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Trapdoor carbine shoots high


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I just purchased an original 1873 45-70 trapdoor carbine.  It shoots way high! What is a good way zero it at 100 yards without a lot of alternations to the carbine

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Just now, Irish-Pat said:

I just purchased an original 1873 45-70 trapdoor carbine.  It shoots way high! What is a good way zero it at 100 yards without a lot of alterations  to the carbine

 

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One of the best ways to get a carbine that is shooting high is to raise  or replace the front sight with a taller one.  Usually it is not possible to lower the rear sight.  This sort of modification is done all  the time in N-SSA shooting.

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I bought an original 1875 rolling block carbine. It was sighted for 200 yards. I knocked the original front sight out. Bought a tall replacement. Filed it down until it was spot on at 50 yards. It's my Plainsman rifle.

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My original shot high too. I was shooting a 330 grn Bullet. I even changed the front site. But it was not quite “right”. 
grried a 405 grn Bullet and it works fine. It does shoot high and right. At our distances I aim at about 1100 and hit center target

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30 minutes ago, H. K. Uriah, SASS #74619 said:

Two questions...

 

1.  What weight bullet are you using?

2.  What kind of a load are you using? 

 

Basically are you trying to recreate the .45-70-405 or the .45-55-405 which was created specifically for use in the carbines?

 

This...I was shooting with a cowboy who could not hit anything with his 45-70 carbine. Finally worked up a load that was not as hot, and he did just fine after.

 

If I remember right, didn't the 45-70 BP gvt carbine loads add a couple cards to reduce the power for accuracy reasons.

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I found a piece of brass laying around that was the same thickness as the front sight. I cut out a piece with a dremel cutting wheel that I felt was overly tall. I then filed it down to POI at POA. 

 

It looks strange but it works.

 

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47 minutes ago, Branchwater Jack SASS #88854 said:

 

This...I was shooting with a cowboy who could not hit anything with his 45-70 carbine. Finally worked up a load that was not as hot, and he did just fine after.

 

If I remember right, didn't the 45-70 BP gvt carbine loads add a couple cards to reduce the power for accuracy reasons.

 

The original round, a .45 caliber, 405 grain bullet, propelled by 70 grains of black powder, worked just fine in trapdoor rifles, but in carbines, it had horribly painful recoil.

The "carbine" round used a .45 caliber, 405 grain bullet, propelled by 55 grains of black powder, and in the carbines had much more comfortable recoil.

When I first started loading this caliber, I worked up some "trapdoor safe" loads which worked just fine in my 1884 trapdoor rifle.  I think it was 4895.  Anyway, when I got a 73 carbine and a Winchester 86 with a 20" barrel, this loading was downright painful to shoot in those lighter guns.   So, I tried a different power.   Switched to Trailboss.   Suddenly the recoil was no longer painful.   And, I found that the loading could still reach out touch things at 300 yards or less with no problem.   Never tried anything further.   Granted, I've not tried my hand at paper targets to see what kind of a grouping I'm getting, just trying to hit the steel targets out there with regularity.

Anyway, I have a feeling that the lighter load, is also probably more accurate in the shorter barreled guns.  For one thing, the sight picture is different from a long barreled rifle, and if memory serves, they used different sights on the carbines as well.   

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Quote

What is a good way zero it at 100 yards without a lot of alternations to the carbine

 

Aim lower.  Sorry, I couldn't help myself.  :D

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If you consider a new front sight that can be tapped in with a brass hammer to be a major alteration, then I'll quit (and you can too) right there.

 

But if you want to PRECISELY know how much taller front sight you need, here's the calculator found at Brownells:.

 

https://www.brownells.com/aspx/learn/learndetail.aspx?lid=13093

 

Same result from calculator can also be applied to the rear sight, if it is adjustable for elevation and has room to be LOWERED..

 

 

As mentioned above, one sure way to get the bullet to hit lower is - a lighter load.   Reduce muzzle velocity.  Now, how much?   Well, that means you need to look at exterior ballistics calculators and perhaps do a few test loads.

