New Developments in Rimfire Actions

Tony K Harper

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I came across this post on another site and I wonder what you guys think of it.

I know nothing about these actions, so I certainly don't know what to think.

If they really shoot as well as claimed, they are away ahead of the ones commonly used in RFBR.

Someone please shed some light.

TKH

Here is the Post:

.

Forgive my ignorance if this is common knowledge, Can you expand on your comments above in yellow especially on revolutionary design?
Sure.

Up until the RimX design was released, your traditional 22LR rifles used extractors with timed extractor grooves cut into the barrel tenon. Also, chambers were cut and headspace was set based off the match ammo you planned to shoot. This is because Eley for example to explain, required less headspace than say Lapua. So if you cut an Lapua based chamber (0.041 - 0.43") and shot Eley for example, you risk the round moving forward under ignition when struck by the firing pin with it being shorter because nothing in a traditional 22LR captured and held the case against the bolt face. In turn, this results in inconsistent ignition which in turn affects accuracy.. This is pretty standard common knowledge stuff for your knowledgeable 22LR smiths.

This is how most of us built custom high end match 22LR up until the RimX dropped. I was one of the first to receive a RimX from Zermatt before its release for testing and review. When Zermatt was explaining to me their new design and how it works and how to cut barrels, it was different than what we all knew and was hard to believe because what we all knew about making a high end accurate 22LR up until this point. When talking with Ray in those early days, he was telling me this action you don't set headspace based off ammo, there is no need and they have a recommended headspace which is much larger than what we all knew for say Eley and Lapua ammo... (Its been a long time since I looked at this data but I believe Zermatt's tenon print calls for a minimum 0.0455 or 0.046" headspace I could be slightly off on these numbers)...

He explained why.. because the RimX, by design, used a tensioner which captures the 22LR round out of the mag and holds it against the bolt face at all times. Because of this, you have consistent ignition on every case because the case cannot move when struck by the firing pin. Because of this, headspace wasn't as important compared to your traditional 22LR's where it was EXTREMELY important.

Once I got the first barrel cut and installed on the test action and got some rounds down it, I realized what Zermatt was saying. In my initial 10 barrel review and testing I produced some unbelievable accuracy numbers and consistency with those numbers. This was unseen in this type of prefit type rifle and not matching headspace to my ammo up until this point. I shot 50rd AGG's @ 50yd in the 0.1's with multiple barrels and multiple different types and lots of ammo! I shot 5rd 50yd groups in the 0.0's, my personal best at that time. I shot 100yd 50rd AGG in the 0.5's and 6x5 30rd AGG's in the 0.3's and 0.4's, another personal best at the time.

Here we are just over 4 years later and I think the RimX performance speaks for itself. I dont know of any other 22LR designed or operating like a RimX which is why I stand by my comments that its a revolutionary design. Barrels can be made cheaper and faster. No more painstaking work of meticulously timing and cutting extractor grooves into barrel tenons so they line up perfectly when the barrel it torqued on and the smith needing the action in hand for extended periods to do all this... No more cutting headspace to match the ammo the shooter plans to use for optimal accuracy. Buy a prefit, screw it on and go shoot with unheard of accuracy and consistency up until the RimX was released. Want another barrel, maybe different length or contour, no problem, keep shooting your current barrel while you wait for the new barrel to arrive. Again, unheard of up until the RimX hit the scene....

With this design, someone can buy a RimX, pick up one of many high end match grade prefit barrels from various sources instantly and be shooting an extremely capable and accurate rifle the next day with various types of high end match grade ammo. The average shooter couldn't do this before, and not without a long wait time on a custom 22LR smith and a lot of money.

Thats my $0.02 on the RimX and I hope that answers your question.

Last edited: Jul 11, 2024
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I came across this post on another site and I wonder what you guys think of it.

I know nothing about these actions, so I certainly don't know what to think.

If they really shoot as well as claimed, they are away ahead of the ones commonly used in RFBR.

Someone please shed some light.

TKH

Here is the Post:


Sure.

Up until the RimX design was released, your traditional 22LR rifles used extractors with timed extractor grooves cut into the barrel tenon. Also, chambers were cut and headspace was set based off the match ammo you planned to shoot. This is because Eley for example to explain, required less headspace than say Lapua. So if you cut an Lapua based chamber (0.041 - 0.43") and shot Eley for example, you risk the round moving forward under ignition when struck by the firing pin with it being shorter because nothing in a traditional 22LR captured and held the case against the bolt face. In turn, this results in inconsistent ignition which in turn affects accuracy.. This is pretty standard common knowledge stuff for your knowledgeable 22LR smiths.

