Ballistics calculation : Can this be possible ??

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ecomeat
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Ballistics calculation : Can this be possible ??

#1 Postby ecomeat » Sat Aug 04, 2012 10:24 pm

I thought I had it all worked out......my BAT actioned 6 x 47 Lapua for 300-500 yds, my Omark action 6.5 x 47 Lapua for 500-700 yds, and a new (just ordered) switch barrel 284 Winchester for the BAT, for 700-1000 yards. Then I did a spreadsheet showing drop and 10 mph wind from 300 yds to 1000 yds, and couldnt believe the result.
Surely this Ballistic calculation cant be correct : My "Ballistic FTE" app on my Ipad shows a 6 x 47 Lapua firing a Berger 6mm, 105 Gr Hybrid (G7 of 0.278) at 3150 fps to be better in the wind (and waaaay better drop) than a 6.5 x 47 Lapua firing either Lapua 123 gr Scenars (G7 of 0.263) at 2790 fps, or the 139 gr Scenar with a G7 of 0.290 at 2690 fps ??
It shows the 105gr 6mm bullet to be 0.73" superior windage at 300 yds, out to 9.6" superior windage at 1000 yards.......and a massive "drop" advantage to the 6mm 105gr of some 78" at 1000 yards !!
Have I got a faulty App or is this for real ? If its correct, it would seem that there is no point in me shooting the "parent" case, 6.5 x 47 Lapua, coz the 6mm version will kick its butt by roughly the same degree that the 284/7mm will kick my 6mm butt !! (OK, McEwens, McGowan,Lewis, Bell, Fairbairn and co...that should be DOES kick my 6mm butt)

Ecomeat
Extreme accuracy and precision shooting at long range can be a very addictive pastime.

AlanF
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#2 Postby AlanF » Sat Aug 04, 2012 10:56 pm

Ecomeat,

If you push your 6.5x47 as hard as you're pushing the 6x47, and use Berger Hybrids in the 6.5, I think you'll find the 6.5 will be just as good or better in the wind, but with better barrel life e.g. a 6.5x47 with 140gn hybrid (BC 0.317) at 2850fps calculates a tad better in the wind at 1000yds than your 6x47 and 105 Hybrid at 3150. At those velocities, I reckon the 6.5 would get somewhere near twice the barrel life. Drop figures don't really matter in F-Class because we shoot to known distances.

And the 284 will be better than either of the above for wind deflection.

Alan

ecomeat
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#3 Postby ecomeat » Sun Aug 05, 2012 12:06 am

Alan,
I have got 1000 of the 6.5 Berger 140 gr Hybrids ready to work with, so I had better see if I can get anywhere nearbto that 2850 fps you listed. Ammoguide shows only a Max load of N550 as being just over that.
I have been using 2209 in the 6 x 47 and Reloader 15 in the 6.5 x 47, and the 6 x 47 is getting to that 3150 fairly easily with 38.5 gr of 2209. There aren't really any pressure signs till 39.2 to 39.6 gr (3200 fps) as per the photos I posted in April re bullet stabilization.
The borescope shows a couple of inches of crazing of the metal surface from the heat, but so far no actual erosion of the throat is either visible or measurable. I guess with "crazing" evident then actual erosion is probably not that far away ? It's now fired approx 850 shots.
This week I intend to try the 105 gr hybrid with a 0.020 jump, as opposed to their current seating of just touching the lands. Would you hazard a guess as to what the velocity loss might be, after I seat them 20 thou shorter ??
I am looking for a cause of the odd vertical flyer that I get, and so far I have only shot the 105 gr 6mm hybrids just touching the lands. The original 105 VLDs were jammed 0.001, and without altering anything on the seater, the new 105 hybrids just happened to be 0.001 shorter and just touching. It seemed to be working, so I have just left it at that, but need to try and and explain these occasional loose shots. Everyone i talk to here in SE Qld seems to talk about the Hybrids being "better" with a jump, so I figured that I had better try it.
Keen to hear your guestimate on velocity loss if I back off 20 thou......will it be piddling like 10 or 20 fps , or maybe 50 or more fps ?
Rgds
Tony Berry - "Ecomeat"
Extreme accuracy and precision shooting at long range can be a very addictive pastime.

