Falling POI

[RBHarter]

I remember something somewhere , probably wrongly , about pistols and rifles behaving differently as speed and bullet weights increased based on platform and dwell time in the bbl . Shorter dwell time in the bbl less rise so in pistols heavier bullets mean higher hits even at the same speed . As speed increases poi comes up as the flight time goes down .

Enter my confusion , I know I know this and how to fix it . I'm loading for this 45-70 and the elevation is on for Privi 405 gr is on at 100 and close enough for 350s over Unique at 50 . Now I step in with some 405s working up to at least Trapdoor loads , plenty for me thanks , and as the velocities go up POI goes down . A lot ! From 1400-1600 it was upwards of 12" at 50yd the 1895G did get warm , 75° day and 50 rounds over about 2.5 hr . So magazine pull could have been a factor but isn't a foot , plus trajectory , even if the 458193 were a full wadcutter , kind of excessive at 50 yd ?

 

[Ian]

I think you're confusing internal and external ballistics here, or relative muzzle rise due to recoil of light vs. heavy bullet, heck I dunno now I'm confused.

Way I understand it, longer barrel time means more time for recoil to change the angle of departure, thus making a higher trajectory, but that doesn't necessarily mean higher POI because velocity outside the gun plus gravity and BC/air resistance control that. Longer flight time to target with lower-velocity loads will make the bullet bullet drop more at the same distance vs a faster-moving bullet and thus hit lower. To further muddle things, recoil impulse (fast vs. slow powders or heavy vs. light bullet) affect how much the barrel rises while the bullet is still inside, and further downrange the BC of the bullet greatly affects deceleration rate and thus drop.

A foot at 50 yards seems like a lot of drop for 200 fps difference, but evidently your "system" is sensitive to that combination and the bullet is getting out of the barrel a lot sooner at 1600 fps MV than at 1400 MV and thus printing lower. I don't think it's "drop" per se that is happening, I think where the muzzle is pointing when the bullet leaves is making the bit difference in your POI with your handloaded 405s.

 

[RBHarter]

As far as the 45-70 goes H322 is pretty slow .
In this case both interior and exterior are in play ..... I think .
The biggest problem is that the group is closing and I'm still in the bottom half of the load window , bottom 1/3 if I count all of the TD and Lever data , and I'm up to the last step on the rear sight elevator at 50 yd . I'm thinking about a 5D Wilson rear sight anyway but not exactly the reason I wanted to buy 1 .
I've seen some strange things happen during load work ups but this takes the cake . Maybe it's just me .

 

[Ian]

Now you mention H322. I can't decipher what you're doing with what that does what when.

 

[RBHarter]

Not having a perfect mould for the 1895G that I've had 4 weeks I have tried it out with some brand new factory Privi Partizan 405 FNSP . We shot it at 100 yd and with 4 of 8 steps it was elevation correct but left about 6" left . With my pre-owned Redding die set and 80 pieces of my buddy Jorge's brass plus my 20 all from 1 lot I set about finding a light can slayer load with a paper patch 453-350 RF custom and a Lee 458-340 F with some Unique , both run 1100-1200 fps and hit about 0-3" high at 50 and about the same low at 100 .

The H322 is under a 458193 414gr .4595 bullet that was found in some salvage buy lead a couple of years ago . At 42 gr they hit about POH at 50 , at 42.5 the cluster was about 4" and that much low . At 43 gr I raised my point of hold from mid sheet on and 8.5x11 to the top and the cluster landed more or less in the same 4" low POI . At this point with the 43.5 load on deck I raised the rear sight to the 7th step I was back to the 1-3" low 2.5" group .

This was over 50 rounds over about 2.5 hours . I know different loads will shoot to different points and normally faster loads shoot higher whether by a higher muzzle release or shorter flight time or both or at least that is what it seems to be , mechanically that seems right .

 

[Brad]

Sometime slower can hit higher. Slower bullet leaver barrel after more barrel rise.

As for the extreme variation, I'm not amazed at all. My Marlin 1894 in 32-20 can have 2 feet of elevation based on different velocities.

Might be the rifle too. Every rifle has it's own temperament off the bags.

 

[RBHarter]

This would be the first time I've seen it but I've decided that it is probably heat pull from the mag tube . If it shoots the first group tomorrow a foot and a half high I'll know for sure .

 

[35 Whelen]

Try loading one at a time and test your theory ........

Could barrel harmonics be coming into play here too?

 

[RBHarter]

Could be the hum . I did let it get pretty warm during the set. In reflection it seems to be stringing also .
Like I said this is the first 1895 and the first 45-70 . I had a 1894CB 357 and couple of 92's in 45 Colts and didn't observe anything like this in them and shot lots of trips over 50 shots an hour let alone over 2 .

 

[Intheshop]

"American Furniture 1680-1880,From the collection of the Baltimore Museum of Art"

Oh,wait..wrong genre(sorry,couldn't resist).

"Accurizing The Factory Rifle" by,M.L.McPherson has a chapter or two on lever actions.Well worth the read.

My input would be,stop shooting levers off traditional "bags".Treat them more like African,big kickers....meaning,get a 4' step ladder,throw a towel on top,grip it and rip it.

Ya'll keep writing about big bores,isn't fareing well with my pocket book...

 

[RBHarter]

I'm shooting field lean over a now gratuitously lead smudged hood . I'm probably 50-60 rounds into this model . I have full upper body flex only slightly more rigid than off hand standing , the sitting 3 point off the knee was brutally uncomfortable , it reminded me of that time I got to close to the sand bank pass shooting .

 

[Intheshop]

The harder the reaction...kick...the more you're gonna need to practice.What a guy "thinks" is proper technique only goes in the dumpster as recoil goes up.

Changing lanes....I can sail a 250cc GP motor cycle around 1k,litre bikes whilst knee down in turns,why?