Very confused. Dope changed big time? What caused this?

[Aimsmall55]

I had something VERY confusing yesterday. I was shooting a GA Precision 6.5 creedmor Crusader with a Bushnell XRS 4.5x30x50 with a 140 hybrid. Temp was 84 F , 29.35 barometric pressure, 70 % humidity. It took 7.8 mils to get to 945 yards. We moved the target back from 920 which my dope has been DEAD on at 7.1 to 7.2 mils. This is with average 90 degree temps and 29.9 barometric pressure. So my dope said 7.35 mils but it took 7.8 to get there ! I shot at 705 last week and 4.5 mils ( using the same ballistic program ) was dead on. What could be causing this??? I might add that while my average mv is 2800 fps this would mean that I was running at 2735 fps. I don't know what to make of it. Meanwhile my dope for my .300 win mag running a 208 amax was spot on at 23.1 moa.
The creedmor load was 42.6 h4350 , fgm210 m , 2.221 to ogive and has proven to be a "killer" round. I checked my zero at 100 yards and put 5 inside a 3/8" group.

Very confused.... AS

 

[Abq-Defense]

Aimsmall,

I had the exact same thing going on for the previous two weeks. I had a 6.5 Creedmoor / H4350 load that I have used for months. I had good dope and muzzle velocity from previous shoots. I was running 2800fps. For the previous 2 weeks, I had to adjust my MV to 2732 to hit the usual targets.

My load didn't change, gun didn't change, shooting location didn't change. I am running off the same 8lb keg of H4350. I assumed the change was due to temperature, because we are 15 degrees cooler now. But, H4350 is supposed to be very temperature resistant. And in your case, the temps didn't really change.

Good Luck... If I come up with anything, I will post back here.

 

[Aimsmall55]

Aimsmall,

I had the exact same thing going on for the previous two weeks. I had a 6.5 Creedmoor / H4350 load that I have used for months. I had good dope and muzzle velocity from previous shoots. I was running 2800fps. For the previous 2 weeks, I had to adjust my MV to 2732 to hit the usual targets.

My load didn't change, gun didn't change, shooting location didn't change. I am running off the same 8lb keg of H4350. I assumed the change was due to temperature, because we are 15 degrees cooler now. But, H4350 is supposed to be very temperature resistant. And in your case, the temps didn't really change.

Good Luck... If I come up with anything, I will post back here.

I too am working on same lot. Bought 10#'s and have never switched. Not even lots of bullets or brass. All the same. I wonder when I was shooting in those 90 to 95degree days the powder was alot hotter due the brass conducting heat so fast. I remember this past march we had a 33 degree morning. My dope at 520 yards dropped one full moa. This was after shooting in 55 to 60 degree temps. I believe it came out to be right at 1.3 fps per degree. I know one thing for sure... It's not as EXTREME as one would hope. Even H1000 I've seen pretty big swings

 

[Abq-Defense]

Yes, I use H1000 in my 338, and for the same 2 week period, the velocities had dropped. Oddly enough, with the 338 / H1000, when I was out shooting last weekend, the MV went back up to its normal fps. It could be temperature related. Although the temperature has dropped 15 degrees an we shot in the morning, the H1000 loads sat in the sun (inside a closed plastic case) for a while, while I shot the 6.5 creedmoor.

Like, you, I am on the same lot of brass, bullets, primers, and powder. Maybe we are seeing changes due to temperature.

 

[gvanhyning]

It might be worth having the throat checked. I shoot a 6.5x47 Lapua and my velocity dropped almost 150fps. I checked loads, primers, powder and found no answers. I redeveloped a load that regained 100fps but at longer ranges the groups looked like a shotgun pattern. When I was picking up a new build the gunsmith scoped the bore and it had really bad throat erosion.

 

[Grump]

Ummm, are you guys entering the ambient temp into your dope calculations on these puzzling days?

A nice temp-stable MV has NO effect on how denser air (like from cooler temps or less humidity) makes you need more elevation at like 450 and beyond, especially beyond 600.

I have to ask because not everyone runs new dope at the range, based on all those nice atmospherics you're posting.

