Excessive bullet drop

[RobG]

Could be a miss-aligned scope... meaning the scope is not parallel to the bore. Your smith might be able to see the miss alignment, not sure how though. It could be out of alignment 1.5-2" at a 100 yards and mess you up that much at 300.

You lost me... how is that different than the elevation adjustment of the scope?

Shoot through a chrono, and sight in for what the expected drop is at 300, and then see where it hits at 100. I have a rifle that is slightly miss aligned. Changing the POI at 100 about an inch set me up where I needed to be at 300 for the expected drop.

Yeah, I'm going to try that. Although with $2/shot ammo I'm not sure I could afford the gas back from the range .

Another option is to get a set of burris rings with inserts.

You lost me again, what would I be gaining with that? The scope seems steady.

 

[npaden]

Something like having a shim on the rear mount but not on the front?

Wouldn't the mis-alignment be linear though?

1.5 high at 100, 0 at 200 then 1.5 low at 300...

The bullet drop would then add to that line and result in the 1.5" low at 200 and would only be 12 - 13 inches low at 300. Still seems like a faster than expected drop.

 

[Southwind]

Factory ammo isn't always what it is published, some hotter, some milder but you are talking 900 fps slower so I am suspecting something different. You will see +/- 100 maybe 200 fps but I wouldn't think that far off. Not saying it couldn't happen.

The limited Vor-tx ammo I have chrony'd has been pretty much spot on. Again doesn't mean it can't happen.

Scope mount set up?, is the rifle bedded?, have you checked all the mounts?,torque settings? (action screws and scope screws) Have you tried any other ammo?

I know there is not such a thing as cheap ammo, but you may want to buy a box of federal fusion in 06, I think they offer a 180 and see what it does at 300. or any 180grain 06 ammo just for a comparison.

 

[Festus]

That is strange. Hard to believe ammo would be that slow.
I like Bambi's idea on the misaligned scope.
Has the gun/scope set up with that ammo (or other ammo for that matter) performed as expected at 300 yds in the past?


Maybe Kyle can help???
http://onyourownadventures.com/hunttalk/showthread.php?t=265592

 

[RobG]

Factory ammo isn't always what it is published, some hotter, some milder but you are talking 900 fps slower so I am suspecting something different. You will see +/- 100 maybe 200 fps but I wouldn't think that far off. Not saying it couldn't happen.

The limited Vor-tx ammo I have chrony'd has been pretty much spot on. Again doesn't mean it can't happen.

Scope mount set up?, is the rifle bedded?, have you checked all the mounts?,torque settings? (action screws and scope screws) Have you tried any other ammo?

I know there is not such a thing as cheap ammo, but you may want to buy a box of federal fusion in 06, I think they offer a 180 and see what it does at 300. or any 180grain 06 ammo just for a comparison.

The stock is not bedded - this is a factory gun from 1939. There doesn't seem to be a lot of space between the stock and barrel, maybe even touching at the end of the stock. I just got it back from the gunsmith (Rocky's out in Logan) who did a complete teardown and cleaning, probably the first time in 76 years... Maybe the stock is touching the barrel where it wasn't before, still, the bullet is falling off a cliff after 200 yds.

I let the barrel cool down after 3 shots, although it might be hot barrel effects (you'd think the groups would be a lot more up/down).

I'm going to feel really dumb if that target was at 400yds.. the data would then make sense, but dangit I know that one is 300 yards. Maybe I was pressing down on the barrel.

Good thing I don't shoot anything beyond 200 yds with this gun!

 

[belly-deep]

Could be a miss-aligned scope... meaning the scope is not parallel to the bore. Your smith might be able to see the miss alignment, not sure how though. It could be out of alignment 1.5-2" at a 100 yards and mess you up that much at 300.

Shoot through a chrono, and sight in for what the expected drop is at 300, and then see where it hits at 100. I have a rifle that is slightly miss aligned. Changing the POI at 100 about an inch set me up where I needed to be at 300 for the expected drop.

Another option is to get a set of burris rings with inserts.

Not uncommon... the bore may not be in the center of the barrel. I highly doubt its slow ammo. The difference in drop would have be signifficant velocity loss to get that far. Assuming the point of aim is the same in relation to the bore at each range is a poor assumption.

Good luck!

I didn't think of that but a 1939 vintage could definitely have alignment issues. Probably came from the factory w/o holes for bases and was later 'smithed for use.

 

[Tex_MT]

RobG if it makes you feel any better, I am having the same problem. I was actually relieved to see this post. I am far from an expert on rifles, bullets, ballistics, etc. I'm a bow hunter who picks up his rifle to continue hunting when the general season opens. I went out yesterday to shoot and was zero'd at 100 spot on. 3" low at 200 yds... couldn't get on paper at 300 yds. I couldn't figure it out. I shoot a 30-06 with 180 gr. bullets. Was shooting Fusion for target practice, but shoot Nosler while hunting. Can't figure how I could possibly have a tight group at 200 and then be completely off paper at 300. Everyone's suggestions have been very helpful for me as well so I also appreciate the replies. I've got to go back out and figure it out. Never had an issue at 300 before, but it was my first time shooting that distance in a few months.

