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Range Report 6.5 mm, 123 gr. vs. 139

wchartz

Full Member
Full Member
Minuteman
Nov 8, 2011
333
9
72
McKenzie, TN
I have determined that in my .260 the 123 SMK has a slightly flatter trajectory than the 139 Lapua or 142 SMK for the velocities that I shoot. The wind drift is the same for both bullets in a 5 m.p.h. wind at 1000 yds. The precison is approximately the same for the 123 and the 139. For tactical competition at ranges up 1200 yards is there any downside to using the 123 gr. bullet?
 
Re: 6.5 mm, 123 gr. vs. 139

If the wind picks up the heavies will drift much less and still have to punch when they get there. I will take my 140's and 142's over the 123's anyday at that distance.
 
Re: 6.5 mm, 123 gr. vs. 139

According to my dope with the 47l. 1000 yards at 6500da

123'scenar will take 6.8 mils elevation and 2.2 for 10mph wind
139 will take 7.2 mils and 2.1 for wind, looks pretty neglible to me, I do prefer the 123 scenars.

Now look at 600 yards
123 takes 3.0 mils and 1.1 for 10 mph wind
139 takes 3.3 mils and 1.1 for the same wind.

At 1000, can you sort out .1mil in the reticle? Nice caveat is that the 123's are flatter at most engagement distances. The 123's do allow you more flex room on distance, since they are flatter shooting. This is with confirmed dope on my gun with both bullets, not some made up numbers.
 
Re: 6.5 mm, 123 gr. vs. 139

Physics dictates that out past 700 or so the heavier bullet will ALWAYS perform better. So it all depends on how far and how consistently you will shoot past 700.

The wind drift is not the same for both bullets. Don't go by what those computers say. Real world experience is the 123 cannot stay with the 140's (or 139s) as long as we're in the average velocity zones.
 
Re: 6.5 mm, 123 gr. vs. 139

If 80% of your shooting is beyond 700yds, go with the 140gr class(139-142).
If 80% of your shooting is under 700yds, the 123's will be great.

If you're the indecisive type, go with 130's......
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: buffybuster</div><div class="ubbcode-body">If 80% of your shooting is beyond 700yds, go with the 140gr class(139-142).
If 80% of your shooting is under 700yds, the 123's will be great.

If you're the indecisive type, go with 130's...... </div></div>

could't agree more.
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: buffybuster</div><div class="ubbcode-body">If 80% of your shooting is beyond 700yds, go with the 140gr class(139-142).
If 80% of your shooting is under 700yds, the 123's will be great.

If you're the indecisive type, go with 130's...... </div></div> I agree as well. I shoot 142 SMK's only in my 260. In my 47L I shoot 123's only. I think between those 2 cases or so is where it goes from one to another. I was already shooting 142 SMK's in my 2 6.5x284's and had tried 123's in it and my 260. It shot it well and you couldn't tell a difference but at the 800 yd line at our range the 123's didn't do as well. But in my 47L the 142's never did what the 123's would do. I think that if shooting shorter ranges the 123 is the ticket. But if your gonna stretch it out there then the 142 should do a better job. FYI I'm shooting in both benchrest rifles as well as field rifles. Good luck. Neither bullet is a "bad choice" by any means. I'm just thinking on wringing everything it has out of it.
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mike</div><div class="ubbcode-body">Physics dictates that out past 700 or so the heavier bullet will ALWAYS perform better. So it all depends on how far and how consistently you will shoot past 700.

The wind drift is not the same for both bullets. Don't go by what those computers say. Real world experience is the 123 cannot stay with the 140's (or 139s) as long as we're in the average velocity zones. </div></div>
You gotta be kiddin.
 
Re: 6.5 mm, 123 gr. vs. 139

How would the 123's do in a 1 in 8" twist?
 
Re: 6.5 mm, 123 gr. vs. 139

Sierra tech support actually recommends a 1-8 twist for their 123gr SMK's. Said it is the length of the bullet that makes a difference, and the 123's are real close to being as long as the 142's.
 
Re: 6.5 mm, 123 gr. vs. 139

Test the berger 130s and the jlk 130s. If you can get them to 2950+ they will work just fine.

