6.5x55 to 6.5x47 could it be done (easily)?

[brown dog]

A Sunday-morning-musings question:

 

Could a factory varmint 6.5x55 barrel be chopped a gnats nadger and re-chambered in 6.5x47?

 

Specifics:

Thinking of a T3 Varmint.

Available in 6.5x55, not 6.5x47; therefore wondering if, rather than throw a perfectly fine 6.5x55 barrel away, the barrel could have a cm or so cut off the back end and be re-chambered - at my muppet level of machining knowledge, I'd think the answer is 'yes' - grateful for the reality!

[gbal]

Matt,interesting and generic-I suspect that any such will depend on the relative cartridge dimensions,not just length-clearly the new can't be smaller in girth.I have a notion that smiths aren't keen on this,and they will have good reason.(chamber trueing to bore?)

I was pondering-it's Sunday here too-on the ease/not of a 6BR to Dasher job,as the latter is "just" a fire formed former....as per Ackley chambers...doable?...but I think hopes will be dash(er) ed by Tuesday....

My engineer neighbour is off to Toledo,Ohio on some commercial steel challenge,so can't get an expert steer til next week...

 

On the other hand,cutting back and rechambering is done,maybe more often to the same chambering,by some BR smiths,to set back after severe neck firecracking etc,with little/no precision loss...so maybe...

 

 

g

[dannywayoflife]

Why bother messing with the mighty sweede? When stoked up to modern pressures it beats the x47 ballistic my using the 140's the lapua brass is the cheapest lapua make and it's usually very easy to tune( mine certainly was!). Also has decent barrel life and very mild recoil what's not to like??

[brown dog]

Why bother messing with the mighty sweede? When stoked up to modern pressures it beats the x47 ballistic my using the 140's the lapua brass is the cheapest lapua make and it's usually very easy to tune( mine certainly was!). Also has decent barrel life and very mild recoil what's not to like??

 

Because I have all the 6.5x47 bits and pieces - brass, dies etc - and I love 6.5x47!

 

[brown dog]

Strikes me that, with the chamber moved forward 1cm, the 6.5x55 will be gnat's nadger smaller than 6.5x47:

 

6.5x55 body tapers from 12.2mm to 11.04

6.5x47 body tapers from 11.95mm to 11.55mm

 

 

 

[Scotch_egg]

 

 

 

 

Cough cough spectre and AX AICS

[Offroad Gary]

Buy a new barrel you tightwad. Labour and proof costs are the same for both jobs.

[brown dog]

Buy a new barrel you tightwad. Labour and proof costs are the same for both jobs.

 

Not sure that it's tight, it's common sense - Tikka/Sako barrels are excellent, why consciously choose to waste £300 on an unnecessary blank by throwing away a perfectly suitable and excellent new barrel that would be 'on hand'?!

 

Just been looking at T3 supervarmints, looks to be plenty of meat there to set a barrel back by 1cm

[Offroad Gary]

Matt. It is tight, fact.

 

Would you have your chosen smith true the new chamber to the centre line of the bore, or the previous chamber??

 

Word of the day is "catawampus"...

[Bianchi]

Believe that the freebore on standard CIP-ed 6.5x55 chambers is long so it takes ages to jam in the lands vs. 6.5x47L. Suspect that more than 1cm will have to go, most likely the whole barrel's thread to allow correct rethreading and to reset the freebore as well.

[brown dog]

Believe that the freebore on standard CIP-ed 6.5x55 chambers is long so it takes ages to jam in the lands vs. 6.5x47L. Suspect that more than 1cm will have to go, most likely the whole barrel's thread to allow correct rethreading and to reset the freebore as well.

 

Thanks Bianchi - good point.

[brown dog]

Matt. It is tight, fact.

 

Would you have your chosen smith true the new chamber to the centre line of the bore, or the previous chamber??

 

Word of the day is "catawampus"...

 

It is tight. Opinion.

It's fkin common sense with a brand new barrel on hand from a world class manufacturer. Opinion.

 

Feel free to add value when your're ready

 

 

 

 

 

 

 

Just for a refresh:

 

Strikes me that, with the chamber moved forward Xcm, the 6.5x55 will be gnat's nadger smaller than 6.5x47:

 

6.5x55 body tapers from 12.2mm to 11.04

6.5x47 body tapers from 11.95mm to 11.55mm

 

 

 

[Gandy]

Not an expert but should not be too much of a job to set back a chamber but the barrel profile may conflict / not help (note you said varmint).

