Load for my New To Me 45 Govt Springfield Trapdoor

[Pirate69]

I recently purchased an 1873 Springfield Trapdoor 45 Govt from a fellow Forum Member, and I am very happy with it. I am currently in the process of developing a 100-yard load that anyone can shoot without recoil worries. Boolits are cast from a NOE 460 mold and PC-ed. The final bullet diameter is running about 0.463”. The barrel slugs 0.4605”. Average PC-ed boolit weight is about 347 grains. My desire is to use Unique powder for my loads.

I have tested some loads and will be settling on a load between 10.0 grains Unique and 10.5 grains. The last 5-shot group using 10.0 grains Unique gave me a 4.3” group: 2.1” to the right and 7.0” low of the POA. The last 10.5 grain load gave me a 4.35” group: 2.4” to the right and 6.2” low of the POA. Both loads were fired on the same target. The spread for both loads (10 rounds) was 4.9”; centered 2.3” right and 6.4” low of the POA. These were fired at 100 yards. Target Calc was used to measure the groups and determine the group centers.

The 0.463” PC-ed boolit allows me to seat the boolit without resizing a fired case. The boolit can not be seated with finger pressure, needs a little extra push from the press. A very slight crimp is added. The boolits are seated to a depth slightly greater than the COAL jam depth (2.545”) and the chambering completes the final boolit seating. I can feel a slight fit of resistance as the trapdoor bolt is closed and the boolit is pushed against the lands. QL indicates chamber pressure should be about 10,444 psi and 1118 fps. Since the boolit is against the lands, the chamber pressure should be a little higher than projected by QL.

A bit of Dacron filler is used over the Unique powder. It probably is not needed but I am using it anyway currently.

The original front sight produced POI groups that were high when using the rifle’s battle sight. Two fabricated front sights were also provided. I switched out the original sight for the shorter of the two additional sights and got the current groups that have a low POI. I can now adjust the Buffington flip-up sight to get the POI where I want it and finalize windage. I would love to be able to just use the battle sight, but I guess I would need to file it down somewhat to get the POI up. May try the other, taller front sight, to see how close it brings me to the POA.

This has been fun so far.

As you can see, I am sparing not expense on targets.

https://i.imgur.com/gvHkDJB.jpg

[Sgt H]

I would up the powder charge some, I seriously doubt your 10-10.5 grain charges are reaching the 1118 predicted by QL. I suspect 950-1000fps. My personal chrono results with a 340 grain boolit over 12 grains of Unique is just under 1100 from a 26" barreled 1886 Browning. This load is also accurate.

[Pirate69]

I had an opportunity to see if the Buffington Sight would work for me. Loaded 20 rounds of 10.0 grains Unique and went out to the farm range. All my previous groups have been shot using the battle rear sight. I shot one round, at 100 yards, using the open sight, all the way down, on the Buffington slide. It hit high of the POA. That won’t work. Next tried the peep sight all the way down. Hit low of the POA. Moved the peep sight up and found that I had guessed about right on the adjustment. Almost exactly the elevation needed. Made a windage correction to get close to desired POI. Used the last windage adjustment shot as the first shot in the first 5-shot group.

The first 5-shot group had a center to center spread of 2.8”. POI was 1.1” left and 1.0” high of the POA. Best 4 shots gave a 1.8” spread. Measures taken with Target Calc.

The second 5-shot group had a center to center spread of 4.0”. POI was 2.1” left and 1.7” high of the POA. Best 4 shots gave a 1.9” spread.

The third 5-shot group had a center to center spread of 2.9”. POI was 1.0” left and 1.6” low of the POA. Best 4 shots gave a 2.1” spread. I must have been seeing a different sight picture for this group since it was a lower POI than the other two groups. I use Dollar Store reading glasses with a +1.25 addition to see the sights clearly. But the target is a bit out of focus. But, I think I am seeing the peep sight better than the open sight.

The three groups averaged a POI of 1.4” left of the POA. Looks like I need to move the rear sight about 0.01” to the right. That should be fun trying to do that.

The three groups averaged a 5-shot center to center spread of 3.2”. The average of the best four shot groups was 1.9”.
I think 10.0 grains Unique is going to be my load for the NOE 460-350-RF mold, at the present time. Just need to tweak the rear sight a bit.

