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View Full Version : Seeking input about the comparitive capicities of the 6x47Lapua case, to a 250 case.



VaniB
03-20-2008, 01:57 PM
I'm still kicking around ideas for my next varmint rifle which could possibly be another 20 cal. I was pondering about using a necked down 6x47Lapua case. I was wondering if the capacity of a necked down 6 x 47 Lapua case (necked to 20 cal) would be greater then the capacity of a 22/250 case necked down to 20 cal.

The 22-250 case necked down to a 20-250 cartridge is already overbore, and if I had a choice, I would prefer that the Lapua case hold the same amount of powder as the 20-250 or less powder. Certainly, I don't want more capacity then the already overbore 20/250 case. The Lapua case is a superior case allowing greater pressure, and also has a small primer which should be advantageous. In case you were wondering why I don't consider going with a less overbore 20BR or 20Dasher.... is because the 6x47Lapua case or 250 case will feed easy in a Rem 700 magazine.

Anybody know the comparative capacities of these two cases?

tylerw02
03-20-2008, 05:05 PM
I forget who it was, but a member of this forum was building a 22-6.5x47 Lapua. I asked him to forward me any information to me when he got it finished. Its only been maybe 2 months. I had thought about a 20-6.5x47, but I thought it may be a bit much for me at this time. If one were to do it, you'd want to find some heavier bullets for higher BCs. The mist-effect just isn't that great with Bergers, however they are quite accurate bullets.

VaniB
03-20-2008, 08:18 PM
Tyler,

I have been told elsewhere by a guy who built a 6x47Lapua necked down to 20 cal, that it was a terrible barrel burner. He even offered to lend me the reamer. I told him that I would take his word about it.....and so "thanks......but no thanks!"

I'm now checking into a 20-250 based cartridge. Some guys love it, but I can't confirm yet just how bad a burner it is. I'd bet it's way overbore.......but would like to hear actual experience about it. Somebody claims that Kevin Weaver told him that he's gotten "over 3,000 rounds on it and it's still going strong".....but that sounds way too optomistic. Maybe the guy meant 300 and added one zero too many to that quote.

tylerw02
03-21-2008, 02:15 AM
5mm SMc and 20 BR look good....

But how about a .204 Ruger Ackley Improved?

alinwa
03-21-2008, 03:34 AM
Maybe this will help.

I weighed the 6X47L at 48.2 in this post http://www.benchrest.com/forums/showthread.php?t=34788&highlight=6.5X47+case+capacity

22-250 is listed as 43.5 in this post http://www.benchrest.com/forums/showthread.php?t=48618&highlight=22-250+capacity

I'm guessing you'd pick up a couple of grains when necking up to 6MM but don't think you'd match the 47Lapua case capacity.


al

VaniB
03-21-2008, 12:27 PM
Thanks Al. That confirms that it is larger and way too overbore. When using either case for a 20 cal, it is is more of a matter of one overbore case being more overbore then the other.

Being I have decided to go back to my original intent of using the Lapua 6x45 case to push 87's out of a varmint rifle, it's nice to know that this Lapua case has a little more capacity then the old 6/250 cartridge. Pushing a 20 cal bullet I wanted the Lapua to be lesser. But to push a 6mm 87 grain bullet, I prefer it to be moorer. (That's not a real word, is it?)

Tyler,
I spent another few hours in the last couple of days doing searches and checking archive posts about the 6mm's and the overbore 20's for my next 600+yard PD rifle. For a 20 cal rifle, I focused on using 50 grain bullets for more energy deliverd at 500-600+ yard shooting. But 50 grains is a fussy weight bullet in the 20 caliber, exibiting less desirable charachteristics then when using the lighter 20 cal bullets. While a 1-9 twist has to be used to stabilize the 50gr bullet, it also slows it down. So it essentially works against itself. Two different guys reported this, and many said that they can't get Todd Kindler's velocities. And when succeeding in pushing the 50gr bullet to high velocities ( aprox 4,100fps and better) inferior brass will possibly allow loose primer pockets. Then, I have to wonder how long the barrel will last too.

So.......it's just easier and safer for me to go with my original plan of a 6x45L catridge, where none of those problems are a major concern.

The Ruger 204AI sounds like an interesting cartridge. But I have concluded that the heavier 50gr bullet that I preferred for 600 yard shooting is a concern for any cartridge case.

Roger T
03-21-2008, 01:13 PM
Maybe you should look at a 20 PPC or a 20-6.5 Grendel (close to the same caps.) good brass available.

tylerw02
03-21-2008, 02:57 PM
Tyler,
I spent another few hours in the last couple of days doing searches and checking archive posts about the 6mm's and the overbore 20's for my next 600+yard PD rifle. For a 20 cal rifle, I focused on using 50 grain bullets for more energy deliverd at 500-600+ yard shooting. But 50 grains is a fussy weight bullet in the 20 caliber, exibiting less desirable charachteristics then when using the lighter 20 cal bullets. While a 1-9 twist has to be used to stabilize the 50gr bullet, it also slows it down. So it essentially works against itself. Two different guys reported this, and many said that they can't get Todd Kindler's velocities. And when succeeding in pushing the 50gr bullet to high velocities ( aprox 4,100fps and better) inferior brass will possibly allow loose primer pockets. Then, I have to wonder how long the barrel will last too.

So.......it's just easier and safer for me to go with my original plan of a 6x45L catridge, where none of those problems are a major concern.

The Ruger 204AI sounds like an interesting cartridge. But I have concluded that the heavier 50gr bullet that I preferred for 600 yard shooting is a concern for any cartridge case.

Honestly, the 50 gr Berger bullet sounds good, but I just went to find the published BC. The published BC is merely 0.295. Meanwhile, the 39 Sierra is .287. Taking a .204 AI and assuming one can push the 39 Sierra to 4,000 (which sounds very doable), you'd have 48" of drop and 3.2" of drift per mph of 90 degree crosswind.

On the otherhand, the 50 gr Berger may be pushed to 3800 (kind of a liberal guestimation), and will have 53" of drop and 3.3" of drift per mph of crosswind.

This is kind of interesting that Berger didn't increase BC much with the extra 11 gr of weight. Are you aware of any custom .204 bullets that are more of a VLD design?

SST
03-21-2008, 10:42 PM
................Then, I have to wonder how long the barrel will last too.


When I had my 20BR built, I asked about barrel life. I was told, "You wanted a hot rod, you got a hot rod. When you burn out the barrel, just put another one on it."

Sandbag
03-29-2008, 05:40 PM
VaniB

Have you considered the Lapua 6BR case? It is still "overbore" but works with the same bolt face as the 22-250, 6.5X47, etc. Excellent, proven brass is readily available and I wouldn't be surprised if Pacific Precision and JGS have some good information on this cartridge as to neck diameters, freebore, etc.

Just a thought.
John