B.D.C. reticles and 1st and 2nd focal plane

[med358-boise]

Is this independent of your zero point reference? i.e. 100 yd zero?

Yes, because MOA subtensions in a BDC type reticle are relative to the main crosshair. Assume you have a 4-12 scope that is set on 12x and you zero the main crosshair @ 100 yards. Your first stadia mark is 2 MOA below 100 if you adjust to 6x it is now 4 MOA below 100. Likewise, if your main crosshair is zeroed at 200, then the first stadia mark will be for 2 MOA below 200 and when you adjust from 12x to 6x the first stadia mark will be 4 MOA below 200.

 

[Stonyman88]

Only issue with a BDC reticle will be matching your rifle and ammo to what they are set at... so at any distance they aren't worth a darn. Better to dial, or train yourself to use a greatvreticle like Horus 59, Tremor 3 or 5, etc. I stopped using BDC's and trained myself to learn my DOPE. Then it doesn't matter what power my scope is, I just dial and blast away. Or you take the next step and you use a "Christmas Tree Reticle" which I prefer, and just use hold overs.

Boy do I ever agree with you, so easy to zero yours at 100 yds. then shoot at the distance's you want, measure the drop and you can figure out how many clicks on your dial you'll need, absolutely the best way to shoot. You then can dial or just use the mil marks on the reticle so simple and never use the wrong **** BDC circle, an who knows what grain your shooting !

 

[med358-boise]

Trajectories for even moderate velocity cartridges like a 308 Win shooting a168 grain bullet with an ~.450 BC are very linear within 100 yard increments all the way out to 800 yards. In other words the trajectory arc between 700 & 800 doesn't vary much more than .25 MOA from a straight line meaning less than 1 click of difference. What's the so what? If I have a BDC reticle with marks out to 600 yards and my animal is at 550, I simply bracket the vitals between the 500 & 600 yard hash. At 525, use the 500 and hold 3/4 up the body, at 575 us the 600 and hold slightly into belly.

Some folks would say that is complicated, others word say they if you have to calculate 29 clicks and then the animal moves 40 yards further you can become so dependent on recalculating and reclicking you lose focus and may lost the shot opportunity.

It is really personal preference.

 

[Palix-Dog]

The Buris Connect app has reticle analysis under the ballistics section. You put in all of the relevant specs, choose a scope modle from their list and you can change the power. It will show the change of dead on bullseye yardage for each hashmark.

 

[hawlejr]

To put a finer point on this, neither scope loses accuracy but the correct zero yardages change on a second focal plane scope for the stadia marks or dots but not for the main crosshair.

Most scope companies, such as Leupold, Bushnell, and Sightron will provide you the relevant MOA subtension values for some or all of the power settings. However, the relationship for the change in the MOA subtension value is constant and works in an inverse manner; i.e., as the power setting goes down, the MOA value goes up. For example if, the scope is a 4-12 with a stadia mark every 2 MOA when set at 12 power; then those 2 MOA stadia marks become 3 MOA at 8 power and 6 MOA marks at 4 power because 12 is 1.5 greater than 8 and 3 times greater than 4. So the formula is divide high power setting by the low power setting and use that numeric value to multiply the "baseline MOA" value.

Good response. The center of the cross hair stays on point at the "sighted in" range. Some of the posts had this a little confused. Using the stadia marks on SFP scopes requires some thought because at lower power the marks will represent more bullet drop in proportion to the max power divided by the lowered power of the scope. I shoot enough SFP at various ranges to apply the ratios. Once you have this down, you can utilize the SFP advantage of not having the reticle blow up too large at high power or virtually disappear at low power. Just realize which one you're using and practice, practice, practice.

 

[med358-boise]

Boy do I ever agree with you, so easy to zero yours at 100 yds. then shoot at the distance's you want, measure the drop and you can figure out how many clicks on your dial you'll need, absolutely the best way to shoot. You then can dial or just use the mil marks on the reticle so simple and never use the wrong **** BDC circle, an who knows what grain your shooting !

For me its the exact opposite, I don't have to put a 1.5 lb scope on my rifle to get a scope that has accurate clicks and I don't have to validate that the clicks are accurate all the way out 50 or 60 clicks. Consider if my clicks are 85% accurate at 45 clicks, I am 7 clicks off.

