Rimfire chambers

[tonykharper]

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.

Kent,

You built some great rifles. Bruce Hornstein's equipment just to note one.

Bruce has won about everything there is to win with your rifles.

Just wish you, and many others were still active so we could do it all over again.

TKH (4628)

 

[Eidolon]

Tony you might or might not remember but when I started shooting I was asking just about everyone about chambering. You included.
It was a secretive world.
Dexter Bumgardner was very helpful. And use his technique to date.
One thing he advised was a carbide reamer. He also advised a plastic reamer stop and how to make one.
Over the past few years I have been able measure casing protrusion on a Calfee barrel, Penrod, Stiller, Langley, Gorham, to name a few. I used the same box of X-Act as a baseline. Could get up to a .020” difference (always less) when checked with a random lot of Eley.
(Due to personal issue/stupidity) I have lost those notes.)

There were some highs. And some lows. But overall it was found case protrusion was .141” or about .100” of engraving. (Minus the .041” rim thickness)

Finishing the chamber is still a black art.

Someone asked about Keven Nevius and his chambers. I have had his chambering info for three years and when this thread came up sent him an email asking if I could share.
He uses the cutting fluid recommended by Richard Gorham on a Rimfire accuracy thread.
He does cut a different chamber for Lapua than Eley. Which according to this mornings response he still uses.

> My best barrels in recent seasons were setup for .078" (minus the .0430" gives .0350" engraving approx.), so I have stuck with those dimensions.

More from Kevin,
Regarding engraving depths, as I mentioned I like approx. .0350" for the 1.5 degree - but have found more engraving is better for the 2 degree (I set them up for approx. .1350" engraving for the Eley / EPS bullet, and approx. .0750" for the round nosed profiles - specifically Lapua stuff).

The .043” mention by Kevin is what he uses for headspace.

How case protrusion is measured.

 

[Kent Owens]

Tony, rimfire BR was definitely a challenge, and I kinda miss it. I enjoy watching what's going on with equipment and the awesome scores you guys are shooting now. Bill Calfee definitely had a handle on building some fine rimfire rifles, and I really respected his work. As for the shooting part, for me it got too tough to make it thru a match. I ran out of energy so fast after experiencing a mild heart attack, and the energy just never came back. Then add worn out hip and bad back to the mix, and it's hard to focus. LOL On chambering, and selecting a great barrel, it's easier to do, than to tell someone else how, and I was alway reluctant to try and tell someone else how to do their work. I always said, I could tell a good barrel from a bad one, but couldn't tell a good one from a great one, until it was shot and proven. Lots of variables. But, it was enjoyable when things worked, back to the work bench when the didn't. But, if a man does end up with a rifle that works, leave it alone! Clean it and shoot it, and don't monkey with it, and screw it up!

 

[doghunter]

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

As most of us are stuck with factory offerings that we cannot alter then finding what ammo suits your chamber is very important.

Sure, one can cut and ream a chamber if one has the equipment and the skill to use it to chamber a good quality barrel but many of us do not have that luxury. But that is of no use if the ammo is not 100% precise.

So we are left to determine what sort of chamber we own and test ammo until we find stuff that works.

The handy PTG reamer chart by TH in post #1 has been quite educational and gives me further insight as to why my 54 Annie is picky and likes Eley Tenex on warm days and Lapua Polar Biathlon on colder days.

Even then, this top shelf ammo can display minor variations within a given batch and the biggest variable that I can measure is the length of the projectile to the top driving band.

Maybe the projectiles were produced on different machines, who knows?

But the bottom line is that a Tenex projectile that measures 0.07mm (about 1.5 thou in) longer than the mean to the top driving band will impact about 3 - 4 mm higher at 50m to the mean and conversely a projectile about 0.07 mm shorter than the mean shall impact about 3 - 4 mm lower.