 

Sure a smith will be along soon.

[Danpd]

Could possibly be done, but limiting factor most likely won't be simply the shoulder/casehead datum dimensions. You also need cleanup on the neck diameter (generous factory 6.5x55 vs min-spec no turn 6.5x47) and the leade/throat section........ most factory 6.5x55s are throated long due the fact that 160+gr hunting ammo is available off the shelf, whereas most 6.5x47s have throats tailored to 120-140 class high bc bullets.

 

Once you've figured that out, then you have a 1.125 Max OD on the barrel shoulder, and a .996 OD on the tenon. Even the varmint barrels have little in the way of a cylinder section to their profile, so you have relatively little available room for setback before the shoulder dimension gets too small to be safely torqued onto the barrel and maintain reliable headspace.

[brown dog]

Could possibly be done, but limiting factor most likely won't be simply the shoulder/casehead datum dimensions. You also need cleanup on the neck diameter (generous factory 6.5x55 vs min-spec no turn 6.5x47) and the leade/throat section........ most factory 6.5x55s are throated long due the fact that 160+gr hunting ammo is available off the shelf, whereas most 6.5x47s have throats tailored to 120-140 class high bc bullets.

 

Once you've figured that out, then you have a 1.125 Max OD on the barrel shoulder, and a .996 OD on the tenon. Even the varmint barrels have little in the way of a cylinder section to their profile, so you have relatively little available room for setback before the shoulder dimension gets too small to be safely torqued onto the barrel and maintain reliable headspace.

 

Thanks Paddy, any feel for how little?

 

I'm guessing setting back sufficiently that the 6.5x47 reamer goes forward by the length of a 6.5x55 neck would take out any issues - so only about 8 or 9mm.

 

I'd hazard a guess that that'd still leave more meat on it than a lite barrel's chamber - and all worries about freebore/leade and case neck would go too.

 

[Danpd]

http://www.cip-bobp.org/homologation/uploads/tdcc/tab-i/6-5-x-47-lapua-en.pdf

 

http://www.cip-bobp.org/homologation/uploads/tdcc/tab-i/6-5-x-55-se-en.pdf

 

 

Here are CIP drawings with throat lengths/angles/dimensions for both cartridges.... get your abacus out, and report back

[Laurie]

Believe that the freebore on standard CIP-ed 6.5x55 chambers is long so it takes ages to jam in the lands vs. 6.5x47L. Suspect that more than 1cm will have to go, most likely the whole barrel's thread to allow correct rethreading and to reset the freebore as well.

 

 

That's my read on what would need doing too. I asked a similar question of a few gunsmiths some years back, not a serious project rather hypothetical. None said they would do this job for two reasons:

 

1) they consider it a poor use of their time and expertise

2) Factory hammer forged barrels are HARD. The risk of ruining an expensive match reamer is much greater than in chambering a virgin blank or rechambering a match quality barrel from the custom barrelmakers.

 

This was in respect of chrome moly barrels and I don't know how today's factory stainless varmint jobs compare machining wise, but I still suspect you'd be hard pressed to find a 'smith who'd take the job on.

[brown dog]

 

 

That's my read on what would need doing too. I asked a similar question of a few gunsmiths some years back, not a serious project rather hypothetical. None said they would do this job for two reasons:

 

1) they consider it a poor use of their time and expertise

2) Factory hammer forged barrels are HARD. The risk of ruining an expensive match reamer is much greater than in chambering a virgin blank or rechambering a match quality barrel from the custom barrelmakers.

 

This was in respect of chrome moly barrels and I don't know how today's factory stainless varmint jobs compare machining wise, but I still suspect you'd be hard pressed to find a 'smith who'd take the job on.

 

Thanks Laurie, I think you'd need to re-examine those answers with a 'wheels within wheels' mindset.

 

As you say, also a different game with stainless barrels.

[brown dog]

http://www.cip-bobp.org/homologation/uploads/tdcc/tab-i/6-5-x-47-lapua-en.pdf

 

http://www.cip-bobp.org/homologation/uploads/tdcc/tab-i/6-5-x-55-se-en.pdf

 

 

Here are CIP drawings with throat lengths/angles/dimensions for both cartridges.... get your abacus out, and report back

 

 

Paddy,

 

You'll have to help me with those; I'm not familiar with CIP drawings - both look to have a distance from case mouth to commencement of the rifling of 0.35mm ('h') and both have the same forcing cone angle (alpha 1) of 90 deg (?)

