To AI or not- re-chambering question

[ogre6br]

It has come time to re-chamber my .223 and I’ m wondering do I re-chamber it to .223 AI or keep it the same .223 but have it throated so the sierra 69HPBT will sit just above the neck shoulder junction of the case??

I usually use a 60 FBHP projectile when hunting and I want this rifle to double as my “ try hard F-class” rifle.
If I get the chamber cut to standard .223 I can compete in F-class standard (FS) if I get it cut to .223 AI I am then bumped up to F-class open (FO).
Will I be horribly disadvantaged using a .223 AI 69 sierra load (1:9 twist) in FO???

I have dies to suit either chambering a full set of .223 dies inc neck dies and micro seater for the AI I have a body die and a collet neck die and the micro seater can be used.

I want to try F-class shooting but don’t have the $$ to have a specialised rifle just for competition.
I have had to sell my 222, 22/250, 243, 6.5x55 over these last recent months of ill health.
I have to make one rifle be a “jack of all trades”, I know but will going AI make him more useful or less??

Thanks
Later
P

[Andrew~Smith]

Hello , if you want to shoot F STANDARD , you can only have a standard 308 or 223 chamber , if you want to shoot OPEN , anything goes ( almost )

Hope this helps .. Andrew Smith

[Lynn Otto]

Hi P

This would depend on whether you wish to be competitive or you just want to go and shoot and have some fun. I shot my first Queens in Open using my .223 with non Std projectiles and faired reasonably well. Your disadvantage will come at the longs where you may run out of steam. If you opt for the Std .223 and do some load development you can be very competitive in F Class Std against the .308's.

Lynn

[Paul Janzso]

Hi Patric

I would stay with the 223 in standard case. Have it throated for the 80gn Sierra MK's and enjoy "F Class Standard"

It is a better way to go than trying to gain 100fps or so by AI'ing a small case and trying to compete with F Class Open.

Is your barrel 1:9 ?

If so , have it throated for the 69gn Sierra MK's as you mentioned and you should be competitive. I'm not sure what range the 69gn'ers stay supersonic to or what velocity you get from them.

Cheers
pb

[AlanF]

In my experience, you're lucky to get reasonable accuracy past about 800yds with the 69 gn factory ammo - reloads may get a few more fps.

Alan

[Paul Janzso]

Thank's Alan.

I knew someone had experience with 69gn'ers.

There ya go Pat, you can play from 300 - 800 meters.

Cheers
pb

[Simon C]

PJ - U shoot 80's dont u? I think John & Will do as well. In any case 80's are the go with a faster barrel like 1:8. Pat, dont go with the AI...stick with the std 223rem.

PB's rifle is a tack driving 223rem with a 20" barrel. If u had something longer like 26-28" using the 80's u will do fine and not have the issue of extractors "falling" off - provided u can read the wind that is

80's are the go in std 223rem...plus std is good fun (says he who has just built a 6mm dasher)

[Lynn Otto]

Didn't you keep your Std rifle Simon??

Patrick I neglected to say that my .223 is 1:8, 30" barrel and uses the 80grners. From what I read in your post your barrel is 1:9 so will suit the 69's, my technical advisor tells me you will have trouble stabilising 80's in a 1:9 barrel and as I said the 69's will probably run out of oomph at the longs. Don't suppose your dearly beloved is about due for a a new barrel is it? Simon is right, Std is fun and challenging

[ogre6br]

HI,

Its a 1:9 and still has lotsa life left- and there is 100% NO chance (make that 200%) of me getting a new 1:8 twist tube out of the budget for a couple of years.

Will end up close to the 24-24.5 mark when re-chambered.

I have acres of space in the Tikka action to be able to seat the 69's or the 80's long.
Do you think I will be able to squeeze in the extra couple of grains that will mean that the 80's will stabalise in the 1:9 twist??

Mathematically what speed do I need at the muzzle for the 80's to stabalise in a 1:9??

What velocity do I need to push the 69's at for them to make 1000 and still be supersonic or at least over the trans-sonic zone while still making the 1000 mark??

Just to confim the only projectiles allowable in FS in a .223 are 69 and 80 HPBT sierras- correct??

Can I shoot the 69's at the short distances and then change to the 80's for the longs?? Or do you have to start with one weight and stick to it all match??

So if I shoot another projectile (other than the above 2) in the 223 I will be classed as FO- Yes/NO???

If yes- if the .223 at all competative in FO with other projectiles??

thanks

later
P

[Simon C]

Hi Lynn...I still have my standard rifle (which remains my first love!) I just had the dasher built as a varminter that I could use in Open

[Ken L]

HI,

Its a 1:9 and still has lotsa life left- and there is 100% NO chance (make that 200%) of me getting a new 1:8 twist tube out of the budget for a couple of years.



Mathematically what speed do I need at the muzzle for the 80's to stabalise in a 1:9??

P

According to Wingyro ( aka Mc Coy dirivative) 80 gn SMK require 1:7.5 at 2800 for a Stability Factor of 1.5 ( USA Preference) or 1:8 for an SF of 1.3 ( UK preference ).
In a 1:9 at 2900 fps the SF is 1.03.

I have been able to shoot projectiles with a SF as low as 1.03 in fine conditions. BUT in light rain they became unstable and wouldn't hold the target frame for a group at 300 metres 4ft + group.

You can download Wingyro/Winload from John Knight's web site free of charge at http://www.stickledown.co.uk/

Ken L