338 thunder project

[JD338]

Re: 338 thunder pics

GG,

Any preliminary stats you can share yet?
What velocities are you getting with the 225 gr AB/250 gr Sinclare bullets?
What kind of accuracy are you getting?
What ranges have you shot?
What kind of brake are you using and how is the recoil?

Sorry for asking so many questions, just excited and drooling. /ubbthreads/images/graemlins/tongue.gif

Regards,

JD338

 

[goodgrouper]

Re: 338 thunder pics

I remember Dr. Thunder from my cola drinking days! That was good stuff! I hope you saved that can. /ubbthreads/images/graemlins/cool.gif

 

[goodgrouper]

Re: 338 thunder pics

Thanks guys for your kind words.

Lerch,
I weighed the gun when it had a Leupold 6.5-20x50 LRT on it and bipod and it came in at 12 pounds. I have since put a 6.5-20x40 LR Leupy on it and changed rings but I haven't weighed it again. I would guess it is right at 10 pounds without the bi-pod.

The 338 Kahn would be a sledge hammer for sure!

 

[goodgrouper]

Re: 338 thunder pics

The only stats I can give you so far are from fireforming.

I used 82 grains of H4350 behind a 200 nosler bt before it ran out. Then I used 82 grains of Imr 4350 until it ran out. Then I used 82 grains of 1946 mil-surplus H4831.

I chronoed the break in bullets and the fireformers at 3050 fps with all three powders.

I never shot paper at 100 yards during breakin, but I did set up my gong at 535 yards to just have fun while doing the fireforming. It was fairly calm this weekend where I shoot and the mil-surp and Imr 4350 stacked a 10 shot group into about 3"!! H4350 opened the group to about 5-6".

NOt bad for fireforming with a load I had never used before!

Breakin took 4 patches of coppermelt up until the 6th shot. THen it went to 3 patches. At 10 shots, I started shooting 5 shots and cleaning and it dropped to 2 patches.

WHen I got to the 25 shot through her, I shot 25 more and cleaned. Still two patches and both just black then gray. Absolutely no more blue patches came out after the 10th shot!!

There was one little spot right out at the end that held copper until the 10 shot and then it went away. 7mmrhb stood there and watched the spot get smaller and smaller with every stroke of Coppermelt until it was gone several seconds later.

I haven't had the spot leave copper now in 145 shots.

Breakin took a total of 2 hours and 50 minutes. Fireforming took two days and finished it up today.

The Carbon wrap did it's job perfectly. I could feel the chamber area was body temp and the carbon in front of the end of the stock was much warmer. It dissipated the farther out I felt. It seemed that the carbon was sucking the heat right out of the chamber! Very cool!

Idaho Preacher has a thermal imaging camera that tells exactly how hot something is just by looking at it. He will look at my barrel next month. Can't wait.


The muzzle brake is a custom Titanium brake that Mike D at ABS makes. It is very effective. I was hip shooting a lot of the fireforming loads with no pain or discomfort. I would say it makes it kick like a 30-06 or less.


MOre info coming tomorrow....

 

[lerch]

Re: 338 thunder pics

I still wonder what it would take to get one of these big 338 cannons in a 800-1000yd capable rig down to 9lbs, bipod, scope and everything else included.

Hell maybe I should just get out with the wife and go jogging more often

Nice rig GG,

take it easy
steve

 

[jb1000br]

Re: 338 thunder pics

[ QUOTE ]
I still wonder what it would take to get one of these big 338 cannons in a 800-1000yd capable rig down to 9lbs, bipod, scope and everything else included.

Hell maybe I should just get out with the wife and go jogging more often

Nice rig GG,

take it easy
steve

[/ QUOTE ]

Armalite tank break...and a 1" terminator pad would be a good start.

I'd rather lug the weight around than lose a retina... /ubbthreads/images/graemlins/wink.gif

JB

 

[lerch]

Re: 338 thunder pics

I think I will stick to the holland breaks, take up less space and I just dont like the look of the armalite brakes.

I guess I will just have to deal with the wieght. Just hate to lug a 12lb gun up and down a mountain.

thanks
steve

 

[wildcat]

Re: 338 thunder pics

GG, good looking rifle !! I can't wait to hear how it shoots. What is this rifle going to be used for.

Wildcat

 

[goodgrouper]

Re: 338 thunder pics

Lerch,

Getting the rifle to the weight you want can be done easily. The main factors in the weight would be the stock and the barrel.

My stock was quoted to me on the phone as being 2.2 pounds. However, when it showed up it weighed 3.2 pounds.

Apparently, the weight of the stock is quoted without the color gelcoat. Once the green was applied, the wieght went up.