I have lots of BDCs reticles. I fire a few test rounds and true my BC. I always want my first hash to be true at 300 yards so I adjust my zero which normally turns out to a be a zero between 200 & 225 and I don't care about being at inch high at 200, I want that first hash zeroed at 300. I build a drop chart for my stock out to 600 and I am done. Never have to worry if my scope dial system got out of calibration, did I turn my dial back to zero when I thought I had a long shot but it didn't work out and up pops an animal at 100 and I have a narrow time opportunity.

I am probably not the norm but I tell lots of friends if you're never shooting past 750, consider a BDC style reticle with drop marks out to 20 MOA an windage to 10 MOA. Might be easier for you.

 

[SSG Graybush]

Trajectories for even moderate velocity cartridges like a 308 Win shooting a168 grain bullet with an ~.450 BC are very linear within 100 yard increments all the way out to 800 yards. In other words the trajectory arc between 700 & 800 doesn't vary much more than .25 MOA from a straight line meaning less than 1 click of difference. What's the so what? If I have a BDC reticle with marks out to 600 yards and my animal is at 550, I simply bracket the vitals between the 500 & 600 yard hash. At 525, use the 500 and hold 3/4 up the body, at 575 us the 600 and hold slightly into belly.

Some folks would say that is complicated, others word say they if you have to calculate 29 clicks and then the animal moves 40 yards further you can become so dependent on recalculating and reclicking you lose focus and may lost the shot opportunity.

It is really then I guess it's personal preference.

No the difference between 700 and 800 is ~22 moa, or ~1.5 mils, or ~ 43 inches with a 308 168 gr smk starting at 2775 fps. Not even close to .25 moa difference, If close is good enough, then yeah, it's a personal preference.
In the field hunting longer then 200-250 yards(depending on wind), I range and check wind, check dope card taped to scope, dail up elevation, and hold for wind using reticle.
We are hunter's, close is not ethical imo.

 

[southpa]

I only use Second Focal Plane scopes because I zero my scopes at 200 yards and know the drop at 300yds and beyond that I only use a laser range finder and turn the dials. I know that there are specific applications where only a First Focal Plane scope is useful but for hunting I've never understood the whole need for FFP.

I get the whole chest size thing but to me that's pretty inaccurate and I'm not about "good enough" in ranging game. I want to know precisely how far game is from me if it's far enough that bullet drop can become an issue.

I owned a FFP NX8 4-32 scope and found it useless at low power because the reticle nearly disappeared and I couldn't imagine it working for me in a low light situation or one where a quick up close shot would be needed but I'm primarily a hunter and will never compete.

You say you understand there are applications where ffp scopes are useful hunting but then you say you don't understand the need for it...
I don't care for 2fp. I understand the uses for each and prefer the benefits of ffp over 2fp for those reasons. You do have a point about the reticle being hard to see at low powers but I too am I hunter. This is a long range hunting forum so be that as it is, I don't have issues with ffp scope reticles in long range applications.
The subtentions are accurate throughout the ENTIRE magnification range in a ffp. That isn't true for 2fp. This is beneficial to me because if I need to make a quick shot it literally allows me to take one step out of the equation by not having to dial OR come off target to make sure my 2fp scope is on the correct magnification to make a shot. Now, the center is always the center so if you dial it makes no difference but sometimes in a quick situation a spotter will range, make a call and I can literally just make a shot with no worries about magnification or dialing etc...or how bout varmints....I certainly can see the benefit of accurate subtentions throughout the magnification range when your ranging, calling wind and shooting varmints that are in and out of holes, anywhere from 50-1000 yards....

 

[ElwoodBlues]

For me, primarily a short range hunter... I want my 300 PRC to be ready for Elk and Colorado, but I also want to use it for whitetail in Missouri. When hunting close range, a FFP would make the reticle extremely small and against a dark background 10 minutes before end of legal hunt, I would not be able to see the reticle at all.

So a SFP allows me to use a 5-25 scope at 5x at close range and know my MBPR is 205 yards at 2"... and past that I can compute yardard and holdover. The SFP 5.25 is *just* for me. The short range hunter that will stretch it out at some point.

