Rimfire chambers

[tonykharper]

In another thread we got off topic and started discussing chambers for RFBR rifles.

People often say they have a chamber for Eley or a chamber for Lapua. I asked the question what is it that makes a chamber unique to one brand of ammo?

I've chambered a number of barrels, but I do not claim to know the best way to do it. What you read here is just me. No claim to be right.

It may very well be the worst way to chamber a barrel. If you choose to use any of this, do it at your own risk.

Many people choose to bore their chambers, some even bore part way, and finish the leade with a reamer.

I've tried it, but didn't like it. Perhaps you need better equipment than I have. I have an old South Bend Heavy 10 Lathe.

This is a pic of my shop and Lathe. This is old equipment, but it still works. The ARA indoor Nationals was just won by a rifle built 13 years ago on equipment much older than this.



Here is a list of popular .22 rimfire reamers. I've only used four of them. The reamer I use now is a spiral cut cobalt Calfee reamer. It is straight sided and has a 2-degree leade.

I think Bill Meyers used a 1.30 degree leade reamer. There may be people that can tell a 1.30 from a 2.0 but I'm not one of them. Does it make a difference? I doubt it.

Who knows what happens to the angle of the leade when you finish the chamber? I bet it changes.



These are reamers I have used.



Now you know the equipment I'm working with you may be able to help me.

I have chambered some really good barrels. Some have even set world records. But only rarely are any of my chambers alike.

I chamber using my best ammo as my guide. I know I want the bullet engraved to the second driving band but not further.

The problem is the second driving band isn't in the same place on every round. Certainly not brand to brand, or lot to lot.

I end up using 20-30 rounds of my best ammo to get an average. I then cut to that number. It is always a compromise.

Before you even ask, when that lot number runs out, I try to find another that was like the last but not always possible.

If anyone out there has magic numbers, please share.

TKH (4628)

 

[Pete Wass]

Do any of you know

how long a Chet Amick chamber is? He built some of the best rifles ever made, according to some. I do know for I measured one.

Pete

 

[tonykharper]

how long a Chet Amick chamber is? He built some of the best rifles ever made, according to some. I do know for I measured one.

Pete

Pete,

I doubt it matters what length his chamber is unless you also know the working length of the ammo he was using.

TKH (4628)

 

[Kent Owens]

Tony, I think it's close to impossible to find the magic number. Too many variables to deal with, ammo length, difference in bore sizes. But, I do think that in a great barrel, it's easier to get it right. LOL But, a very interesting thread.

 

[tim]

Pete,

I doubt it matters what length his chamber is unless you also know the working length of the ammo he was using.

TKH (4628)

I suspect not particularly relevant by current standards since Chet did them all in the era of gold box Lapua M&L which he and most others shot exclusively, mostly L.
A side note, he did them all with one reamer and his own custom formulation cutting lube.

 

[jim1K]

Tony, I'm surprised you use a floating reamer holder over a dead center..... Jim

 

[tonykharper]

Tony, I'm surprised you use a floating reamer holder over a dead center..... Jim

Jim,

There was a time I thought could hold a reamer in a simple hand holder. I tried it a few times. I'm sure there are guys that can do that, but I 'm just not one of them.

I do what I can, and to be honest I haven't found the floating holder to be a determent.

I careful align the tail stock and then use the floating holder. I do steady the holder with my hand. When I study the chambers with a loupe the lands seem to be equal.

When I push bullets into the landings, and back out, they seem to cut the bullet pretty equal. Bullets push all the way through also look pretty equal all the way around.

But most important the barrels seem to shoot as good as my other rifles.

I'm certainly open to suggestions.

TKH (4628)

 

[Pete Wass]

What I think

Pete,

I doubt it matters what length his chamber is unless you also know the working length of the ammo he was using.

TKH (4628)

is its analogous to any loaded round of ammo. Some people stuff them into the lands and some Jump em. Chet jumped em.

I generally use .006" into the lands measured from where land marks are visible, in a bright light, with CF ammo. This would be the working length. Some barrels ( very few), will not shoot best at this setting. I then adjust powder for a single bullet hole group. Obviously we can't do this with Rimfire ammo so we set the seating depth up front and find ammo that shoots in it. Same applies to jumping. Jumping also depends on working length but is a black science I don't participate in with CF rifles.

It doesn't matter the era of the ammo or the brand. It's a simple proposition, either shoot jammed or jumping.

