The Accurate Reloading Forums
Maximum point-blank range for prairie dogs
27 March 2009, 23:55
<slancey>Maximum point-blank range for prairie dogs
I'm shooting a 40 gr hollow point from a 222 Rem. Mag. at 3800 fps this year for prairie dogs. The Sierra manual gives a maximum point blank range for this bullet at this velocity of 290 yards using a zero distance of 250 yards. The notion is that the bullet never goes more than 2.5 inches above or below the line of sight for 290 yards. So at 100 yards it's 2 inches high, at 150 it's 2.5 inches high, at 200 it's 2 inches high, at 250 it's zero, and at 290 it's 2.5 inches low.
Anybody ever use this sight-in? I don't remember using a zero further than 200.
28 March 2009, 00:24
MickinColoYes, use it for every rifle I own. Big game rifles are not as tight as varmint rifles (4 or 6 inches instead of 2.5) but it’s the same idea.
28 March 2009, 00:33
<slancey>So how does it work on the varmint guns? Do you have many shots where you "hold under" for the midrange trajectory?
28 March 2009, 01:30
Roll-CrimpSlancey, when these calculations are performed the size of the target is factored in to provide point blank ranging. It cannot be smaller than the scope centerline to the bore centerline distance, but it can be any size larger. You decide the target size you want the bullet to strike within and the trajectory calculator will determine how far out you can shoot with your sight on dead center and hit within that defined target area. Example: for a deer, you might enter 5" as your PBR target size. An elk might with be large, say 6.5" and would give you a PBR farther out due to the vertical spacing being higher. For a PD, you'll want to stay under 3" and ground squirrel, even less. The advantage is the ability to quickly engage your target if you know it is w/in the PBR distance for your rifle & round w/out cyphering drop ballistics. Your reloading manual uses 2.5" scope height as a generally used distance on hunting rifles. For running vermin the advantage is you only need to focus on windage & lead, and really, all you got to do is tag part of it to slow it down before finishing it off.
Broadside, a fox or yote as a target is much more forgiving target on the horizontal axis (windage) because of the dog's length. The elevation axis is smaller, so using PBR can be a big advantage. PBR works w/ open sights too, and being mounted right on the barrel can PBR very small targets.
The JBM (eskimo) site has a useful ballistic tool that should help you become more familiar with the ballistic track of your rifles
JBM Small Arms Ballistic Calculator28 March 2009, 01:48
Roll-Crimpquote:
Originally posted by slancey:
Anybody ever use this sight-in? I don't remember using a zero further than 200.
Slancey, to sight your rifle, you do not need to find a target 290 yards away and hang paper. Use your regular 100 yard or 200 yard range target placement, aim dead center of target and adjust your sight so that the POI (point of impact) is the number of inches above the bullseye that your ballistic calculator specifies that bullet at that range (100 or 200) should be. You need to know bullet velocity (chrono strings) and BC (most calculators have this data in the form of a built in drop down menu) to give you accurate results.
28 March 2009, 07:03
Shotgun31I sight my .223 and .17 AH to be dead on at 100 yards, and learn the trajectory from that point. I've shot at a few PD's in my time, and with a 2" high at 100 zero I shot over so many of the little devils in any posture other than standing straight up.
I generally use Burris scopes with the trajectory markers. Works for me.
Shotgun
28 March 2009, 09:46
<slancey>I have sighted in for the max PBR, and I was afraid of shooting over too many shorter range dogs. But I'm going to try anyway and see if I can't get the hang of it in the field.
31 March 2009, 08:46
BuliwyfYep, use that concept on all rifles I own except a little Mannlicher I use for dedicated hunting of miniature antelope and calling. It is zeroed at 100 yards dead-aim.
10 April 2009, 08:38
rcamugliaquote:
Originally posted by Roll-Crimp:
Slancey, when these calculations are performed the size of the target is factored in to provide point blank ranging. It cannot be smaller than the scope centerline to the bore centerline distance, but it can be any size larger. You decide the target size you want the bullet to strike within and the trajectory calculator will determine how far out you can shoot with your sight on dead center and hit within that defined target area. Example: for a deer, you might enter 5" as your PBR target size. An elk might with be large, say 6.5" and would give you a PBR farther out due to the vertical spacing being higher. For a PD, you'll want to stay under 3" and ground squirrel, even less. The advantage is the ability to quickly engage your target if you know it is w/in the PBR distance for your rifle & round w/out cyphering drop ballistics. Your reloading manual uses 2.5" scope height as a generally used distance on hunting rifles. For running vermin the advantage is you only need to focus on windage & lead, and really, all you got to do is tag part of it to slow it down before finishing it off.
Broadside, a fox or yote as a target is much more forgiving target on the horizontal axis (windage) because of the dog's length. The elevation axis is smaller, so using PBR can be a big advantage. PBR works w/ open sights too, and being mounted right on the barrel can PBR very small targets.
The JBM (eskimo) site has a useful ballistic tool that should help you become more familiar with the ballistic track of your rifles
JBM Small Arms Ballistic Calculator
Shame on you Roll-Crimp! Suggesting one might need 2 shots to dispatch a varmint!
