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Post by sako75varminter on May 24, 2015 20:28:42 GMT
43gr N160, SMK123gr runs at 2880fps in 27" barrel. Seated at 10" off fits nicely in m595 mag. Easy on my brass with legs for 1200yds+ a bit :-). Looks like mr donkey has aquired a taste for my 95gr Vmax...... Methinks your right Rup!...Mr Donkey is turning into a speed freak!..
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Post by swampdonkey on May 24, 2015 20:49:24 GMT
43gr N160, SMK123gr runs at 2880fps in 27" barrel. Seated at 10" off fits nicely in m595 mag. Easy on my brass with legs for 1200yds+ a bit :-). Looks like mr donkey has aquired a taste for my 95gr Vmax...... Methinks your right Rup!...Mr Donkey is turning into a speed freak!.. Quicker it gets there, the less time for wind and gravity to effect it
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Post by sako75varminter on May 24, 2015 20:57:21 GMT
Methinks your right Rup!...Mr Donkey is turning into a speed freak!.. Quicker it gets there, the less time for wind and gravity to effect it That only applies out to 500 mucker!!...then BC kicks in big time!..
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Post by tisme on May 25, 2015 7:20:56 GMT
BC kicks in after 500 because the of the wind surely.
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Post by arbshot on May 25, 2015 8:35:01 GMT
Current .260 load is 40.5g RS60, 139g Lapua Scenar, CCI standard primer in FL sized Lapua brass, 2.630 COAL, border 1 in 8.5 AW barrel. Spot the error............should read 2.830
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Post by arbshot on May 25, 2015 8:44:32 GMT
Quicker it gets there, the less time for wind and gravity to effect it That only applies out to 500 mucker!!...then BC kicks in big time!.. Drive the a slightly smaller bullet with slightly lower BC a lot faster and it will buck the wind better, the downside is loss of down range energy. I can achieve the same wind bucking ability with both a 69g and 77g SMK in .223 by pushing the 69 at 2850fps as opposed to 2600fps for the 77g. Rups doing a similar thing with the 123g, I am going to try it in my 6.5-284
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Post by swampdonkey on May 25, 2015 14:27:17 GMT
Can't be too bad, just shot a 2.3" group at 500 yards with them
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Post by davet on May 26, 2015 17:16:56 GMT
Just to add to the mix I have used 42.0g of N550 under a 123g SMK or Scenar to get up around 2800 - 2900 from a 26" and 29" barrel respectively.
Reliably accurate out to 1000 yds but going to heavier for longer distance when I get a chance.
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Post by oaken on May 26, 2015 22:55:33 GMT
I'm not disputing that the heavier (higher BC) bullet is more efficient at carrying its energy down range, It's just that with my .260 I can get the lighter 123 out of the barrel considerably faster before pressure becomes an issue. 123 - 2880fps 139 - 2710fps This extra velocity outweighs the BC advantage of the heavies and gives a flatter trajectory. Also, to some extent, the extra speed will also result in reduced wind drift up to the point where the efficiency of the heavier bullet takes over in relation to its velocity. This is of course in my setup and may be different for others. To put this in perspective, I have reduced the drop by nearly 5moa (60inches) and windage by .8moa at 1200yds :-)
Rup
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Post by c18rch on May 27, 2015 15:25:53 GMT
Highest BC every time, however BC's being equal, the lighter the better for more velocity.
Very occasionally you find a bullet that is lighter with a high enough BC so that the extra velocity out weights the loss in BC.
The 7mm 162 A-Max is a good example. The heavy 180gr bullets have higher BCs (0.7 ish) but velocity would be down at 2200fps with the 7-08. The 162 had a BC of 0.625 but I can push it to 2700 fps. That'll keep it supersonic to just under 1400yds.
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Post by sako75varminter on May 27, 2015 22:36:10 GMT
Ok fellas
Lets try to keep each calibre reloading section clean,and not confuse people!....Someone start a new thread in technical ...B.C VS VELOCITY!
Glenn
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Post by rips on May 28, 2015 20:30:43 GMT
I looked at that and thought 'Christ, that 139 grainer must be nearly sat on the primer'! Lol
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Post by davet on Jun 11, 2015 11:09:18 GMT
My 260 loves lapua brass br2 primer 140 hybrid Bergers 42.2 gr h4350 COAL 2.877 26" barrel shoots at 2818 fps as above its a hot load so build up. Just got hold of some 140 Hybrid Bergers so beginning load dev for Summer RRC....looking to use these for the extended range as the 123g SMKs that I have been using seem to run out of 'puff' around 1100 yards according to Applied Ballistics.
My 'on lands' head-to-tip COL is 2.956 so WAY too long for the standard AI mag...I can just about get a Head-to-tip COL of 2.885 into the mag and will reduce this to 2.88 to ensure feeding.
Leaves a jump of about 75 thou !!! .....I normally hope to use .020 or preferably way less......hope the Bergers will group worth a light at that (enormous!) degree of jump!!!
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Post by oaken on Jun 11, 2015 11:46:36 GMT
According to Litz, the vlds want to be either on or close to the lands ... or ... way off! Don't know about the
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Post by oaken on Jun 11, 2015 11:49:24 GMT
Oops ...... hybrids but I found the 80vlds worked well in my .223 with 120thou jump. I tried a few at mag length. What are you paying for the hybrids and do you have a reliable supply?
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