load data for mid sized 6mm with 90 grain lapuas

[Pbike]

I have a wildcat,,my design) that I have used for lighter bullets, 65 grain... Now I am going to try the 90 grain Lapua Scenars in a 30 inch 10 twist barrel. The cartridge is less case capacity than the XC Tubbs, but more case capacity than the 6mm Dasher. V V 550 between 39.5, and 41.7 worked well with 65 grain bullets in a 14 twist. What would be a good starting point for the 90 grain bullets, and should I have to switch powder???

Thanks, Paul\

 

[Pbike]

Ok I've been able to check a few of the 6mm international variations and extrapolate some loading info from there, and the powder of choice seems to be IMR or H 4350. This wildcat will end up being a stout shouldered, long BR Dasher hopefully it works for the 90 grain lapua scenars... I intend to use it for 600 yard club matches. My feelings are that the 107's and the like are just not needed for that range. I will try to post an attached picture. I call it the 6mm STS. I started this project in 1999. It worked great for 300 and 400 yards with lighter 65 grain watson bullets in a 14 twist barrel that was 22 inches long... salvaged BR barrel. Now I am trying the longer bullets in a 10 twist that is 30 inches. I just don't believe in the ultra long and heavy VLD bullets. I think a lot of the sheep that follow their leaders are not thinking the story all the way through.

 

[shcal]

pbike: could you give us the background on forming the sts? What was parent cartridge, what was the forming process, what are the reamer specs, COAL, shoulder angle, H20 capacity, etc.
Thanks, shcal.

 

[Pbike]

Yes I can...

When I started working on this project, the XC, the Dasher, BRX, and a few others were not even heard of then. I had a need to use used up PPC barrels for Varmint hunting. With that in mind reallize I was shooting BR and Varmint hunting on a regular basis. I had plenty of used PPC BR barrels that were at or near 22"in length and no longer held groups that would win the average BR match,,.225 or less at that time). But the barrels still had plenty of accuracy for Varmint hunting. The Brass we were using .220 Russian was too expensive and took too much work to risk losing while varmint hunting.

My Idea was to design a cartridge that would be a little longer than the ppc, and a little thicker in all areas, that way a PPC barrel could be re-chambered in this new cartridge without cutting the barrel tenon off and losing even more from the already short barrel, by going longer, you are into a new throat area and less burned rifling. The origninal design was the TSE,tent stake express), and was called that because it gave a use to a barrel that was nothing but a tent stake. The first design was based on the .22-250 cartridge. And was really nothing more than a blown out .22-250 with 6mm bullets. I kept the tight neck design that I liked in the PPC's,maybe a little too thin on the neck for varmint hunting). These Tent Stake barrels all had 1:14 twist which put me in the 65 to 71 grian range for bullets, and in the .750 and .790 range for jackets, however the .825's worked but not as well as the .790's.

What I found is that the .22-250 brass was the week link in this design. The primer pockets just couldn't or wouldn't hold up to the pounding they were taking. That's why I was surprised to see the first XC's with .22-250 brass. I couldn't fathom going down that road again. I also found that I would get full pressure and still have room in the case for more powder no matter how slow the powder was. The slowest of powders just couldn't build up the steam in the short barrel.

The second go around was a hit for me. First off to combat the primer pocket issue I got a hold of some of the original lot of Remington UBR brass,universal bench rest) basically .308 winchester with small primer pockets. I got a BR set back die from Skip Otto and proceeded in setting the shoulders back. The length of the body or chamber area of this cartridge is slightly larger than the 6BR. Since I had a lot of brass to work with, I kept a long neck on the cartridge, like the original 6 BR Rem.,,I had seen the article in Precision Shooting about the turbulence point of gases in the neck area). I turned the necks to .012,thicker than the .0086 on PPC) for durability. The shorter case body would fill with powder better and hopefully before the preasure was up. Remember I had been using 22" long barrels at this point. So the case was also designed to fit inside the area that was previously chambered as 6 mm PPC. I then decided to keep the Tent Stake theme and call this one the Short Tent Stake, or,STS). Cadillac's brand new rocket sled at that time was STS also. When I got to the test firing I was astonished at how economical this cartridge was for the ammount of powder used in comparison to the velocity I would get in return when using a 66 grain bullet... at that time Mitchell bullets,no longer available). The cartridge worked real well and the guy that I worked on this design with,,Dave Howie) was set to use it for long range high power stages when his work load went haywire.

About then the Dasher showed up... I see close resemblances except the dasher has such a short neck. The BRX sahowed up same story... And now the XC shows up... I think back to my experiments and the .22-250 Brass.

Now David is getting to the point where he can use it again and we ordered a few barrels designed to use the longer bullets with this cartridge... I am scheptical about the very long VLD type bullets, and chose to go a little faster and a little lighter... My barrel is 30" long 10 twist, and I will try the 90 grain,5.8 gram) Lapua scenars. David's barrel is the run of the mill highpower stuff, his is a palma medium taper I believe 8 or 7.5 twist. We both went with Broughton barrels by Tim North. I have had good results there. We also went with the canted land designed barrel... 1000 yard BR guys are talking about bullets comming apart with high speeds and fast twist and thin jackets. The Lapua bullet I will use seems to have a better chance there,less twist). We shall see... I am going to the range tomorrow.

