Vent liner question

[Don Steele]

I acquired a new rifle last June. Colerain B wt 50 cal bbl. The vent liner is an Ampco with 1/4 x 28 threads. When new the opening measures.0625”. I’m shooting pretty mild loads, 55 gn 3f Goex.
I’ve kept track since getting this rifle and as of today, I’ve put 700 rds  through it.
The opening in the vent liner is now measuring.0685”. From time to time lately, I’ve been noticing small amounts of 3f coming through the hole in the liner into the pan when I load.
I’m curious what others experience is with Ampco liners. All I’ve had much experience with are Jim Chambers and they lasted considerable longer before opening up like this one has.
I’m also interested to know which Chamber’s liner to use in this bbl.
Thanks for sharing your thoughts and experience.

[rich pierce]

I’ve got an ampco liner from 1978. I dong shoot that much but it’s my main gun. Hasn’t enlarged noticeably. Yours might have had a very thin wall.

[smylee grouch]

On some liners if they are not screwed in far enough the excess thats filed off flush with the barrel can make that part of the liner quite thin. If so the thin portion might erode faster or wear faster if you pick the vent with a hard vent pic.

[Don Steele]

Thanks for the thoughts.
I don’t pick at all.
Ignition is quite good ( speed-wise) and very reliable since day one.
Not sure when I’ll be replacing the Ampco, but it probably won’t be too much longer given the amount of erosion that has occurred in only 700 shots.

[Old Ford2]

Shooting round ball, it is rare that the touch hole will get larger, but as said above, IF the wall thickness was too shallow to begin with, that could happen.
A new liner should NOT protrude into the barrel, and yet should not protrude into the pan.
A lot depends how thick the wall thickness is. There must be enough to hold the full liner.
I have made many liners from stainless steel screws and never had any problems.
The wall thickness should be at least  0.250" to allow the internal cavity of the liner to exist, which should be about 0.0625 to 0.0825 leaving enough wall thickness.
If you have a slot remaining for a turn screw, the wall thickness is even less.
Have a great day!
Fred

[L. Akers]

Ampco is NOT an alloy--it is the name of a company that makes brass alloy metals.  They do not make end user products.  That means the company that actually makes the products must choose the proper alloy for the purpose.  I have not found any "Ampco" liners with a touch hole smaller than .062 when new.  I have also found they erode faster than a stainless steel liner made of high temperature alloy.  As I prefer .059 dia. touch holes, I make my own from 316 high temp stainless. 

If you were to change your liner, even using another Ampco liner, you will be astounded at how much faster your ignition is.  It helps a lot to cone the inside of the liner, leaving a flash channel of about 1/32".

[hanshi]

All the liners resting in my guns and the spare ones in my shop are stainless steel.  So far I've detected no erosion even with one rifle with over 1,000 shots fired.  Before firing I always drill out the vent hole to 1/16" and cone the inside with a Dremel tool.  As a test I fired a .45 without priming, just with the "self prime" from the vent.  I'd shake the rifle a time or two and try it.  Out of, oh, maybe ten times it fired at least twice.  I use mostly 3F and it's not unusual for a few kernels to end up in the pan. 

[D. Taylor Sapergia]

If you replace that liner which incidentally is made of Berylium, and replace it with a Chambers White Lightning, you must go up in size to a 5/16" x 32 tpi.  Their vent openings are less than 1/16"...I always drill them out to 1/16" though it may not be necessary.
Personally, yours doesn't need changing.

[Don Steele]

Thanks Taylor. That's very helpful.
As far as Ampco liners, looking through various sources online, I've seen them referred to as Bronze, Beryllium, and something called "Copper-Beryllium", or maybe it was "Beryllium-Copper".
My only other (relatively) extensive experience with vent liners has been with a stainless one (unknown maker..) that Mike Davis put in my SMR. Whatever that one was....when we pulled it out ( Thanks Moleeyes)the threads told us it wasn't one of Jim's.
It was getting pretty eroded at something over 3,000 rds. and was replaced with a Chambers. 
I'm not ready to change the Ampco just yet, but the erosion has become sufficiently obvious after only 700 rds. that it got me to wondering what others have experienced, how long this one will last and what the common metric is for changing a liner.

[davec2]

Don,

Ampco is indeed a company that makes alloys of copper.  Many contain iron, aluminum, and tin in small amounts to improve one mechanical characteristic or another.  However, they also make a family of alloys that include cobalt and beryllium (up to about 2%).  The beryllium makes for an incredibly strong alloy that still retains excellent thermal conductivity.  I have made liners out of the beryllium alloy and they hold up as well as any of the stainless steel liners I have used.  In the rocket business, we use beryllium copper for a lot of things because the increased thermal conductivity allows the alloy to maintain strength at high heat flux because the heat is being absorbed by the mass of the material.  The erosion in your case is undoubtedly related to the thickness (or thinness) of the edge of the flash hole and also which Ampco alloy was used to make the liner.  (Ampco makes 30 or so different alloys).

Taylor,

The liner may or may not have some beryllium in it, but it is certainly not made of solid beryllium.  Solid beryllium, although a metal, will shatter like glass in thin sections.  Just 1 or 2 % beryllium added to copper is used to make very strong, non magnetic tools that are used in the explosives industry and military ordnance assembly and disposal applications.  I have added 1% beryllium to silver to make a very strong silver alloy that has a unique characteristic....it will never tarnish.

[rfd]

i'm a recent chambers white lightnin convert and i'd Highly recommend looking into replacing the ampco with a stainless steel 5/16x32 wl.