MOA changes significantly over distance!

[Erik Cortina]

Check the twist rate!!!!

 

[Alex Wheeler]

If you dont find any issues with your rifle, I recommend you tune at the distance you want to shoot.

 

[Tempest]

Check the twist rate!!!!

Erik, can you elaborate on the method you use to determine twist rate?

 

[timeout]

Check the twist rate!!!!

Erik, can you elaborate on the method you use to determine twist rate?

It's pretty straight forward. Check here: http://www.accurateshooter.com/technical-articles/gunsmithing/how-to-determine-barrel-twist-rate/

 

[Erik Cortina]

Check the twist rate!!!!

Erik, can you elaborate on the method you use to determine twist rate?

It's pretty straight forward. Check here: http://www.accurateshooter.com/technical-articles/gunsmithing/how-to-determine-barrel-twist-rate/

+1

 

[savagedasher]

Shoot 5 2 shot targets at 100 the data results is the same as 2 5 shot . I believe even better
2 shots will tell you if you have vertical or horizontal. Vertical normally comes from speed. Post the results with exact size. and the direction they are pointing. Larry Example * is vertical
*

 

[Tempest]

Check the twist rate!!!!

Erik,

Checked it 3 times and it's just a over 1/12.

Using the cleaning rod method, bewteen 12.125 and 12.25".

So I'm thinking of testing some 155 Scenars and see if the rifle likes them better.

 

[BoydAllen]

Keep us posted as to your results.

 

[seymour fish]

and some 155.5's

 

[Tempest]

Update:

Got some 155 Scenars to test. Was not the best conditions to test in, but was eager to see how they compared to the 175 SMK under same conditions. So here is what I found out. All shots were done at 500 yards. I shot a pretty common 155 Scenar load and seated them at .010 variance just to start. Also shot the 175 SMK load that had worked well in another rifle. I chrono'd the rounds and got avg 2956 and ES 9.

Even in a 16 MPH wind that switched from full value from the right to behind me, the Scenar's loaded .030" jump shot about 1/2 size the group of the 175's. Guess that's what we are using next time out and see how they actually shoot in a match.

I did have the barrel looked at at there is some chatter on the lands. If I can get through the rest of the year w/ some decent results (or better than before) I will re-barrel over winter.

This is my son's gun and he is having a blast shooting in some matches. Just wish I would have looked into this earlier as I feel partly responsible for his performance with this rifle so far.

Thanks for the comments/feedback.

 

[BoydAllen]

Thanks for the update. You have learned something, and any time that we can do that we are lucky. Good shooting
Boyd

 

[stubbicatt]

Deep cleaning with JB or Iosso?

 

[DarrellA]

The following wind-drift figures, from "simplified trajectory" @ JBM Ballistics, provide an answer to this old question. The calculation was for .45 BC and 3000 Fps. MV: .45BC, 3000 FPS, 10 MPH wind, Std. conditions.

Thank you for this post! After reading this I went back through my data and realized that I may not suck nearly as bad as I was thinking.

 

[Brians356]

I tried to think "out of the box" on this, and something popped up:

Do you change anything in your bench setup or technique between 100 and 500 yards?

An example of a subtle change might be having to elevate the front rest a lot for a more distant target farther up a hill. (Here in the west we often use mountains for range backstops, and the longer ranges are often farther uphill.) And a subtle change could adversely affect the bags or your hold, or something.

Or, maybe your heart pounds a little more, and you get a little tense, when shooting at the longer distance. (BTW - Are you trying to dope and hold off for wind at all? And what about mirage?)

I know it's a stretch, but it just might not be the load or gun itself at all. Just food for thought ... it's the Zen streak in me.

Brian

 

[Tempest]

I tried to think "out of the box" on this, and something popped up:

Do you change anything in your bench setup or technique between 100 and 500 yards?

An example of a subtle change might be having to elevate the front rest a lot for a more distant target farther up a hill. (Here in the west we often use mountains for range backstops, and the longer ranges are often farther uphill.) And a subtle change could adversely affect the bags or your hold, or something.

Or, maybe your heart pounds a little more, and you get a little tense, when shooting at the longer distance. (BTW - Are you trying to dope and hold off for wind at all? And what about mirage?)

I know it's a stretch, but it just might not be the load or gun itself at all. Just food for thought ... it's the Zen streak in me.