I think a longer chamber in a RF barrel may give more flexibility regarding "Working Length", Just a thought.

Loaded ammo is loaded ammo.

Pete

 

[tim]

is its analogous to any loaded round of ammo. Some people stuff them into the lands and some Jump em. Chet jumped em.

I generally use .006" into the lands measured from where land marks are visible, in a bright light, with CF ammo. This would be the working length. Some barrels ( very few), will not shoot best at this setting. I then adjust powder for a single bullet hole group. Obviously we can't do this with Rimfire ammo so we set the seating depth up front and find ammo that shoots in it. Same applies to jumping. Jumping also depends on working length but is a black science I don't participate in with CF rifles.

It doesn't matter the era of the ammo or the brand. It's a simple proposition, either shoot jammed or jumping.

I think a longer chamber in a RF barrel may give more flexibility regarding "Working Length", Just a thought.

Loaded ammo is loaded ammo.

Pete

He most certainly did not “jump “ them” using any accurate description of the term…..this, first person from him to me as well as a good 10-12 of his chambers I have first hand knowledge of. He usually went to, or slightly into the first band however this was gold box and easy to miss if you try , now, with shorter lots.

As far as “flexibility”, taking him at his published word, why do you think the WLM campaigned so publicly for ELEY
To publish OAL data on lots? Now here is pure speculation on my part but a. It wasn't because of flexibility and b. I’d guess he knows more than you regarding chamber lenght.

 

[tonykharper]

is its analogous to any loaded round of ammo. Some people stuff them into the lands and some Jump em. Chet jumped em.

I generally use .006" into the lands measured from where land marks are visible, in a bright light, with CF ammo. This would be the working length. Some barrels ( very few), will not shoot best at this setting. I then adjust powder for a single bullet hole group. Obviously we can't do this with Rimfire ammo so we set the seating depth up front and find ammo that shoots in it. Same applies to jumping. Jumping also depends on working length but is a black science I don't participate in with CF rifles.

It doesn't matter the era of the ammo or the brand. It's a simple proposition, either shoot jammed or jumping.

I think a longer chamber in a RF barrel may give more flexibility regarding "Working Length", Just a thought.

Loaded ammo is loaded ammo.

Pete

Pete,

In my experience jumping a rimfire soft bullet fouls the leade very fast. This destroys any kind of accuracy we expect in RFBR.

Chet had another thing going for him, he was an avid shooter that put a lot of rounds down his barrels. Whatever his other secrets, they were well kept.

TKH (4628)

 

[jim1K]

Tony this is a good thread glad you started it...... Jim

 

[tim]

Pete,

In my experience jumping a rimfire soft bullet fouls the leade very fast. This destroys any kind of accuracy we expect in RFBR.

Chet had another thing going for him, he was an avid shooter that put a lot of rounds down his barrels. Whatever his other secrets, they were well kept.

TKH (4628)

Tony, from getting to know him pretty well, IMO his real mastery was in lapping barrels. Most of his Hagerstown 250/25X’s were shot with different barrels as to mfr and configuration.
He understood the need for consistent taper and bore dimension and invested a lot in a set of deltronic pins that went to 1/2 a tenth.
He also had some sort of unique lapping compound he got from a buddy at NASA but would not talk much about that.
Amazing that all this was some years before much of it became established practice.
A shame the guy passed away when he did, virtually everything went with him, it would have been something to witness.
Pretty damn good for a guy that ran a transmission shop.

 

[tim]

Tony, another vote for a great thread, lots of good stuff, sorry to side track.
Do you do any post chamber finishing, lapping, etc ?
Lastly, do you vary chamber length after initial cut based on rate of fouling ?

 

[Pete Wass]

The one I measured

He most certainly did not “jump “ them” using any accurate description of the term…..this, first person from him to me as well as a good 10-12 of his chambers I have first hand knowledge of. He usually went to, or slightly into the first band however this was gold box and easy to miss if you try , now, with shorter lots.

As far as “flexibility”, taking him at his published word, why do you think the WLM campaigned so publicly for ELEY
To publish OAL data on lots? Now here is pure speculation on my part but a. It wasn't because of flexibility and b. I’d guess he knows more than you regarding chamber lenght.

is at a minimum .020" longer than the Eck chambers I have. I have a tool to measure rimfire chambers so I know of what I am speaking.

