Will a barrel with a .2225" groove diameter at the muzzle shoot?

Bill Calfee

Gun Fool
Will a barrel with a .2225" groove diameter at the muzzle shoot?

CYA friends:


We never get too old to learn...........

In the past, I would have never started a new build with a barrel that was .2225" diameter in the grooves....at the muzzle..

( By the way, Duck Hawk will be most interested in this thread, since it was because of him I fit a barrel that big in the grooves)

_____________________


This barrel was one of Dan Muller's Accu-Twist, 4-MI's....

But I started to return it....since it was .2225" in the grooves, at the muzzle...

_____________________


But because of the ole Hawk, ( he fit one like it and was impressed), so I decided to fit it....

I fit it to a TCA triple, with it winding up at 27 1/4 inches.......( Like Raging Inferno)


_____________________________


Anyway, it was tested at the Lapua test facility...

__________________

CYA friends, I know nothing about the metric measuring system....

So could someone help?

What does the measurement of an outside diameter of 6.88mm, relate to a center-to-center inches measurement?


Your friend, BC


___________________

PS:

Duck Hawk, don't throw that oversized, Muller ACCU-TWIST barrel away.........

I'm serious, don't you dare throw that oversized thing away..

________________________

Again, I need help.....

What does an outside diameter of 6.88 mm, translate to a center to center inches measurement?

Am I close, does it translate to something on the order of .048" center to center measurement?

That's right .048", or, am I out in left field?....bc
 
Last edited:
Muller Accu-Twist 4-MI

Muller Accu-Twist 4-MI

CYA friends:


I was lying in bed thinking, had to pee-pee....

So I did, then turned on my machine....

__________________

A story:

Dan Muller sent me one of his new Accu-Twist 4-MI's.........was a 30 inch blank as I remember...

Anyway, I carefully cleaned the bore, inspected it, then commenced to evaluate it.....slugging.

Oh, the bore at the breech was extremely pristine, was not washed out from the lapping...

Anyway, I started the first slug, and man that thing felt awesome....

I pushed that first slug to the muzzle end of the blank.....

Then turned the barrel around and pushed the slug the other way.

That bore had that beautiful, gradual taper from the muzzle end of that 30 inch blank, all the way back to the breech end...

Impressive............oh yea.

________________________


Then I got a big let down.....after I picked up my micrometer.

I caught that slug at almost .2225" in the grooves.

I slugged it again, and the same .2225" came up.....

A note.......the micrometer I use most measures about a tenth fat.....

But even counting for that, and using my imagination to try to lessen the reading, it was still .2225" in the grooves at the muzzle...

Although, it was an extremely uniform .2225" in the grooves, even measuring the slug like an 8 groove barrel.....which really tells the tale about how round the bore of a 4 groove barrel is.

________________

Man, you talk about heartbreak.....

I wasn't going to use the barrel.....I just couldn't bring myself to fit a bore that big...

_____________________


Well, Duck Hawk got one of these Accu-Twist MI's too......and it was big in the grooves, too...

But the ole Hawk decided to fit it, cause his slugged so beautiful, too...

____________________


After the ole Hawk fit that oversized thing he called.....

He was kinda cited, and surprised, cause he thought it shot great....

_______________________

So based on what the ole Hawk discovered, I decided to fit the one I had...

So I picked out the best 27 1/4 inches of that 30 inch blank, just because that's the length of Raging Inferno's 12,050 PSL barrel.

And I proceeded to fit it....

Course I used a fully engraved, 2 degree leade chamber.....

This oversized thing was just tested, with Lapua.

Does anyone know how to convert a 6.88 mm outside measurement, to center to center inches?


Your friend, BC

______________________________


PS:

I've never based my work off of "exceptions to the rule"..

Therefore, I'll not be ordering any barrels with .2225" diameter grooves....

But, 6.88 mm will sure make one scratch their head........bc
 
Last edited:
Howdy Bill,
.048 is what I came up with, too. Thaaaaaaat's pretty stout!

And at the Lapua test center........wow!

One of these days I'd like to see a barrel like that on a properly set up Remington 37. Curiosity kills cats.....and Gregs.

.048 at the Lapua test center. WOW!

I'm sorta guessing every single round of that lot was purchased right then, and right THERE!!!

Take care,

Greg
 
25.4 mm/ inch so 6.88/25.4 = .2709 inches rounded without complying with significant digits. Less .224 = .0469
 
Last edited:
Friends 404tbang, Wally and TE

Friends 404tbang, Wally and TE

__________________

Friends 404tbang, Wally and TE:


There is so much to discuss here about this .2225" groove diameter Muller Accu-Twist MI.

I don't know exactly where to begin.

