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375 Snipe Tac...Barrel and Bullet tests

 
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Old 08-14-2008, 08:34 PM
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375 Snipe Tac...Barrel and Bullet tests

Hello to all fellow powder burners!

Recently i built myself a 375 Snipe Tac (375-408 imp) mostly just for fun shooting. As most of you know its an improved 408cheytac case necked down to .375cal and shoulder blown out to 35deg and pushed forward about .050

I ordered a McGowan barrel for this build, i talked with Jon there and he got the barrel out to me in about 3 weeks. It is a 32" light contour 12 twist, fluted, muzzle .925 I finished the barrel at 31.5" plus added a Lawton stainless muzzle brake.

The Action is a 1.550" dia x 10" long Viersco single shot chrome moly with Stainless steel bolt body. The bolt is double diamond fluted, and accented with black Cerakote, as is the entire action. Jewel trigger, extended bolt handle, sako extractor are a few of the little things. On top of the action i cut a steel 40 MOA scope base for the 5.5-22 nightforce scope.

The stock is a Lone Wolf 100% carbon/ hunting style. I completly gutted the inside of the receiver area and filled it in with fiberglass, carbon fiber and resin. I re-inletted the stock for my action and pillar bedded and layed several layers of carbon cloth to seal it all in.
The stock is camo finished with dura coat and a special light weight recoil pad i make myself. The weight of the rifle alone was 13# with the nightforce and rings it came out to 15 3/4 # Here are a few pics of the finished rifle...


375 Snipe Tac, Long range hunter


Viersco Mfg single shot magnum action with fluted bolt


Barrel break in

I finally got some time to get out and pull the trigger on this bad boy. I formed up some brass in my special forming rifle, saves on barrel life. I trimmed the cases and got them ready for the break in loads. I used 260 AB's for the first part of my tests. I ran the loads rather mild at 132gns of Retumbo, vel was averaging 3200fps. The groups from these loads
were running in the .6 range. I also tested a few of the first run of the Sierra 350grn SMK bullets, same powder charge, 132 retumbo. These were flying at 3000fps, groups were about 1". The barrel was breaking in real nice, after the first 8-10 shots cleaning was a breeze. So i decided it was time to ramp it up to the full loads and 3 shot strings.

Next day i loaded up some 260 AB's at 145gns of Retumbo. I moved the rest back to 275yds. I fired the three shots, speed was right at 3500fps, groups were terrible. Might be due to the longer throat and the bullet has too far to jump to the lands.

I wanted to test some 333grain Lehigh solids he sent me. I loaded up two test lots, 140grns and 142grns of Retumbo. I set the bullets .065 from the lands. He told me the calculated BC was .941 From a clean bore i fired three shots on target at 275yds, all three landed aprox 5" left of center bulseye. Group was just at 2" Vel was 3250 average.
The case extracted very easy so i pressed on to the 142gn load, same bullet. I only had three of each so i wanted to take a shot at my steel gong at 700yds and see what kind of results i could get. I fired up the exbal....shoot..batt dead. So i walked back to the house and input the numbers on the main computer, i figured 3250fps with 140grns , 142 should bring it up a bit more. I input the numbers for my area, 1400' elevation, 75deg, 60% hum, ect. BC .941, speed 3295 i put in, just a guess. It came up with 7.75moa at 700yards with a 275yd sight in. So i walk back to the range, a whole 200yds from my house, clicked up the nightforce, held dead center on the plate, BOOOOOOOM, WHAAAAAAAAAAAANG...i was amazed! I fired the remaining two loads and they both hit on target. That steel plate weighs close to 40# or more and it flipped it around like a toy. I got on my UTV and drove out too see what it all looked like, all three shots landed 1/2moa to the right of center with a spread of 4.5" I was happy with this for initial tests. The chrono ave for the three shots was 3297fps. I didn't think these Lehigh solids were going to stabilize to good in the 12 twist barrel, the bullets are right at 2" long, im very pleased. This weekend i will load up the new run of Sierra 350SMK bullets for testing, i might stretch the distance out to 1200yds.

Here is the steel plate target.


It looks like an upside down bell. If you look close you can see these were drops from cutting out man sized sillouettes for the tactical range. Its AR400 steel. Pretty pink!

Dave
Cowboy-Dave
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Old 08-14-2008, 10:07 PM
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Re: 375 Snipe Tac...Barrel and Bullet tests

Very cool rifle , I can only imagine what kind of damage a 260gr accubond would do to an elk at 500yds running out at 3500fps !!

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Old 08-14-2008, 10:31 PM
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Re: 375 Snipe Tac...Barrel and Bullet tests

Quote:
Originally Posted by James Jones View Post
Very cool rifle , I can only imagine what kind of damage a 260gr accubond would do to an elk at 500yds running out at 3500fps !!

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This wasnt even a full load, 3700+ has been reported from this chamber. I'm betting a faster burning powder would be needed with the light bullet. I'm going to stay with the 300grn as the lightest. 300-350 is a good range.

Dave
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Old 08-14-2008, 10:43 PM
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Re: 375 Snipe Tac...Barrel and Bullet tests

Fantastic rifle!

Please do not forget to post your 1200 yards results (data will be useful too!)
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Old 08-14-2008, 10:44 PM
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Re: 375 Snipe Tac...Barrel and Bullet tests

Very nice Dave.

Let us know how the new SMK's work out of that 12 twist.

Getting ready to barrel another up, but I went the other way on the twist. I wasn't 100% happy with the 11.5.
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Old 08-14-2008, 11:30 PM
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Re: 375 Snipe Tac...Barrel and Bullet tests

Dave,
Another work of art! great report. Look forward to reading more on the
big .375-408's.

308nate
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Old 08-15-2008, 12:13 AM
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Re: 375 Snipe Tac...Barrel and Bullet tests

Quote:
Originally Posted by Joel Russo View Post
Very nice Dave.

Let us know how the new SMK's work out of that 12 twist.

Getting ready to barrel another up, but I went the other way on the twist. I wasn't 100% happy with the 11.5.
Joel,
What way did you go? 10? I wanted a 10 twist for this project but McGowan didnt offer it in this length, mainly it was to test their barrels as well for quality and such. I have 3, 8 twist barrels coming for some radical builds in this chamber.



Top bullet is the Lehigh 333 grn
second is the LM 119 408grn
third is the Viking 403 grn
The bullets are almost 3" long



Look at the tiny Nosler 260 acubond with the giants!
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