If you ARE running new dope, then all I can guess is that maybe your barrel passed a tipping point on throat wear and velocities really did drop. That does happen. What was measured at MV two weeks ago might not be the same today. The one variable that can change under conditions you describe is the barrel. It has more rounds through it now. A lot of unexplained voodoo and witchcraft accompanies the performance of rifle barrels at distance.

 

[Grump]

Sorry, browser freaked and resulted in a double post.

 

[Aimsmall55]

Ummm, are you guys entering the ambient temp into your dope calculations on these puzzling days?

A nice temp-stable MV has NO effect on how denser air (like from cooler temps or less humidity) makes you need more elevation at like 450 and beyond, especially beyond 600.

I have to ask because not everyone runs new dope at the range, based on all those nice atmospherics you're posting.

If you ARE running new dope, then all I can guess is that maybe your barrel passed a tipping point on throat wear and velocities really did drop. That does happen. What was measured at MV two weeks ago might not be the same today. The one variable that can change under conditions you describe is the barrel. It has more rounds through it now. A lot of unexplained voodoo and witchcraft accompanies the performance of rifle barrels at distance.

I understand what your saying. I measured my throat. Still good to go. Basically what I'm going to do is take my scope, put it in a vice, and check the tracking at 100 yards. What really makes me sure the barrel isn't bad is I was shooting at 100 yards and put 5 in the same hole. I also think my scope may have been bumped off..... I won't say why... But first I'm going to chrono

 

[varmint slayer]

What did your zero look like on these off days?

 

[Aimsmall55]

What did your zero look like on these off days?

It was high and right. I had to re zero on Saturday. But I shot Monday and I put 5 out of 5 in itty bitty diamond at 100. Maybe 3/8"'s. and it was dead nuts where I was aiming.

 

[varmint slayer]

I had a wandering zero that would do this very same thing to me. If your zero was high then that doesn't explain you needing more elevation. Back to the drawing board...

 

[[email protected]]

Tho sounds like the exact same thing that happened to me last week, thought I had my 300 WM dialed in, all the sudden I went to shoot 400 and 700 yards and both were low! Changed MV 55 fPS, using G7 BR2. It wasn't corriolis because I shoot north every time. I confirmed the data the day before at the same time so it's not temperture, and I checked zero the day after the incident and dead on (NF scope).

 

[George63]

a few things

first try the 920 yds again - is it still the 7.1 to 7.2 ?

and are you getting good reads with the range finder

a loose(ish) scope base often cannot be detected with the scope mounted, that is why I no longer just bed the base but actually epoxy it on ( can still be removed with a hot air gun)

 

[Adam B]

its the scope, I had 2 that did the exact same thing to me. Anytime I would dial a large amount of elevation (4 or more mils) and then bring it back to my zero stop quickly it would always be off, sent them in and bushnell replaced them both

 

[Aimsmall55]

its the scope, I had 2 that did the exact same thing to me. Anytime I would dial a large amount of elevation (4 or more mils) and then bring it back to my zero stop quickly it would always be off, sent them in and bushnell replaced them both

I don't think that's it. After shooting the 945 target. I dialed back down to zero and put 5 shots in a 3/8" group directly in the bullseye. In this case , 3/4" circle stickies I bought at Walgreens

 

[Grump]

Well, your scope stuff has multiple elements and the ones you indicate are okay aren't the whole story.

Stability the bughole groups. That *can* indicate the mounting is also good.

Repeatability is your return to zero after dialing in a handful or two of elevation.

Then there is accuracy of tracking, which theoretically is just a function of thread pitch. BUT various sloppiness factors can in my understanding make 3 clicks on one part of the turn NOT be the same value. Thread backlash and similar problems can then also affect repeatability. That's independent of the tracking element of whether 10 MOA of clicking is really 10 MOA of reticle movement. AFAIK, that type of error doesn't change. That's why in LR shooting we care about "shooter" MOA vs. "true" MOA.

Then there's recoil dynamics. I can put shots about a half-mil high almost on demand by changing how I hold a bipod prone position.

