45-70 velocity/POI question

ckpj99 · October 27, 2014, 06:02 PM

So I have a quick, but sort of complex question about the 45-70 round running at "trapdoor safe" speeds.

I recently purchased a Springfield Model 1884 trapdoor in 45-70. It has a Buffington rear sight AND an addition peep tang sight (so I can pretend I'm Quigley). It also has a modern globe front sight that can take a variety of inserts.

I took it out to shoot it today using Ultramax 405gr lead loads with an advertised velocity of 1050 fps. I was able to get the Buffington sight working well, but the peep tang sight was troublesome. I bottomed it out (putting it at its lowest setting) and the gun was still printing very high, possibly 8-10" at 50 yards. The only reason I was shooting this ammo was to get the brass and have some fun. I plan to start reloading immediately for it.

So here's my question. If my reloads run faster than 1050 fps, which seems likely (the lowest ranges of the powders I plan to use push the bullet at about 1200 fps), will my point of impact be higher or lower?

Now I know what some of you are thinking. In a rifle, faster rounds print higher. I've experienced this with my 30-30. I do ladder tests and the more powder I add to a given bullet, the higher the round prints.

However, at these slow speeds with an extremely long barrel by today's standards, I'm wondering if the gun will behave more like a handgun. The faster the bullet gets out of the barrel, the less the barrel has risen due to recoil and therefore the lower the point of impact.

**Please note, I understand that peep tang sights are built for 50 yard shooting, and bullet drop will make the functional at longer ranges, blah, blah, blah.**

So will a 405gr 45-70 round traveling at 1200 fps out of a 32" barrel impact higher or lower at 50 yards than the same round traveling at 1050 fps?

ckpj99 · October 27, 2014, 06:04 PM

Oh, and in case you were wondering how the gun shoots in general, here are a couple targets from today's shoot.

For this target I was benched, and I had to hold off a little to the left a little because my windage was slightly off and I didn't want to putz with it at the range. I was using the Buffington rear sight for these, and my windage adjustment is very sticky.

About a 1.5" group center to center, which I think is pretty good for factory ammo from a brand not known for its precision.

This next target was also shot at 50 yards, but I was standing, unsupported. For this, just keeping the extremely heavy gun up was hard enough, so I just *tried* to hold right on the target, which is why the shots are further off the right.

This group is about 2.25 inch.

NoSecondBest · October 27, 2014, 07:17 PM

Just get a taller front sight. You need to be able to have some leeway for up and down regardless of the load used. Pick your favorite front sight and call the manufacturer and tell them where your bullet is impacting at 100yds and they can advise you on what height to get to have it hit a little low so you can use the rear sight to bring it into the POI you're looking for. Never alter a load to compensate for a sight problem if the load shoots well. FYI, there isn't that much difference between POI with 1050 and 1200. Almost all of my loads have some leeway and I shoot just about everything between 1100 and 1500fps.

Snyper · October 27, 2014, 07:51 PM

Quote:

So here's my question. If my reloads run faster than 1050 fps, which seems likely (the lowest ranges of the powders I plan to use push the bullet at about 1200 fps), will my point of impact be higher or lower?

A faster load will generally print lower due to leaving the barrel sooner, allowing less time for recoil to raise the barrel

Doyle · October 27, 2014, 09:13 PM

Quote:

A faster load will generally print lower due to leaving the barrel sooner, allowing less time for recoil to raise the barrel

True for short ranges. However, at distance the faster bullet prints higher due to having less time for gravity to act on it. The break-even point varies way too much for this simple mind to even think about calculating.

Snyper · October 28, 2014, 06:25 PM

Quote:

True for short ranges.

From the OP:

Quote:

I bottomed it out (putting it at its lowest setting) and the gun was still printing very high, possibly 8-10" at 50 yards

October 27, 2014, 06:02 PM	#1
ckpj99 Senior Member Join Date: January 25, 2011 Posts: 386	45-70 velocity/POI question So I have a quick, but sort of complex question about the 45-70 round running at "trapdoor safe" speeds. I recently purchased a Springfield Model 1884 trapdoor in 45-70. It has a Buffington rear sight AND an addition peep tang sight (so I can pretend I'm Quigley). It also has a modern globe front sight that can take a variety of inserts. I took it out to shoot it today using Ultramax 405gr lead loads with an advertised velocity of 1050 fps. I was able to get the Buffington sight working well, but the peep tang sight was troublesome. I bottomed it out (putting it at its lowest setting) and the gun was still printing very high, possibly 8-10" at 50 yards. The only reason I was shooting this ammo was to get the brass and have some fun. I plan to start reloading immediately for it. So here's my question. If my reloads run faster than 1050 fps, which seems likely (the lowest ranges of the powders I plan to use push the bullet at about 1200 fps), will my point of impact be higher or lower? Now I know what some of you are thinking. In a rifle, faster rounds print higher. I've experienced this with my 30-30. I do ladder tests and the more powder I add to a given bullet, the higher the round prints. However, at these slow speeds with an extremely long barrel by today's standards, I'm wondering if the gun will behave more like a handgun. The faster the bullet gets out of the barrel, the less the barrel has risen due to recoil and therefore the lower the point of impact. Please note, I understand that peep tang sights are built for 50 yard shooting, and bullet drop will make the functional at longer ranges, blah, blah, blah. So will a 405gr 45-70 round traveling at 1200 fps out of a 32" barrel impact higher or lower at 50 yards than the same round traveling at 1050 fps?

October 27, 2014, 06:04 PM	#2
ckpj99 Senior Member Join Date: January 25, 2011 Posts: 386	Oh, and in case you were wondering how the gun shoots in general, here are a couple targets from today's shoot. For this target I was benched, and I had to hold off a little to the left a little because my windage was slightly off and I didn't want to putz with it at the range. I was using the Buffington rear sight for these, and my windage adjustment is very sticky. About a 1.5" group center to center, which I think is pretty good for factory ammo from a brand not known for its precision. This next target was also shot at 50 yards, but I was standing, unsupported. For this, just keeping the extremely heavy gun up was hard enough, so I just tried to hold right on the target, which is why the shots are further off the right. This group is about 2.25 inch.

October 27, 2014, 07:17 PM	#3
NoSecondBest Senior Member Join Date: December 7, 2009 Location: Western New York Posts: 2,736	Just get a taller front sight. You need to be able to have some leeway for up and down regardless of the load used. Pick your favorite front sight and call the manufacturer and tell them where your bullet is impacting at 100yds and they can advise you on what height to get to have it hit a little low so you can use the rear sight to bring it into the POI you're looking for. Never alter a load to compensate for a sight problem if the load shoots well. FYI, there isn't that much difference between POI with 1050 and 1200. Almost all of my loads have some leeway and I shoot just about everything between 1100 and 1500fps.