Hope this helps...

 

[dreever]

Paul,

Be sure to try the 88LD, 90BT and 95VLD from Berger. I've shot some phenominal groups using the 90BT in a standard 6BR 10 twist.

Danny

 

[Pbike]

In looking at my above post I realize I was rushed when writing it...

We had to go to school last night and meet my sons new teachers,open house). That was just as I was finishing up writing that post...

Another thing I am trying is the .308 Lapua brass... The Remington Brass did the trick, but the Lapua is way more weight consistant and I don't mind giving up a little space inside the cartridge because of the thickness of Lapua. The other change there being that Lapua .308 brass has large primer pockets. Since the first go around TSE's had .22-250 brass with Large Primer pockets and large or fast pressure spikes, and the new design STS has thick base Lapua Brass I don't think there will be a problem... Another thing we shall see.

I also had been using a Panda action with a PPC bolt face before with the STS's, which is why the base of the STS looks rebated... It is. The Bolt Face on that gun has been opened up to a .473 base and I can use straight up 308 brass.

My Varmint hunting has also gone by the wayside and I am trying this gun in F class. I believe it will work, that's why the money was spent for a barrel length and twist to compete. It is no longer a project that was driven by cheap barrels to use while varmint hunting. A barrel that is no longer good to use for BR competition won't be on my gun for F class competition either.

Paul

 

[Pbike]

I was able to get out later this afternoon and do some testing...

The H4350 powder was too slow. I worked my way up to a full case of 39.0 grains and yeilded 3196 fps, that was a crammed full and compressed load. It was very accurate, less than .200 at 100 yards. The Standard Deviation was 7.8! However I don't like the powder pushing on the rear of the bullet that much unless I am going to shoot it immediately. Bullets will move out in the case that way.

The next try was Vhit 550. It worked pretty decent. As I worked up, I got to a load of 37.0 grains. The case was less full with a full pressure load, however very close to the bullet. I would venture to say 98 %ish. The load was 37.0 grains and it yeilded 3234 fps. Just over 3200 is what I was looking for. This was also a very accurate load the group shot was better than the groop with the H4350, closer to a .180 at 100 yards. The Standard deviation was 10.3 for this load All the testing so far is done at 100 yards, I am still checking the powder choices. This V V 550 looks good though.

The bullet I have been using is the Lapua 90 grain Scenar. The BC is advertised at .420, I will check. At 3225 fps that bullet should still have 1340 fps at 1000 yards, and 1965 at 600. I just got done uniforming some meplats. That montour rifles tool is great. By the way... A leupold 30mm 45X45 Comp is 2.1 inches over the bore on a Panda, I had to measure it. Kelbly's should have the information listed on their site for the various actions and ring combo's. The barrel is just a hair over 30 inches and 1:10 twist. I will be able to do a little more testing this weekend. Tomorrow I will be able to try it at 300 yards for stability.

Paul

 

[Forum Boss]

PBike,

Your STS Wildcat is basically exactly what we've been suggesting to Lapua that they build, albeit with a small primer pocket.

Regarding the H4350, I've also gotten impressively small ES readings with that powder in a couple different cartridges.

I think you'll find the Lapua 90s should shoot up to their published BC. The question is--for 600 yards is the extra velocity worth it over the 105s' better BC. I might say yes if the 105s didn't shoot amazingly well at all distances.

I can run the Berger 95s at 3060 with a standard case, and that gives me a little advantage in wind drift vs. the 105s at 2900. But... the 105s were more consistent dimensionally and produced fewer flyers.

Definitely keep us apprised of your project. Maybe I can set up a page on this site and you could update it with photos and test results.

 

[Cheechako]

Paul

It's interesting that you were not able to reach the velocity levels you are after with H4350. There are at least 3 versions of this cartridge that I'm aware of. My own, the 240 Orphan, appears to be identical. Using H4350 I am able to reach 3100 fps in comfort with all bullets up to and including the 115 DTAC. I use the CCI SR Match primer which lights 4350 with no problems. When I first started testing the Orphan in 1999 I used the CCI SR Magnum primer but use of the Match primer cut my groups in half. I have never tried to reach velocities above 3200 with the heavy bullets because accuracy began to drop off noticeably above 3100. My standard load is now 38 grains H4350 with the 105 or 107 bullets and 38.5 grains with the 115 DTAC. Both loads give me an even 3000 fps and I have used these loads at both 600 and 1000 yard NBRSA Benchrest. I'm now on my 3rd barrel, a Hart 30 inch Max HV.