This is how most of us built custom high end match 22LR up until the RimX dropped. I was one of the first to receive a RimX from Zermatt before its release for testing and review. When Zermatt was explaining to me their new design and how it works and how to cut barrels, it was different than what we all knew and was hard to believe because what we all knew about making a high end accurate 22LR up until this point. When talking with Ray in those early days, he was telling me this action you don't set headspace based off ammo, there is no need and they have a recommended headspace which is much larger than what we all knew for say Eley and Lapua ammo... (Its been a long time since I looked at this data but I believe Zermatt's tenon print calls for a minimum 0.0455 or 0.046" headspace I could be slightly off on these numbers)...

He explained why.. because the RimX, by design, used a tensioner which captures the 22LR round out of the mag and holds it against the bolt face at all times. Because of this, you have consistent ignition on every case because the case cannot move when struck by the firing pin. Because of this, headspace wasn't as important compared to your traditional 22LR's where it was EXTREMELY important.

Once I got the first barrel cut and installed on the test action and got some rounds down it, I realized what Zermatt was saying. In my initial 10 barrel review and testing I produced some unbelievable accuracy numbers and consistency with those numbers. This was unseen in this type of prefit type rifle and not matching headspace to my ammo up until this point. I shot 50rd AGG's @ 50yd in the 0.1's with multiple barrels and multiple different types and lots of ammo! I shot 5rd 50yd groups in the 0.0's, my personal best at that time. I shot 100yd 50rd AGG in the 0.5's and 6x5 30rd AGG's in the 0.3's and 0.4's, another personal best at the time.

Here we are just over 4 years later and I think the RimX performance speaks for itself. I dont know of any other 22LR designed or operating like a RimX which is why I stand by my comments that its a revolutionary design. Barrels can be made cheaper and faster. No more painstaking work of meticulously timing and cutting extractor grooves into barrel tenons so they line up perfectly when the barrel it torqued on and the smith needing the action in hand for extended periods to do all this... No more cutting headspace to match the ammo the shooter plans to use for optimal accuracy. Buy a prefit, screw it on and go shoot with unheard of accuracy and consistency up until the RimX was released. Want another barrel, maybe different length or contour, no problem, keep shooting your current barrel while you wait for the new barrel to arrive. Again, unheard of up until the RimX hit the scene....

With this design, someone can buy a RimX, pick up one of many high end match grade prefit barrels from various sources instantly and be shooting an extremely capable and accurate rifle the next day with various types of high end match grade ammo. The average shooter couldn't do this before, and not without a long wait time on a custom 22LR smith and a lot of money.

Thats my $0.02 on the RimX and I hope that answers your question.

Last edited: Jul 11, 2024
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I will make an attempt, since I have shot ARA Unlimited, sharing a bench with a gentleman shooting a RimX action.
RimX actions are created not far from where I live. I drive past the town of Bennett, Nebraska on my way to my monthly ARA shoot.
RimX actions are controlled round feed actions. If you try to manually load a round into the chamber and close the bolt over it, you will most likely break the extractor.
Here is a URL for the RimX barrel tenon blueprint.


As you can see, the barrel does not require extractor cuts. Thus barrel manufacturers can produce 'pre-fit' barrels, not having to worry about extractor timing.

(As an aside, on traditional RFBR rifles, I do not like coned breeches. I do not think the breech cone supports the head of the cartridge well enough for ultra-reliable ignition. Maybe the one I own was not machined correctly, but I do not like it. I realize this is my personal opinion; I know there are a lot of coned breeches out there...I guess this is off-topic but I could not resist...)

I was not super impressed with the accuracy of the only RimX action rifle I have seen up close and personal. However, as with most all of these little lead bullet spitters, the barrel manufacturer and the precision and care of the gunsmith, chambering and crowning, have much to do with the accuracy of the finished product.

Personal opinion here: I do not like having to load rounds from a magazine. I think (my opinion) there is too much chance of deforming, dinging, scratching or otherwise damaging that soft lead bullet running it out of a magazine.

I hope I do not create a problem sharing my opinions, above. That is not my intent. Just sharing my experience and thoughts.

--Mike McAllister
 
I will make an attempt, since I have shot ARA Unlimited, sharing a bench with a gentleman shooting a RimX action.
RimX actions are created not far from where I live. I drive past the town of Bennett, Nebraska on my way to my monthly ARA shoot.
RimX actions are controlled round feed actions. If you try to manually load a round into the chamber and close the bolt over it, you will most likely break the extractor.
Here is a URL for the RimX barrel tenon blueprint.