It has been suggested that I try 12.0 grains of Unique. I tried loads up to 12.0 grains earlier when I was looking for the best load. I got a wider extreme spread with the 12.0 grain load than I did with the 10’s. But, again, I was using the open battle sight. I seem to be able to shoot the peep sight better than the open sight. Maybe I need to revisit the higher loads and do some chrono measurements using the peep sight.

https://i.imgur.com/JuqZ5fq.jpg

[TCLouis]

10.5 grains of my #105 (think Unique) out of a 1886 gave me right at 1100 fps on more than one occasion. That is pushing a 340 grain Boolit.
Precise at 106 yards from one measured 3 shot group.

I have shot the #105 back to back against Unique, and yes, they provide same velocities.

[StrawHat]

… The final bullet diameter is running about 0.463”. The barrel slugs 0.4605”…

It is hard to measure those Springfield bores. I usually use a boolit that is as large as I can chamber. But, I use black powder so if it is under size it obturates to bore size. Accuracy has been very good.

My customized Springfield Model 1866,



Kevin

[Pirate69]

I got a chance to do a little chronograph work on the 10.0 grain Unique load I have been playing with. Also measured a 12.0 grain Unique load as well.

I am shooting previously fired, un-resized, cases. The PC-ed boolit is large enough that I am getting a slight neck tension without a crimp. But I am adding a slight crimp to ensure the boolit is held in place. I seat the boolit to a COL of 3.540". Upon chambering, the final COL is 3.538". It is a COAL jam and I can feel the pressure needed to seat the boolit the final 0.002". I also use a piece of dacron to keep the powder position uniform from round to round.

Since I am keeping the chamber pressures low, I wanted to see if I could determine a different between using a LRP and a LPP while keeping all the other variables constant. Wolf LPPs and LRPs were used in the test. Ten rounds of each primer load were fired and the velocities, at 10.5', were measured with a CED M2 Chronograph.

The LPP loads averaged a velocity of 1,056 fps. The maximum velocity spread was 30 fps. The Standard Deviation was 9.6 fps.

The LRP loads averaged a velocity of 1,067 fps. The maximum velocity spread was 23 fps. The Standard Deviation was 6.6 fps.

Next, I fired ten rounds of a 12.0 grain Unique load using Wolf LRPs. The LPP loads averaged a velocity of 1,178 fps. The maximum velocity spread was 21 fps. The Standard Deviation was 6.1 fps.

Since I rushed off from the house and forgot my rests, group sizes are immaterial. They were larger than the groups I have been getting in the past.

The SD for the LPP loads were 45% higher than the LRP loads with almost the same average velocity. I thought it was interesting that the SDs, for both the 10.0 gn and 12.0 gn loads, both using LRPs, were almost identical (6.6 fps vs 6.1 fps).

The muzzle velocity predictions from QuickLoad are overpredicted by 5.1% for the 10.0 gn load and 5.4% for the 12.0 gn load. That is fairly good consistency. I would love to understand what is driving the differences between projected and actual measured.



Unique
10.0 gn
LPP
High 1072 fps
Low 1042 fps
Avg. 1,056 fps
S.Dev. 9.6 fps


Unique
10.0 gn
LRP
High 1078 fps
Low 1055 fps
Avg. 1,067 fps
S.Dev. 6.6 fps


Unique
12.0 gn
LRP
High 1189 fps
Low 1168 fps
Avg. 1,178 fps
S.Dev. 6.1 fps

[Pirate69]

I have been thinking about taking a whitetail deer with the trapdoor. I will probably limit the maximum shooting range to 100 yards. But I thought I would see what the drop was at 125 yards and 150 yards.

I first shot a 5-shot group at 100 yards. POA was the bottom of the red sticker. The front sight was a little high when I touched-off the first shot. I walked down to the target to verify that it's POI was high. I did a better job on the next four rounds and got a decent group that centered about 1" high of the POA.

I moved the target to 125 yards and using the same POA, fired two rounds. The POI was about 3" low of the POA.

I moved the target to 150 yards and using the same POA, fired two rounds. The POI was about 10" low of the POA.

This load appears to be grouping pretty well.
https://i.imgur.com/GWLqLeC.jpg

[cpaspr]

Two things that come to mind on the velocities being 5+% higher than QL projections. I have no idea if either of these is what is actually happening, but are just what came to mind.