I'm of the *opinion* that a barrel is more than its throat, and that they can change performance (velocity, accuracy, how easily they foul, etc.) before tools like a throat gage would show any significant change,

 

[Adam B]

I don't think that's it. After shooting the 945 target. I dialed back down to zero and put 5 shots in a 3/8" group directly in the bullseye. In this case , 3/4" circle stickies I bought at Walgreens

glad to hear that, both of the scopes I had issues with were dead nuts at 100 yards, I dialed them up 4+ mils and then when I would dial them back down to the zero stop it would either be 1.5 or so mil high or 2+ mil low, there was no pattern either

 

[Aimsmall55]

Well, your scope stuff has multiple elements and the ones you indicate are okay aren't the whole story.

Stability the bughole groups. That *can* indicate the mounting is also good.

Repeatability is your return to zero after dialing in a handful or two of elevation.

Then there is accuracy of tracking, which theoretically is just a function of thread pitch. BUT various sloppiness factors can in my understanding make 3 clicks on one part of the turn NOT be the same value. Thread backlash and similar problems can then also affect repeatability. That's independent of the tracking element of whether 10 MOA of clicking is really 10 MOA of reticle movement. AFAIK, that type of error doesn't change. That's why in LR shooting we care about "shooter" MOA vs. "true" MOA.

Then there's recoil dynamics. I can put shots about a half-mil high almost on demand by changing how I hold a bipod prone position.

I'm of the *opinion* that a barrel is more than its throat, and that they can change performance (velocity, accuracy, how easily they foul, etc.) before tools like a throat gage would show any significant change,

It's a 2200$ scope that I've had for 1 month. Damn thing better work. Haven't even put it on a breaked or magnum rifle. I'll be honest ... I have no idea what your talking about. But it's on a GA p that will shoot lights out. Tracking is fine. Haven't even set the zero stop. Mark IV 34 mm rings torqued to specs. I think it's the load....

 

[Dan Newberry]

Run your scope turrets up and down, end to end about 6 dozen times... that'll help burnish in the turrets and improve tracking.

I've also seen scopes that when they're new, the windage will zig-zag on the way up... work the turrets in good, and often things will improve.

Dan

 

[2Shots]

I don't think you can always explain it. I know when we all get pretty versed on all of the variables we should be able to figure it out. But I'm not sure you always can. Oh I'm sure if you had the right measuring equipment and could chart all of the variables maybe, but it's not practical, and you would have conditions change by the time you think you had it. A wise instructor once said "believe the bullet" don't try to figure it out, just believe the dope is different right now under the current conditions and learn how to deal with it. You can't always think like a scientist, you have to think like a shooter and make the shot. I have also had light angles on the target mess with my head because of the impact point, I guess its the way the lenses work, but you have to not always believe something major has changed, you can talk yourself into believing its all screwed up and it really isn't.

 

[Cossack]

You have to count for powder temperature change. Some powders will swing as much as 200 fps from 0 degrees to 100. Heck my 308 with Varget goes from 2,635 on at 60F to 2,690 at 80F and up to around 2,723 fps on a 90 degree day. If you want to get particular with it, get one of those laser thermometers and track muzzle velocity as the ammo temperature changes.
Check out my trajectory cards for 308 and how much temperature effects drop even at close range like 300 yards. Only way I can make it work is if ammo is at the ambient temperature.
Hope this helps.
https://docs.google.com/spreadsheet/ccc?key=0Aq9z_qUBYesSdFZKMEpIbk1VUEZjSlFEaEtFTHJpUEE#gid=11

 

[varmint slayer]

You have to count for powder temperature change. Some powders will swing as much as 200 fps from 0 degrees to 100. Heck my 308 with Varget goes from 2,635 on at 60F to 2,690 at 80F and up to around 2,723 fps on a 90 degree day. If you want to get particular with it, get one of those laser thermometers and track muzzle velocity as the ammo temperature changes.
Check out my trajectory cards for 308 and how much temperature effects drop even at close range like 300 yards. Only way I can make it work is if ammo is at the ambient temperature.
Hope this helps.
https://docs.google.com/spreadsheet/ccc?key=0Aq9z_qUBYesSdFZKMEpIbk1VUEZjSlFEaEtFTHJpUEE#gid=11

Varget swinging almost 100 fps over 30 degrees is not likely at all. Somebody put something close to Varget it a bottle and sold it to you as Varget cause I have never heard of Varget swinging that bad. Hell not even over 30-40 fps from -20-120.