As you can see, the barrel does not require extractor cuts. Thus barrel manufacturers can produce 'pre-fit' barrels, not having to worry about extractor timing.

(As an aside, on traditional RFBR rifles, I do not like coned breeches. I do not think the breech cone supports the head of the cartridge well enough for ultra-reliable ignition. Maybe the one I own was not machined correctly, but I do not like it. I realize this is my personal opinion; I know there are a lot of coned breeches out there...I guess this is off-topic but I could not resist...)

I was not super impressed with the accuracy of the only RimX action rifle I have seen up close and personal. However, as with most all of these little lead bullet spitters, the barrel manufacturer and the precision and care of the gunsmith, chambering and crowning, have much to do with the accuracy of the finished product.

Personal opinion here: I do not like having to load rounds from a magazine. I think (my opinion) there is too much chance of deforming, dinging, scratching or otherwise damaging that soft lead bullet running it out of a magazine.

I hope I do not create a problem sharing my opinions, above. That is not my intent. Just sharing my experience and thoughts.

--Mike McAllister
Mike,

Thanks for the update. I share your opinion. What I was most surprised about was the claimed accuracy.

I've been shooting RFBR since the BR 50 days where it all began, and I would expect if this system produced the accuracy claimed a few would have showed up at our matches.

To date I have never seen one win anything at an ARA match or an IR 50.50 match. I have seen a few wins with the Vudoos but not many.

With the National events coming up later this year maybe they will show up and show us a thing or two.

TKH
 
Mike,

I reread your response and I quote your words here:

"Personal opinion here: I do not like having to load rounds from a magazine. I think (my opinion) there is too much chance of deforming, dinging, scratching or otherwise damaging that soft lead bullet running it out of a magazine.

I hope I do not create a problem sharing my opinions, above. That is not my intent. Just sharing my experience and thoughts".

One should never feel stating their opinion or experience on a forum such as this will cause a problem. The intent of these forums is or at least should be to help likeminded readers learn from others and improve their performance. They are not to protect anyone's pet rock from criticism.

Of course, there should never be personal attacks or threats, but opinions or reciting experiences is what this is all about.

If your dog will hunt let him off the porch, if he won't or can't, accept the fact and move on.

Note to admin: If I've got this wrong tell me about it.

TKH
 
Seems an interesting action design and, at least, reveals people continue to think about development.

One thing that puzzles me, on the above (1st post) description, is the different head space approach.
From those words, I understood that the major difference is not needing to be so precise on head space, because a retainer kept the ammo case tensioned against bolt face. This is also, and explained on the post, why with "conventional" actions, if a too big head space, can lead to having the case pushed once striked by the firing pin.
Question is, can a tensioning retainer, hold a case firmly enough against the bolt head, not allowing it the move forward when hit by the firing pin?
Also, in fact another question, can this retainer allow a rims thickness variance?

Those are the 1st ones I have, and maybe I'm missing something, as I never saw that action.

Of course, a couple more questions had surfed, but related to accuracy accomplishments made possible using different barrels, ammo, and so on.

One thing is certain, some times we loose a great opportunity to use a greater tool, just because we are used to other ones.
 
Seems an interesting action design and, at least, reveals people continue to think about development.

One thing that puzzles me, on the above (1st post) description, is the different head space approach.
From those words, I understood that the major difference is not needing to be so precise on head space, because a retainer kept the ammo case tensioned against bolt face. This is also, and explained on the post, why with "conventional" actions, if a too big head space, can lead to having the case pushed once striked by the firing pin.
Question is, can a tensioning retainer, hold a case firmly enough against the bolt head, not allowing it the move forward when hit by the firing pin?
Also, in fact another question, can this retainer allow a rims thickness variance?

Those are the 1st ones I have, and maybe I'm missing something, as I never saw that action.

Of course, a couple more questions had surfed, but related to accuracy accomplishments made possible using different barrels, ammo, and so on.

One thing is certain, some times we loose a great opportunity to use a greater tool, just because we are used to other ones.
Pedro,

This new design goes against some of the things I thought I knew about rimfire accuracy. If it works as well as reported, I will have to rethink the way I do some things.

One example. Currently I go to great trouble to ensure that the extractor and ejector clips makes little to no contact with the case rim while the cartridge is in battery.

Purpose built bottle cap rifles don't use extractors or ejectors at all. This is to ensure the extractors and ejectors do not make any contact with the case.

