Rimfire match camber info.

[scasa]

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

-I'd like more information on chamber polishing If you would care to elaborate on that. Methods and materials.

 

[PWNolan]

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.

You beat me to it!

 

[Tony K Harper]

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

You probably didn't mention the single most important factor in chambering a barrel.

Too obvious, but for those that may not know centering the chamber to the bore is the single most critical thing that must be achieved or none of the rest of it will matter. This is especially true with M.I. (minimally Invasive) barrels. The more M.I. the more critical.

Piloted reamers help but are not foolproof.

Even if you cut targets on the barrel as Calfee mentions in his book by finding the center of the bore and cutting the outside of the barrel on both ends it is a good practice to center on the bore before you start your piloted chamber reamer. This should not be necessary, but it is such a critical part it pays to take the extra time to do it or at least check it.

A post chamber lap will help a barrel shoot to its full potential right from the start. But it is a pain to do.

TKH

 

[Mt.Boy]

You probably didn't mention the single most important factor in chambering a barrel.

Too obvious, but for those that may not know centering the chamber to the bore is the single most critical thing that must be achieved or none of the rest of it will matter. This is especially true with M.I. (minimally Invasive) barrels. The more M.I. the more critical.

Piloted reamers help but are not foolproof.

Even if you cut targets on the barrel as Calfee mentions in his book by finding the center of the bore and cutting the outside of the barrel on both ends it is a good practice to center on the bore before you start your piloted chamber reamer. This should not be necessary, but it is such a critical part it pays to take the extra time to do it or at least check it.

A post chamber lap will help a barrel shoot to its full potential right from the start. But it is a pain to do.

TKH

Do you mean a post chamber lap of the chamber or the whole length of the barrel. Thanks for your info Mr Harper

 

[Dgd6mm]

Since TKH said chamber and skeetlee said chamber, I would believe it's just the chamber to be polished to get accuracy potential from the get go. But I'm sure I'll be corrected if I'm wrong, and that's ok because I'll learn something.

 

[Mt.Boy]

Since TKH said chamber and skeetlee said chamber, I would believe it's just the chamber to be polished to get accuracy potential from the get go. But I'm sure I'll be corrected if I'm wrong, and that's ok because I'll learn something.

I agree. I just like to learn all I can.

 

[TRSR8]

-I'd like more information on chamber polishing If you would care to elaborate on that. Methods and materials.

For a DIY type guy, one of the better ways to make a round chamber oblong. The guys that know what their doing often use a chamber lap which is indexed……not a DIY . Few, if any, will discuss their proprietary methods.

 

[Tony K Harper]

Do you mean a post chamber lap of the chamber or the whole length of the barrel. Thanks for your info Mr Harper

Whole length of the barrel after the crown and chamber have been cut and finished. It is the last step of the process and it is intended to only remove any metal that has been upset during the machining process.

Not many see a need for it but some do. It certainly adds more work to the process and there is a risk of undoing all the good work you have done.

TKH

 

[Mt.Boy]

Whole length of the barrel after the crown and chamber have been cut and finished. It is the last step of the process and it is intended to only remove any metal that has been upset during the machining process.

Not many see a need for it but some do. It certainly adds more work to the process and there is a risk of undoing all the good work you have done.

TKH

Thank you. Was just wondering cause I just had a rifle rebarreled and my gunsmith told me he did that as a last step.

 

[Dgd6mm]

Whole length of the barrel after the crown and chamber have been cut and finished. It is the last step of the process and it is intended to only remove any metal that has been upset during the machining process.

Not many see a need for it but some do. It certainly adds more work to the process and there is a risk of undoing all the good work you have done.

TKH

Thank you.

 

[skeetlee]

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.