 

[Cossack]

Varget swinging almost 100 fps over 30 degrees is not likely at all. Somebody put something close to Varget it a bottle and sold it to you as Varget cause I have never heard of Varget swinging that bad. Hell not even over 30-40 fps from -20-120.

Two can play this game, so no need for smart ass comments.
Have you chronographed Varget loaded ammo at different powder temps?

 

[varmint slayer]

Two can play this game, so no need for smart ass comments.
Have you chronographed Varget loaded ammo at different powder temps?

Settle down there man....I wasn't trying to be a smart ass. Hard to convey actual demeanor through text.

I don't have to chrono my Varget loads as the POI will tell me if there is a significant change it muzzle velocity. I shot 155 Amaxs from 20°-95° a few winter/summers ago before i ditched the .308 and my dope never changed enough during those different temp changes for me to ever have to change the muzzle velocity in my calculator which can only mean that the muzzle velocity wasn't changing. I took these out to 1K yards to btw. I don't trust chronographs anyway. They are good to get you in the ball park but I have seen them so a ES of 100 fps but on paper at distance there is no signs of that much spread.

 

[Cossack]

Settle down there man....I wasn't trying to be a smart ass. Hard to convey actual demeanor through text.

I don't have to chrono my Varget loads as the POI will tell me if there is a significant change it muzzle velocity. I shot 155 Amaxs from 20°-95° a few winter/summers ago before i ditched the .308 and my dope never changed enough during those different temp changes for me to ever have to change the muzzle velocity in my calculator which can only mean that the muzzle velocity wasn't changing. I took these out to 1K yards to btw. I don't trust chronographs anyway. They are good to get you in the ball park but I have seen them so a ES of 100 fps but on paper at distance there is no signs of that much spread.

I guess I jumped the gun, my bad!
I see your point about chrony not reading out real data, that does make sense. Like you said only way to find out is to find out. One need to keep a very detailed DOPE book and go from that.
When I get more data I'll make a separate post about velocity change due to powder temperature and we can discuss it at length in a new thread.

 

[Aimsmall55]

I guess I jumped the gun, my bad!
I see your point about chrony not reading out real data, that does make sense. Like you said only way to find out is to find out. One need to keep a very detailed DOPE book and go from that.
When I get more data I'll make a separate post about velocity change due to powder temperature and we can discuss it at length in a new thread.

H4350 is about 1.25 to 1.3 fps per degree. 0-100 degrees... That's 125 to 130 fps. That you said your varget is changing that much is totally believable. There's one thing I've learned over the past year.... Hodgdon " extreme" powders are not that extreme....

 

[varmint slayer]

H4350 is about 1.25 to 1.3 fps per degree. 0-100 degrees... That's 125 to 130 fps. That you said your varget is changing that much is totally believable. There's one thing I've learned over the past year.... Hodgdon " extreme" powders are not that extreme....

Seeing 100 FPS over 30° isn't believable according your numbers with any if the Extreme Powders like Varget. Even at 1.3 fps per degree, it only comes out to 39 fps which is a ways from 100 fps.

Hodgdon's extreme line of powders (Varget, anything with H in front and a couple others) are very temp stable. That's their selling point and why so many people use them. You don't have to worry about over pressure as much when shooting in extreme heat or slow rounds in extreme cold. If they failed to do this as badly as 130 fps over 100° then they wouldn't be as popular as people would realize this and word would get around.

 

[Aimsmall55]

Seeing 100 FPS over 30° isn't believable according your numbers with any if the Extreme Powders like Varget. Even at 1.3 fps per degree, it only comes out to 39 fps which is a ways from 100 fps.