Brian

Thanks for the feedback but not sure if you saw the last update. Pretty sure it was the twist and bullets used. It literally shot over twice as good w/ the Scenar 155's as the 175 SMK's with the 1/12.25 twist last time out.

Will update how it does at the next match.

 

[seymour fish]

The 155 scenar has in my experience done extremely well in a 1:13 30" bbl down to 20 deg F, with a DA of negative 1000-1500 or so, at 550 yds. Very well also out of a 22" 1:12 at 2620 fps at 550 yds, and plenty ok to 1000 in mild conditions. If these results conflict with shopworn theory, so be it. Some modifications to the Miller stability formula have been found necessary of late to reflect the latest scientific testing. Apparently a stability factor of 1.23 is shown to give the highest BC over distance. Don't have a link, but not hard to find. Also note some top flight LR shooters have done well with the 185 Juggs out of a 1:13 30 " at 40-50 deg F and above. In the end, we are empiricists.

 

[seymour fish]

GS, agree with you as well. Could be less recoil is easier to handle, load effects a better tune, Published bc of the 175 is optimistic (Litz), thus more speed and a narrow BC spread wins the wind battle. Or power of positive thinking. Another good trade he could make would be to run the 155.5 Berger which IMHO is twice as accurate, and can give increased speed as it occupies less case volume. Lazer to 1000, but best usage is out to 600, where under a half INCH is doable, with a facdtory Savage of course.
\

 

[mac86951]

I tried to think "out of the box" on this, and something popped up:

Do you change anything in your bench setup or technique between 100 and 500 yards?

An example of a subtle change might be having to elevate the front rest a lot for a more distant target farther up a hill. (Here in the west we often use mountains for range backstops, and the longer ranges are often farther uphill.) And a subtle change could adversely affect the bags or your hold, or something.

Or, maybe your heart pounds a little more, and you get a little tense, when shooting at the longer distance. (BTW - Are you trying to dope and hold off for wind at all? And what about mirage?)

I know it's a stretch, but it just might not be the load or gun itself at all. Just food for thought ... it's the Zen streak in me.

Brian

Thanks for the feedback but not sure if you saw the last update. Pretty sure it was the twist and bullets used. It literally shot over twice as good w/ the Scenar 155's as the 175 SMK's with the 1/12.25 twist last time out.

Will update how it does at the next match.

Good luck! Thanks for the help, I'll jot down in my notes that a 1:12 might be marginal for 175gr and I should test before buying 2000 bullets.

-Mac

 

[coldboreshot]

If what i read is correct, you are running the same load from a 1-10 twist barrel (Im assuming 24-26") to a 1-12 twist 29" barrel? This may be one of your issues. Your pushing 175 grainers with 43.5 of Varget in a 1-10 with good results where that barrel is more suited for that load. You then use the same in a slower twist pushing the 175s with the same charge? You may want to back down the charge. I have the same 12BR and I have printed 1-5/8" at 565 yards running 185 Berger VLDs with 41.6 of Varget and 210M primers with 0.005" jam and 2650fps.
Contrary to what most believe, speed is not everything. 1-5/8"@565 speaks for itself. It also worked pretty well at 600 yard F Class matches.
Issue 2:
100 yards for the most part is not the best test-bed, unless you plan on shooting only at 100 yards. If you can, open up the test distance to 300 yards or so. Example; Berger VLD bullets for the most part tend to stablize at distances greater than 100. I've seen more than enough people get frustrated testing them at 100 yards and give up on those bullets without giving them the proper test-bed.

The ES you described during Chrono is a normality that describes a good consistent loading process. The 175's arel traveling down that 29'' 1-12 barrel consistently. You should be getting the same consistency from the 10BA as well.

I have also discovered, a barrel with a less than desireable cleaning regimen will prove itself at long distance as apposed to 100 yards. (Minute differences may not be seen at 100 yards but are greatly expressed at long distance). I'm still not sure what you mean by "crappy" results. I would like to know what exactly your print at the longer distance is.

I would first start with a clean barrel (polish if neccessary), then back down the charge on that load. This might rersolve your issue. Also, start the jump on those Sierras from 0.005" and work back in 0.005 increments. I.E. 0.010, 0.015 etc...

 

[coldboreshot]

Regarding my previous input, I apologize, Im old and confused. The group shot with the 185 VLDs @ 565 yards was actually (7/8"). I mistook the 1 5/8" group I shot with my 50BMG the same day at same distance.