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

[gbal]

Matt,as Sunday is slipping away,and I've got my new set of Weatherby inert cartridges ( antique shop!) to try in standard chambers, it seems pretty much as if my brief first post was in the ball park,but detailed expert input explains why the idea isn't seized upon.

 

Gary,I believe the opposite of 'tight' is 'profligate'.

 

The prudent man like Matt-or even me, takes a more balanced view.

 

However,I will admit that if I had all the money I've spent on less than perfect rifle projects in the last fifty years,I'd spend it all again on less than perfect rifle projects. :-)

 

gbal

[Danpd]

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.

It would only be worthwhile on a new rifle. Picking up threads, and re-establishing the tenon is just basic machine work. In terms of dialling in it is also not hard with a two point cat-head type arrangement, or the GTR action truing jig, or the Tru-Bore alignment system... Which is what I use. There is no scope for chopping off the entire tenon, and you can dial the barrel in all you want, but the reamer will only follow the existing chamber unless you can pre-bore a concentric feature to follow.... The reamer pilot will do absolutely nothing to correct any misalignment.

[baldie]

There isn't scope to remove the existing chamber.

 

This means at some point you will have to stick a good reamer into a factory hole. It wont pick up the bore [the pilot] before it starts cutting.

 

At best, you will probarbly have an un concentric chamber.

 

At worst, when the reamer has cut to the point where the pilot enters the bore, if its not concentric, it will snap the neck off the reamer like a carrot.

 

Its like sticking your dick into a mucky woman.

 

Russian roulette.

 

Its also a well known fact, that despite how well most shoot, sako and tikka barrels are the most unconcentric ones fitted to factory guns. The runout on them can be horrendous.

 

Get a Bergara Matt, and do the job a bit cheaper, but right.

[Offroad Gary]

Or pay £50 more and have a LW, or £160 more and have a benchmark. Remember, a rifles for life, not just for christmas

[gbal]

Dave,is the re-reaming of standard 223 or 243 to 'Ackley Improved',also compromised,to the point of impracticality,or 6BR to Dasher.

I don't want to encourage an epidemic of STDs,but I get these naughty desires sometimes.

g

[baldie]

Any chamber that is cut and that the reamer starts cutting before the pilot engages runs the risk of problems. Some people risk it, some don't.

[brown dog]

 

 

I'm not understanding how is this different to 'setting back'? That's an entirely routine gunsmithing service in the States, same same, as George mentioned, ackleying.

There must be a normal and routine way of doing this - what happens when you ream a chamber to half depth and have to stop for some reason; and then restart? I'm not clear why that's different to this?

[brown dog]

It would only be worthwhile on a new rifle. Picking up threads, and re-establishing the tenon is just basic machine work. In terms of dialling in it is also not hard with a two point cat-head type arrangement, or the GTR action truing jig, or the Tru-Bore alignment system... Which is what I use. There is no scope for chopping off the entire tenon, and you can dial the barrel in all you want, but the reamer will only follow the existing chamber unless you can pre-bore a concentric feature to follow.... The reamer pilot will do absolutely nothing to correct any misalignment.

 

I think Mike's point is that the 'new' tenon would have the 'old' tenon's relief cut in the middle of the new tenon threads; are you seeing a way around that?

[baldie]

Setting back is using the same reamer in the same chamber Matt, and its usually being done on a custom chambered barrel.

 

Ackleying is changing not only the shoulder angle, but also the tapered case sides to parallel or almost.

 

Imagine this.

 

The reamer is being pushed from the rear on a floating holder. This allows it to move in ALL directions. The only thing that guides it up the bore, is the tight fitting pilot on its nose. If that pilot isn't engaged, it has no guidance.

 

The only way I could think it could be done properly, is if the everything was proved concentric, and the reamer pushed from a completely fixed postion a la cnc.

 

When someone uses a roughing reamer, and this is where the muppets often show themselves up, its only used to cut enough material from the bore, so that the finish reamer's pilot can still engage the bore, BEFORE it starts to cut, otherwise you have no control over what it does.

 

I dont even use these, preffering to cut the entire chamber from the rear, with the finish reamer. That guarantees it will follow the bore as perfectly as possible.

[Danpd]

I think Mike's point is that the 'new' tenon would have the 'old' tenon's relief cut in the middle of the new tenon threads; are you seeing a way around that?

That will make absolutely no difference to anything. I regularly convert AE barrels with a partially threaded tenon to AW compatible fully threaded tenons, this leaves a 2-3mm gap between threaded sections and they torque up perfectly with no detrimental effects to accuracy. Most of the torque is borne by only 3-4 threads in a 60 degree thread form anyway.... Especially in sloppy factory threads. There is a descriptive investigation into this in Rifle Accuracy Facts by Vaughn, which is by no means chapter & verse on all things rifle related, but certainly has some interesting concepts within its covers.

[brown dog]

That will make absolutely no difference to anything. I regularly convert AE barrels with a partially threaded tenon to AW compatible fully threaded tenons, this leaves a 2-3mm gap between threaded sections and they torque up perfectly with no detrimental effects to accuracy. Most of the torque is borne by the first 3-4 threads of a 60 degree thread form anyway.... Especially in sloppy factory threads. There is a descriptive investigation into this in Rifle Accuracy Facts by Vaughn, which is by no means chapter & verse on all things rifle related, but certainly has some interesting concepts within its covers.

 

Ah, OK. Yup, that rings a bell, got Vaughn's book here somewhere.

[brown dog]

Setting back is using the same reamer in the same chamber Matt, and its usually being done on a custom chambered barrel.

 

Ackleying is changing not only the shoulder angle, but also the tapered case sides to parallel or almost.