 

[Southwind]

If they are old miss aligned holes there are plenty of folks out there that can make a custom set of bases and they don't have to be price prohibitive.

http://murphyprecision.com/Page/Custom_Services

 

[RobG]

I didn't think of that but a 1939 vintage could definitely have alignment issues. Probably came from the factory w/o holes for bases and was later 'smithed for use.

I think we have a winner at least with that observation. I'm pretty sure the holes for the redfield base needed to be drilled in when my dad put a scope on it a long time ago.

I didn't realize the inclination of the scope mattered but after sketching it I can see the effect. It sure seems like it would have to be off quite a bit to have that effect but I'll have to do the math.

I take it there are burris ring inserts that can be used to adjust for this, I'd have to raise the back end of the scope?

Hopefully I'll get out to the range and figure this out... but the area I hunt in doesn't offer many opportunities past 200 yds.

 

[MinnesotaHunter]

Rob,

I had heard some stories of the Barnes ammo having consistency issues early on, specifically with pressures. I have shot quite a bit of it, and not had problems, but I think shooting through the chrono might be a good start.

I am not sure I caught it, but had it shot ok in the past?

 

[RobG]

I am not sure I caught it, but had it shot ok in the past?

I tried 300 yds a few years ago, but I don't remember where I had it zeroed or what ammo I was using so it doesn't help much. It was hitting on that 2nd diamond so about a 12" drop, maybe 14" so it was a little low back then too, but not 20".

 

[noharleyyet]

Can you borrow someone's dirty-naught and run your ammo thru at the same target?

 

[----]

Have you tried firing the rifle upside down?

 

[Bambistew]

Burris Signature Rings they have inserts from 5-15 moa? Short of shimming the bases, these are the best bet.

When you shoot at a target at various range your line of sight is straight, but not necessarily parallel to the bore, if its not you will see dramatic changes in elevation/drop once you get into the 250-350 yard range. You can also run into this issue with windage. I have a rifle that was fugged from the factory... there's a reason that Leupold makes those bases with windage screws.

If the velocity was really that low, it would feel like a cap gun when you shoot it. I've rolled "light" ammo for the 30-06 before, down to about 2200fps with 150s. It has very little recoil.

 

[npaden]

Have you tried firing the rifle upside down?

If Bambi's theory is correct it would shoot pretty close to dead on at 300 yards if you shot it upside down. Maybe get someone to hold you by the ankles?

 

[npaden]

I think we have a winner at least with that observation. I'm pretty sure the holes for the redfield base needed to be drilled in when my dad put a scope on it a long time ago.

I didn't realize the inclination of the scope mattered but after sketching it I can see the effect. It sure seems like it would have to be off quite a bit to have that effect but I'll have to do the math.

I take it there are burris ring inserts that can be used to adjust for this, I'd have to raise the back end of the scope?

Hopefully I'll get out to the range and figure this out... but the area I hunt in doesn't offer many opportunities past 200 yds.

You would need to raise the front end of the scope. The theory is that the back end is higher than the front causing to to point slightly downward. Just a tiny fraction of an inch could cause a big different at decent yardage.

 

[sbhooper]

I never thought of that, but I had the same problem with a .308 one time. I forgot a spacer that was part of the mount.

 

[deflave]

I need to go back out to the range but this is haunting me...

Last night my rifle was 1.5" low at 200yds and 20" low at 300yds. I don't remember what it was at 100yds - ball park +1.5".

20" is way too low. The box says -8.4" if zeroed at 200yds. My Federal ballistic chart says it should be -11.6" if drop is -2.3" at 200yds.

I'm shooting 180gr Barnes VOR-TX tipped TSX BT 30'06 factory ammo. The gun is a 1939 Savage bolt action, 24" barrel. It was cleaned by a gunsmith. I shot 6 normal jacketed bullets to foul the barrel and this was after about 15 shots with the the all-copper TSX bullets.

Why would it be so much lower at 300yds?

Have you noticed that if you count from the lowest of the two diamonds the amount of drop is in there like swimwear?

I'd hit the range once more before you go tearing anything apart.



Travis

 

[deflave]

I shot with a friend with a chronograph this weekend and my shoots averaged 3,160 fps when the specs say they should be shooting 3,200 fps. Pretty close and some actually ended up at 3,210 as the barrel warmed up. The first shot was the slowest at 3,115 fps.

No idea what that means to trajectory, I was shooting at 100 yard paper.

Nothing.




Travis

 

[npaden]

You would need to raise the front end of the scope. The theory is that the back end is higher than the front causing to to point slightly downward. Just a tiny fraction of an inch could cause a big different at decent yardage.

Nevermind, I think you were right. The scope is pointing slightly up compared to the barrel so you would need to shim the back of the scope not the front.

Had to do some hand gestures to figure it out!