 

good luck, GJ

 

 

 

Edited by Garrison Joe, SASS #60708
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are you loading your own ammo?  lighter bullet weight usually bring poi down (as will dropping 5% of your powder charge).

Edited by WOLFY
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1 hour ago, Ramblin Gambler said:

 

lighter bullets do?  seems like heavier bullets would bring it down because they'll drop more. 

 

Lighter bullets spend less time in the barrel and exit at lower velocities. That is why, when looking at load data, lighter bullets will require more powder to reach the same speed as a heavier bullet.

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4 minutes ago, Branchwater Jack SASS #88854 said:

 

Lighter bullets spend less time in the barrel and exit at lower velocities. That is why, when looking at load data, lighter bullets will require more powder to reach the same speed as a heavier bullet.

 

Wow.  That's the exact opposite of what I expected.  Can't even say it's 180 degrees off.  More like 900 degrees off cause it did a couple of full rotations first.  In most commercial loadings, lighter bullets usually mean faster bullets.  I guess the extra case capacity lets them add more powder.  Or is what you said only true for blackpowder? 

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On 3/28/2021 at 11:11 AM, Irish-Pat said:

I just purchased an original 1873 45-70 trapdoor carbine.  It shoots way high! What is a good way zero it at 100 yards without a lot of alternations to the carbine

Had to do the same with my original trapdoor.  I just drove out the pin holding the original front sight. Then I took an old brass key and made my own front sight.  Leave it a bit long and take rifle to range with a file and get it exactly where you need it.

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47 minutes ago, Ramblin Gambler said:

 

Wow.  That's the exact opposite of what I expected.  Can't even say it's 180 degrees off.  More like 900 degrees off cause it did a couple of full rotations first.  In most commercial loadings, lighter bullets usually mean faster bullets.  I guess the extra case capacity lets them add more powder.  Or is what you said only true for blackpowder? 

 

you might want to quit while you’re ahead... lighter bullets spending less time in the barrel is because they’re pushed to higher velocities with less of a charge.  

 

black powder is more influenced by volume (compression) than smokeless.  now that has me wondering... do any smokeless powders even begin to fill a 45-70 case?  

 

Edited by WOLFY
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33 minutes ago, WOLFY said:

 

you might want to quit while you’re ahead... lighter bullets spending less time in the barrel is because they’re pushed to higher velocities with less of a charge.  

 

black powder is more influenced by volume (compression) than smokeless.  now that has me wondering... do any smokeless powders even begin to fill a 45-70 case?  

 

 

I'm not sure what you mean.  If I'm ahead it's only because I'm learning something new.  I'm not sure if I'm ahead right now though.  In fact if I had to guess, I'd say I'm a little behind because now I'm confused.  What you said makes more sense regarding why they spend less time in the barrel.  I kind of assumed he was backwards on that part and I didn't see where time spent in barrel was relevant so I didn't pay no attention to it.  It was the lighter bullet needing more powder that has my head spinning.  Jack's latest post makes me think he has more to say about that. 

 

I imagine there are some smokeless powders that will fill a 45-70 case, but when I was talking about commercial loadings tending to be faster with smaller bullets, I was thinking of all cartridges.  Specifically 9mm and 45 acp where the big slugs are the ones likely to be subsonic. 

 

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Lighter bullets need MORE smokeless powder also because they provide less resistance (inertia) to force the pressures to peak as fast.  So, powder burn is less efficient with a lighter bullet (because of the progressive nature of the burning of smokeless).  When the powder burn becomes very incomplete, a switch to a faster burning powder is needed as well as an increase in powder weight.

 

good luck, GJ

Edited by Garrison Joe, SASS #60708
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that was me being snarky, cause in your post prior to that it looked like you were doubting my suggestion for bringing your point of impact down.

 

i mighta done better suggesting “carbine ammo” but i only learned about it existing because of this thread, so thanks for starting it, Ramblin Gambler.

