Paddy, here's some discussion by the experts from previous posts. I have both a 10 twist 375 and 12 twist 375 and both are very accurate. One is a Krieger barrel and the other a McGowan:
Re: 375 Snipe Tac...Barrel and Bullet tests
I just came back from testing the new style 350gn SMK.
Seated .015 off the lands.
Retumbo powder
Fed 215M
140grns ave fps 3149 ES 8
142grns ave fps 3211 ES 9
I fired the 140grn loads at my 700 yard plate, 8.75moa added...all three shots landed on steel, spread was about 4" The cases extracted easy, no marks on case head at all.
The 142grn load was .5 moa less, all shots landed on steel as well. The cases extracted easy, just a bit of shiney mark on case head. Temp was in the low 80's I used .770 for the BC in Exbal, came out perfect. This is one big Thumper!
700 yard steel target
Cowboy-Dave
08-16-2008, 02:46 PM
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Re: 375 Snipe Tac...Barrel and Bullet tests
Dave,
Sounds like your new 375 is working well for you.
Why did you move the shoulder forward compared to your 338 Sniper Tac?
Your loads look right where they should be comparing them to the tests I have run on my 375. I am getting 3250 with 143 gr of Retumbo and 3300 fps with 146 gr.
Like you are seeing, they are very friendly in warmer temps compared to the 338 siblings. Just wish there were more bullets available but the 350 gr is good enough to get the rifles shooting well.
I am not a fan of the solids, certainly they are ballistically impressive but to bore sensitive and not usible for big game hunting. Not even legal to use here in Montana on big game and I beleive there are other western states that require an expanding bullet for big game. With enough interest maybe we will get some more bullet options with a lead core bullet design.
Ya need to double your range and see how your lightweight rig runs for you.
That is a unique gong design. Good use of scrap metal however!!! May be trickier to hit at longer ranges though.
Anyway, good looking rifle.
Just curious, why do you not make your own muzzle brake? If you want something that will really tame down your rifle, let me know and the PK brake will make a believer out of you!!! LOL
Take care,
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Kirby Allen(50)
08-16-2008, 05:26 PM
Black Diamond 408
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Re: 375 Snipe Tac...Barrel and Bullet tests
Kirby,
I normally make my own brakes, but like you know...when your busy its hard to work on your own guns. Yes your PK brake works real well, i did one similar on a 408 several years ago. When i get my CNC Mill up and running i can do more of that type of machining. The Lawton brake will be installed later on a customers rifle, and ill put one of mine on this boomer.
My original 338 snipe tac has the same case profile, when i put some of the taper back into the case i shortened it just a bit, all during the R&D phase, It worked well so i just stayed with it. Either one has plenty of case capacity and if i use the cheytac magazines they will still feed from them, any longer and they wont fit at the shoulder retaining area.
I am surprised the solids shot so good in a 12 twist, they are mostly for shooting vermin or steel at long distances.
I was out looking at my range today, max distance is 700yds, there is a county road right behind my shooting table, if i go across the road i have another 800yds or more, but i have to do some figureing, there is a set of electric lines that crosses my line of sight. Im sure at 1500yds i would be way over them but need to make sure first.
I have lots of 1/2" steel plate, 3'x4' square, but the darn bullets dont want to stop when they hit it. yea i wish the AR400 drops i have were bigger, lots of small pieces.
I think i will stay with the 142grn load, it seems to work good and no real pressure signs.
Have you experimented with different twists?
Dave
Black Diamond 408
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Re: 375 Snipe Tac...Barrel and Bullet tests
I have tested the 1-10 and 1-12 from Lilja and Krieger. With the 350 gr SMK I have never really seen any NEED for the 1-10 but use it more then anything simply for the reason I am hoping soon we will have some very long 370-380 gr aluminum tipped lead core bullets to play with!!!
At the velocities we are using the newly designed 350 gr SMK has no issued in either twist from what I can see so far as far as overspinning them.
I did take some of my last TTI cases and form them up. As you know they will take alot more pressure then the Jamison hulls. Got the 350 gr SMK up to 3445 fps with very practical base life, 5 firings per case is where I stopped testing.
I had several of the early SMK design come apart at these speeds in the 1-10. I have also had a couple instances where the new design has mysterious failure to impact issues at 1500 yards. I can only come to the conclusion that this was due to a weakening bond between the core and jacket. There was no visable blue-grey puff by my spotters and bystandards but they did not make it to the target or land close enough to make it obvious where they hit??????
At 3300-3350 fps I have never had any problems at all in the 1-10. Like you, I keep things in this level to keep pressures lower, still plenty of punch!!!
I had a couple custom contoured barrels made for me by Dan Lilja, They are actually lighter then a #8 contour barrel with a 1.250" shank diameter. They will finish up at 32" in 338 and 30" in 375. I suspect they will get me down to under 16 lbs with a conventional A-5 stock and BAT Model M receiver. Have to just find time to get away from customers projects and spend some time on a couple of my personal ones.
That will likely not happen until well after big game season!!!
Take care, keep us posted. For extreme range steel slappin, those solids sure look like the trick!!!!
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Kirby Allen(50)
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