Dope doesn't match up with muzzle velocity cz 455 pt

[EKIM1428]

I'm thinking its a cheapo scope problem but it is a predictable problem. I'm shooting wolf match target at 1072 fps through the chrony. The scope is a hawke sidewinder 30 mil/moa. The elevation for 100 should be 7.5 moa but is actually 5.25 moa (50 yard zero) the dope for 200 is 26 and change moa but is actually 22 moa. This suggests that my MV is around 1200 which I know is not according to the chrony on the same day. I verified that all atmospheric data and ammo temp is correct. I set my BC to 1.3 as suggested by everyone. Conditions are sea level, 29.68 pressure, 75 degrees ammo temp and air temp. 76% humidity.

What gives? This is verified on Strelok and Ballistic AE along with my own dope cards. Right now I have the MV in the calculators set to match the hits now but it's still off at different distances. Maybe I'm way off on the BC? What is your dope for these ranges? For you Mil guys, that is 1.5 mills at 100, 6.1 mills at 200 to hit and suggested is 2 mills at 100 and 7 mills at 200. It gets much worse further out.

I know it's not a big miss but it's driving me nuts trying to figure this out or at least find a pattern to get the dope cards dialed in.

 

[Va_Gentleman]

In my humble opinion, the .22lr bullet is the hardest to dope against calculators and with changing atmospheric conditions... primarily due to a lack of firm or stated Ballistic Coefficient. My thoughts only... certainly not expert.

 

[EKIM1428]

I can definitely agree with that^ I never had to chase my 308 around like this

 

[Biggerhammer50]

Your BC is way off. You need to be about .134 instead of 1.3 I think your decimal is in the wrong spot. It would really nice to have a .22lr bullet with a BC of 1.3.

"ΜΟΛΩΝ ΛΑΒΕ"

 

[bunsen27]

The issue isn't the ammo or scope, but the ballistic application used to calculate the DOPE. I'm not a ballistician, nor did I stay at a Holiday Inn express last night, but the ballistic mathematical model used to calculate centerfire trajectory (G1 or G7) does not handle 22LR very well (ball park at best). I believe there was an online application for calculating air rifle trajectory that worked quite well for 22LR as the projectiles are closer than 22LR to centerfire. I've shot enough 22LR at distances in excess of 100yds to know that trajectory will significantly depend on current conditions, especially headwinds and tailwinds. Empirical data (Data Of Previous Engagement) is the better choice and the data of 6.5MOA @100yds and 22MOA @200yds from a 50yd zero is spot on in my experience. Last Conover TSC I shot we had a fairly consistent headwind that increased my previous matches DOPE by 1.5-2.5MOA dependent on wind speed and distance.

LR rimfire shooting is much more art then science. You need more of a Zen be the bullet approach than the I'm going to measure and account for every variable, build a mathematical model, then calculate the results. This is from the guy who gets paid to do science for a living.

 

[Defusion]

Are you holding or dialing?
If dialing, did you verify your clicks at a single range?

If you checked it, you need to calibrate your ballistic solver to your real-world data.

 

[melloyello]

As stated above, your BC should be more like .13
At 1220fps my dope is verified 5.8" @100yds and 22.6" @200yds (my zero is also 50yds)
First thing is that you can't rely solely on what a ballistics calculator spits out. You have to ensure your zero and then shoot at known distances and record your dial up and conditions. Then you can true up the ballistics calculator to match what is actually happening. DOPE is what you have observed to be correct for the conditions you have actually shot in not what a calculator tells you it should be.

 

[MPrimo]

I shoot Federal GM Match in my 455 PT and I am exactly 20 clicks up from 50 to 100 yards. That puts me at 5 MOA (like you) so you can use that as a reference. Calculated DOPE is just a reference IMO. Have fun getting it to shoot where you want it ... that's part of the enjoyment for me.

 

[EKIM1428]

Biggerhammer50
Your BC is way off. You need to be about .134 instead of 1.3 I think your decimal is in the wrong spot. It would really nice to have a .22lr bullet with a BC of 1.3.

Sorry I have it set at .13 1.3 was a typo


bunsen27
The issue isn't the ammo or scope, but the ballistic application used to calculate the DOPE. I'm not a ballistician, nor did I stay at a Holiday Inn express last night, but the ballistic mathematical model used to calculate centerfire trajectory (G1 or G7) does not handle 22LR very well (ball park at best). I believe there was an online application for calculating air rifle trajectory that worked quite well for 22LR as the projectiles are closer than 22LR to centerfire. I've shot enough 22LR at distances in excess of 100yds to know that trajectory will significantly depend on current conditions, especially headwinds and tailwinds. Empirical data (Data Of Previous Engagement) is the better choice and the data of 6.5MOA @100yds and 22MOA @200yds from a 50yd zero is spot on in my experience. Last Conover TSC I shot we had a fairly consistent headwind that increased my previous matches DOPE by 1.5-2.5MOA dependent on wind speed and distance.

