Why do my trapdoors shoot less accurately after several shots

[Iron Jim Rackham]

My trapdoors shoot less accurately after 6 rounds. When I initially starting shooting, the rifles are X ring accurate at 100 yards, 10 ring at 200 yards, and 9-8 ring at 300 yards. However, as I continue shooting, accuracy evaporates after the first six rounds. This happens weather I shoot blackpowder or smokeless. When I shoot black powder I clean every other shot. By the 7th round, by accuracy declines from X ring accuracy at 100 yards to 8 ring accuracy.  The accuracy continues to decline at any distance. As a hunting rifle, the gun is fine, since the first shot is always on the money. For competitive shooting, it's frustrating since we typically shoot 10 round relays.  Any idea what causes this?

Thanks

 

Iron Jim

[Eyesa Horg]

Wild arse guess, you're shoulder is getting sore and therefore a slight flinch! Actually is it possible it is losing accuracy as the barrel heats up?

[El Sobrante Kid]

Does the group open up in all directions, or does the group make more of a vertical line (stringing)?

[Oklahoma Dee]

I will ask, are these original 1870's or 1880's Springfield, 32" round with Buffington ladder sights, in 45-70?

 

 Or are they a replica and if so, what is the maker, model  and what is the barrel length, round or octagon and caliber your shooting?

 

Round barrels can be dicey for distance.

 

What is your load information?  Do you weight each bullet, each powder charge, and each brass?

 

Edited October 20, 2025 by Oklahoma Dee
correction

[Flanigan Flats]

Black powder? Fouling? Are you swabbing the barrel between shots?

[Boggus Deal #64218]

22 minutes ago, Oklahoma Dee said:

I will ask, are these original 1870's or 1880's Springfield, 32" Octagon with Buffington ladder sights, in 45-70?

 

 Or are they a replica and if so, what is the maker, model  and what is the barrel length, round or octagon and caliber your shooting?

 

Round barrels can be dicey for distance.

 

What is your load information?  Do you weight each bullet, each powder charge, and each brass?

 

The originals all had round barrels. 

[The Original Lumpy Gritz]

If using real BP, you're fouling out the bore. What are you doing for fouling control after each shot?

[High Spade Mikey Wilson]

3 hours ago, Eyesa Horg said:

 Actually is it possible it is losing accuracy as the barrel heats up?

I would be inclined to agree with this.

[Badlands Bob #61228]

As your barrel heats up, it changes the harmonics of the barrel.  Your groups will open up.  That is why precision rifles have heavy barrels.  They can shoot more rounds before accuracy deterioration.  Let the barrel cool down and your groups will improve.

[watab kid]

mine were all old-original-well used , i never expected them to shoot well , if you have made improvements to it i cant speculate beyond this 

[Sedalia Dave]

Barrel heating is the most likely culprit. 

 

Accuracy is also affected by the temperature of your rounds.  If you leave them in the sun as they warm up the velocity changes. Keep your ammo at a consistent temperature.

[Oklahoma Dee]

5 hours ago, Boggus Deal #64218 said:

The originals all had round barrels. 

Correction done.  Thanks Boggus Deal, 

[H. K. Uriah, SASS #74619]

I know that after 2 or 3 shots with my Model 1884 Trapdoor rifle, it starts to get very heavy, and harder to shoot accurately.

My 1873 carbine does not have this problem, but it does have more recoil.  Or at least, my original loading did.   I eventually found a load with a 405 grain bullet that did not have much recoil to speak of.   That helped.

[Three Foot Johnson]

Switch to F-600 or F-1000 targets. X ring all day long.

[Stump Water]

Another vote for barrel heating.

[Iron Jim Rackham]

Thank you all very much. I'm shooting an original Trapdoor with Buffington sight as well as a Pedersoli Trapdoor infantry rifle with Lee Shaver sights, and a Pedersoli officer carbine with Lee Shaver rear sight and tunnel front sight with interchangeable inserts. I experienced the poor groups as the barrel heats up.  Shots start to string and the string height increases with each shot after the 6th shot.  When I shoot Shuetzen 2F I clean every other shot with a spit patch. When I shoot smokeless, (IMR4198) I try to  shoot one shot every 2 minutes. My smokeless loads are within 50 fps of my blackpowder loads. 

 

Is the trapdoor design toolight for sustained shooting? I would assume an infantry rifle would be designed for high volume fire. In a five round match, I'm very competitive at 100-300 yards. A 50 4X at 100 is repeatable. But, a 10 round match is unimpressive, and by the time I'm shooting at 300 yards, the target more resembles a shotgun pattern than a rifle group. 

 

 

[Flanigan Flats]

Heat is probably the issue. I guess you can’t start at distance and work in?? I’m new to this cowboy LR game and am very far from an expert. Would a blow tube help????