 

[SSG Graybush]

For me, primarily a short range hunter... I want my 300 PRC to be ready for Elk and Colorado, but I also want to use it for whitetail in Missouri. When hunting close range, a FFP would make the reticle extremely small and against a dark background 10 minutes before end of legal hunt, I would not be able to see the reticle at all.

So a SFP allows me to use a 5-25 scope at 5x at close range and know my MBPR is 205 yards at 2"... and past that I can compute yardard and holdover. The SFP 5.25 is *just* for me. The short range hunter that will stretch it out at some point.

that's what illumination is for

 

[med358-boise]

No the difference between 700 and 800 is ~22 moa, or ~1.5 mils, or ~ 43 inches with a 308 168 gr smk starting at 2775 fps. Not even close to .25 moa difference, If close is good enough, then yeah, it's a personal preference.
In the field hunting longer then 200-250 yards(depending on wind), I range and check wind, check dope card taped to scope, dail up elevation, and hold for wind using reticle.
We are hunter's, close is not ethical imo.

Sarge,

I am not sure how you interpreted what I wrote but to be clear I am referring only to the trajectory between 100 yard increments; e.g.,100 to 200, 200 to 300 etc. Since 700 & 800 is obviously the greatest curve lets look at the actual calculations, I regularly shoot the Barnes 168 TTSX around 2725 fps a pretty modest cartridge with a G7 of .222. I zero at 215 yards because that's what works for my BDC reticle. Here are the calcs.
Drop at 700 = 124.7" or 17 MOA Drop at 800 184.6" or 22 MOA. Drop between 700 and 800 59.9" and 5 MOA.

What does the straight line/linear drop equal between those two points on the trajectory in 5 yard increments, it's .25 MOA and 3 inches per 5 yards, the totals divided by 20 since there are twenty 5 yard increments in 100 yards. So let's compare that "straight line" or "linear trajectory" to the actual trajectory. You will see at no point does it exceed two inches or .1 MOA which is less than a single click.

Yardage	Actual Drop Inches per JBM	Actual Drop MOA per JBM	Linear Drop Inches 2.995 per 5 yards	Linear Drop MOA .25 MOA per 5 yards	Deviation Between Actual & Linear Inches	Deviation Between Actual & Linear MOA
700	124.7​	17​
705	127.4​	17.3​	127.695	17.25	0.295	1
710	130​	17.5​	130.69	17.5	0.69	0
715	132.7​	17.7​	133.685	17.75	0.985	0.05
720	135.5​	18​	136.68	18	1.18	0
725	138.3​	18.2​	139.675	18.25	1.375	0.05
730	141.1​	18.5​	142.67	18.5	1.57	0
735	143.9​	18.7​	145.665	18.75	1.765	0.05
740	146.8​	18.9​	148.66	19	1.86	0.1
745	149.7​	19.2​	151.655	19.25	1.955	0.05
750	152.7​	19.4​	154.65	19.5	1.95	0.1
755	155.7​	19.7​	157.645	19.75	1.945	0.05
760	158.8​	19.9​	160.64	20	1.84	0.1
765	161.8​	20.2​	163.635	20.25	1.835	0.05
770	165​	20.5​	166.63	20.5	1.63	0
775	168.1​	20.7​	169.625	20.75	1.525	0.05
780	171.3​	21​	172.62	21	1.32	0
785	174.6​	21.2​	175.615	21.25	1.015	0.05
790	177.9​	21.5​	178.61	21.5	0.71	0
795	181.2​	21.8​	181.605	21.75	0.405	-0.05
800	184.6​	22​	184.6	22	0	0

 

[SSG Graybush]

Sarge,

I am not sure how you interpreted what I wrote but to be clear I am referring only to the trajectory between 100 yard increments; e.g.,100 to 200, 200 to 300 etc. Since 700 & 800 is obviously the greatest curve lets look at the actual calculations, I regularly shoot the Barnes 168 TTSX around 2725 fps a pretty modest cartridge with a G7 of .222. Here are the calcs.
Drop at 700 = 124.7" or 17 MOA Drop at 800 184.6" or 22 MOA. Drop between the two 59.9" and 5 MOA

What does the straight line/linear drop equal between those two points on the trajectory in 5 yard increments, it's .25 MOA and 3 inches per 5 yards, totals divided by 20 since there are 20 5 yard increments in 100 yards. So let's compare that linear "trajectory" to the actual trajectory. You will see at no point does it exceed two inches or .1 MOA which is less than a single click.