I think that's what's driving me up the wall here. I can't seem to figure out a mathematical solution to this that fits in every scenario. If for example the calculations were off by 10% elevation at all points suggested by the calculators, I could easily correct for that and make it predictable. The deviation in elevation at different ranges is not linear which means all kinds of trig problems beyond what I am comfortable with. I'll give chairgun a try (the air gun ballistic calculator)


DFOOSKING
I use Shooter....same as for my centerfire.

Although its not perfect...it doesn't need to be. Your supposed to use the initial card as a guideline not a crutch.

I run .125 (for all my .22 rimfires) for a B.C. and enter the weight and hypothetical speed in fps.

I then zero and shoot 100yds and 200yds using the "flawed" card and note actual versus stated drop.

I use shooter calibration tool to correct it somewhat and then write down a full card (I shoot out to 250yds-ish). You can kinda do this using JBM by modifying the MV and re-running the data if spending money on a calculator is a no-go.

Then I shoot the distances in between at my leisure and note any huge discrepancies. Usually there is not.

Failing at getting accurate hits out to 200yds (given the accuracy expectation of rimfire) is usually a myriad of issues.

And unlike Bunsen, as of right now...I don't get paid to do anything.



I understand that calculators are for ball park numbers, I have strelok and ballistic AE which both give me the same answer with the g1 drag model. The problem is I can't seem to adjust them to spit out reliable data (even with the calibration feature) at ranges not in the data book already which wasn't a problem for me before shooting center fire. I'm thinking of just doing what you suggest and setting up a ton of targets in 10 yard increments and making a real life range card and leave the calculators to my center fires. I try to learn the math behind the calculators but I can't seem to get a handle on this one. I guess it's just my goofy way of teaching myself for those times I just know the calculator's suggested elevation can't be right.

 

[EKIM1428]

Defusion: I am dialing elevation most times and holding wind every time. Calibration gets me alot closer but I'm still a little off depending on the range. I think I need more field data to see if I can't get it dialed in perfectly.

Melloyello and MPrimo. At least I know my dope in the field is right and my scope isn't the issue here. Maybe I'm just over thinking this. I have a data book for it with ranges from 50-100-150-200. I'm just trying to figure out a pattern or equation so I can accurately predict a shot at say 265 yards without ever actually shooting and recording it previously. Nothing is better than the feeling of those first round hits. Cold bore first round hits are the next piece of data after I get this dialed in. These pea shooters sure are addicting though.

 

[EKIM1428]

I think that might be part of my problem Dfoosking. While I don't expect any dimes at any range past 50 or even less than that, The rifle is capable of minute and a half on average at 100. 2 minutes at 200 etc. With me shooting. Sub minute groups passed 100 are not the norm despite what the internet commandos have been telling me lol. However my current calculations equate to a miss over the top on a 5 inch gong at 200 and a miss on a 3 inch target at 100. Once I correct the elevation, I can make hits all day at that range on those targets.

The point of my post here is just one of the steps in collecting data to make the hits. I need to beat it into my head that it's a rimfire with the bc of a brick and results change much more than I expect. That and collect as much field data and experience as I can to become more confident in the rife and myself. I never stop working on improvement, I just got hung up on making an accurate range card and wanted some help from more experienced shooters.

I plan on shooting more of the local rimfire matches and need to start preparing so I can be competitive. I don't expect to win, but I want to go home knowing I did the best to my ability.

 

[MPrimo]

These pea shooters sure are addicting though.[/QUOTE]

I could not agree more! I grab the 22 way more than the center fires when I head to the range!

 

[armorpl8chikn]

I think it has been said already more than once. Shoot all conditions and record your data, all data. The only thing your dope card should contain is OBSERVED data, it is the only thing I have ever found that mattered to a rimfire. Write it down.

The guys that shoot TSC have a wealth of data available during a year of matches. The ones who write it down end up ahead of the curve most months.

 

[RTH1800]

I have been writing data for years and occasionally consolidate it and carry it over. At some point the picture becomes clear. The mysteries are no longer mysterious, as the data predicts events prior to occurrence. I am going to do some testing this summer shooting up and down very steep hills. I have read many post that indicate shooting up into trees at squirrels changes POI to the degree that misses result. I have shot thousands of squirrels and not encountered a problem. In the last few years I shve switched to target velocity ammo. Still no problems, but I want to check data, and get it in the book.

 

[EKIM1428]

Luckily my local rimfire comps rarely exceed 200 yards so it shouldn't be an issue collecting all the data I need to remain competitive in different conditions. I ordered up a couple more data books from impact to start fresh. Thanks for the insight guys.

 

[citation04]

you also need to go get your hands on an accurate rolling tape measure and walk out 100 m one day with a largee board drawn out with the approptiately spaced mil dots or drops or whatever and then very carefully walk through your adjustments.

Scopes are very often not calibrated perfectly and its somethign that not enough people seem to realize.

but ya in all likelihood, .22 is just a bitch to dope