I don’t disagree but hitting your proper headspace is easy enough to get right so why wouldn’t ya. You’re correct though. RimX actions are widely popular and unless you modify the bold face you have to set the headspace right around .050. Now I don’t care for that even though they will shoot well with that headspace. There again it’s not difficult to modify the bolt face and then set the headspace at .044

Lead angles are another subject you can dive into. I think or actually know, there are ways to make most common lead angles work. Bullet jams being the alternative. I don’t ever sell this to my customers but I do have a JGS reamer with a 5 degree lead. This is the first reamer I purchased long ago before I really knew much about any of this. I’ve chambered two shilen barrels for myself with this reamer and these two barrels are crazy impressive. Nobody ever uses a 5 degree lead , why JGS even cuts this reamer I am unsure. Dam thing shoots though.
A 1.5 and 2 degree being the norm I like 1.5 for lapua and 2 for Eley but both can work for both bullet design. Like I say, I think bullet jam is more important. All interesting for sure!

 

[PWNolan]

I don’t disagree but hitting your proper headspace is easy enough to get right so why wouldn’t ya. You’re correct though. RimX actions are widely popular and unless you modify the bold face you have to set the headspace right around .050. Now I don’t care for that even though they will shoot well with that headspace. There again it’s not difficult to modify the bolt face and then set the headspace at .044

Why would you setup the headspace tighter for something like Eley and then have issues using Lapua? Why limit yourself when you can use .043 or .044 and shoot good lots of any brand you want? Eley hasn't been putting out consistent enough ammo over the past several years to really bother with anyway. But at .043 or .044 if I do come into a good lot of Eley I can shoot it and have expectations that the rifle will shoot as well as it would if the headspace was a few thou tighter

 

[VLNBYR]

Why would you setup the headspace tighter for something like Eley and then have issues using Lapua? Why limit yourself when you can use .043 or .044 and shoot good lots of any brand you want? Eley hasn't been putting out consistent enough ammo over the past several years to really bother with anyway. But at .043 or .044 if I do come into a good lot of Eley I can shoot it and have expectations that the rifle will shoot as well as it would if the headspace was a few thou tighter

Because if you are down on the floor picking up the smallest of crumbs you are perceived as smarter than the guy at the table eating on the whole piece of pie.

 

[marazzi59]

In regards to the OP it's not about how much engraving but more about matching chamber to ammo selected

 

[Mt.Boy]

In regards to the OP it's not about how much engraving but more about matching chamber to ammo selected

Thanks

 

[TRSR8]

In regards to the OP it's not about how much engraving but more about matching chamber to ammo selected

A good chamber in a good barrel will shoot any quality ammo worth shooting.

 

[skeetlee]

Why would you setup the headspace tighter for something like Eley and then have issues using Lapua? Why limit yourself when you can use .043 or .044 and shoot good lots of any brand you want? Eley hasn't been putting out consistent enough ammo over the past several years to really bother with anyway. But at .043 or .044 if I do come into a good lot of Eley I can shoot it and have expectations that the rifle will shoot as well as it would if the headspace was a few thou tighter

It’s very simple. A lot of my customers know what brand of ammunition they want to use. When this is the case why would I not set the headspace properly for that ammo brand or type.
I usually don’t build squirrel rifles. Most of what I’m doing in my shop are match rifles. If I have a customer who doesn’t know what they want to shoot ammo wise then of course you set the headspace appropriately.

 

[PWNolan]

......When this is the case why would I not set the headspace properly for that ammo brand or type.

Because it doesn't improve how the rifle shoots. In my previous post I was referring to RFBR UL rifles not squirrel rifles.

See the previous post by TRSR8 regarding what the top RFBR gunsmiths are using (.043/.044) and the article Calfee did awhile back regarding headspace

 

[TRSR8]

Because it doesn't improve how the rifle shoots. In my previous post I was referring to RFBR UL rifles not squirrel rifles.

See the previous post by TRSR8 regarding what the top RFBR gunsmiths are using (.043/.044) and the article Calfee did awhile back regarding headspace

That, plus, down the road the whole ammo choice deal is a wildcard and subject to change based on availability. Why paint yourself into a corner?

 

[MUP]

Just stock up and be prepared. A little late for that now tho for sure, unless $$$ isn't an issue that is