Hoyt Thumper Carbine Velocity results..chronographed

[chorizo]

Weather cooperated and I got some velocities for my three Hoyt Thumper carbines.

Parameters :

Triple 7 FFFg powder, 50 degrees 45% humidity, oversized by one caliber OP wonder wad, RIO Musket caps. Each gun was shot twice from the bench prior to chronographing velocities and an alcohol swab was run in and out of the bore between shots. 3 shots were then chronographed. Last shot was with chrono removed and fired from standing to assess felt recoil

Gun # 1.............58 Cal 1:38 twist 24" barrel 500 grain minie ball .582 diameter. 100 grains powder

1. 1471 fps
2. 1496 fps
3. 1476 fps
Average 1481 fps SD 13
Recoil no more than a heavy game load in a 2 3/4" 1 1/8 oz 12 ga load

Gun # 2...........54 cal 1:38 twist 24" barrel, 485 grain conical .542 diameter. 110 grains powder

1. 1592 fps
2. 1571 fps
3. 1585 fps
Average 1582 fps SD 10
Recoil not discernably different than the 58 cal

Gun # 3.........54 cal 1:38 twist 21" barrel 425 grain .544 diameter concial. 100 grains powder

1. 1527 fps
2. 1574 fps
3. 1641 fps * powder was compressed harder than above
Average 1590 fps SD 57
Recoil...same as the others

OBSERVATIONS:
1. The powder was fully burning within the barrel. No bright flashes or smoke rings. Observer noted that no great blast/flash more than standard smokeless powder guns and only slightly more smoke.
2. Velocities realized exceed my max expectations by 80 fps to 100 fps in all three guns.
3. Bores are rough and need polishing. Lots of cutter chatter marks on the rifling and the bullet hangs up when seating it. Shot #3 in the 21" gun was seated HARD as it hung up and when pressure was applied it let go and seated much harder than the other two rounds. *I attribute the higher pressure of the third shot to the hard seating.


After cleaning then polishing these bores, I will then shoot for accuracy while adjusting powder loads. The bullets were grouping fairly well considering that I wasn't looking to group and was shifting sight adjustments to center rounds on target.. Surprisingly, the #3 21" gun needed very little adjustment to center rounds.

All in all, very satisfied with the progression. A little fine tuning on these guns, polishing the bores and after the lousy weather of the next week subsides it will be back to the range for some accuracy results.


@SDSmlf @SOLANCO @Bad Karma @Urban Coyote @Brokenbear @Relic shooter @ETipp @Dale Allen Raby @wganz @TDM @tenngun

 

[chorizo]

Here are the three external ballistics calculations for those bullets and velocities

 

[64Springer]

Those are seriously impressive numbers.

Anyone who says black powder can't compete with modern powder is ill informed.

Good Job and thank you.

 

[Thingamajiggy]

View attachment 200098

Weather cooperated and I got some velocities for my three Hoyt Thumper carbines.

Parameters :

Triple 7 FFFg powder, 50 degrees 45% humidity, RIO Musket caps. Each gun was shot twice from the bench prior to chronographing velocities and an alcohol swab was run in and out of the bore between shots. 3 shots were then chronographed. Last shot was with chrono removed and fired from standing to assess felt recoil

Gun # 1.............58 Cal 1:38 twist 24" barrel .582 diameter 500 grain minie ball. 100 grains powder

1. 1471 fps
2. 1496 fps
3. 1476 fps
Average 1481 fps SD 13
Recoil no more than a heavy game load in a 2 3/4" 1 1/8 oz 12 ga load

Gun # 2...........54 cal 1:38 twist 24" barrel .542 diameter 485 grain conical. 110 grains powder

1. 1592 fps
2. 1571 fps
3. 1585 fps
Average 1582 fps SD 10
Recoil not discernably different than the 58 cal

Gun # 3.........54 cal 1:38 twist 21" barrel 425 grain .544 diameter concial. 100 grains powder

1. 1527 fps
2. 1574 fps
3. 1641 fps * powder was compressed harder than above
Average 1590 fps SD 57
Recoil...same as the others

OBSERVATIONS:
1. The powder was fully burning within the barrel. No bright flashes or smoke rings. Observer noted that no great blast/flash more than standard smokeless powder guns and only slightly more smoke.
2. Velocities realized exceed my max expectations by 80 fps to 100 fps in all three guns.
3. Bores are rough and need polishing. Lots of cutter chatter marks on the rifling and the bullet hangs up when seating it. Shot #3 in the 21" gun was seated HARD as it hung up and when pressure was applied it let go and seat much harder than the other two rounds.


After cleaning then polishing these bores, I will then shoot for accuracy while adjusting powder loads. The bullets were grouping fairly well considering that I wasn't looking to group and was shifting sight adjustments to center rounds on target.. Surprisingly, the #3 21" gun needed very little adjustment to center rounds.

All in all, very satisfied with the progression. A little fine tuning on these guns, polishing the bores and after the lousy weather of the next week subsides it will be back to the range for some accuracy results.