 

 

Yup, that's why I'm puzzled, to my mind reaming a shortened x55 chamber to a x47 is a tiny change akin to ackleyizing (or setting back with a different reamer to the one used to cut the original chamber) - I'm trying to visualise why the pilot wouldn't be engaged?

[baldie]

If enough material is removed from the threaded tenon to allow the pilot to engage before cutting starts, then yes.

 

That doesn't allow for the fact that a factory chamber will or will not be true Matt, you will then get a new, untrue chamber as the reamer will only cut whats there.

 

The distance from the pilot to the reamer shoulder is short, and its the reamer shoulder, or rather its outward edge that starts cutting first.

 

Imagine a loaded round. You have the distance from the bullet tip to the back of the shoulder. That is roughly the maximum distance the shortened tenon can be.

[Ronin]

FFS…….

 

The wheel has gone 360 degrees….

[Offroad Gary]

FFS…….

 

The wheel has gone 360 degrees….

I shouldn't take the p!ss if I were you...

 

"Andy, it's Matt, I was just wondering if........"

[MJR]

But that was a round wheel....

[Ronin]

If you two had put money on the lottery,,,,,,,,

[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.

 

 

 

Paddy,

 

Wondering if, since this chat, curiosity has got the better of you and you've had a go at this?

[gunner]

Was having a read at this , interesting thread . I Couldn't help wondering if using the floating reamer , could you not buy reamer with longer than normal pilots ? Surely that would get over the problem of a std length reamer /pilot cutting before its properly engaged with the bore ? So that its cut concentric to the bore - not concentric to the old chamber . But im also thinking a longer one may be more prone to breaking ? Especially it the old chamber was cut untru itd prob stress and break the reamer as dave said ? Any thoughts? Atb-tim

[brown dog]

Was having a read at this , interesting thread . I Couldn't help wondering if using the floating reamer , could you not buy reamer with longer than normal pilots ? Surely that would get over the problem of a std length reamer /pilot cutting before its properly engaged with the bore ? So that its cut concentric to the bore - not concentric to the old chamber . But im also thinking a longer one may be more prone to breaking ? Especially it the old chamber was cut untru itd prob stress and break the reamer as dave said ? Any thoughts? Atb-tim

 

This concentricity business....... if the original Tikka barrel is sub- 0.25MOA on the original calibre; empirically, it wouldn't matter if the chamber is off by 90degrees and then shortened at the same offset, it's still a 0.25MOA barrel.

 

Tikka rifles/ barrels are renowned for their out of the box accuracy; this concentricity piece is a wee bit of a hunt for a problem that (if the rifle shoots awesomely as a 6.5x55) is having no effect - a distraction/irrelevance - if the barrel worked before having the chamber shortened by 9mm, it'll work afterwards too.

[Scotch_egg]

This concentricity business....... if the original Tikka barrel is sub- 0.25MOA on the original calibre; empirically, it wouldn't matter if the chamber is off by 90degrees and then shortened at the same offset, it's still a 0.25MOA barrel.

 

Tikka rifles/ barrels are renowned for their out of the box accuracy; this concentricity piece is a wee bit of a hunt for a problem that (if the rifle shoots awesomely as a 6.5x55) is having no effect - a distraction/irrelevance - if the barrel worked before having the chamber shortened by 9mm, it'll work afterwards too.

Isn't the concentricity to do with when the reamer and barrel are clocked up. The machinist would have to match any offset perfectly or risk the reamer. Well that's my understanding.

[brown dog]

Isn't the concentricity to do with when the reamer and barrel are clocked up. The machinist would have to match any offset perfectly or risk the reamer. Well that's my understanding.

 

I still think we're on the search for problems here.

 

I believe Tikka/Sako barrels are hammerforged; they wouldn't be able to get the mandrel out if it wasn't straight enough (enough to enable 0.25MOA factory barrels).

 

I feel there's a temptation to let 'excellent' get in the way of 'good' .........bottom line is that Tikka barrels work 'good enough' (in fact, significantly more than good enough).

 

(Clearly there'd be no point in doing this to a tikka that doesn't shoot in it's original guise; but if it's a hummer, I can't imagine how a problem would be created).

[MJR]

The reamer will follow the existing chamber whether its concentric to the bore or not. Until you'd actually clocked the barrel up in the lathe you would not know if the chamber is concentric to the bore. If it was wildly out I'd say you have three options.

1 stop there and forget about it

2 re chamber following the chambers run out with suitable tooling to allow the reamer to float

3 chop barrel and re chamber - a sporter barrel probably wouldn't allow this but a varmint contour might?

 

One thing strikes me. What's so bad about running a 6.5x55? With the exception of burning more powder (which extra cost is more than offset by the re chamber work) and a slightly longer bolt throw I'd say the 55 has no disadvantage other than not being 'Gucci'

In fact it has longer legs in the heavier range bullets and can be an excellent long range performer.

[Finman]

One thing strikes me. What's so bad about running a 6.5x55? With the exception of burning more powder (which extra cost is more than offset by the re chamber work) and a slightly longer bolt throw I'd say the 55 has no disadvantage other than not being 'Gucci'

In fact it has longer legs in the heavier range bullets and can be an excellent long range performer.

The voice of good sense well said MJR! Not to mention cheaper brass and availability of 'off the bench' ammo...

 

Finman

[brown dog]

One thing strikes me. What's so bad about running a 6.5x55? With the exception of burning more powder (which extra cost is more than offset by the re chamber work) and a slightly longer bolt throw I'd say the 55 has no disadvantage other than not being 'Gucci'

In fact it has longer legs in the heavier range bullets and can be an excellent long range performer.

 

Short answer: AICS and or AW short action magazines.