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The Lapua D166 revisited revisited again...

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Goosic View Drop Down
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    Posted: May 30 2021 at 10:12pm
 I was cleaning up and found two full boxes of the 200grn D166 7.62x54R bullets and 25 loaded rounds. I originally tested these using a 2 groove barrel and was getting rather crappy results. The $75.00 Long Branch has a 5 groove barrel that looks as good as new, almost. I know with the 174grn GRAF BTHP bullets, it can get 1"- 1.5" MOA's. I took that huge @ss scope off and I am setting up my PH5C with a Gehmann 1.5x - 3.5x Diopter currently.  I intend to wring these rounds out to the best of my abilities. Hopefully in a couple of weeks I can get down to work. The charge weight is 35.0grns of IMR4064, GM215M primers and a C.O.L. of 3.030". From the ogive to the rifling is .0025". The last time I chronographed these, the averaged fps was 2485. I am very optimistic that the results will be positive...
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Pukka Bundook View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pukka Bundook Quote  Post ReplyReply Direct Link To This Post Posted: June 03 2021 at 5:24am
I am really looking forward to seeing your results, Goosic!
 
You can shoot, and know your stuff, and these bullets are very interesting to me, as I use them in my Finn M-N.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: June 03 2021 at 5:28am
I would think the 5 groove barrel will support the smaller diameter bullets better than the 2 groove.  Three of the lands were omitted to make the 2 groove barrel, resulting in a larger mean diameter (the width of the lands are the same for 2 groove and 5 groove).   
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Goosic View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: June 03 2021 at 7:39am
The rifling is as fresh as it was when it left the factory.  When I tested it by having my daughter fire it out to 100 yards, it showed the capability of a 1" - 1.5" MOA.  That was using PPU  174grn .311 bullets. The Lapua bullet is .3105".
My original issue was having the bullet hit the target sideways. 
 (I read an excerpt stating that the D166 was designed to destabilize in flight and strike the badguy sideways leaving a bigger than normal wound channel.) 
It made me pause for thought because i had no issues running 168grn .308 bullets through it.
 (There is more surface area making contact with the 303 rifling on a .308 bullet than that of the D166 rebated boattail .3105" bullet.) The 2 groove barrel I used was by all practical standards, wore out. I currently have 80 rounds loaded. The practical sight in test will be conducted at 50 yards so I can get myself acclimated to shooting without a scope again. Any anomalies such as keyholing during that time and the testing will stop.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: June 03 2021 at 10:31am
Originally posted by Goosic Goosic wrote:

My original issue was having the bullet hit the target sideways. 
 (I read an excerpt stating that the D166 was designed to destabilize in flight and strike the badguy sideways leaving a bigger than normal wound channel.) 

If the bullet destabilizes in flight, I doubt it’s possible to get any decent accuracy.  They may have designed it to destabilize (yaw) when hitting a human target to maximize damage, that is a design feature of the Mk VII bullet as well. 


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