Preliminary accuracy results with the Thumper Carbines

[chorizo]

Hit the range yesterday and unfortunately couldn't start working at 50 yards and had to share the 2 man 100 yard enclosed range so it was slow going and not optimal for testing. I did get some decent work in however.

I started with the 58 cal with 560 gr T/C Hunters and it immediately started showing pressure issues and also discovered that the threads for the nipple were quite worn with gas leakage on the first shot and on a subsequent shot did pop out the nipple. I stopped and set that aside.

I then went to the 54 cal 24" starting at 110 grains of fffg T7 I moved up 115 grains and down to 100 and 90 with no real change in groups, so settled on the 110 grain load. Results below:



I then switched to the 21" 54 cal. I started 100 grs of powder with the 425 CVA Deerslayer HP bullets and after 4 attempts at 3 shot groups sliding up and down the powder charges in 10 gr increments I had not real success. I then switched to a 450gr plains bullet and it immediately grouped with 100 grains of powder. Results below: I did call the high right shot before looking at the target



With the success of the 450 gr, I decided to try it in the 24" barrel gun and it grouped nicely also with 110 gr of powder. Results below



I am changing out the front sights (I need more "down") and heading back out to do some verification and sighting in. I will also chronograph the 450 grain with 100 gr of powder, but I suspect it will be close to 1550 fps mv.

I have a insert coming to replace/repair the worn threads on the 58 cal so after repair I will start again with it and work up, but I suspect it will not meet my 125 yard parameters as I won't be able to push the heavy bullets fast enough. But I will check and develop accuracy and I am confident that I can make it a 100 yard gun.

When looking at these groups do remember that I am using ghost ring sights and a fire sight front bead so a fine sighting for accuracy is difficult and I am quite pleased with the sub 3" results above. Most of the issues are sighting errors, not gun accuracy errors

More to follow!

 

[kelvinator]

That would be good grouping for me at 50 yards, nice work!

 

[Dobegrant]

very nice group

 

[paulab]

Hit the range yesterday and unfortunately couldn't start working at 50 yards and had to share the 2 man 100 yard enclosed range so it was slow going and not optimal for testing. I did get some decent work in however.

I started with the 58 cal with 560 gr T/C Hunters and it immediately started showing pressure issues and also discovered that the threads for the nipple were quite worn with gas leakage on the first shot and on a subsequent shot did pop out the nipple. I stopped and set that aside.

I then went to the 54 cal 24" starting at 110 grains of fffg T7 I moved up 115 grains and down to 100 and 90 with no real change in groups, so settled on the 110 grain load. Results below:

View attachment 206711

I then switched to the 21" 54 cal. I started 100 grs of powder with the 425 CVA Deerslayer HP bullets and after 4 attempts at 3 shot groups sliding up and down the powder charges in 10 gr increments I had not real success. I then switched to a 450gr plains bullet and it immediately grouped with 100 grains of powder. Results below: I did call the high right shot before looking at the target

View attachment 206717

With the success of the 450 gr, I decided to try it in the 24" barrel gun and it grouped nicely also with 110 gr of powder. Results below

View attachment 206718

I am changing out the front sights (I need more "down") and heading back out to do some verification and sighting in. I will also chronograph the 450 grain with 100 gr of powder, but I suspect it will be close to 1550 fps mv.

I have a insert coming to replace/repair the worn threads on the 58 cal so after repair I will start again with it and work up, but I suspect it will not meet my 125 yard parameters as I won't be able to push the heavy bullets fast enough. But I will check and develop accuracy and I am confident that I can make it a 100 yard gun.

When looking at these groups do remember that I am using ghost ring sights and a fire sight front bead so a fine sighting for accuracy is difficult and I am quite pleased with the sub 3" results above. Most of the issues are sighting errors, not gun accuracy errors

More to follow!

You might want to consider getting some platinum lined nipples to handle the loads you are shooting.

 

[chorizo]

You might want to consider getting some platinum lined nipples to handle the loads you are shooting.

Nope, Treso nipples are what I use. But thanks for mentioning the option! My experience has shown that the Treso is THE best option

 

[Idaho Ron]

If you get a platinum lined nipple there are a couple things to keep in mind.
The platinum lined nipple is longer.
The picture I added left to right.
Treso nipple, BACO platinum lined, and TC hot shot.
I ran into trouble with that extra length of the platinum lined one. On My green mountain LRH stainless steel barrel. The so called "clean out " screw was long enough that the longer platinum lined nipple hit the clean out screw.
The second thing. The platinum lined nipple I got from BACO measured .028" a TC hot shot nipple measures. 034".
I have determined that pyrodex likes a nipple hole size of at least .034" and they are shot out at .038.
I had to drill out the nipple to .034 for consistent ignition with pyrodex.

 

[Idaho Ron]

It didn't load the first time.

 

[chorizo]

Thanks! Appreciate the visual and the experience. I am going to stick with the Treso...I have had good luck with them, ignition and service life. The issue is when you rehab used barrels the thread in the breech may be worn. That is the case here and can't take the increased pressure. I have a carbon steel insert coming and I will drill the hole out, reline it and start anew working up. If I could find a plains style conical in the 500-510 gr range for the 58 cal, I think things would work, but they are not available and I am not going to start casting just for that.

 

[chorizo]

Just got back from day 2 at the range. It was a wash. Wind howling and cold, so all I accomplished was to get the right height front sights and get a rough zero.

Rethinking the 58, my over pressure signs might have been the nipple letting loose. I am going to re-approach it after I repair it.

Really didn't get to shoot the 500 gr minies for accuracy or the 560 gr hunters.

