School me in 22 chambers

Jamie

Jamie

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After not being overly happy with my bergara B14r dumping the first round .4-5 low every time it sits for a few minutes I am thinking it’s barrel time.

Thinking 22” heavy and what chamber for true match specs?

Well match as in must feed from a mag PRS rimfire style
 
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When it comes to .22LR chambers, a good question is what is meant by "true match specs"?

There are many chambers that are called "match" but they aren't all the same. Some rimfire forum posts offer the over-simplified view that if a chambered bullet gets engraving on it that determines whether a chamber qualifies as a match chamber. Unfortunately, however, there's no specific definition.

What distinguishes match chambers from those that are not is in the dimensions. Match chambers are generally tighter and shorter than non-match chambers. The latter must easily accommodate a wide variety of .22LR ammunition which can vary in dimensions, especially in less expensive varieties.

The Bergara is a CIP spec rifle, which means it will have a CIP size chamber. The CIP specs have the minimum dimensions permitted. Some CIP chambers which are called "match chambers" -- such as those on some CZ 457 models and the Bergara B14R -- will have dimensions closer to the minimum allowed. How much closer is known to the manufacturer and to those who are able to accurately measure them. But since Bergara rifles would be expected to shoot a variety of .22LR ammo, it is unlikely that they are made to the tightest dimensions allowed.



In any case, as a repeater, it is not unusual for such rifles to have chambers that are not the narrowest in diameter. This allows feeding from the magazine to be done easily without risking damaging the bullet.

When a custom barrel is selected, it's often possible to select one of the more commonly used .22LR match chambers. Some of these chambers are made with certain makes of ammo in mind. For example, there is an Eley EPS chamber. Vudoo repeaters have a proprietary chamber that is supposed to be designed with Lapua ammo in mind.

Below are the reamer dimensions of a number of the .22LR match chambers in use.



 
I have a chamber cast I took from a Vudoo. I believe its called a Ravage chamber. I'm about to order a reamer to match. Could just as easily order two if you're interested.
 
I wouldn't worry too much about feeding into whatever chamber you might select. If you study the list grauhanen posted, the "match" chambers are all 0.22x", varying only by a couple thou +/- the average. My custom Remington 597 barrel was chambered with a "match" reamer. I can't confirm, though I suspect it is likely the 22LR Match chamber on the list, possibly the Clymer Match reamer that Brownells sells. So, a match chamber can function just fine on a semi-auto, despite some saying that semi's need a looser Bentz chamber to function. The Bentz chamber won't engrave the bullet. Really the only issue that could crop up with a Semi is that the bullet fails to fully seat due to the engraving stopping the bolt, a non-issue with a manual bolt action. Chamber style doesn't necessarily equate directly to bullet engraving, that is something the gunsmith performing the chambering has control over. Theoretically one could cut a Bentz chamber to engrave the bullet to some degree. To ensure reliable feeding, the gunsmith should chamfer the mouth of the chamber slightly. Some reamers will do this as a built in function.

A note on the match chambers geared towards benchrest style shooting is that they are typically cut to engrave the bullet heavily. This can cause an issue if the need to extract a live round occurs, such as may be the case in PRS shooting. Failure to extract is possible, or leaving the bullet stuck in the chamber and pulling just the case out, dumping powder everywhere. It would be interesting to see the dimensions of the Ravage chamber, I understand it was designed to permit extraction of live rounds so I would say the bullet engraving is much less than what you'd see on a Benchrest rifle. A couple of my barrels have chambers designed by former gunsmith known as djdilliodon on RFC. Specs are not known, though I can say they engrave the bullets pretty heavily. On an Anschütz 64 and CZ 455, I'm still able to pull live rounds without issue. I'm not sure what the engraving limit is where extraction becomes an issue, and each brand of action will have different tolerances to this as well.

Suffice to say, I don't think you can go wrong choosing any chamber listed as "match". If you have an Anschütz rifle handy, you can see how much they engrave the bullet, and you'd be fine going just a little heavier on the engraving. Remember, engraving depth is something largely in the gunsmith's control no matter what reamer is used. Make sure they know how much engraving you want.
 