Hodgdon's extreme line of powders (Varget, anything with H in front and a couple others) are very temp stable. That's their selling point and why so many people use them. You don't have to worry about over pressure as much when shooting in extreme heat or slow rounds in extreme cold. If they failed to do this as badly as 130 fps over 100° then they wouldn't be as popular as people would realize this and word would get around.

I was referring to a 100 degree change. And yes compared to R22 or other Reloader powders, hell yes they are temp stable. But you should be smart enough to know that every powder has some sensitivity to moisture, temp... Ect. That 130 degree swing from 0 to 130 is hypothetical but my #'s show 1.25 to 1.3 ft/ second per degree. How much that actually changes when there is a 100 degree spread in temp. I hope to never lnow

 

[Cossack]

H4350 is about 1.25 to 1.3 fps per degree. 0-100 degrees... That's 125 to 130 fps. That you said your varget is changing that much is totally believable. There's one thing I've learned over the past year.... Hodgdon " extreme" powders are not that extreme....

Well the velocity swing isn't linear, it's kind of like a hockey stick type of curve. Like I said, right now I'm gathering data that will be compiled in to chart/spreadsheet/write up for everyone to debate over and cherry pick my findings/conclusions.

 

[Aimsmall55]

Seeing 100 FPS over 30° isn't believable according your numbers with any if the Extreme Powders like Varget. Even at 1.3 fps per degree, it only comes out to 39 fps which is a ways from 100 fps.

Hodgdon's extreme line of powders (Varget, anything with H in front and a couple others) are very temp stable. That's their selling point and why so many people use them. You don't have to worry about over pressure as much when shooting in extreme heat or slow rounds in extreme cold. If they failed to do this as badly as 130 fps over 100° then they wouldn't be as popular as people would realize this and word would get around.

I've been thinking about this. You say you shot from 20 to -95 degrees F and never saw a shift in impact at ALL. I'm sorry Slsyer but I'm gonna have to call BULLSHIT..... That is ridiculous. You say a 115 degree change and your dope was constantly the same. The fact that I'll shoot with 25 degree temp changes and see a mil or so difference tells me that there is no way. If you don't mind what was your Altitude , weapon , (bc most rifles won't even operate in temps that low ... Maybe an AIAW. ) , scope and dope at 1k???

 

[varmint slayer]

I've been thinking about this. You say you shot from 20 to -95 degrees F and never saw a shift in impact at ALL. I'm sorry Slsyer but I'm gonna have to call BULLSHIT..... That is ridiculous. You say a 115 degree change and your dope was constantly the same. The fact that I'll shoot with 25 degree temp changes and see a mil or so difference tells me that there is no way. If you don't mind what was your Altitude , weapon , (bc most rifles won't even operate in temps that low ... Maybe an AIAW. ) , scope and dope at 1k???

That's 20° to 90°, not -90° lol. I would agree on bullshit there lol.

 

[Aimsmall55]

Oh my bad

 

[J-ROD]

Weird, i have some test loads saved that i always start with prior to load development to make sure i am good to go as well as my magneto chrono. I've shot varget and h4350 in freezing weather and in the summer, 90+ F in direct sun, i've never seen my avg fps on those rounds change.
Fwiw, while i'm at it, i've got a 5 yr old 1# bottle of varget that chronos exactly the same as a new 8# jug...guess i got lucky.

Are you saying PP2000mr is more stable than varget or h4350?


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[Aimsmall55]

Weird, i have some test loads saved that i always start with prior to load development to make sure i am good to go as well as my magneto chrono. I've shot varget and h4350 in freezing weather and in the summer, 90+ F in direct sun, i've never seen my avg fps on those rounds change.
Fwiw, while i'm at it, i've got a 5 yr old 1# bottle of varget that chronos exactly the same as a new 8# jug...guess i got lucky.

Are you saying PP2000mr is more stable than varget or h4350?


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Not exactly. What I'm saying is that power pro isn't nearly as bad as the Reloader series. But varget and h4350 isn't exactly extreme as people think. That's being said , I did a good bit of testing on power pro 2000 mr and it was a little less than equal to varget in terms of fps/temp. But not that far off ....