On a positive note, Bobby Hoyt just mailed me my 22" 54 cal 1:32 twist barrel, so with repairing the nipple hole and mounting sights and stock on the new barrel, I will have plenty to do next week during the wet weather projected.

 

[Semisane]

Not a thing wrong with those 100 yard groups. Good shooting.

 

[TDM]

Your on the right track @chorizo, almost there.

 

[Fastleo]

Thanks! Appreciate the visual and the experience. I am going to stick with the Treso...I have had good luck with them, ignition and service life. The issue is when you rehab used barrels the thread in the breech may be worn. That is the case here and can't take the increased pressure. I have a carbon steel insert coming and I will drill the hole out, reline it and start anew working up. If I could find a plains style conical in the 500-510 gr range for the 58 cal, I think things would work, but they are not available and I am not going to start casting just for that.

Can you document and post up the repair? I’d like to know what brand you use and see the results.

 

[chorizo]

Click on the part number, it will take you to the page in mcmaster-carr on line catalog.

Keensert

1/4"-28

3/8"-16

__

3/8"

Q

0.332"

Slotted

10

90259A136

10.00

 

[Urban Coyote]

Good stuff, thanks for sharing your results and please keep them coming. Pretty cool project.

 

[chorizo]

Well, having studied the situation and taking extensive measurements and consulting with my "engineering expert" ( @SDSmlf ), a liner isn't going to work. Just not enough depth and steel for the coarse thread of the insert. Another issue is getting the alignment correct and I do not have the tools for that, so I would have to take it to a machinist. The cost would be north of what it would take me to get another barrel bored out. Also an oversize musket nipple likely will not work as I can only get a .255 (.005 step up). Just not enough metal I will try it and see, but the question is pressure and it will be about 1000psi on it if the chamber pressure is at 20, 000 psi (which it is)

As I have a 58 cal 22" being bored and cut, I will set this 58 cal one aside for now and concentrate on the 54 cal. On Monday a 22" 1:32 twist 54 cal barrel is arriving, so I will have three to shoot. until I can figure out what to do with this 58.

The hard head in me says keep trying, but sometimes you got to quit while you are ahead. So this barrel is going on to the broken toy pile until I can figure something out with it.

 

[kelvinator]

Could an over sized 1/4-28 nipple be an option? TOW lists them from .005" to .025" over size in .005" increments.
Not Treso but might keep that barrel out of the "broken toy pile".

[IMG alt="Oversize threaded nipple, .260-28, 1/4-28 with .010 oversize thread, for CCI #11 cap, stainless steel Cone length: 0.440 Thread journal length: 0.195 Overall length: 0.635 Diameter of base: 0.307 "]https://cdn.trackofthewolf.com/imgPart/rst/rst-s_0.jpg[/IMG]​

Oversize threaded nipple,.260-28, 1/4-28 with .010" oversize thread, for CCI #11 cap, stainless steel Cone length: 0.440" Thread journal length: 0.195" Overall length: 0.635" Diameter of base: 0.307"

Part Number: ROS-10-S Availability: Price: $6.99 Order Quantity:

 

[chorizo]

Not a musket nipple, rather those are #11. I tried installing a 5/16 x 24 musket nipple but all you get before it bottoms out is 2.7 turns (threads) without using a square face mill bit to give you maximum room and as I don't have a mill that was all I could get and that wouldn't hold. The recommendation that you install an insert won't work either. The threading on an insert is 3/8 x 16...even less threads to work with. You have about 6.5 mm of depth from seat to bottom of flash channel. The way the breech is set up and bored, at best you have 4.5mm-5mm of thread. With a 28TPI that is only 5 turns (5 threads) 24 tpi even less (4 threads), 16 tpi less still (2.8 threads) considering that the first part of the threading on a nipple only starts a 0.5mm in on the shank...all of those calculations are best case...you can really deduct 0.5 turns from those numbers. So on the broken toy pile it goes until I can find a breech replacement, if ever.

All calculations have shown me that I can get what I am after by using a 54cal. Sometimes you just got to step back. that will be the case this time. Not that the 58 isn't capable as I haven't gotten to the accuracy eval stage, I screwed up and didn't thoroughly inspect the breech and nipple threads before I sent it off to be bored out.

So, I fall back onto my 54 guns. A 54 barrel with 1:32 twist and 22' length arrives today. That will give me three guns to play with. I will stay busy for a while.

5/16x24 musket nipple on left, standard 1/2x24 musket nipple on right

 

[kelvinator]

Ah, musket nipple, duh, brain fart, my bad.

 

[chorizo]

Well, the world balances itself....just as things go wrong, things go right. Today I had been anticipating my 22" 1:32 twist 54 cal barrel I sent to Mr. Hoyt 4 weeks ago. When the postal lady handed me my tube, it was too heavy for one barrel. Surprise, surprise, surprise....he did the 58 cal barrel 22" 1:32 twist I sent 11 days ago also. So now I am back in the 58 game. Got to mount sights and I am waiting on Williams to send those, but I got some shooting to do!

So a recap of guns:

24" 54 cal 1:38 mounted in Renegade stock
21" 54 cal 1:38 mounted in WMC stock
22" 54 cal 1:32 mounted in WMC stock
22" 58 cal 1:32 mounted in Big Boar stock

 

[longcruise]

@chorizo Not to beat a dead horse, but you may be underestimating the ignition potential of the #11 nipples which are readily available in the oversizes. I have used musket nipples and #11 nipples interchangeably on several cap guns and find there is no noticeable difference in ignition. If a #11 works fine on any given load then there should be no difference with your dinosaur loads. Once a charge is started it does the rest all by itself regardless of what sets it off.