Anybody ever build a 6-300WSM?

[IdahoCTD]

I bought a reamer for one several years ago and ordered a barrel last week for it. Well a week later the barrel is on the way. I don't know how I got that lucky but I'll take it, they said 8-10 weeks when it was order. I remember reading about a 6 Mach IV years ago that was pretty impressive and this should be close to the same. It was based on a blown out 7rm case. When you get that overbore it takes a lot of extra powder to get a significant gain so I would bet I'll be close to the velocity they got. I also have a 30" barrel and I'm pretty sure the one they did the 6 Mach IV on was 25 or 26". I also ordered it long incase it wasn't all that it was cracked up to be. If not I can cut it off and set it back to another .243 AI. I have 30 or 40 pounds of WC872 that I bought when I was shooting my .30-.378 Imp quite a bit. Hopefully it is the ticket but I have Retumbo and 50BMG as well.

The link below is a similar caliber and they got 3930fps with a 95gr Nosler in a 28.5" barrel. I think Ross Seyfried got 3650 out of a 105gr VLD in the shorter barrel and 4000fps with a 85gr Barnes X. So I'm going to start with 105 Amax's, it's a 8 twist barrel, but might have to try some 95gr Accubonds. It would be really cool to see 4000fps with a 95gr AccuBond. That would definitely be a stress test for them.

http://www.singleactions.com/240Incinerator.pdf

Hopefully I'll have the barrel by the end of the week and be shaving metal this week end. I might even get to shoot it this weekend. Since the rockchucks are basically down their holes for the year I might take it with me to WY for antelope if it proves accurate enough. Using 105 Amax's at 3600fps and a 300yd zero it only has 165" of drop to 1000yds. It also has 1200ft/lbs of energy out to 700+yds.

 

[nvbroncrider]

Impressive. Isn't that too much overbore though? There is no doubt in my mind that 90gr AB will hold together. I put one into jugs @ 25 yards from muzzle at 3714.

 

[Woodycreek]

It's just a bit overbore, but I like the way this project could go!

 

[usmc 89]

Sounds brief and fun let us know if and what jacketed bullet holds up under that rpm load.

 

[onesonek]

And they say the 6-284 is hard on throats,,, .
Sounds interesting!
I too am curious to see how the rpm comes into play with various bullets. Might make a very good combination for the E-Tip, if not the other's.

 

[usmc 89]

At 4000 fps that is 360000 rpm even if it does stay together until impact your going to have a mess, I like it.

 

[CZ]

Long ago i had a builup for a 6mm Mach IV, still have the reamer and throather, I made my builup with a long throat to get those preasures down, its a 7mm mag Case necked down to 6mm, had a hart barrel on a remy700 action, well you get velocity for sure but its too much of something too good, got those 95gr in a 26" at 3700fps, but was hard on the barrel.
Someone saw it and purchased the deal, it didnt got my attention, I like much better big bore rifles.
If I would start again I would go to a 6mm-06 for sure, not the WSM or the 7mag case.
What H2o capacity do you have in the WSM?? are you going to do it long throated i think youll need it to get down those preasures, could you get out those bullets out enough?? what twist did you used t8???
Well you will have some entertainment.
good luck with your projects.

 

[IdahoCTD]

I better baby it until next spring if it shoots. With that kind of rpm's a close range rockchuck should be pretty spectacular.

I've got another barrel ordered to do a .30-.338 Lapua Imp. So chuck hunting next spring might be quite the explosive en devour.

 

[IdahoCTD]

CZ,

I necked some .270WSM down with a 243WSSM die and got 77grs of water (un-fired). I also checked some fired 6-284 brass I had and it was 67grs of water. I'm not sure what the throat is on the reamer. I bought it instead of ordering it to spec. So the neck is probably big and the throat is what it is. If it has a rather short throat but it shoots I might order a throating reamer so I can seat the bullets out. Seating the bullets deeper isn't the end of the world though with the capacity it has. It may not be the best for accuracy but being this overbore I doubt it's going to be a 1/4" gun. If it doesn't shoot I'll cut the chamber off and make a 6-284 or a .243AI.