_____________


If the 50 meter, 55 yard performance, was mind boggling, what they did at 110 yards, meters, was double so...

I'm much more impressed by the 110 yard performance of this .2225" MI, and that lot of Lapua.

_____________________


I've tested some at 100 yards over the years, and even at 110 yards, meters...

But I haven't ever seen anything like what this .2225" MI and that Lapua did...

Every Olympic smallbore position shooter on earth, would literally kill for a gun and ammo like this....

___________________

And then there's that goofy compensation nonsense...

This .2225" MI was fitted with a standard HH/MD...

That MD was not changed between 55 yards and 110 yards, yet the vertical was mind blowing at both ranges...

This nonsense about having to change the MD setting as the range changes is just that, nonsense..

When one has the muzzle stopped, it's stopped.....

________________


Oh by the way, this .048" C to C grouping, ( 6.88 mm) has a vertical dispersion of, now get this, just .022".....

Talk about flat.....

__________________________


I'm cited......

Cause we may be learning something about barrels, maybe.......and maybe this is simply a fluke...

_________________

CYA friends, as bad as the 55 yard accuracy is for this .2225" and Lapua, the 110 yard performance shadows it bad...

Simply mind blowing amazing....

Your friend, BC
 
Last edited:
Hi Bill!

10 shot group ? 6,88 mm outside to outside to 50 m is amazing.If it was made to electronic target it is more amazing.

If you can give 2 first numbers of this lot I am grateful.

Priming force changes & crimping changes and how they change bullet expanding are on my intrests.

Thats why I am intrested of 2 first number of this lot which works good on 0,2250 barrel.

BR, Timo
 
Friend Timo

Hi Bill!

10 shot group ? 6,88 mm outside to outside to 50 m is amazing.If it was made to electronic target it is more amazing.

If you can give 2 first numbers of this lot I am grateful.

Priming force changes & crimping changes and how they change bullet expanding are on my intrests.

Thats why I am intrested of 2 first number of this lot which works good on 0,2250 barrel.

BR, Timo

____________________

Friend Timo:


To me the most impressive part of it all, is the 110 yard accuracy.....(100M)

The gentleman bought all of that lot they had...

Here's the first two numbers, that stand alone, then the first two of the long row of numbers:

27 28XXXXXXXXXX

Your friend, BC


PS:

It still blows my mind about this happening with a .2225" groove diameter at the muzzle......bc
 
Bill,
I may have simply missed it if you posted the info........what did the 100 meter groups measure?

Take care,

Greg
 
Friend 404tbang

Bill,
I may have simply missed it if you posted the info........what did the 100 meter groups measure?

Take care,

Greg

______________________

Friend 404tbang:


I'll answer your question this way:

Every RFBR shooter needs to take the time to set a target up at 110 yards....

Use a tall target so you don't have to correct your scope setting......just aim at the highest bull and let the group form below.

Then fire 5 foulers off to the side.

__________________________________


Then fire a 10 round group, either RTB or aim between rounds......either way.

Don't sit there are keep firing 10 rounds groups, then pick out the best one....

Now remember, this is 110 yards.

I'd love to know the truth about how many folks who try this, kick out a group in the fours the first group...

And I'd be even more interested to know the truth about how many folks kicked out a single 10 round group, in the fours, even if they sat there all day and tried.

________________________


Greg, I've shot quite a bit at 100 yards, and some at 110 yards......

10 round groups in the fours, at 110 yards, are mind boggling, even if one sat there all day shooting to obtain just one of them..

And to kick it out the first pop........at 110 yards....

_______________________


I can imagine there might be someone reading this thinking; "Calfee, I can do that all the time".

All I've got to say is this, "I'm from Missouri"......."I'd have to sit there and watch them do it."

_________________________


What an amazing performance that oversized, Muller, 27 1/4" Accu-Twist kicked out at the Lapua test facility.

And with a fully engraved, 2 degree leade chamber.......which I've always used for Eley in the past.

And when I say fully engraved, I mean, there's just enough left between the beginning of the leade and the case mouth, for the very minimum of CL growth.

Your friend, BC


_____________________

PS:

I've got to add one other thing here, because it's too important not to.

CYA is dedicated to advancing rimfire accuracy, only.

I would like for everyone to ponder something with me here.

If this Muller Accu-Twist is .2225" in the grooves at the muzzle, and has a beautiful taper to the breech, you can imagine what the groove diameter there is...

I used my standard, straight sided, 2 degree .2250" diameter chamber in this barrel...

Which means, the differential between the chamber diameter and the groove diameter, provides even less CL room growth than do the traditional groove diameters I, and everyone else, normally works with.

In other words, this whole thing is even more mind boggling as it is explored in detail..