RDavies
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#4 Postby RDavies » Sun Aug 05, 2012 8:24 am

Going from jammed .010" to jumping the hybrids .020" gave me a 50 fps drop. i had to bump the load up .4gn to keep the same speed.
As for the occaisional verticle flier, my nickname for it is 6x47itis :D
While some of the most accurate rifles I have seen are 6x47s, a lot of people using them still find they cant get them as accurate as shorter 6mms. In 3 different barrels, I still got occaisional verticle fliers, maybe only 1 in 10 or one in 20. I havent yet heard of anyone complaining about a 6.5x47, which seems to be gaining popularity as a great alrounder.
BTW, if you want max velocity from your 6x47, I have dies, cases and reamer for a 6x47 Shehane going cheap, or swap for 6.5 gear. :wink:

bruce moulds
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#5 Postby bruce moulds » Sun Aug 05, 2012 9:01 am

ecomeat,
go back to 1000 yd & 9.6" doesn;t look much.
trajectory is of no importance to us because we can wind the sight.
rod nailed it by alluding to accuracy. nothing hurts more than dropping a point at 12 or 6ó clock, but you can learn wind deflection.
you can have the best of both worlds by rinning the 6.5 reamer in an extra 4mm and having a 6.5 super lr chamber.
failing that try re 17 in the 6.5x47 chamber and get 2900 with a 140 berger.
another option is to shoot the 284 at all distances.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM

ecomeat
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#6 Postby ecomeat » Sun Aug 05, 2012 12:35 pm

Rod, thanks for that info re 3 x barrels and all with flyers and no similar reports heard so far re 6.5 x 47. Very good info for me to hear.
I have only been shooting F Class for a bit over a year, but fully understand the irrelevance of "drop" in F Class with known distances, but in a strictly trajectory sense, (think hunting !) I was still shocked to realize the fairly significant superiority of the 6mm 105 gr over the 6.5mm 140 grainer.
"I only missed that dog by 6 feet" wouldn't do the ego much good !
I actually built the BAT/Krieger/McMillan in 6 x 47 Lap as a specialist wild dog rifle ......... tried F Class just to learn a bit about the new rifle and improve my shooting..... got hooked badly and now can't wait for every Sunday to come around so I can get my weekly "hit" ! Needless to say it doesn't spend any time bouncing around in the front of a ute like I thought it would when I first decided to build it.
Bruce, I know I have to work up carefully, but how much Reloader 17 gets a 6.5 x 47 to 2900 fps with 140 gr Bergers ??
And who is shooting this 6.5 Super LR here in Australia ? Hadn't ever heard of it, but just did a quick google ...........bloody hell....another calibre that I want to try !
Re "Shehane" : Phil Jones from Redback Precision actually tried to talk me into doing that initially, but I was already set on the idea of a straight 6 x 47 Lap so went with the original.
Rod, what velocities did you get to with the Shehane ? And barrel life was ....?
I presume you still had some flyers, even with the Shehane shoulder ?

I am a bit of a (self confessed) sook with recoil, and don't think I am ready to shoot a 284 at all ranges. I remember a certain Grafton based F Classer bringing his 284 to Beaudesert for the first time after he had fired 100 or so rounds thru it the day before. To say he was "bruised and a bit sensitive" would be an understatement ! Got to admit though that Julie McEwen makes the transition to 284 look simple and effective. Her husband was the only one who beat her home at Ipswich OPM last weekend, so she rolled some very good shooters using her own new 284. Cam actually commented on how she improved once they adjusted the scope back a bit, and with a better shoulder fit she has no recoil issues whatsoever and she clearly continues to shoot very well indeed.
I might just need to add some cement to my diet to harden up a bit :oops:
Tony Berry
Extreme accuracy and precision shooting at long range can be a very addictive pastime.

bruce moulds
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#7 Postby bruce moulds » Sun Aug 05, 2012 1:20 pm

tony,
i used to shoot a 6.5/284, and went to the 284 purely for improved barrel life.
this is just personal, but i find the 6.5 version easier to shoot. in fact i could shoot it free recoil, whereas the 7 mm needs a little shoulder contact, another potential for variability.
personally, the 284 is my max for precision shooting. the 7mm saum would be too much violence, and while pestbird can do great damage with a 30 cal, it would wear me down.
like clint eastwood said "a man's got to know his limitations." there is no shame in this.
another thing is the 6mm super lr. with appropriate twist, it will poke out 115 vld bullets pretty well.
a friend has dato on re 17 in the 6.5 x 47. will try to get from him, or he might chime in.
2209 data is usually pretty close for this powder, but always start lower.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

DaveMc
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#8 Postby DaveMc » Sun Aug 05, 2012 4:04 pm

I tried the 6.5*47 with Rel 17 for a while. 40.4 to 40.8 grains was a nice load. I maxed out at 41.4.
Seemed to me to be a very finicky powder but got some great groups and occasional good score which kept me pushing. Just when it looked great I would often be plagued with vertical. Messed up a queens trying/hoping! I have now given up on REL 17 for F class.

Cheers,
Last edited by DaveMc on Sun Aug 05, 2012 6:02 pm, edited 1 time in total.

