Newbie question, why is my 6.5 creedmoor dropping 4.25 inches from 100 to 200 yards?

T

TheArmyMan204

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Hey guys, been away from shooting for a few years but jumped back into the sport with a budget build.

Rifle: Savage 10T-SR 24" barrel 1:8 twist.
Base: factory 20 moa base
Scope: Vortex viper pst gen2 5-25x50 in Vortex precision rings.
Ammo: Sako TRG HPBT 136gr 6.5 creedmoor (claimed) 2820fps G1 BC 0.526
Scope height over bore: 2 inches
Left to right wind 5mph

Prior to taking it to the range I cleaned and retorqued all fasteners to spec, action, base, rings etc. So finally got to the range for the first time with the new rifle today. Fired a total of 60 rounds. Zeroed at 100 yards.

Printed multiple groups around 0.75 inches at 100 yards. Before I left I wanted to see what drop I had at 200 so I could start building some DOPE cards.

So without touching the elevation or windage and using the exact same point of aim on the same style of target I was printing 2 inch groups at 200 but they were all 4.25 inches low. Windage was still dead on.

All the ballistic calculators and charts I can see say bullet drop should be 2 to 3 inches from a 100 yard zero to 200 yards. The only way I could get the hornady app to match my results was to lower the muzzle velocity to 2600fps and the height over bore to 1.5"

So where am I losing an extra 2 inches? I don't have a chronograph yet but could ammo really be that much slower? New barrel not broken in? It groups beautifully and consistently, just seems to be dropping alot faster than the famous flat shooting 6.5 I've heard so much about.

Basically looking for any advice on what to do before and on my next range trip on Monday, to verfiy equipment and myself are in check. I managed to find another brand of ammo (Barnes precision match 140gr OTM BT).
 
If it was me, I would borrow a chrony, just to see what is exactly happening

Sounds like you are doing everything correct at the workbench at home
 
My calculator shows +2.95 inches.

Would it have anything to do with your sight heigh calculations?
Maybe the Sako ammo is a bit slower than stated?
 
If you can, shoot at 300yds and see how the drop progresses. Odds are the velocity in the real world is not what is printed on the side of the box.

My experience with 140gr class bullets with the 6.5 Creedmoor showed velocities around 2600fps. BCs can also be over rated but the difference at your distances wouldn't make a huge difference.

When I am helping shooters get set up, I caution them on focusing too much on LCD screens. Firearms don't always follow the 'book' ... if it is repeatable, it is likely actionable. If you want to know the answers, then you need the tools to confirm the data.

slow and accurate beats fast and irratic anyday... and I have shot my 'slow' loads very accurately to 1550yds so I dont care how fast any of my rifles shoot

MOA at 200yds with factory ammo indicates a good combo... don't obsess about drops. They are easily adjusted for and mean very little at the end of the day.

Good luck with your progress

Jerry
 
OP, The 6.5 CM is not really a “flat shooting” cartridge, at least with 140 class. It does fantastic however. Bullet BC could be wrong and for sure that velocity looks too high in my opinion.
With my 6.5 and 140 Berger VLD’s at 200 meters I get 4.4” drop. 2710 fps at the muzzle.
Just find your real dope and adjust your apps to match. Or find a lab radar buddy to get you there quicker.
h ttps://youtu.be/BjnSVOu_yXk
^
 
Lead hammer said:
OP, The 6.5 CM is not really a “flat shooting” cartridge, at least with 140 class. It does fantastic however. Bullet BC could be wrong and for sure that velocity looks too high in my opinion.
With my 6.5 and 140 Berger VLD’s at 200 meters I get 4.4” drop. 2710 fps at the muzzle.
Just find your real dope and adjust your apps to match. Or find a lab radar buddy to get you there quicker.
h ttps://youtu.be/BjnSVOu_yXk
^
Click to expand...

There you go - great info and 4" or so drop is usual with 140s is usually due to 2600 fps at the muzzle .... not a particular flat shooting round but, use a CDS or BDC type scope and shoot easily out to 500 or 600 yds for hunting ... My go to load is 2580fps 143gr ELDX .25 moa and I shoot out to 1500 using a high end scope. QD rings and for hunting I'm using a Leupold 3x9x40 with their ballistic scope: it's simple and after a 200 yd zero it gives me 3 more aiming points 300, 400 + 500 respectively great for my hunting. Its 3.5" at 100 BTW...

So rein in the expectations - get ur most accurate load, then sight in accordingly based on scope ur using. Enjoy it - mine is my main 500 yd hunter or longe range shooter.
 
First off, make sure you have measured your sight height correctly. Second, I would get a chrono if you have access to one.