Not only is the chamber "fully" engraved, with the very minimum of CL room growth, but that growth room is further restricted by the lessened differential between the chamber diameter and the groove diameter of that oversized Muller....

There is so much to ponder here, Greg......bc
 
Last edited:
Hi Bill!

You know better than I that this RF ammo,chamber & barrel game is that most of changes means that you get something but same time many times you lost something.

Thoughts around "oversized" barrel: Oversized barrel left bullet near same model what "ballistic expert" has designed on his table when it left barrel.In tighter barrel bullet comes longer and thinner and bullets designer work is mostly worthless.
We get better external ballistic from "oversized" barrels.

Also this "oversized" barrel is not so sensitive to bullet hardness changing.Smokeless powders burning speed depends VERY much of pressure.

Also it is easier to wax going to the muzzle...

IF we have enough priming power & powder power and less wax on bullet we can get enough sealing to "oversized" barrel and results are good.

On the old days we can buy different bullet diameters from shop,but not anymore.

BR, Timo
 
Friend Timo

Hi Bill!


Thoughts around "oversized" barrel: Oversized barrel left bullet near same model what "ballistic expert" has designed on his table when it left barrel.In tighter barrel bullet comes longer and thinner and bullets designer work is mostly worthless.


BR, Timo

__________________

Friend Timo:


You took the words right out of my mouth.....that's why I like dealing with you about this rimfire accuracy stuff.

You think.

You are correct....

A .2225" 4-MI barrel, is more "MI" than a .2220" 4-MI barrel.....

Because, like you say, the bullet isn't elongated and distorted as much....

__________________


Friend Timo, maybe we're learning something here.....may not be an "Exception to the rule"...

Timo, if the Duck Hawk had not fit the oversized Muller he got, like mine, and found it extremely accurate, I would not have fit the one I had...

So the ole Hawk kinda forced me to fit mine.....

And man, how glad I am that I did.........

_____________________


The 6.88MM is mind blowing.....

But not near as much as what that Muller did at 110 yards.......mind blowing does not properly describe that performance.

I still find it hard to believe......and I've seen the test results from Lapua.


____________________


Timo, are we really about to chart some new waters in our search for rimfire accuracy?

I've got a gut feeling.....bc


_____________________

PS:

CYA friends, if you receive one of the Muller, Accu-Twist 4-MI's, and after you evaluate it, you find the groove diameter at the muzzle is over .2220"......

Get your reamer or boring bar out, and get to work...............

I hope you realize I'm just kidding.....at least for now.......bc
 
Last edited:
This is the reason of my post on barrel wear. I suspuct the more MI of the barrel with .2225 is the result of small group. It should really shine in real world conditions. Todd
 
Bill!

If you have possible to get this "lot owner" to measure bullets thickness it is intresting.

From Lapua ammo I have found 5,68/5,69/5,70 mm thicknesses on different lots (0,2236/0,2240/0,2244 ") by years.

My old Valmet RF.s barrel is 0,222 on the muzzle and all best lots has bullet diameter 0,2236, very few 0,2240 and NEVER 0,2244)
This is with Lapua ammo.

But with RWS there has been good lots with bullet diameter 0,2246 but they have been good only on inside and calm conditions.
(Thought before that this wind drifting is coming from fast speed,but is it also of bullet distorting?...)

I dont think this is not accident that it eats thin Lapua bullets best.Tested many hundrets lots by years and both 50 m and 100 m.

BR, Timo
 
Friend Timo

Bill!

If you have possible to get this "lot owner" to measure bullets thickness it is intresting.

From Lapua ammo I have found 5,68/5,69/5,70 mm thicknesses on different lots (0,2236/0,2240/0,2244 ") by years.

My old Valmet RF.s barrel is 0,222 on the muzzle and all best lots has bullet diameter 0,2236, very few 0,2240 and NEVER 0,2244)
This is with Lapua ammo.


But with RWS there has been good lots with bullet diameter 0,2246 but they have been good only on inside and calm conditions.
(Thought before that this wind drifting is coming from fast speed,but is it also of bullet distorting?...)

I dont think this is not accident that it eats thin Lapua bullets best.Tested many hundrets lots by years and both 50 m and 100 m.

BR, Timo

____________________


Friend Timo:


The idea of the MI rifling, minimally invasive, is of course to keep from distorting the bullet....as much.

___________________

A question or two:

Why would the thinner Lapua, according to your findings, shoot better than the fatter Lapua in that .2220" groove diameter barrel?

And second, why would that same .2220" groove diameter barrel shoot fat RWS?

( Timo, I've got a feeling you know where I'm headed here )

Your friend, BC
 
Last edited:
Hi Bill!