Our testing has shown that the jlk is close to .600 g1

R
 
Re: 6.5 mm, 123 gr. vs. 139

I love the JLK's and I show an actual bc around .610. The 123 scenar has an actual bc around .545, which is the same for the 130 bergers but that you can push to over 3000fps instead of low 2920's(atleast in my accuracy node). The numbers I provided above are actual dope of the weekend prior, not some made up numbers. The real catch is energy and the lighter bullets will always loose that battle with the heavy pills. JFI, the 123's (both SMK and Scenars) work will in the 8.5 twist of my guns. Good luck.
 
Re: 6.5 mm, 123 gr. vs. 139

Pretty sure the true BC for the 123's is somewhere around .517-.519

I could be wrong but that's what I found when investigating the same. You might be able to tip them and get to .545 but that's a big unknown.
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Pusher591</div><div class="ubbcode-body">Pretty sure the true BC for the 123's is somewhere around .517-.519

I could be wrong but that's what I found when investigating the same. You might be able to tip them and get to .545 but that's a big unknown. </div></div>

SMK's are in the .515 range but the scenars are .547, just double checked it in Applied also and that is what Bryan has for them. To me, the 123 scenar has the bc of the 130's but being able to push them almost 100fps faster within my accuracy nodes.
 
Re: 6.5 mm, 123 gr. vs. 139

Below is a post by Bryan Litz from 12/17/2011:

Regarding Lapua, good on them for stepping up and providing radar based G7 BC's for their bullets. For quite a while they had the radar data (Mach-CD data) available for download which was a tremendous resource. Problem was they were still listing G1 BC's that represented vastly different performance than what was reflected in the radar data. I think it's been about a year ago now that they re-assessed all their BC's to be in better alignment with their radar data, and also provided the BC's referenced to the G7 standard. These radar based G7 BC's are, for the most part, very similar to what I've assessed.

The performance I measured for the 6.5mm 123 Scenar is:
G1 BC: .519
G7 BC: .265
(both averaged from 3000 to 1500 fps)

Lapua has this bullet at G1: .527 and G7: .263. Odd that one's + and one's -, but we're talking about 1.5% difference in the G1 and 0.8% difference for the G7. So Lapua and I are practically representing the same performance. I suspect the larger difference in the G1 comes from velocity dependence (we probably averaged over different speed bands). The G7 BC of .263/.265 is the number I would use."
End Quote

It may have changed again and if it has, please let me know, that would be a great BC for that bullet.
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Azprc</div><div class="ubbcode-body">
SMK's are in the .515 range but the scenars are .547, just double checked it in Applied also and that is what Bryan has for them. To me, the 123 scenar has the bc of the 130's but being able to push them almost 100fps faster within my accuracy nodes. </div></div>

What is the source on this 123gr Scenars BC? Is this BC for a pointed version of the unpointed bullet? My copy of Applied has got then at 0.52-ish and the Lapau website has got them at around 0.52-ish as well.
Thanks.
 
Re: 6.5 mm, 123 gr. vs. 139

Any downside? Besides what little difference that has already been posted, your barrel may appreciate the heavier bullets at a more moderate velocity.

I shoot heavier arrows from my bow for the same reason.
 
Re: 6.5 mm, 123 gr. vs. 139

Thanks for the input guys. I will make one comment on some of the comments. The best ballistic programs out there can be trusted. If you think real world experience trumps those programs then your inputs are suspect. I highly recommend Byran Litz's latest book "Accuracy and Precision For Long Range Shooting". It addresses this very issue very well. I will try the 123 SMKs for a while to compare to the 139 Lapua's.
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wchartz</div><div class="ubbcode-body">Thanks for the input guys. I will make one comment on some of the comments. The best ballistic programs out there can be trusted. If you think real world experience trumps those programs then your inputs are suspect. I highly recommend Byran Litz's latest book "Accuracy and Precision For Long Range Shooting". It addresses this very issue very well. I will try the 123 SMKs for a while to compare to the 139 Lapua's.</div></div>

Not quite. The output is only as good as the input and some "inputs" cannot be known. Have you shot at 1000 yards? Have you measured the wind swirling through trees at every 10 yards or so simultaneously? Of course not. So you must use EXPERIENCE to help. Real shooting does not occur on a square range with wind flags and perfect conditions. There are more than one who had a great deal of success hitting targets at long range and didn't have a ballistic calculator. Use your tools, use ALL your tools.