Yardage	Actual Drop Inches per JBM	Actual Drop MOA per JBM	Linear Drop Inches 2.995 per 5 yards	Linear Drop MOA .25 MOA per 5 yards	Deviation Between Actual & Linear Inches	Deviation Between Actual & Linear MOA
700	124.7​	17​
705	127.4​	17.3​	127.695	17.25	0.295	1
710	130​	17.5​	130.69	17.5	0.69	0
715	132.7​	17.7​	133.685	17.75	0.985	0.05
720	135.5​	18​	136.68	18	1.18	0
725	138.3​	18.2​	139.675	18.25	1.375	0.05
730	141.1​	18.5​	142.67	18.5	1.57	0
735	143.9​	18.7​	145.665	18.75	1.765	0.05
740	146.8​	18.9​	148.66	19	1.86	0.1
745	149.7​	19.2​	151.655	19.25	1.955	0.05
750	152.7​	19.4​	154.65	19.5	1.95	0.1
755	155.7​	19.7​	157.645	19.75	1.945	0.05
760	158.8​	19.9​	160.64	20	1.84	0.1
765	161.8​	20.2​	163.635	20.25	1.835	0.05
770	165​	20.5​	166.63	20.5	1.63	0
775	168.1​	20.7​	169.625	20.75	1.525	0.05
780	171.3​	21​	172.62	21	1.32	0
785	174.6​	21.2​	175.615	21.25	1.015	0.05
790	177.9​	21.5​	178.61	21.5	0.71	0
795	181.2​	21.8​	181.605	21.75	0.405	-0.05
800	184.6​	22​	184.6	22	0	0

First off a sarge is a scum sucking fish at the bottom of the ocean leg. lol But seriously, I don't see any advantages to knowing drop in linear increments. All that matters is bdc's are not good at long ranges, imo they are useless, they are not accurate, not repeatable. Unless your luckily enough run across game at the exact range of a holdover. And then what about wind?
Anchors are all bdc scopes are good for and then not really. IMO a person is better off learning to do it correctly with a ffp mil scope.

 

[Crockett12]

I get the whole chest size thing but to me that's pretty inaccurate and I'm not about "good enough" in ranging game.

I had one of the original Redfield Accu-range scopes that had 2 horizontal wires for estimating range based on the depth of chest! It was way back in the late 70's and I think it was a 4x12. Not only are chest sizes different on different ages of game animals but also on different deer/elk of the same age/sex etc. However, having used that scope to try to estimate distance on numerous game animals from deer to elk, it was difficult to hold steady enough as well as judge where to hold -- and the thickness of the wires were an issue to know how to hold on an animal at a great distance! I remember trying to judge several bull elk at a very long distance and depending on where I held the wires and how steady my hold, I could get anywhere from 700 to 800 yards! It was a ball park estimate at best and certainty not very accurate!

 

[med358-boise]

First off a sarge is a scum sucking fish at the bottom of the ocean leg. lol But seriously, I don't see any advantages to knowing drop in linear increments. All that matters is bdc's are not good at long ranges, imo they are useless, they are not accurate, not repeatable. Unless your luckily enough run across game at the exact range of a holdover. And then what about wind?
Anchors are all bdc scopes are good for and then not really. IMO a person is better off learning to do it correctly with a ffp mil scope.

well, I am glad we got the scum sucking fish part straight... Now on a more serious note (which is really hard for me to be) it's not about knowing drop in linear increments it's about knowing the linear increments are going to be very close to the real trajectory. So if I run across an animal that is close to 1/4 or 1/2 or 3/4 of the way between known "BDC points or Stadias" I can split differences or hold a touch high and be very **** close even out between 700 and 800 yards and less than that if I am even closer. With respect to wind, I find 2 MOA wind hashes work great for me.

But I am an old guy and can't remember what I had for breakfast this morning plus I could pass out between trigger break and impact on 1000 yard shot.

BTW, thank you for your service to this great nation. My nephew just made SSG in the Army.