By the 'mean' I use this to define the average length of a given batch. Usually about 90% meet this average, but the remaining 10% had me mystified until I started looking for answers for the occasional flyers. I also found that the cheaper the ammo, the greater the variation.

I tried the usual stuff with measuring rim thickness and weighing but this was a waste of time as the top quality manufacturers have this issue well sorted.

That's when i started to measure the overall length to the first driving band, as this does affect chamber pressure.

Another interesting observation that I made was that if I saved all the long and short reject ammo until I had enough to test fire a few targets the rejects all shot consistently small groups, just to a different POI than the 'mean'. This was actually re-assuring as it meant that the case, primer and powder were ok, so this seems to confirm my 'theory'

Regards * doggie *

 

[Rimfireshooter]

As most of us are stuck with factory offerings that we cannot alter then finding what ammo suits your chamber is very important.

Sure, one can cut and ream a chamber if one has the equipment and the skill to use it to chamber a good quality barrel but many of us do not have that luxury. But that is of no use if the ammo is not 100% precise.

So we are left to determine what sort of chamber we own and test ammo until we find stuff that works.

The handy PTG reamer chart by TH in post #1 has been quite educational and gives me further insight as to why my 54 Annie is picky and likes Eley Tenex on warm days and Lapua Polar Biathlon on colder days.

Even then, this top shelf ammo can display minor variations within a given batch and the biggest variable that I can measure is the length of the projectile to the top driving band.

Maybe the projectiles were produced on different machines, who knows?

But the bottom line is that a Tenex projectile that measures 0.007mm (about 1.5 thou in) longer than the mean to the top driving band will impact about 3 - 4 mm higher at 50m to the mean and conversely a projectile about 0.007 mm shorter than the mean shall impact about 3 - 4 mm lower.

By the 'mean' I use this to define the average length of a given batch. Usually about 90% meet this average, but the remaining 10% had me mystified until I started looking for answers for the occasional flyers. I also found that the cheaper the ammo, the greater the variation.

I tried the usual stuff with measuring rim thickness and weighing but this was a waste of time as the top quality manufacturers have this issue well sorted.

That's when i started to measure the overall length to the first driving band, as this does affect chamber pressure.

Another interesting observation that I made was that if I saved all the long and short reject ammo until I had enough to test fire a few targets the rejects all shot consistently small groups, just to a different POI than the 'mean'. This was actually re-assuring as it meant that the case, primer and powder were ok, so this seems to confirm my 'theory'

Regards * doggie *

doghunter

Interesting information. Could you share a photo of how you measure? I assume from the case bottom up to top driving band. Specifically, I'm interested in exactly where on the band you measure to? I would like to check some of my Eley Match and Lapua Midas + but need some help to know exactly where to measure on the top band? Also, could you share your mean value you use to draw your conclusion?

Thanks very much for sharing this info.

RFS99

 

[tim]

If you have a chamber bored in a short piece of blank barrel without taper you end up with a nice little die the allows a clean bullet a nice hard stop for OAL measurement which works pretty well.
Mine is only about 1”, even with a caliper you get pretty good relative lengths. Seems better for lot evaluation than individual rounds within a lot. ELEY, for instance, can be a full .010” on lots, short to long.

 

[tim]

Tony, another couple questions question regarding chambers vs ammo.
Have you personally cut anything you would call Lapua specific?
Also, have you found one of the favorable things with Lapua is the tendency to foul the leades at a slower/lesser rate than ELEY ?

 

[tonykharper]

Tony you might or might not remember but when I started shooting I was asking just about everyone about chambering. You included.
It was a secretive world.
Dexter Bumgardner was very helpful. And use his technique to date.
One thing he advised was a carbide reamer. He also advised a plastic reamer stop and how to make one.
Over the past few years I have been able measure casing protrusion on a Calfee barrel, Penrod, Stiller, Langley, Gorham, to name a few. I used the same box of X-Act as a baseline. Could get up to a .020” difference (always less) when checked with a random lot of Eley.
(Due to personal issue/stupidity) I have lost those notes.)