 

[Dan Newberry]

I think the most likely cause is the scope needs a good breaking in... I don't think you're dealing with that much velocity variance.

 

[J-ROD]

Good points. Well that has me worried as i have great loads using varget & h4350 as well as 2000mr but have been steering way from it due to temp stability. I can definitely see the pp move with temp but as i said not the hodgdon powders. Now i haven't had a chance to check dope at distance when the weather changes so can only assume my chrono is giving me good numbers.
Do you still use 2000 mr for long range work?
My apologies for taking your thread off course.


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[Skigolfmike]

I was tuning my Kestral AB to my 6 creedmoor this weekend and I saw the same thing. I had shot a couple weeks prior at PNTC and was seeing 3090 as the velocity in ~85* temps using brass on it's first firing. This weekend I was at TVP with all once fired brass and the same load to continue tuning the kestral. On Sat. in cool temps and rain I ended up doing an MV correction to 3030. (67*, ~1K MSL, 80% RH and 29.98") This gave me 7.1 mil to 1K. On Sunday I used that info to calculate my dope for the short course. Afterwards I verified dope to 1K yards. (84*, ~1K MSL 40% RH, 30.12") The calc said 7.0, but the impact was consistant at 6.8. Running the MV callibration gave me 3070. Obviously, temps affected the MV. FWIW, the load is 42.0 gr H4350, Fed 210, Hornaday 6 CM headstamp brass trimmed 1.920", 269 bushing, 105 hybrids @ 2.755" OAL.

I saw this before with my 308 and Varget. (Load 43.5gr, cci 200, Lapua brass trimmed 2.010" Berger 175 OTM seated 2.806" OAL) I used .4fps/* and I got results that were right on from 10* - 95* using AB on my phone.

It appears with the 6 CM it's 40 fps in 17* or 2.3fps/*. Not really sure about that though as on Saturday I was shooting in the rain and I think the cartridges were probably cooler than ambient, so maybe 1.4-1.5fps/degree is a better approximation.

If you dig deep into Hodgdon's data you'll find the Extreme powder still have velocity change with temp changes. It's just not as much as a temp sensitive powder; although, I think they understate the affects. I am am also thinking that lighter bullets may be affected more than heavier ones when it comes to seeing MV change due to temp changes based on what I saw with the 308 vs. the 6 Creedmoor.

There are certainly other affects at work here, such as gear lash in the scope and zero creep could be factors too. I have learned not to get comfortable with my zero and that it needs to be checked now and then.

 

[Aimsmall55]

One thing I should mention is that I have noticed a tipping point where mv falls drastically with h4350. It's right around 30* F. Once it gets that cold, better know your #'s!! Atleast in my case. As far as the scope goes , it's now on my ELR .300 win mag. Have had zero issues with it... Great scope.
I should also mention that the mv swings aren't nearly as noticeable shooting in higher temps , it's the cold that really gets this powder. I don't have my notes, but it think it was 2800 to 2810 fps at 80 to 90* F, then dropped to 2740 to 2730 at around 34*.
I know this isn't the point of the thread , but I thought it would be nice to relay some info. Everything was shot over a V2 or a Ohelor 35p

 

[bruddah]

Run your scope turrets up and down, end to end about 6 dozen times... that'll help burnish in the turrets and improve tracking.

I've also seen scopes that when they're new, the windage will zig-zag on the way up... work the turrets in good, and often things will improve.

Dan

I think the most likely cause is the scope needs a good breaking in... I don't think you're dealing with that much velocity variance.

Are there any scopes in particular you'd recommend this for?

Vortex Rasor?

US Optics???

I bought both of these for long range work due to their reputation for accurate tracking.

 

[ahhshoot]

H4350 is about 1.25 to 1.3 fps per degree. 0-100 degrees... That's 125 to 130 fps. That you said your varget is changing that much is totally believable. There's one thing I've learned over the past year.... Hodgdon " extreme" powders are not that extreme....

Have you tried the IMR4350 yet? Cheaper, more available, and from my experience more accurate in at least 3 guns that I've tried it with.