Rimfire match camber info.

[Mt.Boy]

Well, here is what you can do if you feel that the chamber is holding it back. Have your new Smith, pull the barrel and set it back just enough to get the stick out close to where you want it. I would go with .070-.090 Remember to clean the wax off the bullet. Then cut the shoulder to match. You may have to change to a cone breech if you have extractor slots, if you already have a cone, it will just need dressed up.

It’s at a gunsmith now. And we are deciding which is the best route to take thanks

 

[1813benny]

It’s at a gunsmith now. And we are deciding which is the best route to take thanks

Cut the 2” or so off of the breech and cut an entirely new match chamber with an appropriate amount of engraving.

 

[Mt.Boy]

Cut the 2” or so off of the breech and cut an entirely new match chamber with an appropriate amount of engraving.

That’s the plan if it don’t leave my barrel to short.

 

[Tad_Earhart]

If the chamber is straight, with zero stick out, 16tpi threads, facing the breech face back in half turns (about 0.031") or full turns (about 0.0625") may get it somewhere close to where it needs to be. If the extractor slots are not 180 degrees on centerline, then full turns will be about all you can do without a bunch of mess on the breech. With zero stick out, and some measuring to see about how far from touching I was, I would likely do two turns worth of face-back and go from there. Maybe 2.5 turns if I could and was a long way from touching to begin with. Just no more than 0.140" of stick out generally speaking.

If the chamber is not straight, then the full cut off and redo will be about the only option to save the barrel.

 

[Mt.Boy]

If the chamber is straight, with zero stick out, 16tpi threads, facing the breech face back in half turns (about 0.031") or full turns (about 0.0625") may get it somewhere close to where it needs to be. If the extractor slots are not 180 degrees on centerline, then full turns will be about all you can do without a bunch of mess on the breech. With zero stick out, and some measuring to see about how far from touching I was, I would likely do two turns worth of face-back and go from there. Maybe 2.5 turns if I could and was a long way from touching to begin with. Just no more than 0.140" of stick out generally speaking.

If the chamber is not straight, then the full cut off and redo will be about the only option to save the barrel.

Thanks for the info Tad.. Much appreciated

 

[padom]

My 22LR Match Eachus Chamber I designed for Lapua ammo engraves to just touching the second driving band and ejects a live round. 2 degree... it's chambered 100s and 100s of RimX barrels with amazing accuracy.

It also shoots RWS extremely well

 

[shoot4fun]

While I don't want to derail the topic of the thread, I am curious about the effects of another aspect of chambering.
We see that all the top shooters in rimfire (probably as CF BR shooters do) want the bullet in the rifling when chambered.
I am seeing headspace have a great deal to do with how ammo performs as well and wonder what you "top guns" prefer headspace to be set to.

 

[PWNolan]

I am seeing headspace have a great deal to do with how ammo performs as well and wonder what you "top guns" prefer headspace to be set to.

044" is what a few top RFBR gunsmiths have recently said they use. Headspace has less of a effect on how a rifle shoots than a lot of people think. As long as it's not too loose that it causes ignition issues and it's not too tight that the rims are being crushed the rifle should shoot well providing everything else is up to it.

(Edited out the dupe sentence)

 

[Idaho-Lefty]

Yes I can push it in to the rim. And extract a round.

I actually had to, "Polish" my Benz Match chamber with, a little JB's on, a Patch before my Green Mountain "Benz Chambered" barrel, on a Ruger 10-22, would give, reasonable "Extraction" with, LIVE, Match ammo.
It still "Engraves" the Bullet, just NOT as tightly / sharply. Runs and shoots, "Awesome",.. Now !
But, I'm NOT a Competitor ! Unless, stacking up, Sage Rats is counted as,.. Competition,. LOL !

 

[shoot4fun]

044" is what a few top RFBR gunsmiths have recently said they use. Headspace has less of a effect on how a rifle shoots than a lot of people think. However, headspace makes less of a difference accuracy-wise than a lot of people think. As long as it's not too loose that it causes ignition issues and it's not too tight that the rims are being crushed the rifle should shoot well providing everything else is up to it.