10 April 2009, 18:45
Roll-Crimpquote:
Originally posted by rcamuglia:
quote:
Originally posted by Roll-Crimp:
Slancey, when these calculations are performed the size of the target is factored in to provide point blank ranging. It cannot be smaller than the scope centerline to the bore centerline distance, but it can be any size larger. You decide the target size you want the bullet to strike within and the trajectory calculator will determine how far out you can shoot with your sight on dead center and hit within that defined target area. Example: for a deer, you might enter 5" as your PBR target size. An elk might with be large, say 6.5" and would give you a PBR farther out due to the vertical spacing being higher. For a PD, you'll want to stay under 3" and ground squirrel, even less. The advantage is the ability to quickly engage your target if you know it is w/in the PBR distance for your rifle & round w/out cyphering drop ballistics. Your reloading manual uses 2.5" scope height as a generally used distance on hunting rifles. For running vermin the advantage is you only need to focus on windage & lead, and really, all you got to do is tag part of it to slow it down before finishing it off.
Broadside, a fox or yote as a target is much more forgiving target on the horizontal axis (windage) because of the dog's length. The elevation axis is smaller, so using PBR can be a big advantage. PBR works w/ open sights too, and being mounted right on the barrel can PBR very small targets.
The JBM (eskimo) site has a useful ballistic tool that should help you become more familiar with the ballistic track of your rifles
JBM Small Arms Ballistic Calculator
Shame on you Roll-Crimp! Suggesting one might need 2 shots to dispatch a varmint!
I'm sooo.... veryyy sorryyyeee. I'm a baad man.
I'll try better at taking more shots.
11 April 2009, 02:57
BuliwyfAbsolutley. For every rifle except a dedicated rifle for minature antelope on safari which is dead-nuts 100 meters.
14 April 2009, 01:05
TEANCUMI would recommend a 1" high at 100 yards with that rifle and then learning and plotting your trajectory out to say 400 yards. That load is fast enough to really shoot a rope at the most common ranges, I think.
It always seems easy to shoot at the head of a standing varmint when it is a long shot than to shoot at the dirt at his feet on a short shot if he is at the mid range curve.
18 May 2009, 07:10
sdgunslingerthe concept is fine , but I think you will find 2.5 inch way to high......1 to maybe 1.5 inch @100 yards is enough....
21 May 2009, 09:30
groundhog devastationI myself prefer the, "Know thy rifle well" method. That means shooting it at the ranges you intend to shoot at stuff with it. There are computer programs that pretty much give you the data but until you pull the trigger on YOUR RIFLE at THOSE RANGES it is at best, a "darn sure close approximation" of reality! GHD
Groundhog Devastation(GHD)
quote:
Originally posted by groundhog devastation:
"Know thy rifle well" GHD
Amen Brother...
Also, 2 1/2" high at 100 yards is exactly 1" too high for me. However, YMMV..
Don
21 May 2009, 19:55
DuggaBoyeUse MPR sighting on my Rifles that I walk/ride with.
My varminters are set up with Mil-Dot scopes now, for quick estimations of range. But in general I use a laser range- finder and the dial in, much more effective than when I used to set them up for 100 zero and " learn" the trajectory.
DuggaBoye-O
NRA-Life
Whittington-Life
TSRA-Life
DRSS
DSC
HSC
SCI
quote:
Originally posted by Roll-Crimp:
Slancey, when these calculations are performed the size of the target is factored in to provide point blank ranging. It cannot be smaller than the scope centerline to the bore centerline distance, but it can be any size larger.
The bore to scope CL distance on my CZ223 is 1.62" but I do my PBR calculations for ground hogs using +/- 3/4" from line of sight. For the 40g Nosler BT as I load it the PBR is 27 yards to 206 yards. The 27 yard number is determined by the bore to scope centerline distance and is the range where the bullet comes up into the 3/4" band. The 206 number is based on bullet ballistics and MV as usual. I've never found the near limit to be an issue, so I'd say use what ever distance from the line of sight suits the target regardless of bore to centerline distance, then just be aware of the short range limit.
Fitch
20 June 2009, 19:12
LHowellquote:
Originally posted by slancey:
I have sighted in for the max PBR, and I was afraid of shooting over too many shorter range dogs. But I'm going to try anyway and see if I can't get the hang of it in the field.
Slancey,
I always use this MPBR method for zero.
Then in the field, with a rangefinder, if the PD's are some under the MPBR zero I aim at their feet if they are much beyond the zero I aim at their heads.
I generally do not shoot much beyond 450yds, though. Just have not needed to!
Les
21 June 2009, 06:30
sscoyoteI also use it--calcd' for 3/4ths target size at the most. It would be more accurately referred to as CMPBR--C=Conservative.
Steve
22 June 2009, 23:18
stillbeeman2" high at 100 yards. The bunch I shoot with, if you shoot at a 100 yard Pdog, they make you walk back to town, and they call you "chip shot" for the rest of the trip.
23 June 2009, 17:10
<slancey>Just back from a South Dakota prairie dog shoot using the MPBR method. Actually, it was a little more frustrating than I expected. We were shooting over a lot of dogs in the intermediate ranges. The "hold under" factor was too great. I was not using a rangefinder, so that made it more challenging. I'll likely go back to the 200 yard zero and just hold over for the longer ones. Probably add a rangefinder as well.