View attachment 200081
@SDSmlf @SOLANCO @Bad Karma @Urban Coyote @Brokenbear @Relic shooter @ETipp @Dale Allen Raby @wganz @TDM @tenngun

Impressive! Especially the .58 pushing a 500 grain slug at almost 1500 fps. I have a couple .58's coming, one being built and an Investarm on it's way. Would be interesting to see what numbers I can get. Good info, keep up the good work.

 

[Urban Coyote]

Wow! Impressive and interesting info. Keep us posted and thanks for sharing.

 

[ETipp]

Impressive work. Well done!

Are those stocks from TC New Englanders?

 

[chorizo]

Impressive work. Well done!

Are those stocks from TC New Englanders?

The 58 cal is from a Big Bore, the other two are 54 cal White Mountain Carbine stocks

 

[Stykbow]

@chorizo is there a reason you used 110 grains of powder in gun #2 and only 100 grains in the others or was that just a typo?

 

[chorizo]

@chorizo is there a reason you used 110 grains of powder in gun #2 and only 100 grains in the others or was that just a typo?

No typo. I started at 100 grains but it only gave me 1450 fps, so I upped it to 110 grains then ran three velocity checks. The 10 grain addition bumped the velocity 130 fps giving me my desired velocity.

100 grains was a load starting point with the ultimate result, a desired velocity, the goal. I took several print outs of the external ballistics I wanted to achieve. but was unsure what I would get using Triple 7 FFFG as no charts gave me exactly the bullet or loads.

I knew 100 grains was still below maximum and if needed I would work up to achieve the velocity. Fortunately, that load was the only one I needed to bump and fortunate only one 10 grain bump was needed.

Out of ease and to lesson confusion on the results I omitted that I shot one extra, as it didn't give me what I wanted, I deleted it from the string, I bumped the load and started fresh

 

[TDM]

A most impressive test, great info and great results. I like it!

 

[chorizo]

I was using a Magnetospeed V2, fixed grain powder measures, 91% isopropyl alcohol for between round swabs, Minies from Maplewood Bullets, 485 grain conical from No Excuses, and the CVA 425 grain 54 cal concial that I dug up from an auction (over 100 of them).

I used a calculator provided by @Dale Allen Raby for powder burn, velocity and pressure estimates.....internal ballistics P-Max black powder internal ballistics

Hodgdons Triple 7 Data sheet for velocity and max load estimates

The 2nd edition Lyman BP Handbook written by Sam Fadala for ballistic coefficients of the bullets with additional information on pressure and velocities of various powder loads.

For external ballistics I used the Hornady Ballistic Calculator Ballistic Calculators - Hornady Manufacturing, Inc

I also read in depth Ned Roberts book and was inspired by Val Forgetts' experimentation with FFFG in large bore guns with heavy charges...for the same reason I was...complete burn and higher velocities in carbines

A combination of these, by cross checking and using one to validate the other, gave me a starting point and a zone to work in I felt was safe and I was comfortable in.

ASSUMPTIONS:

1. T7 is about 10% more vigorous than standard BP
2. FFFG burns more rapidly, thus providing an earlier pressure peak and a more complete powder burn in short barrels
3. That I was taking a chance because everything was an estimate based upon what other propellants and bullet weights were doing.

There were lots of stubby pencils by the time I got done. It seemed to work out well. You got to love it when a plan comes together. Now onto the real work...ACCURACY

 

[TDM]

The Lyman BP Handbook is a good one. I swear I have a copy, but can’t find it!!!

 

[Slinginslugs]

VERY impressive my friend. Your research and preparation look to be giving you the results you are looking for. You get your development finished and sighted properly that is going to be a heck of a trio!

 

[Dobegrant]

Really interesting information, it will also be interesting to see the accuracy results you get.

 

[longcruise]

Anyone who says black powder can't compete with modern powder is ill informed.

That was modern powder!

If I ever feel incredible guilt I'm going to by pass the hair shirt and shoot a couple shots out of something like #1.

 

[chorizo]

Really interesting information, it will also be interesting to see the accuracy results you get.

Yep, velocity is just one piece of the puzzle.

Previously stated goals:

A hunting gun with a 100 yard zero, with adequate accuracy (less than 3" moa), with 3" or less drop at 125 yards, and with a minimum of 1100 ftlbs of energy, in a carbine form factor with ghost ring hunting sights.

Not asking for much.

 

[TDM]

Admirable goal and you’re well on your way there. Once I get 50 yards somewhat perfected I will follow your footsteps.

 

[Dobegrant]

I have a Lyman Deer stalker which is .54 cal, 24” barrel and is 1-48 twist rate so this is all very interesting to me.

 

[chorizo]

I have a Lyman Deer stalker which is .54 cal, 24” barrel and is 1-48 twist rate so this is all very interesting to me.

Shoot the cva 375 grain Deerslayer bullet with 100 grains of T7 FFg. Adjust your load up or down for accuracy. Buddy has one and gets good results with that.

The only way your going to find out is to burn powder and time. I figure you will get around 1500 fps with that load.

 

[Dobegrant]

Thanks I will order some, have 1 pound of 777 but have never used it, only goex ffg