Maple57 said:
I have a chamber cast I took from a Vudoo. I believe its called a Ravage chamber. I'm about to order a reamer to match. Could just as easily order two if you're interested.
Click to expand...

Are you doing your own barrel blank? Or going to redo your bergara?

And I just might be interested.
 
Chambers that involve a very tight fit on the bullet usually require the gunsmith makes sure the extractor grooves and the extractors are carefully fitted and tested to ensure live round extraction. I see many comments about failures to extract chambered live rounds - that usually is the fault of the gunsmith... the primary extractor needs to be sharp and the groove allowing the tip of it to get in front of the rim.
 
There are also custom reamers supposedly designed around using Lapua ammo and some around Eley. I believe Voodoo recommends lapua in their chambers.
 
Ryan at IBI recently did a segment on one of the rimfire channels where he briefly talked about their pre-fit barrels and the chambers that they cut. He also gave a heads-up on their new Bergara pre-fit barrels which should be available soon.
 
Jamie said:
Are you doing your own barrel blank? Or going to redo your bergara?

And I just might be interested.
Click to expand...

The plan is to replace the barrel with one that is longer and heavier. Since the Vudoo is so popular I figured their chamber would be a solid place to start, so I took a Cerrosafe chamber cast.

I don't want to change the chamber in my Bergara because it shoots really well.

The low first shot problem discussed is nothing I am particularly concerned about as I am not sure it was in any way something I would call repeatable and could just as easily be attributed to wind. Time will tell.

I have stated many times how important balance is to PRS shooting and that is the goal, just to get the rifle so it can sit unassisted on a barricade.

If the rifle had the right barrel weight on it now, I would not be changing it as accuracy is not the problem.
 
@Jamie, I've been doing some research on this since December and it seems like the EPS II is a very popular option.

As for extraction failures with live rounds, it can depend on your chamber/ammo combination. Some chambers engrave more deeply than others on certain brands of ammo. Your gunsmith can adjust the amount of engagement during chambering.
 
EHG said:
Do you have a link for that?
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Rickster from CRPS interviewed IBI and if you find his YouTube channel you can find a video on it. Not sure if its the same one Hooked is talking about. Some of the content is a bit hard to swallow so take it with a grain of salt and a wide tolerance level for pain. Some of the guys speak confidently to points that are well out of their depth.
 
Johnny Boom said:
@Jamie, I've been doing some research on this since December and it seems like the EPS II is a very popular option.

As for extraction failures with live rounds, it can depend on your chamber/ammo combination. Some chambers engrave more deeply than others on certain brands of ammo. Your gunsmith can adjust the amount of engagement during chambering.
Click to expand...

Thank you very much for the Email!
 
tiriaq said:
Isn't headspace control also a factor in maximizing .22LR accuracy?
Click to expand...

Much is often made of Eley match .22LR ammo having rim thicknesses that average less than it does with Lapua. The result is that some shooters insist that a tighter headspace works better with Eley match ammo. But it's worth remembering that all .22LR match ammo is designed to meet CIP and SAAMI .22LR ammo specs.

Headspace is probably not as significant a factor with regard to accuracy as many might assume. Bill Calfee, the sometimes controversial rimfire gunsmith, said "If your headspace is safe, and if you have killer ignition with it, the headsapce [sic] itself, no matter what it is, has absolutely nothing to do with rimfire accuracy... I recommend setting HS at .043", with the ammo we have available today.....same as I've done for years now...."

According to Calfee and others, what's much more important than headspace with regard to accuracy is the length of engraving.
 
With regards to headspace, what can happen with factory made rifles and parts made within a tolerance range, is that headspace can be on the loose end of "in spec" combined with the firing pin length/mechanical stop being a little too short. What you get is the firing pin bottoming out on the mechanical stop before complete rim penetration, resulting in inconsistent ignition and subsequent accuracy issues. Tightening the headspace can improve the ignition, when really one could have just milled back the firing pin stop to achieve the same effect. You don't wan't the firing pin to contact the mechanical stop when actually live firing.
 
So the real question I ask all you shooters what is your Chamber spec of choice? For PRS shooting not single shot bench.
 
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