First, having the boolit jammed into the threads to begin with is causing a greater pressure than QL may be factoring in.

Second, your projectile diameter vs bore diameter may be a bit greater than assumed in QL, but at the same time the PC may be allowing less friction.

So, higher velocities due to more pressure behind the boolit but less friction slowing it down in the barrel.

[Pirate69]

The QL projections were higher than the actual velocities measured. Agreed that there should be a greater than normal starting pressure with a jammed boolit.

[firefly1957]

My smokeless load for my Model 1884 trapdoor used a charge of Reloader 7 from a old Hercules booklet however todays Reloader 7 is not the same powder !

I figure the load gives 1150 f/s but have never timed it it shoots the same as 55 grains of FG black powder . The bullet is the Lee 405 .459 hollow base that cast at .461" which is my guns groove depth so they are pan lubed and shot as cast . It is not a powerful load but has taken my largest buck at 55 yard hammered him right there. That Lee mold throws a 417 grain bullet for me with the alloy I used .

[Rockindaddy]

A Mississippi Trapdoor! That's a rare one. Never saw a critter like that before. Looks like an Allin Conversion too. Neat gun.

[Pirate69]

My smokeless load for my Model 1884 trapdoor used a charge of Reloader 7 from a old Hercules booklet however todays Reloader 7 is not the same powder !

I figure the load gives 1150 f/s but have never timed it it shoots the same as 55 grains of FG black powder . The bullet is the Lee 405 .459 hollow base that cast at .461" which is my guns groove depth so they are pan lubed and shot as cast . It is not a powerful load but has taken my largest buck at 55 yard hammered him right there. That Lee mold throws a 417 grain bullet for me with the alloy I used .

I figure today's R-7 powder will give your 417 gn boolit (32.6" barrel) 1150 fps at 24.0 gn to 24.5 gn. Is that in the neighborhood of what you are using?

And, at 50 yards, you have about 1050 ft-lb of energy. That would be a hammer.

[firefly1957]

Oddly I did not save the load in my reloading notes , I did save the FG data and how the bullet was lubed .

I was figuring about that same as you over the years someone shortened my barrel to 22" it still hammered my largest buck . Today I can not hunt with the gun as it is I can not see the sights in the woods .


I have some new Re-7 and it seems to be a little harder to ignite then the older Re-7 that had finer grains . The new 2400 seems to be harder to light as well as a old standby load of just 10 grains worked great under a 200 grain bullet but the new powder often does not ignite in same very light load.

[Pirate69]

I am guessing that your Reloader 7 load is only about 50% of the available case capacity and the R-7 is a slower burning powder than 2400. Are you using a filler with the R-7 loads?

Oddly I did not save the load in my reloading notes , I did save the FG data and how the bullet was lubed .

I was figuring about that same as you over the years someone shortened my barrel to 22" it still hammered my largest buck . Today I can not hunt with the gun as it is I can not see the sights in the woods .


I have some new Re-7 and it seems to be a little harder to ignite then the older Re-7 that had finer grains . The new 2400 seems to be harder to light as well as a old standby load of just 10 grains worked great under a 200 grain bullet but the new powder often does not ignite in same very light load.

[firefly1957]

I did not use a filler and am not using that load or rifle anymore as I can not see the fine sights of my Trapdoor . I do shoot modern loads in a 1895 Marlin now it is scoped for hunting .

The old Re-7 is fine grains with red identifiers it is much finer then Red Dot powder which is flakes . The new Reloader 7 powder resembles IMR 4227 and is a bit harder to ignite . I have been happy with it in 30-30 shooting new white sabots with a 40 grain Nosler all copper varmint bullet with dark red plastic tip .
The load of NEW 2400 under a 200 grain bullet did use a filler to keep it at the primer and had erratic ignition.

[flintlocke]

Pirate, I have some experience with several trapdoors and a thought occurs to me...have you considered that you are jumping from 10 gr Unique to 12 gr, you are going right through the transitional speed of sound?
In my case, at my elevation and relative humidity average, the 405 needs only 11 gr to stay below sos of 1120 fps....and to avoid transitional instability with the 405 I need to jump up to 1,350 or so to stay supersonic at 100 yds. Does transitional instability affect group size? IMO yes.
But, the qualifier here is...I know nothing of PC coated bullets, it may be a whole 'other ball game. But a trapdoor with a reasonable bore condition should be shooting a bit better than 4" at 100 yds. Anyway, some food for thought. Good luck.