[Nostrum Damus SASS #110702]

3 hours ago, Iron Jim Rackham said:

... Is the trapdoor design too light for sustained shooting? I would assume an infantry rifle would be designed for high volume fire. ...  

 

 

I bet it still shoots minute-of-man after heating up.  That's all that was needed.

[Bison Bud]

It pretty much has to be one or more of four possibilities, all of which I think have been mentioned previously.  One, fouling of the barrel, which probably isn't it since it does this with smokeless as well as black power, but it wouldn't hurt to swab the barrel before shooting again.  Two, heating of the barrel, which is the most probable cause and is pretty common in long range shooting.  Three, a possible flinch after shooting several rounds, which is not uncommon and hard to prevent as well, especially when dealing with substantial recoil.  Four, your bullets could be causing a leading issue, but you didn't mention any problem with that, so I am assuming that the hardness of your bullets is appropriate for the rounds.  In any case, I'd take steps to prevent fouling, let the barrel cool whenever possible, and work on my technique as much as possible.  Good luck and good shooting to all.

[Uriah, SASS # 53822]

Iron Jim,

 

Here is what I use.

 

405 hollow base Lee mold or 457193 Lyman 415 gr. Large lube grooves.

25:1 lead tin

459 size, Lee shot unsized

Lube with SPG, vigilante lube, Emmett, bee wax/oliver oil - no smokeless lube.

Unsized cases so the bullets dropped in.

65-68 gr 2F, depends on the case capacity, RP, Win

Card wad - tablet backing or Walter‘s wads. No card wad on the hollow base. In the early days, I would shoot the hollow base with cards wad, and they seem to do OK.

Compression die. 0.15”- .20”

Seat the bullet- drop in.

Slight crimp.

 

Blow tube I just use a half inch fuel line cut at an angle for inserting in the breach.

3-4 deep breaths. The air deep in the lungs has 100% humidity. The air in the airway is not. Deep breaths.

Remove Condensation from the tube. I like the fuel line because it wraps around let the leg nice.

 

Uriah

[Iron Jim Rackham]

Thank you all very much

[Bailey Creek,5759]

A blow tube is a very important, when shooting Black Powder.

They are easy to make.

 

[Diamond Jake]

Scientific method: Change one thing at a time.  I suggest the following test:

 

1) Shoot rather quickly until the groups start to open.  The barrel should now be well-fouled and hot.

2) Wait several minutes for the barrel to cool down, but don't swab the bore.

3) resume firing with the cool, fouled barrel and see if the accuracy is back to original level.  If so, then I'd say heat was the issue.  If the accuracy is still bad, then heat isn't the issue.

 

Second test:

 

1) Shoot  several shots with a lot of time between (10 minutes?) so the barrel doesn't get hot.  Swab between every other shot as before.

2) If accuracy deteriorates after 6 or so shots, but barrel is still not hot, then again I think heat isn't the issue.

 

After (if) you determine heat isn't a significant factor, try cleaning the barrel more diligently after each shot.  If accuracy deteriorates after several shots with clean cold barrel, then the issue is either equipment, ammo, or technique.

[El Chapo]

Send me some of your bullets and I'll powder coat them and return them.  That will eliminate barrel leading as an issue.  Size them after I return them (you can size them before as well, just make sure you size them after as well).

Edited October 30, 2025 by El Chapo

[Garrison Joe, SASS #60708]

Poor barrel bedding/fit into stock would be the most common cause of vertical stringing.   Not familiar with how the furniture fits to a trap door, but it should be snug around the action and may need to be snugged to hold barrel down to the forearm bedding spots.   If the "barrel bands" on the stocks are not tight vertically, might try shimming the wood to tighten them up. 

 

Hint - I just tightened the barrel bed in a Springfield 1903A3 by making a thin brass-stock shim to place on the foremost 3 inches of the stock.  Tightened 100 yard groups from 3" to 1", and let me shoot second in a 300 yard match (my two poor shots were ones I pulled off the steel targets). 

 

Lots of BP competitors use a blow tube to both cool barrel and let breath moisture keep the fouling soft.   Some smokeless long range fellers use a battery-powered barrel fan between shot strings. 

 

I'm sure that you have cleaned any jacket copper out of the barrel from previous jacketed bullet shooting - ANY copper fouling has to be removed before switching to black power rounds, for best accuracy.

 

 

True black powder burns out lead deposits - leading of barrel is not a problem.

 

good luck, GJ

Edited October 30, 2025 by Garrison Joe, SASS #60708

[Bailey Creek,5759]

In shooting Black Powder annual there was an article on original Springfields. 

The article said a lot of Springfields  45-70's. Were over sized more like a 46 caliber.

The person writing the article said he shot a lot of Springfields. And only a few true 45 caliber.

Slug the barrel.