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Special Interests - Groups & Societies => The Barracks => Topic started by: Guns Garrett on August 12, 2019, 07:22:56 am

Title: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: Guns Garrett on August 12, 2019, 07:22:56 am
I have an 1884 Springfield rifle, that I used at this past Muster, and I am very pleased with it.  Using standard .45-70-405 Government load, it  shoots "dead on" at 200 yds ("on steel", anyway) by aiming center mass, and hits consistently at 100 yds aiming at the base of the B27 steel silhouette. Both ranges shot with the Buffington sight folded down ("battle sight").  During the Main Match, I had only a couple of misses with the rifle, and believe I shot two stages clean on the rifle targets.   I ran into trouble on the 300 yd long range.  I used my Buffington sight standing up, with the slide set for that range, and didn't get any hits for 9 shots, and those spotting really couldn't tell where I was hitting.

I have only a 100-yrd range available to me locally, and was considering using a large butcher-paper backing for my target, and attempting to shoot at 100 yds (aiming at the base of the B27 target) using sight settings for 300...I should print hits about 24"  centered above center mass, or about 34-35" above point of aim, shouldn't I?   Once I get in the ball park, I can travel 100 miles or so to a known-distance range to tweak it.  This makes my head hurt...
Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: Ranch 13 on August 12, 2019, 08:37:40 am
Most of the Buffington sights I've been around will print dead on to the markings of the sights when shooting a 405 gr bullet at 1300+- fps. You may want to chronograph your loads to see what the velocity is.
Second place to start would be what sort of groups is your load giving at 100? If they are not 3 minutes or less, the chances of hitting much at 300 grows slim.
 Next time when you get into a situation where spotters can't see where the misses are going, lower the sights to get low hits in front of the target and walk them up to the target.


Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: Drydock on August 12, 2019, 09:07:41 am
The other thing to note here is that the Buffington sight is calibrated for the .45-70-500 load. That is a 500 grain roundnose at just over 1300 fps.  The lighter bullet load will shoot under the sight settings.  IE it will print lower on the target than the 500 grain loads.  I believe you were indeed going low, and the soft ground (lots of recent rain) hid the impacts.
Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: Drydock on August 12, 2019, 09:15:33 am
https://www.trackofthewolf.com/Categories/PartDetail.aspx/225/1/BOOK-SPG

Lots of useful bullet drop data in this book.
Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: Niederlander on August 12, 2019, 09:38:38 am
The other thing to note here is that the Buffington sight is calibrated for the .45-70-500 load. That is a 500 grain roundnose at just over 1300 fps.  The lighter bullet load will shoot under the sight settings.  IE it will print lower on the target than the 500 grain loads.  I believe you were indeed going low, and the soft ground (lots of recent rain) hid the impacts.
Yep.  We were having a heck of a time seeing the bullet strikes due to how soft it was.
Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: Guns Garrett on August 13, 2019, 11:12:07 am
Thanks, guys.  I had forgotten the Buff sight was graduated for the later 500gr bullet.
Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: cpt dan blodgett on August 13, 2019, 11:32:19 am
you can use trig to figure out how many inches a .001 change in the sight makes at 100 yards and use a dial or digital calculator to measure you sight changes. They used to have a site micrometer to shoot matches like creedmore. 
A chronograph and knowing the BC of your bullet you can use any ballistic calculator to figure the inches you need to come up from 100 to 300 yards
Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: Sagebrush Burns on August 13, 2019, 10:40:53 pm
Hornady's web site has a ballistic calculator which I have found very useful for this type of problem.  If you know your muzzle velocity, bullet weight, and ballistic coefficient (a reasonable approximation works), it will give you usable drop figures for various ranges at 50 yard intervals.  If you input a given zero range, it will tell you where to zero at 100 yards.  All of this sort of thing must, of course, be confirmed by actually shooting at the various distances, but this info will get you "in the ball Park".  I have used it successfully with many different calibers and loads.
Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: ira scott on August 13, 2019, 10:46:33 pm
"Sage" advice Andy!
Title: Re: Sighting .45-70 for 300 yds on 100-yd Range?
Post by: Dutch Al on August 18, 2019, 11:03:36 am
I ran a calculation for a 420 grain bullet, at 1200 ft/sec.  The ballistic coefficient for the 420 is quite similar to the 405 grain bullet.  With a 100 yd zero, the bullet drops 27 inches at 200 yards, 90 inches at 300 yards.  If you use a come up of 30 minutes of angle, that will give you a 300 yard zero, 33 inches high at 200, and 30 inches high at 100.  Hopefully these figures will get you on paper at 300.  Good luck.

Can you just imagine, what soldiers who had used the 45-70, thought when introduced to the Krag.  They must have been amazed by how flat that rifle would shoot.