There have been any number of shooters playing with these mid-sized 6mm cartridges for at least the last 15 years and probably longer. At first we used a 244 reamer run in short ala the HLS. Then later the 244 Ackley run in short. Finally in 2002 I had a designated reamer ground for my 240 Orphan but the end result is no different than using a 244 Ackley run in short. Now I see there's yet another guy playing with something along the same lines,see the thread below this one).

Fact is, all of these cartridges are about the same ballistically and none of them will do anyting different. A good barrel will shoot them all equally accurate and a not-so-good barrel will shoot them all equally bad. I'm a certified wildcatter and enjoy this kind of stuff but the fact is that as I get older the "factory" cartridges like the 6.5/284 and the 6XC look better and better. Load 'em and shoot 'em.

See any openings here? I don't. And this isn't all of them.

Ray

 

[Forum Boss]

Cheechako,

That's a very impressive line-up of cases, and certainly shows that there are many variations on a theme. Lapua is rumored to be working on a new BenchRest/Competition cartridge in this capacity range. If you were a betting man, which variant do you think they'll pick?

 

[Cheechako]

Good question. I would think they would go with something that required the minimum of new tooling and machinery. 30 degree shoulder. The 6XC would be a good choice but whether or not they would want to duplicate an existing cartridge is hard to say. Maybe the 6 x 44 with a shorter neck,for some reason factories don't like long necks) but I hope not because the capacity is marginal for the big bullets. So, I'd guess they would go with the maximum length case they could make with existing 6BR tooling, something along the lines of the 46mm case with a shorter neck and a 30 degree shoulder. I'd switch to it in a heartbeat. What's your guess?

Ray

 

[Pbike]

More shooting was done this weekend. I was able to get some more shooting done with IMR, and Hodgdon 4350, and more with the Vihtavouri 550. In the final round I would choose the V V 550 over the others. This powder allows you to get a little more speed with less pressure, and still be at or above 3200 with the .420 BC 90 grain bullet.

Very strange happenings here... Every once in a while I get the chance to shoot 1/2 galloon milk jugs filled with water for some very explosive results. Saturday I was shooting and found a good load of 36.9 grains of 550 at 3220 fps and a SD of about 9... The load was working well and I had my son with me. We set the scope for 300 yard sight in and sighted in on the target at 300 yards. Nice groups under an inch, and just high of what the computer said it should be. Reason for that later. Anyway since my son was with me and we wanted some fun shooting,exploding milk jugs), we set 4 jugs near the 300 yard burm. I had five rounds loaded and we were ready. My first shot, nothing happened, Hmmmm. So I shot again, this time I could see the bullet hole in the label of the jug at 300 yards. This was with the Leupold 45X45mm Competition scope. so with three shots left I let my son shoot the next three jugs. I watched through the spotting scope. Three hits and no exploding jugs? Could it be that this bullet is so aerodynamic, that it actually sliced through the water filled milk jugs without a lot of hydrolic energy effect? Who knows I have shot hundreds of milk jugs and never had this happen.

Back to the high hits at 300 yards. Long story here maybe some of you have done this. When a barrel is chambered and the chamber end is indicated with a long deltronic pin in a spider, you'll see that the chamber end of the barrel is true line and the muzzle end is not in that true line. as much as we like to think our barrels are stright they aren't. John Pierce, when he chambered this barrel made sure that the barrel's curve was pointed up. What we did was with the chamber end of the barrel indicated in with zero runnout we indicated the muzzel end the find the high spot, marked this spot, and when threading the barrel tenon, we made sure this would be the top of the barrel. the result would be less drop at 600 and 1000 yards because the barrel is pointing upward. my computer told me that a 2.7 high sight in at 100 would put me dead on at 300. In fact because of the upward pointing barrel I ended up at 1.5 high at 300 yards. Nice to know my gunsmith keeps these things in mind while we are chambering.

The cartridge is doing what it was designed to do. We have to take it out to the long range next.

Paul

 

[6Dasher]

New Lapua brass... my bet is on 6x47 Swiss Match

 

[Cheechako]

Jim

Can you, or anybody else, summarize what you know about the 6 x 47 Swiss match? There has been so much written about it and yet few have ever seen one. Who makes it? Why is it impossible to get? What are the dimensions? It appears to me that the dimensions are pretty close to what I described above. If Lapua doesn't make it why would they,Lapua) duplicate it. Any help, anybody?

Ray

 

[Pbike]

I dug through this forum, and as you have probably seen the 6 x 47 I thought I would still bring a picture over to this post. It deffinatly looks like a winner and if the brass can be obtained it is all the better than a Tubbs XC.

Paul

 

[6Dasher]

 

[Forum Boss]

I called Lapua in Finland last night and I've got the skinny on the new cartridge--though no photos yet. I've promised not to give out any more details yet, though I can say it will initially be manufactured as a 6.5mm, and it is primarily intended for 300m shooters. But that won't us Yanks from necking it down to 6mm for the 105-107s and the 115 DTAC and shooting it at 600, heh-heh.

 

[Pbike]

Not the 6.5mm Grendel? A little too small for big bullets, me thinks.

Paul