20/47

[Kevbee]

Has anyone any info on 20/47 ie throat life, bullet speeds and case prep? I have a .243 and I'm getting it rebarreled. I was thinking 22.250 and then someone mentioned 20/47 and it sounds exciting but I can't find much info.

[swagger]

No experience or real info but I'd guess barrel life to be rather short!

Though probably very enjoyable!!

[Kevbee]

Yes that's what I was thinking.

[pork chop]

Would a 20 br or 35 smc be a better option, not got a clue personally but worth a look

[Big Al]

What is it's intended use and with what weight of bullet?

[OSOK]

Google Bruce Potts on the web as he started the 20x47 years ago and Ballistic Hamster here on UKV has run one .

 

OSOK

[Sherlock]

Hi Kev.

The lack of choice of High BC bullets that expand is the main problem is with opting for an overbore 20 cal. Plus I guess you will be lucky to get 800 shots from your tube before the throat is gone. The 39/40 grn range have a true bc of in the mid 0.200's. Berger do a 55 grn varmint bullets with a nice BC.

 

Unfortunately when I was looking to build a rifle to shoot this pill, I found out they did not expand reliably.... I think Big Al might be able to confirm either way.

 

Another worry was, If the 55 grn Berger Bullet, just didn't shoot in my rifle - what then ???? there is no alternative bullet without dropping down a lot on BC

 

If you only plan to run 39/40 grn varmint bullets, then they will be screaming from the muzzle , but velocity will soon bleed off and any advantage over the ballistically better 22 cal will be lost.

 

Other options is you want something different - 22 Middlestead - basically a 243 necked down to accept a 0.224 bullet.

A friend of mine goes shooting with a guy (Scott Liddle) who is driving a 77 grn TMK at close on 3800 fps from his 22 MS. There not much than can match this.... and I am guessing that it will still give you more barrel life than a 20/47

 

A standard 22.250 will zip a 53 grn Vmax over 3900 fps... or with the right twist rate, a 75 grn Amax at 3300 fps. Lapua cases available - tons of loading data - dies and everything easy to get. . that is more preferable to my mind than all the case prep and fkin about you will have to do. But whatever floats ya boat , I guess.

 

ATB

S

[gbal]

243w 58g Vmax @ 3750 BC .25 SAAMI pressure etc commercial ammo.

A boat floater more than scupperer,perhaps for the faint hearted.

I wonder what the pressure in a 77@3800 necked 243w case might be?

 

g

[OSOK]

gbal , I now run 90's through my Middlestead at 3,200 but originally i shot 80's at around 3,550 out of a 30 inch barrel and wouldn't of wanted to push anymore . I've heard about 75's running at 3650 ................... My guess is 65,000 plus

 

OSOK

[The_Dogge]

What's really wrong with the .243? It's already a bit of an overbore cartridge, if you want more speed and something different how about a .243AI? That way a lot of your current kit and consumables may be usable, plenty of bullet options from warp speed 55/58gn up to heavies with BC >0.5, though you may have to pick your twist with your intended bullets in mind.

.243 is a superbly versatile cartridge, I would think that in practice you could load it to match or better a 22-250 in any respect.

 

Given the rather modest differences between any centerfire rifle cartridges in real world shooting I would personally choose something proven with a good availability and variety of consumables. I know people like something different and high performance, the 243AI is both, but you can still feed it regular 243 ammo!

[gbal]

Thanks OSOK.

I lusted after a Middlestead in the mid 60's-having been brought up ballistically by Warren Pge (243,&Rem Mag ,Bench Rest/Varminting ) in my formative years,it seemed the bees knees-and could probably shoot them off...but by the time I left student life,I'd seen the sense of a 243 (sako),and a 222 for the close in bees.

The introduction of 55/58g 6mm bullets much later,really made the standard 243w pretty close ,but the itch is still there-call it charisma?

Thanks for your velocity data- I can see 75/3650 and maybe a tad more....maybe it's just as well we don't have affordable pressure guages-I remember when chronos came out,it set back MVs by about 200fps (ie to reality,not wishfull thinking).Great stuff. :-)

 

g

[gbal]

The-Dogge,absolutely-the 243 is so versatile,especially if you have all the reloading gear etc,it really only needs a superb heavy varmint terminating bullet (thanks,sherlock) to be close to the top of the pyramid,and no fuss.

.

It would have to be called the 6-08 ,of course,but afficionados could live with that,no?

 

gbal

[Kevbee]

Thanks everybody and Sherlock I think you are right and I'll get it a new 22.250 barrel. Steve kershaw is doing the work, and I'm getting a 24 inch Sasson barrel, it's a 1-9 twist and would mainly use 53 vmax but would like to try it on 75 Amax for long range. Is there anything I should ask for before he starts work on it?

[Rob1562]

Hi Kevbee

 

Steve is in the process of making me a 20x47.

 

I've got the similar problem to you......a 6.5x47 bolt face but a real itch for a 20 that needs to be scratched.

 

I've thought about 20br,5/35smc and just about all the others, but I've got a Stiller Predator action in an AI stock and want a calibre that will cycle from AI mags.

I know that there will be lots of case prep and probably a reduced barrel life but when you gotta scratch that itch !!!!

 

Regards, Rob.

[duey]

Kevbee

1-9 probably wont work for 75gr but should for 69gr, if you really want the 75gr-80gr then you will need 1-8 twist

[Alycidon]

gbal , I now run 90's through my Middlestead at 3,200 but originally i shot 80's at around 3,550 out of a 30 inch barrel and wouldn't of wanted to push anymore . I've heard about 75's running at 3650 ................... My guess is 65,000 plus

 

OSOK

That is a good way to go with a 243. I can see no benefit at all in running a 20x47, max bullet weight is the 55gr Berger match, driving that at maybe 3750/3900 wont kill anything deader than if driven at 3200 all be it drops and drifts would be a bit easier but thats why we have range finders, wind meters and ballistic aps.

 

Note the long barrel on OSOKs rifle, ensures max powder burn, BUT you might want a new cabinate to get it in as most with a lock top box wont take much more than a 27" barrel.

 

Thanks to advice from OSOK ten years ago I built a 20BR, throated to suit the now discontinued Berger 50 gr which downloaded it moves at 3500.

 

Most of the time I tend to use 39gr SBK at anything sub 300 yards slightky less powder ( N150) to keep velocity at 3500.. I have killed front on foxes with the 39 at a few yards short of 300 yards, instant lights out. That for 99% of shots is good enough. That rifle has missed 3 foxes in 10 years. However 3500fps with a 39gr SBK is 204 Ruger territory.

 

There are some good posts on the 20x47 on Saubier, looks like loading it hot you might get 1000 rounds or so, downloading with a cooler powder then that can be extended. Barrels in the US are far cheaper than they are here. If you do go that way have a look at the advice on twist rates, Berger say 1 in 8 from memory but most US users are getting excellent results from 1 in 9 and 1 in 10. Not tried 55s myself yet as I have stock of 50s.

 

I would avoid 5/35SMC as I hear tales of accuracy problems, 20BR properly built and well shot will shoot .2 - .3 easily enough.

 

A

[Kevbee]

Thanks everyone for the input, I've thought a lot about it and I've come to a conclusion , and after talking to Steve Kershaw I'm now getting for my sako 85 varmint a new 24 inch .243 barrel 1-12 twist to shoot a 58 gn bullet! And now I don't need new dies, or a variation. So I've almost gone full circle lol

[gbal]

Kev ,nice round scenic trip,right destination!

[Kevbee]

Haha gbal thanks again to a really helpful group!