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Discussion Starter · #1 ·
I have been lately shooting my new Ruger M77 chambered in .270 win at 200 meters ( 218 yards) and 300 meters (328 yards) respectively. I was shooting 130 grain, Winchester power points. Temperatures were above 80F and at low altitudes.

The rifle was zeroed at 218 yards and much to my surprise it was hitting the 328 yards target 12 " low!! According to winchester's charts, it should be hitting 7.7 inches low.

Has anyone had similar experiences with these or similar factory loads?
 

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The Shadow (Moderator)
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Rule #1, Sex sells
Rule #2, Speed sells

What a factory claims for launch velocity is advertising. Unless you know what YOUR launch velocity from YOUR gun is, you really can't estimate much. The other issue is B.C. bullets don't have one B.C. they have different ratings based on speed. So going back to YOUR launch speed, what you think your B.C. is, may not really be.
 

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That is more of a departure from factory claims than I would expect. As Darkker mentions, until you know what the actual velocity is from your specific rifle, we can only speculate on the cause. If you had a chronograph, that could possibly point to ammo issues, or barrel issues, if velocity was not meeting expectations. Or, if velocity is what it is supposed to be, scope or shooter issues.
 

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Probably the #1 reason trajectory varies in a particular rifle from that shown in trajectory charts is sight height. Most of then use a "standard" sight-height-above-bore of 1.5". With today's love of high-power, big-objective-diameter scopes, the line of sight is often higher than that, which makes comparisons with the charts worthless; a small difference in height can make a whale of a difference in trajectory. The only way to know the trajectory of a load in your rifle is to shoot it in your rifle at the various ranges.
 

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Discussion Starter · #5 ·
Thanks for the suggestions. Unfortunately, I do not have a chronograph so as you guys say, we may only speculate on the cause.

According to Darkker, since the ballistic coefficient of a bullet is correlated with the speed at the muzzle and varies within every rifle, then, correct me if I am wrong, but if a specific factory load “A” claims a superior ballistic coefficient than a factory load “B”, assuming that both loads are fired from the same rifle and that powder type and quantities are similar, then B.C of factory load “A” should be always higher than factory load “B”?

If this is the case, then I could shoot with two different factory loads, with two different B.C. advertised, maybe from the same brand to minimize potential differences and compare their performance at different ranges. I could also shoot my other .270 and compare the performance of each rifle with the same factory load. What do you think?

With regards to the sight height above the bore, I have not measured it yet but I have been taking the 1.5 inches standard for default as the scope is a Leupold VX-2 3-9 x 40, mounted on the #5, #4 ruger rings, which I believe is currently the standard.
 

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Discussion Starter · #6 ·
Thanks for the suggestions. Unfortunately, I do not have a chronograph so as you guys say, we may only speculate on the cause.

According to Darkker, since the ballistic coefficient of a bullet is correlated with the speed at the muzzle and varies within every rifle, then, correct me if I am wrong, but if a specific factory load “A” claims a superior ballistic coefficient than a factory load “B”, assuming that both loads are fired from the same rifle and that powder type and quantities are similar, then B.C of factory load “A” should be always higher than factory load “B”?

If this is the case, then I could shoot with two different factory loads, with two different B.C. advertised, maybe from the same brand to minimize potential differences and compare their performance at different ranges. I could also shoot my other .270 and compare the performance of each rifle with the same factory load. What do you think?

With regards to the sight height above the bore, I have not measured it yet but I have been taking the 1.5 inches standard for default as the scope is a Leupold VX-2 3-9 x 40, mounted on the #5, #4 ruger rings, which I believe is currently the standard.
 

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One thing is your rifle has a 22 inch barrel I think, and the MV stated by the manufacturer for that load is based on a 24 inch barrel, there will be a little loss in MV having a 2 inch shorter barrel. I reduced the MV by 40 fps and using a little lower BC than the stated .372 and using a zero of 218 yards I get a 9.18 inch drop at the 330 yard mark. As the other guys have stated without knowing the exact MV it's difficult to get a real close number. The Hornady Superformance line offers the 130gr GMX @ 3190 fps with a BC of .460 and the 130gr InterBond @ 3200 fps with a BC of .460. The InterBond load with a 200 yard zero drops 5.7 inches at the 300 yard mark and the GMX load is about identical. There's several others with bullets that have much higher BC's and will shoot flatter overall at extended ranges. Best to ya
 

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The Shadow (Moderator)
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According to Darkker, since the ballistic coefficient of a bullet is correlated with the speed at the muzzle and varies within every rifle, then, correct me if I am wrong, but if a specific factory load “A” claims a superior ballistic coefficient than a factory load “B”, assuming that both loads are fired from the same rifle and that powder type and quantities are similar, then B.C of factory load “A” should be always higher than factory load “B”?
No, you missed the boat, or at least my intent on this one.

If you go to Sierra's website they list the BC for each bullet, at various speeds; because the BC changes at various velocities. Most everyone else just does an Average number, and advertise that as THE BC.

So if your ammo assumed a BC which was...perhaps the best word is "hopefull", AND you have a lower launch velocity starting out, then what they publish(an average number based on the likelihood of spending most of the time in the higher velocities), and what YOU will see, are totally different things.