Recently, I took considerable time and care in sorting Lapua Long Range by both headspace (.040-.042 in one lot and .043-.044 in the other) and by weight (within .1 grain) for my Vudoo. I had chrono data for the same lot but unsorted and wanted to see if there was enough difference to make it worthwhile.
For that days shooting I fire sighter rounds from the .040-.042 group that were not weight sorted. For record rounds I fired the ammo sorted by weight and headspace. In the end, looking at all 100 rounds fired that day, the total number of rounds was the same and so were the overall velocity, ES and SD readings. I then broke out the sighters from the record rounds and got a surprise. ES and SD were actually HIGHER for the headspace & weight sorted ammo than in the sighters that were of .040-.042 with no weight sorting.
The only difference I noted at all was that during this match I would normally see a couple of unexplainable fliers but, having discarded two round from the 200 sorted that fell well out of the headspace and/or weight lots, there were none.
From outward appearance of these numbers I would think my rifle's ignition was liking the .040-.042 headspace better but accuracy was basically unchanged by the experiment.
In other words, except for culling two poor outliers, all that time and all that data was not necessary.

 

[Pete Wass]

I have seen a number of rifles shoot great jumping bullets and a lot of jump. I have measured some of those chambers so I know from where I speak.

 

[MUP]

Recently, I took considerable time and care in sorting Lapua Long Range by both headspace (.040-.042 in one lot and .043-.044 in the other) and by weight (within .1 grain) for my Vudoo. I had chrono data for the same lot but unsorted and wanted to see if there was enough difference to make it worthwhile.
For that days shooting I fire sighter rounds from the .040-.042 group that were not weight sorted. For record rounds I fired the ammo sorted by weight and headspace. In the end, looking at all 100 rounds fired that day, the total number of rounds was the same and so were the overall velocity, ES and SD readings. I then broke out the sighters from the record rounds and got a surprise. ES and SD were actually HIGHER for the headspace & weight sorted ammo than in the sighters that were of .040-.042 with no weight sorting.
The only difference I noted at all was that during this match I would normally see a couple of unexplainable fliers but, having discarded two round from the 200 sorted that fell well out of the headspace and/or weight lots, there were none.
From outward appearance of these numbers I would think my rifle's ignition was liking the .040-.042 headspace better but accuracy was basically unchanged by the experiment.
In other words, except for culling two poor outliers, all that time and all that data was not necessary.

I would say you accomplished what most shooters set out to do, and that's reduce fliers. A lot of work, but those two or three random fliers that didn't happen during the sorted ammo test could have been the difference between 1st and 4th place at a match.

 

[plinker4life]

I have seen a number of rifles shoot great jumping bullets and a lot of jump. I have measured some of those chambers so I know from where I speak.

As in rimfire rifles? One's that compete in sanctioned events? How much jump are you talking?

 

[USMCDOC]

It’s amazing how many folks can’t seem to shake off the centerfire mode when they are in the rimfire section.

 

[1813benny]

It’s amazing how many folks can’t seem to shake off the centerfire mode when they are in the rimfire section.

Doc...it's the recoil.

 

[VLNBYR]

It’s amazing how many folks can’t seem to shake off the centerfire mode when they are in the rimfire section.

Perhaps the best example would be Tony Boyer. He tried RFBR....gave it everything he had....100%+....for a while....then he quit.

 

[USMCDOC]

Doc...it's the recoil.