 

I've always had the impression that, subject to minimums, distance to commencement of rifling and forcing cone angles were something within the remit of the reamer designers and would vary by mfr?

[Offroad Gary]

Heres value.

 

Buy a s/h .243/308 and stick a new tube on it, save yourself the cost of buying the right sized mag.

 

Or buy one in .260, its better than the 47l according to tackb...

 

Youre still a tightarse!

[Akeld]

I asked a simiar question a while back on another forum regarding .243, the main reservation in doing it seemed to be damaging the reamer

[Danpd]

This was intriguing me somewhat,

 

i produced solid models of both cartridges including the throat dimensions and overlaid them with concentric alignments, adjusting until one entirely removed the other.

 

here is the result

 

 

 

on a theoretical basis, 8.5-9mm of reaming would clean up the 6.5x55se chamber and throat.

 

I have also measured some Tikka take off barrels, and 12mm is about all the setback you could squeeze out of one.... reducing the shoulder diameter by .5mm.

 

So yes, I reckon it is possible, whether there is any point in doing it is another question, the reamer will be guided by the existing chamber, so if you happen to have a misaligned existing chamber, you will also have a misaligned new chamber, thereby losing any accuracy potential and wasting more money in powder and bullets than a new barrel would have cost to start with.

 

 

[brown dog]

This was intriguing me somewhat,

 

i produced solid models of both cartridges including the throat dimensions and overlaid them with concentric alignments, adjusting until one entirely removed the other.

 

here is the result

 

6.5x55comp.jpg

 

 

on a theoretical basis, 8.5-9mm of reaming would clean up the 6.5x55se chamber and throat.

 

I have also measured some Tikka take off barrels, and 12mm is about all the setback you could squeeze out of one.... reducing the shoulder diameter by .5mm.

 

So yes, I reckon it is possible, whether there is any point in doing it is another question, the reamer will be guided by the existing chamber, so if you happen to have a misaligned existing chamber, you will also have a misaligned new chamber, thereby losing any accuracy potential and wasting more money in powder and bullets than a new barrel would have cost to start with.

 

 

 

Excellent Paddy - thanks! (Pretty impressed with my calibrated eye SWAG of 8-9mm )

 

Yup, take the point with misaligned chamber - but that's only a concern if it is misaligned

 

- bit 'cup half empty' to assume all Sako barrels have chambers that are off; I imagine the vast majority are 'on'.

 

Presumably it'd be easy to measure/check before starting any work on the barrel?

[MJR]

With a new gun with only maybe proof rounds or very few fired I like the thinking here.

 

I'd say the 1cm is a no go. Why? Well because you'd have to pick up on the same threads without interruption and I don't know if T3 tenons have a relief cut for the end of the thread. I'd be looking to see if there is enough material in the first three inched or so of the barrel to allow the complete tenon to be removed and effectively re chamber in x47. Removing the tenon and moving the chamber forward removes any possible leade/throat issues as a one would be cut. I'd also be looking to see if the reamer pilot will engage in the barrel with the still partial chamber of the x55 in the barrel and if the barrel could be accurately chucked prior to machining, probably with a long range rod or similar.

 

Interesting project.

[brown dog]

With a new gun with only maybe proof rounds or very few fired I like the thinking here.

 

I'd say the 1cm is a no go. Why? Well because you'd have to pick up on the same threads without interruption and I don't know if T3 tenons have a relief cut for the end of the thread. I'd be looking to see if there is enough material in the first three inched or so of the barrel to allow the complete tenon to be removed and effectively re chamber in x47. Removing the tenon and moving the chamber forward removes any possible leade/throat issues as a one would be cut. I'd also be looking to see if the reamer pilot will engage in the barrel with the still partial chamber of the x55 in the barrel and if the barrel could be accurately chucked prior to machining, probably with a long range rod or similar.

 

Interesting project.

 

You'd have to explain that to me pointing at bits of metal and machine ! I can't follow your tenon thoughts (in that, I'm a man who can usually identify the difference between a drill and a hammer - as long as it's obvious) I don't understand the threading issues you describe, but I could rustle up a pic of the back end of a T3 barrel if that'd be of use? Want to go halves on a reamer, or is it too early!?