 

[IdahoCTD]

My 6mm barrel showed up yesterday and my .30 barrel showed up today. I have to run down and get them from my buddy tomorrow so I can start making metal chips. I'll update when the metal work is done.

 

[SJB358]

It's just a bit overbore, but I like the way this project could go!

Same here! Very cool! That WSM in a 6mm should be a screamer and a very fun rifle to shoot! Good luck with it Nathan.

 

[IdahoCTD]

Well I got all the metal work done and my buddy let me use one of his HS SA stocks that is opened up for a 1.25" straight barrel. I started working on the brass with a 6.5WSM die and a 243WSSM die. Well the WSSM die wouldn't neck it down enough to fit in the chamber. So I started measuring things. Without the expander ball the WSSM die shrinks the case to .275. I can force it in the chamber but the ID of the case neck runs .242-.244. So then I look at SAMMI specs on a .243WSSM and low and behold the neck diameter is .287. .287-.243= .044 so either WSSM brass is insanely thick or the chambers are cut way oversize. That means I'm going to have to build a neck die or buy a bushing die for a .270WSM/.300WSM. I'll probably build a neck die as I've done it many times before.

For this chamber job I got more "anal" as my buddy calls it. I used my inside indicator on the chamber end and a range rod with a indicator on the muzzle end. There wasn't even a wiggle in the bore when it was spinning in the lathe (you don't see any movement how I use to do it either). I pre-drilled the bore with a 1/2" drill bit for 1" and then used a boring bar to cut it to .537. The best I could tell the reamer was .541" at the shoulder so it cut very little for the first inch (just enough to clean up the boring bar marks). I only had 5 port 1.25" muzzle brakes so I put one of those on as well .

 

[SJB358]

Nathan, that sounds pretty cool man. I do think WSM brass is thicker than most other brass I deal with.

That is very cool about the boring job. I would love to watch you do it someday. Can't wait till you get it up and worked out. It should be a fun blaster.

 

[IdahoCTD]

Well I got to shot the rifle tonight. There was barely enough light to bore sight it and send a few rounds down range at 25yds (it was hard enough to see the 25yd target). I loaded 1 each of 60grs, 61grs, 62grs, 63grs, and 64grs of H5010. Then I loaded 5 of 65grs and 5 of 66grs. I was shooting in the dark here since there isn't any data to be found. The first shot was 60grs and it seemed pretty mild. So I shot one of the 65gr loads. It was about 1/2" away from the 60gr load. Since that went well I decided to shoot a 3 shot group at 25yds with the 65gr load. I took a picture of it and will post it when I get it loaded on my computer but it was in the high .1's and looked like a clover leaf. I didn't think that was bad for being nearly dark and guessing at a load. It was dark enough that it was nearly impossible to have a consistent point of aim. I tried to chronograph them but it was too dark to get a reading as well. The fireball out the end of the barrel was pretty cool though.

 

[SJB358]

Awesome! I can imagine that was a sweet fireball! Were you shooting the AMax?

 

[IdahoCTD]

Yes it was with Amax's.

 

[SJB358]

Man, now that should make the chucks move when you hit them!

 

[IdahoCTD]

I'll jug test one or two when I get a load worked out. If it destroys 2 then I know it will work for a wimpy antelope.

 

[Greg Nolan]

Man, a close miss may be all you need. The Mach 5.5 sonic boom will stun them and the air/bullet friction will singe the hair off of them. They'll be ready for the Bar-B-Q. :wink:

 

[IdahoCTD]

That would suck for them to just be stunned yet singed at the same time. That's kind of like being cooked alive. I guess I better just hit them instead.

I'm going to try and shoot again in the morning. I think a ladder test with Retumbo is in order and I might shoot a group with 65 and 66grs of H5010.