Matt P
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#9 Postby Matt P » Sun Aug 05, 2012 5:18 pm

Felt recoil has a lot to do with stock design and rest set up, and weight. A club mate uses a 284 and with his set up, shooting it free recoil isn't a problem.
I'm using 37.5 of 2208 with 130 Bergers in my 6.5 x 47 with good results, I haven't shot it over a chrony but going on come ups it's doing about 2900 fps.

Matt P

Woody_rod
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#10 Postby Woody_rod » Tue Aug 07, 2012 12:21 pm

My 260 INCH chambering worked pretty well while I was using it. I think the claim about the 6mm being better than the 6.5 just isn't true, you are simply not pushing it hard enough.

My MV was 3200fps for the 123 6.5mm Scenar and 3060fps for the 139 Scenar. This will shoot inside any std 284, but not as good as a 7RSAUM.

Recoil was almost non-existent, so free recoil was the go. My last comp at home yielded a 240.20 from 240.40 on day one so it was running pretty sweet!!!

Barrel life is really bad though :(

Brad Y
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#11 Postby Brad Y » Tue Aug 07, 2012 12:46 pm

Rod why do you think the barrel life was so bad?

Pushing 6.5x284 velocities must be same pressure?
That very short neck and steep shoulders?

Just ordered a reamer for a 260 wildcat myself and hoping not to chew through barrels as quick as a 6.5x284 if I can help it.

ecomeat
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#12 Postby ecomeat » Tue Aug 07, 2012 1:44 pm

Woody_rod wrote:My 260 INCH chambering worked pretty well while I was using it. I think the claim about the 6mm being better than the 6.5 just isn't true, you are simply not pushing it hard enough..............

Barrel life is really bad though :(



How bad was "bad" ? 800 ??
My "On paper" ballistic calculations were based on the 139 gr Lapua factory load as a starting point for the 6.5 x 47, which is 2690 fps.
I will try to get to 2850-2900 fps this week with the 140 gr Berger Hybrids. I have plenty of 2209, and Reloader 15 on hand, and i went up to Custers in Brisbane yesterday and took advantage of their run out pricing to get. Kg each of VV140, VV150, and VV550 for $83-00/kg. I will see if I can work up to a VV550 load that is listed on Ammoguide ......41.5 gr maximum load for 2905 fps.
Called at QRA on the way home to put my Queens entries in, and hopefully get some RE17, as per Bruce and Dave's suggestions but the Q Store was shut. Bugger !! Then couldn't drive past BRT without my ute driving itself there....... Left there with some 168 gr Bergers in 7mm ready for a switch barrel 284 that Redback Precision are going to do for me straight after the Qld Queens. Still no 180 gr Hybrids on the shelf.
Back to reality and the 6.5 now, and hopefully get to 2850 fps plus using VV550 with the 140 grainers. Keen to hear any other suggestions re powder choice/load for 2850 plus using 140 gr Berger Hybrids in 6.5 x 47'
Many thanks.
Tony Berry
Extreme accuracy and precision shooting at long range can be a very addictive pastime.

Woody_rod
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#13 Postby Woody_rod » Tue Aug 07, 2012 2:54 pm

Brad Y wrote:Rod why do you think the barrel life was so bad?

Pushing 6.5x284 velocities must be same pressure?
That very short neck and steep shoulders?

Just ordered a reamer for a 260 wildcat myself and hoping not to chew through barrels as quick as a 6.5x284 if I can help it.


Its the same as a 284 pretty much = bad. There are no steep shoulders, still the same 20deg of the original.

It uses a LOT of powder, which will contribute to the barrel wear...it is still going now with over 1000 rounds, so end life is not yet known.

Cameron Mc
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#14 Postby Cameron Mc » Tue Aug 07, 2012 3:22 pm

Woody_rod wrote:
Brad Y wrote:Its the same as a 284 pretty much = bad. There are no steep shoulders, still the same 20deg of the original.

It uses a LOT of powder, which will contribute to the barrel wear...it is still going now with over 1000 rounds, so end life is not yet known.


Rod , I have nearly 3000rds on one of my 284 barrels, it still shoots 60's. I realise it could die at any time now, but a 284 should go well over 1000rds.

Regards

Brad Y
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#15 Postby Brad Y » Tue Aug 07, 2012 5:22 pm

I've been told by quite a few 260 shooters that hitting the 3000fps and above bracket is hard on barrels. I was planning to shoot around the 2900-2930 bracket if it is accurate. On Bergers website ballistic program it's losing 0.32 MOA in a 10mph drift to those 284's at 2800. Sure it may not work that way in real life but its a heap better than the 308 and 155's at 1000.

I honestly don't think the 6.5x47L is going to see any benefit with 140's. It's not that you can't try to drive them faster but something is going to limit it- brass life, double base powders causing pressure spikes or primers piercing from pressure. It's perfect for the 130's though.

Cameron I think Rod was referring to the 6.5x284 I originally suggested.


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