Good Luck.
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mike</div><div class="ubbcode-body">
Not quite. The output is only as good as the input and some "inputs" cannot be known. Have you shot at 1000 yards? Have you measured the wind swirling through trees at every 10 yards or so simultaneously? Of course not. So you must use EXPERIENCE to help. Real shooting does not occur on a square range with wind flags and perfect conditions. There are more than one who had a great deal of success hitting targets at long range and didn't have a ballistic calculator. Use your tools, use ALL your tools.

Good Luck. </div></div>

Well said!

Now....everybody repeat after me, "I...am a tool"
 
Re: 6.5 mm, 123 gr. vs. 139

I did this very thing. Compared the 123 to the 139 scenars. Mike will tell you that I only shoot the 139s now. I did this testing in 2008 with a new Surgeon scalpel and used the range at Pascagoula. The real world data and the computer guesses were close. But the 139 beat the 123 in the wind at 600 and 1000. At 1000 by .3mil. I have since cut my barrel down, started shooting suppressed and only get out to 500 yards lately. But I use the 139 scenar to kill all sorts of game.
However I now have same VLD 117gr. that I am going to load way past max and see what they do.
grin.gif
 
Re: 6.5 mm, 123 gr. vs. 139

I agree with Mike. I have 6.5s and 6MMs. On paper the 6MMS should shoot as good or better than the 6.5s but I have always found the heavier bullets tend to drift less no matter what the computer says.
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JamesBailey</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Azprc</div><div class="ubbcode-body">
SMK's are in the .515 range but the scenars are .547, just double checked it in Applied also and that is what Bryan has for them. To me, the 123 scenar has the bc of the 130's but being able to push them almost 100fps faster within my accuracy nodes. </div></div>

What is the source on this 123gr Scenars BC? Is this BC for a pointed version of the unpointed bullet? My copy of Applied has got then at 0.52-ish and the Lapau website has got them at around 0.52-ish as well.
Thanks.
</div></div>

Did not check on his new book but just run it through his Applied Ballistic and he shows G1 of .547. I have run them to 1450 with good results in moderate wind. Confiming AB with FFS, shows within .1 mil to 1250 with a .547 on AB. I do prefer the 130jlk in the wind and for obvious reasons.
 
Re: 6.5 mm, 123 gr. vs. 139

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mike</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wchartz</div><div class="ubbcode-body">Thanks for the input guys. I will make one comment on some of the comments. The best ballistic programs out there can be trusted. If you think real world experience trumps those programs then your inputs are suspect. I highly recommend Byran Litz's latest book "Accuracy and Precision For Long Range Shooting". It addresses this very issue very well. I will try the 123 SMKs for a while to compare to the 139 Lapua's.</div></div>

Not quite. The output is only as good as the input and some "inputs" cannot be known. Have you shot at 1000 yards? Have you measured the wind swirling through trees at every 10 yards or so simultaneously? Of course not. So you must use EXPERIENCE to help. Real shooting does not occur on a square range with wind flags and perfect conditions. There are more than one who had a great deal of success hitting targets at long range and didn't have a ballistic calculator. Use your tools, use ALL your tools.

Good Luck. </div></div>
I don't think we are disagreeing here. I have shot up to 1100 yds. On the ranges that I have shot on up to this point the terrian is very irregular with heavy woods on part of one or both sides. If there is wind it usually is so irregular that at times I have seen wind flags pointing in different directions at the same time. I still maintain that if the inputs are correct the solution will be correct. The trouble is you cannot input all of the data that a ballistics program would need to get the correct firing solution so we use Kentucky windage to come up with the wind drift many times. I agree that a shooter experienced in reading wind will be better off making a shot based on his experience and observations rather that trying to reduce those observations to a single input and enter that input into a program to find the solution. We can get so involved in the solution that we miss the point. TAKE THE SHOT! So back to my point. The good programs are correct but imputing correct wind value is more art than science and good shooters can many times do better by observing and firing. It is enlighting to study ballistic read outs to see how much drift really occurs with a steady wind over a long distance. It is usually more that the average shooter would guess.