Now, with that being said, the velocity on the box will not be the same in every rifle. It's possible your rifle may have a slower barrel, or the velocity on the box is assuming a 26" barrel, or your barrel is just not broken in yet. There's honestly a lot of variables to list. I've had barrels speed up about 100 fps after 150 rounds.
If you don't have a chrono, your best bet would be to shoot out to further distance and record your bullet drop as accurately as possible. Use MOA/MRAD, whichever your Viper has for a reticle, instead of measuring in inches.
Also, I'd avoid using the G1 drag model, and try to find the G7. That'll give you a much more accurate portrayal of the ballistic performance of your bullet.
 
I always thought the Sako TRG 136 6.5CM were loaded quite hot, especially compared to the normally very slack loaded Sako hunting loads I measured. We had 2730fps out of a 24" CTR barrel, close to 2800fps out of a 24" Hawk Hill barrel, 2650 ish out of a 20" Hardy carbon barrel.
edi
 
Like others have said, real world drop trumps theoretical dope, especially when using the velocity off a box of ammo. If you can get access to one, I'd highly recommend chrono'ing your ammo. Also, as others have said, it's not abnormal to have a 6.5 speed up almost 100fps as the barrel breaks in during the first 100-150 rds.
 
Thanks for all the info guys.

Went back to the range today to confirm zero and 200 yard dope. Come up at 200 is 0.7 mils so all is good.

My average 5 shot group at 100 was 0.875 inches, which considering it's been years since I've shot and my set up is less than ideal (Harris bipod on concrete bench and a sock filled with popcorn kernels for my rear bag) I'm extremely happy with the results so far.

Can't wait to start reloading my own ammo and dial it in a bit more. Used to reload. 30-06 but it's been years since I've done that aswell.
 
4.25 inches drop with a 136gr bullet when sighted in at 100 yards is not crazy out of spec.

I don't have a 6.5 CM, but I do have a 260 Rem which is ballistically identical, except the .260 case has a tad more powder capacity.

I have seen a 4 inch drop at 200 yards with the 139gr Lapua Scenars shot from my .260 Rem Tikka Varmint with its 24 inch barrel.

The industry often tests with longer barrels like 26" as mentioned in posts above, which will gain 30-50 FPS over a 24 inch barrel (i.e. 15 to 25 FPS per inch, depending on the bore, primer, powder and bullet). So the industry's testing variables could account for a significant difference in velocity, and therefor ballistic model calculations. As folks have mentioned, you need a chronograph to figure out your rifle's muzzle velocity for this ammo.

I looked at Vihtavuroi's reloading data website for 6.5 CM and the 136gr Lapua Scenar, and that velocity on the box of your Sako ammo is do-able, but its on the maximum charge weight (with N-550 and N-555) and on the hot side.

On hot loads, some rifles, like my Tikka .260 Rem Varmint, will shoot lower on the hottest loads and higher on the mid-range charge weights, with the same bullet and seating depth. This is because each barrel + action + bedding combo has its own unique harmonics. So the pattern I see is a gradual rise in POI from min charge to middle of the charge range, and then approaching max charge I see the POI go down. For some reason on this Tikka, the harmonics in the barrel makes the node go down as the charge reaches max.

In summary, my Tikka .260 Rem Varmint shooting a 139gr bullet shoots with a lower POI, approaching 4-ish inches lower than 100m zero, as the load approaches max charge weight.
 
My Tikka CTR, shooting 140 hybrids right at 2700, is a hair over 4" low at 200m with a 100m zero. What you're seeing seems to be within range of the rest of us
 
My experience with 140gr class bullets with the 6.5 Creedmoor showed velocities around 2600fps.
Click to expand...

I'm not overly familiar with the 65CR but a 308W pushes a 150gr bullet at ca 2800 fps. Why would the CR be so much slower when it is essentially the same case necked to 6.5mm? If the CR really is slower, then why has it been more successful than the 260, which was just a 308 necked down?
 
The 6.5 creedmoor can seat high BC bullets above the neck-shoulder junction and still fit in a mag. Not happening in a 260 without going to a XM action. Not that you have to seat them that way, but by doing so you never have to worry about donuts.
Lots of guys get 2800fps+ out of their creeds and 140s. 2600 is slow, but plenty of us run ours around 2700fps.
If you find a good node at less than 2800 in a creed there is little reason to try to push it to the next node. Just dial an extra click or two of elevation. Not pushing things to the max is easier on brass.
 
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I Dont Care About You said:
I'm not overly familiar with the 65CR but a 308W pushes a 150gr bullet at ca 2800 fps. Why would the CR be so much slower when it is essentially the same case necked to 6.5mm? If the CR really is slower, then why has it been more successful than the 260, which was just a 308 necked down?
Click to expand...

6.5 CM has less capacity than the 260. All else being equal, it will be slower. - dan
 
Shoot it at a further distance. One group could be an anomaly. You could have been dealing with a lighting issue, the position of the sun relative to the direction you were firing for example. 200 isn't a far enough distance to get good resolution in your data. Try 400 on a calm windless day.
 
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