I dont have "patented answer" to this but thinking that different bullet hardness between Lapua & RWS should be the one reason.

And to other one I dont know right english word but RWS bullet dont have "expanding groove" on bullets back side as other brands has.
(Expanding heel or how can I tell that).
Maybe it needs to be fat to sealing (expanding) in the beginning?

On the old days it was possible to buy different bullet diameter Lapua ammo L & M,but not any more.

This barrel is 6 groove with VERY narrow "beams".Lenght is 27,5 " from action end to muzzle.

Thats why I am intrested this lots bullet diameter which gives excellent results from this 0,2225 barrel.

If it is thin I loose 1 theory-:).

BR, Timo
 
Friend Timo

Hi Bill!

I dont have "patented answer" to this but thinking that different bullet hardness between Lapua & RWS should be the one reason.

And to other one I dont know right english word but RWS bullet dont have "expanding groove" on bullets back side as other brands has.
(Expanding heel or how can I tell that).
Maybe it needs to be fat to sealing (expanding) in the beginning?

On the old days it was possible to buy different bullet diameter Lapua ammo L & M,but not any more.

This barrel is 6 groove with VERY narrow "beams".Lenght is 27,5 " from action end to muzzle.

Thats why I am intrested this lots bullet diameter which gives excellent results from this 0,2225 barrel.


If it is thin I loose 1 theory-:).

BR, Timo

_____________________

Friend Timo:


I'll try to find out...

_______________________


I was looking for the word "wax".....as a possible difference as to why smaller Lapua seems to shoot in your .2220" barrel and fat RWS too.

I'm not sure I like the grease that Lapua uses, as opposed to the wax that Eley uses.

____________


Timo, right now Lapua is having some great results.....

But, I still believe if Eley can figure a way to make their bullets as uniform as Lapua, Eley will continue to dominate RFBR shooting.

On the other hand, if Eley doesn't, Lapua will take Eley's place as King of rimfire accuracy ammo....

_______________


I do not have any killer Eley or Lapua.....

But the other day I did some casual testing......such a pretty October day, and I just wanted to spend it at the range playing and enjoying the afternoon weather......cause winter is not far off...

_____________________


Anyway, the Lapua I have beats the Eley I have, by actual group size, probably 75% of the time.....at least.

But the Eley I have produces more "same hole" rounds in the groups...

In other words, if I could throw out maybe 1 out of 10 Eley shots, the Eley I have would out group my Lapua....

Put another way, if I measured the best 4 out of 5 shots in both my Eley and Lapua groups, not just the Eley, my Eley would win easy.

But when I measure all 5 rounds of both my Eley and Lapua groups, my Lapua simply measures better...

___________________


So, it gets back to the thing I said earlier............if Eley ever figures out how to make their bullets as uniform as Lapua, Eley wins.

Because I have no doubt that the Eley "wax" is superior to the Lapua "grease".


Your friend, BC
 
Last edited:
Lapua diameter

_____________________

Friend Timo:


I'll try to find out...

_______________________


I was looking for the word "wax".....as a possible difference as to why smaller Lapua seems to shoot in your .2220" barrel and fat RWS too.

I'm not sure I like the grease that Lapua uses, as opposed to the wax that Eley uses.

____________


Timo, right now Lapua is having some great results.....

But, I still believe if Eley can figure a way to make their bullets as uniform as Lapua, Eley will continue to dominate RFBR shooting.

On the other hand, if Eley doesn't, Lapua will take Eley's place as King of rimfire accuracy ammo....

_______________


I do not have any killer Eley or Lapua.....

But the other day I did some casual testing......such a pretty October day, and I just wanted to spend it at the range playing and enjoying the afternoon weather......cause winter is not far off...

_____________________


Anyway, the Lapua I have beats the Eley I have, by actual group size, probably 75% of the time.....at least.

But the Eley I have produces more "same hole" rounds in the groups...

In other words, if I could throw out maybe 1 out of 10 Eley shots, the Eley I have would out group my Lapua....

Put another way, if I measured the best 4 out of 5 shots in both my Eley and Lapua groups, not just the Eley, my Eley would win easy.

But when I measure all 5 rounds of both my Eley and Lapua groups, my Lapua simply measures better...

___________________


So, it gets back to the thing I said earlier............if Eley ever figures out how to make their bullets as uniform as Lapua, Eley wins.

Because I have no doubt that the Eley "wax" is superior to the Lapua "grease".


Your friend, BC

_________________


Lapua diameter:


Friend Timo:

I just received correspondence from the gentleman with the .2225" Muller, Accu-Twist MI....

.224" diameter.

Your friend, BC
 
Back
Top Bottom