 

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I've used Trailboss and been really happy with it. I highly recommend it.

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On 3/29/2021 at 5:41 PM, WOLFY said:

that was me being snarky, cause in your post prior to that it looked like you were doubting my suggestion for bringing your point of impact down.

 

i mighta done better suggesting “carbine ammo” but i only learned about it existing because of this thread, so thanks for starting it, Ramblin Gambler.

 

To be clear, I am doubting that, but not in an argumentative way.  It's in a 'want to know more' way.  That is counter intuitive from what I know of ammo.  I was this guy. 

 

Desire to know more intensifies | [Intensifies] | Know Your Meme

 

 

 

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On 3/29/2021 at 2:45 PM, WOLFY said:

 

 

black powder is more influenced by volume (compression) than smokeless.  now that has me wondering... do any smokeless powders even begin to fill a 45-70 case?  

 

H4831 will fill the case and with a lightly compressed load will give good accuracy.

 

Duffield

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or you can go with a taller front sight.  or is changing that too much of an alternation?

Edited by WOLFY
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On 3/29/2021 at 7:43 PM, Bailey Creek,5759 said:

5744 is a good powder for 45-70 . Fills the case. 

You could take some J B Weld build up the sight that way .

I would first look at the Western Powders website for load data. For 45-70 with 5744, there is data for Trapdoor and similar rifles, data for standard loadings, and data for high pressure loadings. I have been loading 45-70 with 5744 recently, starting with a minimum load for standard loads, but I am loading for a 1886 Winchester.  I would definitely be careful with loads for a Trapdoor rifle.

http://www.accuratepowder.com/load-data/    Page 84 begins load data for rifles in this caliber for various powders.

Horace

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On 3/29/2021 at 7:43 PM, Bailey Creek,5759 said:

5744 is a good powder for 45-70 . Fills the case. 

You could take some J B Weld build up the sight that way .

I like 5744 for my Sharps rifle with a535 grn Bullet. But 25 grns does not come close to filling the case. 
 

for my H&R trapdoor I use 14.2 Unique with a 305 grn Bullet. For my original trapdoor I use a full case of APP or BP with a 405 grn Bullet. 

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All y'all are over-simplifying  the "lighter/heavier bullet vs POI" calculation, and in some cases, stating it wrong.  In general, at the SAME powder charge a lighter projectile will have a lower POI due to higher muzzle velocity and lower recoil... ie muzzle rise.  But, small changes in bullet weight makes for small changes in POI.  ANY CHANGE TO THE POWDER CHARGE THROWS THAT OUT THE WINDOW.

1stLaw.jpg?width=1920&height=1080&fit=bo

 

GET A TALLER FRONT SIGHT!  Then keep the original for when you move the carbine along.

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And before someone jumps all over the above... yes, Load Density plays a part in determining POI.

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I'd rather just adjust sights to get what I want.  Whether it's by turning a screw or filing off metal or putting a new sight part onto the gun.   I'm getting too old to fiddle with loads that already work or remember hold offs.

 

good luck, GJ

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Original Trapdoor Springfields, as well as the cartridge conversion Sharps carbines, ALL shot high at the common ranges we shot at today.  Typically, 12-18" high at 100 yds.  The reason is that they were "combat sighted" to hit a man on a horse out to 320 yds or so, depending on whether the rifle or the carbine.  (I have the figures for each somewhere in my library, but too lazy to go dig it out right now!)  While the .45-55-405 was intended for the carbine, for the reasons of lower recoil stated by others above, a few cavalry company commanders requested the rifle loads for their troopers!  True, you can play with the loads to compensate, but the "easier" thing is to simply raise the front sight, either by replacement of the blade (easiest where the front blade is pinned in to the base, or by putting some epoxy on top of the existing blade.  For just plain target shooting, pin two large targets one-above-another and hold at the bottom of the lower target.

Happy Easter or Passover, Pards!

Stay well and safe!

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