You can easily demonstrate the negative effect it has on accuracy simply allowing significant contact to be made. One can argue about why accuracy goes south, vibration, moving cartridge off center balance. etc, etc, but you can't argue that it doesn't have a negative effect.

I really need to see one of these actions to know exactly how the case is being held. More than that I want to see this accuracy in the zeros and 1's.

Sure, I've shot groups in the zeros. and 1s but they are rare and not nearly the average.

As you know our RFBR targets are based on 1/2 inch bull targets. That is outside to outside.

While it is true 250's and 2500s are shot often they are not the expected scores. I think they would be if we were shooting rifles that delivered zeros and 1s accuracy in average/normal conditions.

I was hoping Bill Calfee and others would shed more light on this design. Perhaps others can provide examples of their accuracy.

I agree with you it is great to see new designs and I salute everyone doing them. At the same time, I'm going to be skeptical until I see them on the firing line.

We are going to have the IR 50/50 Nationals at Fairchance Gun club in Pa. late September.

They are going to do the Sporter National, 3-Gun Nationals, Unlimited Nationals, and Factory Nationals all in one weekend.

If these rifles show up at the Nationals and deliver the claimed accuracy, they are going to need a trailer to take the trophies home.

TKH
 
Here’s a link to a video I found on YouTube that shows the extractor setup and how it works:

 
Here’s a link to a video I found on YouTube that shows the extractor setup and how it works:

Anthony,

Thanks for the video. That explains a lot.

These actions are a whole different kettle of fish from true RFBR actions.

It is apparent they were developed to meet a different set of requirements.

In terms of RFBR it is not a fair comparison between these and your Turbos or PQP 2500/Trident actions.

The accuracy claims had me thinking we were about to have a paradigm shift in RFBR. I think we have a little longer to wait.

TKH
 
Yes, indeed, and thanks Anthony for providing the video. First time I saw the action in action.
After all, headspace is as critical as on other actions.
Looks like it's more adapted to PRS than to BR. I'm old school, but don't believe, feeding from a magazine could be the way to accuracy.
Haven't a clear view on the bottom's action, but looks like OEM triggers could be installed.
 
I will ask my acquaintance to bring his RimX to our CF F-Class shoot this coming Saturday. I want to look a the bolt to determine how the extractor interacts with the chamber face and 10-degree cone. According to the tenon blueprint if the flat diameter at the chamber face wants to be .030" larger than a case rim, then I am thinking the ejector is going to hit the flat. As explained in the video, the 10-degree cone is just for debris. Then, the headspace of this design would be determined by the distance from the back side of the ejector lip to the face of the bolt. Then wouldn't there be a gap at the bottom of the chambered round? And this is where the firing pin strikes. I guess I had better just look at it and report back...
 
Having looked at a RimX action and barrel today, I found the lip of the extractor is very thin; only about .010" thick. It must be made of very tough steel.
The extractor does contact the barrel tenon on the flat around the chamber. I also noticed there was an approximately 1/32" wide chamfer on the mouth of the chamber. I assume this is to help the new round find the chamber smoothly. At the 6 o'clock position on the bolt face there is no support for the cartridge rim in battery, due to the lip of the extractor above it. These rifles shoot OK, but I find it hard to believe that the unsupported rim where the firing pin strikes is conducive to consistent ignition.
I just looked at the rifle, I did not shoot it.
 
These are repeater actions for PRS/NRL , prime design considerations are Rem700 footprint with AICS mag form factor, reliable feed and extraction, Rim-X has the best mag in the industry so had that going for it , fixed extractor was supposed to deliver reliable controlled round feed and extraction while enabling prefits, prefit barrel option is 'nice to have' .Something that comes from Centerfire PRS/NRL where about 35+% of top competitors run prefits .
Chambers typically used are huge compared to what is being used in BR to facilitate feed and extraction, Most common is JGS match chamber. Tennons are lareg on purpose as folks run 1.20 barres ,to better balance the rifles
These were never meant to be run against singleshot BR actions. Folks also do not clean barrels or just clean chamber area , as we do not have sighters or fouler shots , one of the reasons you see folks taping shut muzzles each time they finish shooting a stage to maintain the bore condition. Most of our shooting is 100+m typical comp tops out at 200+m hence the folk experimenting with faster twist barrels and manufacturers launching all sorts of 'long range' branded ammo


As for prefits and extractor cuts , we have a while ago designed an insert that would protect the breech face on cone breech , will likely be used in new L3i Stinger action that is still a bit of a work in progress
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