 6 oclock firing pin - Bolt is 3.75 inches long & Bore Deposits

_22-Bore-Deposits.jpg

Bleiker-Bolt.jpg

[Tom C.]

thanks for the photos how does it load
feed ramp, magazine? any pictures?

[Outback]

Tom C,

No magazine - the loading port is on springs & drops down as the bolt is pushed forward

[Tom C.]

beautiful bolt. i'll do some searchs. what price
range they run in. 5k-10k.usd?

[tim]

Originally Posted by Outback

Tim
Photo of Bleiker "Challenger" Bolt with 6 oclock firing pin - Bolt is 3.75 inches long & Bore Deposits

Attachment 8746

Attachment 8747

Outstanding, thanks. Does the bolt handle act as a lug as well or just the front 2 lugs? Any chance of an image of the breach end? This has been very informative. By the way I know several of the Aussie intl team use Bleikers, you one of them? Understand if you defer.