Over the course of several years, Hornady's Superformance ammo in 204 Ruger has been HORRIBLY sandbagged. I have chrono data over half a dozen different lots, and several years; showing 200-400 fps SLOWER than the advertisement.
 

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The Hog Whisperer (Administrator)
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Barrels can do funny things with very similar loads. I have one rifle that put two different loads, with the exact same weight bullet and powder charge (but two different brands of bullets), 4 inches apart horizontally at 100 yards. Odd, but that's what it did.

Also, I have seen tests that suggest the exact B.C. numbers can vary by 10% or so just by the individual barrel and load. Just one more reason things need to be verified.

I wouldn't put too much into what you've observed. You did a good thing by checking it before heading out to the field, instead of assuming the factory numbers were exactly accurate.
 

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All of the above points are good. I note that in the original real-life example of the 130 gr. .270 load that the POI obtained at 328 yds. was precisely what was predicted for 350 -- not really much of a downgrade if you know it's that way and have good range information. I would gladly sacrifice 22 yds. if a load was accurate enough.
 

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In the OP, you state you're sighted in at 218 and the load is 12" low at 328 yards. For this to be true, with just about any sight height, your MV would have to be down around 2,500fps.

Something is clearly amiss, as I doubt your MV is that low. When you shoot at 100 yards, is your POI roughly 2" high? Are these certified distances you're shooting at? What you're reporting is incongruous with what one would expect, so the next step is to identify where things are going wrong. Are you shooting a rifle with an 18" barrel? Is your 300 meter target really at a greater distance? Are you shooting uphill or downhill at an appreciable angle? (That should result in higher POI, anyway...)

I'll be interested to hear the outcome on this one. :)
 

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Gents,

When I have chrono'd factory loads, 100 fps difference between shots was not uncommon. Funny, sometimes those loads with the most spread still shoot the straightest. Factory Win power points in 307 will group better (MOA) at a 100 yards with a 130fps extreme spread, then my handloaded FTX Horns with an extreme spread of 24. Curious.

There are also variances from lot to lot, and rifle (chamber) to rifle. Looking at your numbers, just under 5 inches difference what what you expected? I could live with that, at 300 Meters, sure enough. The great thing is that you know your rifle, and what it'll do, at least generally. Another trouble is that the ground also may have something to do with it, assuming that its not table top flat at your range.

The issue with this thing of ours, is that we have the science to form the mental baseline, but to make the science work properly, it has to be practiced artistically. One cannot expect the science to be consistant with so many varibles.

If it were me, I would find a chrony from hook or crook, and if the numbers didn't suit me, start over with a new load. Chrony, and then shoot this load in 50 meter increments out to 300 and map your progress. The good news is with that much shooting, regardless of your up and down, you'll be able to hit, correct?

Best to you fellows.

Steve
 
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Discussion Starter · #13 ·
Strange things happened again at the range this morning. This time I took two .270s. The 22’’ and a 24’’ barreled mannicher schoenauer. I zeroed both rifles at 25 meters (27 yards) using the same winchester power point factory loads. Then, I put 3 shots from the 22’’ barrel rifle into the 200 meter target from a steady rest, distance measured personally, and found out that it was hitting zero, but with a 4.13 MOA group. Next thing I did was to change loads for winchester’s ballistic silvertip boat tail bullets and shot each rifle 3 times at the same target. Now the story changed, the 22’’ barrel rifle shot 0.97 MOA, 3.3 inches high and 24’’ barrel rifle shot 1.38 MOA group 2.5 inches high.

Then, I switched to the next target placed 300 meters away from my bench (also personally measured). Both rifles grouped at the center; the 22’’ grouping 0.95 MOA and the 24’’ 1.64 MOA. But according to the charts, groups should be hitting about 5 inches low.

I didn't shoot at 100 yards so I do not know the POI at that distance yet. By the way, though targets are located uphill and I don’t know the exact slope angle, I presume that it shouldn't be more than 10 degrees and I can tell you that the slope is so gentle that it shouldn't be that significant.
 

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Sounds like your guns like the boat tail polymer tipped bullets. The BC should be quite a bit higher on that bullet over the power point, the 2.5 inches high vs 3.3 inches high is the difference of the muzzle velocity between the 22 and 24 inch barrels with the 24 being faster. I agree that 10 degree's uphill or downhill won't have a significant effect on the POI. Still with factory ammo unless you chronograph it there's no way to tell what it's real world muzzle velocity really is verses what is stated by the manufacturer. Federal has a 130gr High Energy Trophy Bonded Tipped load that is 3200 fps at the muzzle and is equal to the Hornady Superformance InterBond 130gr load at 3200 fps. Maybe one of those will flatten out your trajectory, both are polymer tipped boat tails.
 

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For every 15 degree in elevation change you can reduce your target distance by roughly 10%. So, your 328 yard target, uphill at 10 degrees, would shoot for right around 300 yards.

All of the results from your recent post are close enough to normal and exhibit typical velocity of ~3,000 fps from your 130gr bullets. Carry on! :)
 
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