You may be right

 

[skeetlee]

I chamber rimfire barrels darn near ever day here in my shop I was taught by an old school benchrest smith. There are only a few things that must be right and a few things that are not as important as you might think.
First your headspace needs to fit the ammunition your shooting. thats easy. second is bullet jam. here again its best to set your jam depths per the type of ammunition your going to shoot. these numbers are not absolute but you gotta be close. I can share my numbers if someone cares to ask me via private message. the third thing that i know for a fact gets overlooked by more than most is chamber finish and polish. with the 22LR craze we live in today ever shop with a cnc is making prefits. Id just about bet 90% have no idea how or why a 22LR chamber needs to be polished. The reason is obvious i think. Polishing a chamber allows the barrel to shoot right off the bat with very little to no break in, All reamers leave tool marks no matter your technique. If you don't think so, hit that chamber with a little 600 grit and take a look! will an unpolished chamber shoot, sure it will but it can take several bricks of high $ ammo to get you there. This subject just doesn't get the attention it needs, and this is a craft learned through practice and patients.
Headspace bullet jam and chamber finish, these are the big ones. chamber sizes and lenght if kept respectable are not so important, in my opinion! If you want a good solid all around match 22LR chamber reamer, buy a JGS 22LR match reamer With good practices your barrel will shoot!!
Lee Gardner Precision

 

[Mt.Boy]

I chamber rimfire barrels darn near ever day here in my shop I was taught by an old school benchrest smith. There are only a few things that must be right and a few things that are not as important as you might think.
First your headspace needs to fit the ammunition your shooting. thats easy. second is bullet jam. here again its best to set your jam depths per the type of ammunition your going to shoot. these numbers are not absolute but you gotta be close. I can share my numbers if someone cares to ask me via private message. the third thing that i know for a fact gets overlooked by more than most is chamber finish and polish. with the 22LR craze we live in today ever shop with a cnc is making prefits. Id just about bet 90% have no idea how or why a 22LR chamber needs to be polished. The reason is obvious i think. Polishing a chamber allows the barrel to shoot right off the bat with very little to no break in, All reamers leave tool marks no matter your technique. If you don't think so, hit that chamber with a little 600 grit and take a look! will an unpolished chamber shoot, sure it will but it can take several bricks of high $ ammo to get you there. This subject just doesn't get the attention it needs, and this is a craft learned through practice and patients.
Headspace bullet jam and chamber finish, these are the big ones. chamber sizes and lenght if kept respectable are not so important, in my opinion! If you want a good solid all around match 22LR chamber reamer, buy a JGS 22LR match reamer With good practices your barrel will shoot!!
Lee Gardner Precision

Thank you. Great info

 

[TRSR8]

I chamber rimfire barrels darn near ever day here in my shop I was taught by an old school benchrest smith. There are only a few things that must be right and a few things that are not as important as you might think.
First your headspace needs to fit the ammunition your shooting. thats easy. second is bullet jam. here again its best to set your jam depths per the type of ammunition your going to shoot. these numbers are not absolute but you gotta be close. I can share my numbers if someone cares to ask me via private message. the third thing that i know for a fact gets overlooked by more than most is chamber finish and polish. with the 22LR craze we live in today ever shop with a cnc is making prefits. Id just about bet 90% have no idea how or why a 22LR chamber needs to be polished. The reason is obvious i think. Polishing a chamber allows the barrel to shoot right off the bat with very little to no break in, All reamers leave tool marks no matter your technique. If you don't think so, hit that chamber with a little 600 grit and take a look! will an unpolished chamber shoot, sure it will but it can take several bricks of high $ ammo to get you there. This subject just doesn't get the attention it needs, and this is a craft learned through practice and patients.
Headspace bullet jam and chamber finish, these are the big ones. chamber sizes and lenght if kept respectable are not so important, in my opinion! If you want a good solid all around match 22LR chamber reamer, buy a JGS 22LR match reamer With good practices your barrel will shoot!!
Lee Gardner Precision

Lee. It has been shown headspace is simply not that critical as long as minimum is achieved.
WLM ran extensive tests running as much, as I recall, .047”……no degradation to accuracy. I dare say most top flight RFBR smiths are going established .043”-.044”
As far as matching jam lenght, depending on specific chamber, FWIW, back when ELEY was king lot to lot OAL could vary as much as .010”. Unless you were shooting a super MI barrel, if it was a good one…..shot everything well.
Last thought…..do you realize how many top flight guns were chambered for ELEY that are currently tearing up matches now shooting Lapua which is absolutely not same OAL.
A properly cut “ mid depth “ chamber is a wonderful thing.