[iron brigade]

That rifle was a joy to shoot! I am glad you are having fun with it.
When I first got the TD I went to the Lyman cast bullet hand book and picked out a load of 34 grains of imr 3031. Using the Lee hb 405 the rifle shot a 1" 3 shot group @ 100 yards but high.

If you can find some 5744 I would try some of that or shooters world buffalo powder.
I just ordered a noe mould for the 45-70, this mould will produce 4 different weight bullets, 292 HB, 350,405, and 500 grain bullets by switching out base pins. Nose pour design.
I'm hoping the HB bullet will shoot well in my high wall.

I'm enjoying the journey with your trapdoor. Keep trying different things and it will come.

[Pirate69]

Pirate, I have some experience with several trapdoors and a thought occurs to me...have you considered that you are jumping from 10 gr Unique to 12 gr, you are going right through the transitional speed of sound?
In my case, at my elevation and relative humidity average, the 405 needs only 11 gr to stay below sos of 1120 fps....and to avoid transitional instability with the 405 I need to jump up to 1,350 or so to stay supersonic at 100 yds. Does transitional instability affect group size? IMO yes.
But, the qualifier here is...I know nothing of PC coated bullets, it may be a whole 'other ball game. But a trapdoor with a reasonable bore condition should be shooting a bit better than 4" at 100 yds. Anyway, some food for thought. Good luck.

It may not be the rifle. It could be the person behind the trigger. On occasion I have gotten 4 shots around 2 inches with the 5th shot opening the group up. Have wondered if it is me or my load. Could be both.

[Pirate69]

Pirate, I have some experience with several trapdoors and a thought occurs to me...have you considered that you are jumping from 10 gr Unique to 12 gr, you are going right through the transitional speed of sound?
In my case, at my elevation and relative humidity average, the 405 needs only 11 gr to stay below sos of 1120 fps....and to avoid transitional instability with the 405 I need to jump up to 1,350 or so to stay supersonic at 100 yds. Does transitional instability affect group size? IMO yes.
But, the qualifier here is...I know nothing of PC coated bullets, it may be a whole 'other ball game. But a trapdoor with a reasonable bore condition should be shooting a bit better than 4" at 100 yds. Anyway, some food for thought. Good luck.

You make a good point with the transitional instability.

[Pirate69]

Thanks to “openbook”, I was able to try some 155 gn Collar Button boolits in the Trapdoor. I loaded 20 rounds using Unique powder. A 0.7 cc Lee Dipper was used to get approximately 6.4 gn of Unique. My RCBS Chargemaster has problems with loads below 8 gn overshooting. Thought I would start the quick and easy way to see if there was any potential with the buttons. The boolits were tumbled lubed and Wolf LRPs used. They were seated to a depth where the lube groove was covered and a moderate crimp applied. Not a lot of room to work with. A case filler was not used in the button boolit loads. Previously, I had used a case filler with the heavier boolits even through it was probably not necessary. Those loads were being considered for hunting and I was concerned about a powder shift from hunting from an elevated tree stand.

I set up a target at 25 yards. Not knowing where the POI would be, I used the V-notch on the sight ladder. Sight was still set for the loads I was shooting at 100 yards with the peep sight.

I fired 10 rounds. The 10-shot group measured 1.5” center to center. One ragged hole. The POI was about 9.5” high of the POA.

Thought I would try 10 shots at 50 yards. Fired two shots and walked down to check the target. Both shots were off the cardboard. I figured that they were both high. I then dropped down to the peep sight on the sight ladder. POI back on the cardboard. At 50 yards the 8-shot group really opened. A lot of vertical spread.

I think an increase in velocity/powder will help tighten the 50-yard group. Thinking 10 gn Unique will be the next load tested.

I was a little surprised by the predicted chamber pressure for the 6.4 gn Unique load. QL predicted a chamber pressure of 2,990 psi. I checked the load using the GRT software and the 6.4 gn load was predicted to give 2,848 psi. Unique appears to be a very forgiving powder with respect to chamber pressure. Even the 10 gn load is not excessive. QL and GRT predict 6,092 psi and 5,837 psi, respectively. This is very kind to a grand old rifle that you want to preserve.

https://i.imgur.com/CTCHPkm.jpg