There were some highs. And some lows. But overall it was found case protrusion was .141” or about .100” of engraving. (Minus the .041” rim thickness)

Finishing the chamber is still a black art.

Someone asked about Keven Nevius and his chambers. I have had his chambering info for three years and when this thread came up sent him an email asking if I could share.
He uses the cutting fluid recommended by Richard Gorham on a Rimfire accuracy thread.
He does cut a different chamber for Lapua than Eley. Which according to this mornings response he still uses.

> My best barrels in recent seasons were setup for .078" (minus the .0430" gives .0350" engraving approx.), so I have stuck with those dimensions.

More from Kevin,
Regarding engraving depths, as I mentioned I like approx. .0350" for the 1.5 degree - but have found more engraving is better for the 2 degree (I set them up for approx. .1350" engraving for the Eley / EPS bullet, and approx. .0750" for the round nosed profiles - specifically Lapua stuff).

The .043” mention by Kevin is what he uses for headspace.

How case protrusion is measured.

Eidolon,

There is always more than one way to skin a cat.



This tool was made by Mike Boland. It is very useful in the shop.

I normally use this gauge when the barrel is set up and dialed in. I just set a round in the chamber and I use very light spring on the gauge to push it into the lands.

Then I push up against the barrel face to take the reading.

That is the same measurement you are getting on your indicator. I'm not saying one is better than the other only that there is more than one way to get that measurement.

I can cut the shoulder or the barrel face to get to the number I want without ever having to re dial in the barrel.

The hard part is picking the round to measure. I normally measure 20-25 and get an average. Then I find a round that is that average.

Most good lots are pretty close, but I'm trying to make sure I don't use an outlier for my yardstick.

TKH (4628)

 

[tonykharper]

Tony, another couple questions question regarding chambers vs ammo.
Have you personally cut anything you would call Lapua specific?
Also, have you found one of the favorable things with Lapua is the tendency to foul the leades at a slower/lesser rate than ELEY ?

Tim,

No, the thing I find that is somewhat consistent is the rim thickness. Lapua is normally a little thicker than Eley. Sometimes if you have a feel to your bolt closing it will go away if you change to Eley.

But this normally isn't an issue, I think most are using .044 or more headspace.

The synthetic lube on Lapua is much better than it was in days gone by. I'm sure you remember when Eley had a gob of wax on the bullets. Not so much anymore.

For a long time, I thought Eley's sucess was partly because of the wax. But now the wax is gone and so is much of the success. Who knows, there may have been something to that.

TKH (4628)

 

[doghunter]

doghunter

Interesting information. Could you share a photo of how you measure? I assume from the case bottom up to top driving band. Specifically, I'm interested in exactly where on the band you measure to? I would like to check some of my Eley Match and Lapua Midas + but need some help to know exactly where to measure on the top band? Also, could you share your mean value you use to draw your conclusion?

Thanks very much for sharing this info.

RFS99

I made a gauge using a dial indicator with the probe replaced with a delrin cup that just contacted the top driving band. I am measuring from the inside face of the rim as this determines the length inside the chamber.

I have attached my original drawing from 6 years ago. One thing that I quickly discovered was that the delrin cup required a pressure relief hole (about 1mm) drilled into the side of cup due to the air seal caused by the lube.

As for my 'mean value' it is not an actual dimension. When I am grading a batch of ammo, the dial indicator swings to some arbitrary number so I note this down and sort all the ammo of that size or within a thou into one pile, any that deviate by 2 thou or more get sorted into their own piles.

I have never found an Eley Tenex round that deviated by more than 5 thou.

I also made a gauge for the local biathlon team and they told me that it was a real eye-opener when they started to batch their ammo and also their scores had improved by about 10%.