Pete

 

[Pete Wass]

That hasn't been my experience

Pete,

In my experience jumping a rimfire soft bullet fouls the leade very fast. This destroys any kind of accuracy we expect in RFBR.

Chet had another thing going for him, he was an avid shooter that put a lot of rounds down his barrels. Whatever his other secrets, they were well kept.

TKH (4628)

A person who cleans their barrel frequently shouldn't have any problem. Unfortunately it is difficult to discuss this sort of stuff in detail because some folks don't want the world to know what their equipment is. I'm not one of them but I have seen rifles with big jumps work very well.

If I were more interested, I would start with engraving to where there is just a touch, try that and increase by .003" each time to see if there was any improvement. There will be a point where there will be an improvement and an optimum. I am all about starting with an exact, measurable amount with anything I do, a measurable amount, with real measuring tools, a Benchmark, if you will. Then one advances or retracts by an exact measurable amount, the mystery of how much or how little goes away. Just the way I have always done things. Good machining practices. Folks sell micrometers to fit around reamers that will easily allow increment of .001" to be cut. I'm sure I am not the only person who has used this approach.

Where does it get one? I don't know for sure but I do know that .003" increases is the number many people who tune rifles use and why I would approach investigating Rimfire seating depth or engraving, if you will, in that way.

Pete

 

[glynn angle]

If we were allowed to make our own rimfire ammo, this would be a very interesting Forum !

 

[tonykharper]

ammo tool

I have something I would like to share and I'm not sure if it belongs here or in the ammo thread. I'm going to put it here and maybe add it to the ammo thread as well.

As I mentioned before my chambers are rarely identical, then again, the ammo I shoot, lot to lot isn't identical.

Pete my benchmark is to engrave the bullet up to the second driving band and no further. When I first discovered this, I thought I could fix it, so I came up with a tool.



This tool allows me to do several things. I can spin the bullet to see if it runs true.

Years ago, the crimp on Eley was so loose you could rotate the bullet in the case. Sometimes the indicator would straighten the bullet as I turned the handle.

But the main purpose of this tool was to cut the first driving band so the driving band started the same place on every round. My thought was it would be consistent.

I spent hours fixing my bullets. At this same time, I was weighting and measuring the rim thickness on each round.

I look back now, and wonder was it really worth it. I don't think so, but you would never have talked me out of doing it.

Tim,

I do finish my chambers or at least try to. But I also believe every barrel can benefit by having a "Post Chamber Lap".

This is a lot of trouble, but I believe, worth it.

This is quite different from lapping an unlapped blank. At least the way I do it.

Paul Tolvalstat is probably the best barrel lapper in the world today. He will probably laugh if he reads this.

But after I cut my chamber and do my finishing work, I clean the barrel thoroughly. Then I cast a lap in the barrel and work it lightly, just a couple of passes all the way through the barrel.

Yes, I have gotten the lap stuck in the bore, and yes it pisses me off, but when I finish, I feel I have done all I can do.



I rarely have trouble with fouling, so I don't recall ever reworking a barrel for fouling. That said, most of the time I have to take the barrel back off and make adjustments.

I try not to cut extractor cuts until the rifle is shooting to my satisfaction. I have cut chambers off and had another go. Every time I've done this the barrel never seemed to get better.

TKH (4628)

 

[tim]

Great stuff Tony…thanks.

 

[linekin]

Chambering a rimfire barrel is not difficult. Its pretty basic machining. The art is knowing where, & the finishing of it.
I do not finish a chamber because, well,, I do not know how. The barrels all seem to shoot fine however I've always felt I've left something on the table.All you ever get or hear is "proprietary" method whatever that is. Tony,or anybody, would you care to share your method?

Keith

 

[Kent Owens]

Tony, thanks for sharing. Over the years I've seen a lot of discussion on chambering, but seems like a lot gets left out, either by design, or by actually not knowing properly how to explain it. Kinda like telling a beginner how to shoot the wind on a blustery day, with the sun going behind the clouds now and then. LOL I enjoy reading how other folks do their work. I had my own ideas on chambering, and it worked for me, or seemed to. I experimented a lot, ended up using a straight sided reamber, .2252 diameter with a 2 degree leade angle(supposedly). And I had a piloted hobb made to mirror the reamer leade angle. What the advertised leade angle is, and what you get is a crap shoot too. But, you do what you can.