If you were to go with one of their ultra light stocks with no gel-coat and ordered a carbon fiber barrel or a regular barrel in #5 or #6 contour, you would easily have a 338 super dooper whacker in the 8 pound range. /ubbthreads/images/graemlins/wink.gif

 

[goodgrouper]

Re: 338 thunder pics

Thanks wildcat.

The rifle will be used as my primary big game rifle for all game near and far.

The old (but lethal) 300 win mag will be retired for a few seasons unless I need it for weight concerns.

 

[lerch]

Re: 338 thunder pics

I looked up some pricing on the carbon barrels, ouch!!!

I will probably settle on something in what ever barrel contour kirby decides on for stabilizing the 300gr uld and the 325gr FB bonded bullet. I wonder how much one of those A-3 stocks would weigh?????

Well that is a project for another day, right now instead of worrying about how to get a rifle light me and BJ are trying to build the heaviest one possible.

crazy world aint it.


steve

 

[goodgrouper]

Re: 338 thunder pics

Well, after five days of continous load development I have some numbers for those who are interested.

I have only worked with the 250 grain Lapua Scenars up to this point and have had them jammed into the leade as well as .030" and .040" off.

My barrel is 26.5" long.

My lot of H1000 is fairly slow, my lot of IMR 7828ssc is average, and my lot of RL25 is on the slightly quick side.

All groups at 100 yards in fairly blustery conditions all week.

All loads fired through a Oehler 35 chrono with 4' spacing between skyscreens and 10' from muzzle.
AV= average velocity
SD= standard deviation

3 shot groups

90 g RL25
av 2984
sd 15
.505"

91 gr RL25
av3039
sd 15
.788"

92 gr RL25
av 3061
sd 13
.330"

93 gr RL25
av 3109
sd 2
.818"

93.5 RL25
av 3116
sd 3
.992"


87 gr. IMR7828ssc
av 2928
sd 15
.690"

88 gr. IMR7828ssc
av 2969
sd 4
.957"


89 gr IMR7828ssc
av2982
sd 24
.970"

90 gr IMR7828ssc
av 3031
sd 5
.467"


94 gr H1000
av 2994
sd 7
.734"

94.5 gr H1000
av 3005
sd 1
.979"

95 gr H1000
av 3015
sd 5
.539"


95.5 gr H1000
av 3037
sd 5
.514"

96 gr H1000
av 3042
sd 7
1.221"



Then I repeated a few of the really good ones to double check the load:

90 grains IMR7828
av 3050
sd 7
.241"


95.5 gr H1000
av 3030
sd 5
.333"

Then I tried 95.5 grains of H1000 and a different seating depth at 1000 yards and got an 8.75"x6.5" five shot group. Then this load shot a .787" group at 100 yards.

RL 25 was fast but eratic in group size.
IMR7828ssc shot vertical strings until at top end loads.
H1000 had consistently the best sd's and group size was more consistent.

But the fact that the largest group after trying 3 different powders was barely over an inch proves that the gun shoots pretty good so far and is not terribly finicky. This I attribute to good metal working by Kirby and Mike Rock, and good bedding by 7mmrhb. I'm pretty sure the shooter had nothing to do with it! /ubbthreads/images/graemlins/wink.gif


Still tinkering and fine tuning the 1000 yard load. Will update soon.....

 

[royinidaho]

Re: 338 thunder pics

If I may ask....

What were your observations/methodology to stop at the max loads you listed?

Poor question but: how much more room remains for powder over the max loads shown?

 

[goodgrouper]

Re: 338 thunder pics

None of the loads listed above were "max" for pressure except the high load of RL25. I started on the low side of powder charges because I didn't know what the .339 caliber Scenars might do with pressures nor the 5r rifling.

As it turned out, neither one made much effect that was distinguishable.

I don't know if I will find max on any of them as far as pressures go because I really don't need top end speed with this bullet. WHat would separate max load from these loads might be another 100 feet per second and that is nothing at 1500 yards. I would rather have primer pockets that stay the same size then have an extra 100 fps.

Normally, when working up loads, I let the chrono tell me what pressures are and when the powder is not going to give me anything more. I load powder in small increments while watching what the sd's do. If the sd's go from say 15 to 10 to 7 to 3 and then start going back up to 10 or 15 or 20, then I know the sweet spot was passed up and I load the load with the sd of 3 again and re-test it.

SD is king at long range and velocity is what I look at last.

I tried a load at 1k that shot under half inch at 100 yards but had an sd of 14 and I couldn't hit the broad side of a barn at 1k. Vertical dispersion was probably 20".


By looking at the chrono as you fire an entire powder charge from low to high and reading between the lines so to speak, you can find the optimum load without having to do any "ladder test" or "OCW". When the chrono tells you that you've hit an internal ballistic sweet spot, then you re-test the exterior ballistics of the load at farther and farther distances to determine if the load is good. At least, that is how I do it. /ubbthreads/images/graemlins/wink.gif