* doggie *

 

[Bob1949]

I've been reading this thread and found that this is one measurement I had not considered.
Looking at the photos of some of the instruments that have been constructed leads me to think there may be something there.
Not having a lath or mill, I came up with this idea.
A bullet with the lead inserted into an empty brass, a little bit of math and you have the length from the base of the bullet to the top of the lands.
Using this method I found the shortest at 0.772” and the longest at 0.778” and the rest somewhere in between.
The average worked out to be 0.7745”.
As I was doing this I noticed that applying a little pressure onto the lead I could push it into the brass approximately 0.003”.
My system may not be very accurate but it dose show that engraving can vary.

Bob

 

[doghunter]

I've been reading this thread and found that this is one measurement I had not considered.
Looking at the photos of some of the instruments that have been constructed leads me to think there may be something there.
Not having a lath or mill, I came up with this idea.
A bullet with the lead inserted into an empty brass, a little bit of math and you have the length from the base of the bullet to the top of the lands.
Using this method I found the shortest at 0.772” and the longest at 0.778” and the rest somewhere in between.
The average worked out to be 0.7745”.
As I was doing this I noticed that applying a little pressure onto the lead I could push it into the brass approximately 0.003”.
My system may not be very accurate but it dose show that engraving can vary.

Bob

I designed my gauge after thinking about how a micrometer seating die is used to fine tune center-fire reloads and the effect that seating depth, jump and jam has on the final velocity, accuracy and the POI.

Since rimfire ammo is already pre-loaded this was my attempt to reduce this variable by batching the cartridges by length to the top driving band.

Your method looks good and is inexpensive, it should be interesting to hear what results you obtain after target testing.

* doggie *

 

[linekin]

I used a "Nevius" reamer on the last barrel I did & have .035 engraving on the lot of Midas I was using at the time. Shoots Eley fine.
Keith

 

[tonykharper]

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.

View attachment 25113View attachment 25114

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.

View attachment 25115View attachment 25116

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)

The attach is a file I took from Calfee. I was only going to copy the pic but couldn't figure how to get the pic without all the other stuff on the page.

The pic shows the engraving I try to achieve. AS I said before that point is not the same on every round, lot to lot, or brand to brand, so I take an average of the ammo I'm shooting and use that as my target.

From reading this thread it seems many different ways work.

TKH (4628)

View attachment 2021-07-30 Calfee Leade Length.pdf

 

[Bob1949]

Interesting Thread

Hey doggie, just got back to my laptop.
The little thing I through together was just to see how much change there was in the length of the bullets we shoot.
I only looked at a few random rounds ,13, just to see if it worked.
I don't think I'm about to do a large scale inspection just to see results.
With no technical resources at hand, the measuring would be rather arduous, figuring that a least 500 rounds would need to be checked.
About 20 years ago I weighed 1000 rounds and separated them into 6 groups.
Took them to the range and discovered I wasted my time and learned nothing.

Bob

 

[Eidolon]

Screen shoots from Calfee website

Mr. Calfee published this information on his website.
The photo info indicates I saved them September of 2016.

 

[jim1K]

I know you don't see any land marks on the Nevius chamber..... Jim

 

[tonykharper]

I know you don't see any land marks on the Nevius chamber..... Jim

Jim,

Let me make sure I understand what you said.

Are you saying when one inserts a round into a Nevious chamber, and closes the bolt, you will not see any engraving marks on the bullet where the lands cut the bullet?

TKH (4628)

 

[tim]

Tony, another question.
I used to know this but just cannot recall, approximately when and by how much did ELEY move the drive bands on Tennex/Match ammo ?

 

[tonykharper]

Tony, another question.
I used to know this but just cannot recall, approximately when and by how much did ELEY move the drive bands on Tennex/Match ammo ?

Tim,

I don't recall. You are referring to when they introduced the EPS bullet aren't you.

I remember there being two schools of thought. Some thought the round nose shot best others thought the EPS bucked the wind best.

I don't recall anyone doing a test between the two when they were both still available.

TKH (4628)