I am interested in rechambering a Sako AV from 7mm Rem mag to 7mm Dakota or Ultra mag. I don't know much about the dimensions of these two rounds. My questions are:

What,if any, modifications will have to be made to make it feed properly?

How much velocity will I lose using the existing 24" as opposed to a 26" barrel?

Will I have to open the bolt face greater than .532?

[ 05-29-2002, 08:46: Message edited by: DOCTOR LOU ]

What,if any, modifications will have to be made to make it feed properly?

I'm not familiar w/ the Sako, but there may be some minor grinding needed on the feed rails, though likely it'll feed fine as is.

How much velocity will I lose using the existing 24" as opposed to a 26" barrel?

I would guesstimate 60-100 fps.

Will I have to open the bolt face greater than .532?

The UM has a rebated rim .532" in dia, so no need to open the bolt. The Dakota has a .545" rim, so the bolt and extractor will need to be opened up slightly.

Well said, Paul. Lou, you might also take into account that while your Sako magazine holds 4 rounds of 7mm Rem Mag (and would also hold 4 rounds of 7mm STW if rechambered), you can likely only get 3 rounds of the fatter Dakota or RUM into it. Don't know if this is important to you or not, but it is often overlooked.

Thanks for the info. Is the UM or Dakota case diameter the same as the belt diameter on a standard magnum case? If so, it should feed ok.

The belt dia is .532". The 404 case is .545" at the head, that is the case the Dakota cartridges (excepting the 450) are based on, and the ultra mag is also based on the 404, though the rim has been rebated to .532" so that bolts would be common.

Even magnum actions sometimes require rail work to feed the ultramag cases feed properly.I know this from experience as I once made the same assumption you are making and was proven wrong.

[ 05-30-2002, 06:24: Message edited by: stubblejumper ]

DrLou,

I had this conversion done to a Ruger #1S. Obviously I have no comment on feeding or bolt face, but the extractor did have to be modified. I like the 7Dakota alot. I easily get 3250fps from the 26" bbl. w/ 160gr NP o/ RL22 or IMR7828. Good luck w/ your project.

DOCTOR LOU,

Are you looking to move to the 7mm Dakoata for extar velocity or to go from belted to rimless.

If it is only extra performance you might consider the 7mm STW, which has about the same case capacity as the Dakota.

If you are not familiar with the 7mm STW, it is just like your 7mm Remington with but with the case body about .35" longer.

Brass is cheap H&H belted cases and readily available.

If want both rimless and more speed, the 7mm Rem Ultra will offer more than the 7mm Dakota and with far cheaper brass. Also, the case rim will fit your existing bolt face.

Basically, the 7mm Rem Ultra compares to the 7mm Dakota like the 7mm STW compares to the 7mm Remington.

Mike

How much real-world performance/velocity would I gain going to the 7mm stw with my 23" barrel(Sorry I thought it was 24)? Perhaps I would be better off puting a new 26" barrel on.

"How much real-world performance/velocity would I gain going to the 7mm stw with my 23" barrel(Sorry I thought it was 24)? Perhaps I would be better off puting a new 26" barrel on." NOT MUCH REAL-WORLD IMPROVEMENT!! You would most definitely profit from going to the 26" tube. I have a 7mm Rem. mag. with a 26" barrel, and mine will deliver velocities within 100 FPS of a 24" 7mm STW with 140, 160, and 175 grain bullets. I once considered rechambering it to 7mm STW, but decided about all I would gain would be increased muzzle blast and shorter barrel life.

With 81gr 7828 nos150bt 27"doug. barrel =3475=STW

[ 06-06-2002, 01:28: Message edited by: toto ]

DOC! I will echo MIKE 375 words of wisdom. The 7mmSTW is one whale of a round and ammo right at present is easier to come by than the Ultra stuff.
Brass is a lot cheaper, and in performance the STW takes a backseat to none of the 7mm at all.

I for one don't really see the logic in doing the conversion at all. If you have a 7mm Rem Mag and it shoots well, what do you have to gain by changing? Both of the rounds you mention burn more powder and give a little more velocity, but not enough to make much of a difference in the field.

I've shot an out of the box Model 700 ADL in 7mm Rem Mag for nearly 25 years. It is incredibly dependable on the deer, elk, antelope and mtn goats I've hunted here in Colorado. It's also been in the African game fields 4 times and has done it's job there as well. Plus if I run out of ammo or it gets lost in transit I can go into any gun shop in the world and pick a box off the shelf.

Sounds to me like you are trying to fix something that ain't broke. Just my $.02 worth. But hell, whatever turns you on drives me crazy.

Mac

Mac, there is no real logic here. I am just a capricious individual that is never satisfied with the status quo. I have three Sakos in 7 rem and decided to convert one of them to something a little different without changing the barrel. You're right there is not enough difference between the 7 mags, so I think I will have it rebarreled to 458 Lott or 358 STW.
Thanks for the feedback, Dr. Lou

DR LOU

I would pick the Dakota over the RUM since the capacity is more balanced to the caliber than the RUM. You will get the same velocity with both. My option would be to go for a 26 inch barrel no question. Another betless wildcat based on the 8X86S case is made by Dave Tooley, you get 7mm STW/RUM performance with less powder check it out www.tooleyrifles.com

Dave is a man who knows his work and won't blow sunshine up your butt. He will ask you which bullet weight you want to shoot and how fast to push it, then he picks the cartridge. However you have to handload to choose this type of cartridge, which I hope you do?

Cheers
JOHAN

Dr Lou, I too am one who likes to try new ideas, and cartridges. However, here I must agree with MAC. With a 24" barrel, all you will gain is a bigger fireball and a more impressive muzzle blast by going to a bigger case in the 7mm. The 7mm Remington Mag. has about all the capacity that a 24", .284" barrel can use!!