The 6x47 experiment begins.

[DanDeMan]

Kevin,

I'll let ya in on a little secret...107 SMK's can be heat-treated and thereby significantly improve ram knock-down. But, accuracy will diminish a bit. I did the testing years ago. On new rams and stands, regulation I might add, the rams were carefully placed on the stands with the back of the feet at the back of the stands; and, both stands and the bottom of the ram's feet were cleaned. A 6BR, sporting a 6-twist PacNor barrel, was used for the testing, all shots, off the bench, in calm conditions. All rams were hit just behind the front leg, just above the bottom of the belly. With the standard load, only 3/10 rams went down. When the heat-treated bullets were used, on the same 10 rams after a cleaning and reset to insure a fair test, 7/10 rams went down. It was a very calm, quite morning when the testing was done. We could hear the difference in clang from the heat-treated bullets, much louder. And, instead of the SMK gray spray-paint-like splash, the heat-treated bullets made a shinny dime-sized mark. Whenever a bullet impact creates a shinny mark, that bullet is transferring its momentum efficiently to steel. Gray splashes mean just the opposite.

To heat-treat lead-antimony alloy there must be at least 2% antimony by weight. Lapua Scenars will not heat treat; well, they couldn't years ago. But, the SMK's used to have 3% antimony. I don't know if they've change the antimony content. I have the notes from the testing on a crashed hard drive, so I can't give you all the details. One thing that was determined was the minimum temperature to attain full heat-treating effects, with the idea that minimum heat would cause minimum bullet distortion. And, a special bullet holder try was made so the bullets would always be pointing straight up from insertion into the preheated oven all the way to quenching. The bullets need to age-harden for 10 days before using them. IIRC the original load was under 1/4 MOA for 5 shots at 100-yds. With the heat-treated bullets the group opened up to a bit over 1/2 MOA. To the best of my recollection, the bullets were heat-soaked for one hour in an over that was preheated to 400F. After 1 hour they were quenched in a large bucket of tap water and allowed to dry.

[DanDeMan]

Kevin,

Below are two pictures of the bullet tray used for the heat-treating precess. This tray was made for 6mm, 107'gr SMKs. The top holes should be as small as possible and still allow the bullets to slide though. The bottom holes should be the diameter of the middle of the boattail. The number of washers between the top and bottom aluminum sheets should give enough separation so that the front part of the bullet's shank is at the top hole. The bullets in the pictures are 95-gr Berger VLD's that have a short shank so they are not held as well as the SMK's would. The machine screws had wire attached that formed a handle in the middle, above the top sheet so that the loaded tray could be picked up with a dowel rod that had a slot sawed into it. That way the tray could be loaded into the over with the dowel rod, removed from the over and quenched. The tray is a bit beaten-up, but you get the drift I'm sure.

[kevinbear]

I love this stuff, heat treating Matchkings!!!!

[kevinbear]

Hey 7-08 Guru, build me one of the trays tomorrow during your lunch hour, I'll pick it up after work!

[Snake]

Er...wouldn't it be easier to just go to a bigger projectile...? You 6.5 guys are a trip My 7mm don't need no stinking heat treatment

[Jerry G]

Kev, be sure not to burn your fingers when the bullets are hot.

[Trent]

Er...wouldn't it be easier to just go to a bigger projectile...? You 6.5 guys are a trip My 7mm don't need no stinking heat treatment

6mm... not 6.5. Kevin just had shoulder surgery and is trying to make the best of a "tender" situation.

By the way, I heat treat my 7mm bullets. I do it with about 38 grains a Varget!

[DanDeMan]

Hey Kevin,

If you want my 6mm SMK heat-treating tray, let me know. It's yours for the asking.

[kevinbear]

Thank you Dan, next time I buy bullets from you put it in with them.
kev

[Jim T.]

Try a 7-08 improved..40 degree and have it throated .025 longer. The try RL15 and 19....its a superb short action long range combo

Snake:

I agree with your conclusion regarding this cartridge. Reliable data on it is hard to come by, but "Cartridges of the World-13th edition," page 205-206 has data on the 7mm SGLC which is the same configuration put together by Layne Simpson. Out of a 24 inch barrel he got the following:

140 gr. Nosler Partition, 49 gr. H414, 3010 fps

160 gr. Nosler Partition, 51 gr. RL 19, 2902 fps

175 gr. Nosler Partition, 49 gr. RL 19 2738 fps

I have loaded 175 SMK's with 50 grains of RL 19 and with a 27 inch Krieger hope to be getting in excess of 2800 fps.

[kevinbear]

Working up loads for a cartridge {especially when there is no data} is often not a linear process.
Last week I was looking at the chronograph results from the testing done so far and decided to run a primer test.
My initial thought when starting was to use the CCI 450 with BLC-2 because of the success I've had with the .223 and that combination.
Testing commenced the early part of last week, I won't bore you guys with the details but will say that this little cartridge is as component sensitive as some of the small varmint cartridges.
It has a marked preference for Federal 205 primers and Sierra bullets.
Here's my two loads I've settled on for now.
Ram Load; 115 DTAC ............ CPT load; 95 grain Sierra MK
28.0 BLC-2................................. 28.5 BLC-2
Federal 205................................. Federal 205
Average velocity 2654............ Average velocity 2838
High 2671.................................. High 2856
Low 2644................................... Low 2826
Extreme spread 26.6............ Extreme spread 30.5
Standard deviation 10.8............. Standard deviation 13.0
Average deviation 8.4............. Average deviation 10.8
Groups hovered just over 1/2 min. @100m...............

Now if I could find some bullets for less than 40.00 a box I'd be happy.

[kevinbear]

Next phase of the testing will be a reduced load for practicing at short range and possibly a hunting load, one of my longtime friends likes to shoot a big game animal with any unusual caliber I get and this one qualifies I'm thinking!
As far as I know I'm the first one {although probably somewhere someone's tried it} to have a 6x47 throated long with a fast twist with the intent to use it for highpower silhouette.
With that in mind I'm dubbing it the KLR6mm {Kevin's low recoil 6mm}, how's that for self promotion and delusions of grandeur!

[kevinbear]

I went out and shot a few preliminary 4759 loads this afternoon with 105gr. A-max's, I'm totally amazed by the efficiency of this cartridge. Without data I extrapolated a starting load from other somewhat similar cartridges to be about 30% of a full power load. I thought this might be on the low end so I brought a good solid rod and a can of spray lube in case the bullet stuck in the barrel.
On the report of the rifle I seen and heard the familiar whack of the bullet on the 60yd gong so the bullet definitely made it out of the barrel! 10 grains turned in an amazing 1446fps, much faster than my target speed of 1050, loads in one grain increments up to 17gr. didn't show any pressure with a top speed of 2169.
Next time out I'll see if I can get them slowed down a bit and check the accuracy, BTW the recoil and muzzle blast if you could call it that is on par with a 22lr, those will be fun to practice with when a load is developed.
KB

[Jim T.]

"With that in mind I'm dubbing it the KLR6mm {Kevin's low recoil 6mm}, how's that for self promotion and delusions of grandeur! "

Might I make an alternative naming suggestion: "6mm KDT." Kind of has a nice ring to it, sort of like the OKH line of wildcats.

[kevinbear]

"With that in mind I'm dubbing it the KLR6mm {Kevin's low recoil 6mm}, how's that for self promotion and delusions of grandeur! "

Might I make an alternative naming suggestion: "6mm KDT." Kind of has a nice ring to it, sort of like the OKH line of wildcats.

Ok I'll bite, what's KDT?