PRB Ballistics

[Santa Fe]

So I never shot any muzzleloader over a cronygraph so today I fired 5 round balls from my Lyman GPR .54 caliber thru my crony it was most interesting. Each round fired got a little faster. The load was Speer .530 RB .18 patch 90 grains of 3F Goex powder first shot was 1610 FPS
1660 FPS
1683 FPS
1707 FPS
1739 FPS
I also fired 4 of the same loads thru my T/C renegade .54 26” barrel
1550 FPS
1636 FPS
1682 FPS
1537 FPS
I fired 5 rounds but the sun was getting low so last shot didn’t read on the crony extreme spread was a lot more than the Lyman. The longer barrel makes a difference

 

[jcs266]

Thanks for sharing this info. I've been wondering what the velocities are for PRBs. I know when I shoot the 1/2" thick AR500 steel plate on my home range here the .530" prb hits it plenty hard.

 

[Grimord]

I suspect the reason the velocities increased with each shot was due to fouling buildup in the barrel. Did you swab between shots?

 

[CoHiCntry]

What’s the Lyman barrel length?

 

[user 36911]

It's 32"

I agree the fouling was giving a better seal and gave higher fps.

 

[Grenadier1758]

@Grimord and @MtnMan and Dutch Schoultz among many others have identified the build up of fouling in the barrel as resulting in an increase of pressure. That increase of pressure ups the velocity on subsequent shots. The change in velocity will result in larger groups. That is why so many of us will wipe the bore between shots or use a wet patched ball to try to keep the fouling in the bore at some consistent condition.

 

[user 36911]

I swab between shots. I simply made a statement of why the fps increased.

No wet patch for me though. I swab between shots with dry tow. However, i'm a hunter and not a target shooter.

 

[Santa Fe]

Ok so the Lyman GPR I bought new the renegade I bought used. The T/C renegade has ruff spot about 8” from the muzzle it got a lot harder to load with each shot and the 4th shot was the slowest

 

[Santa Fe]

I didn’t swab or wipe between shots

 

[Santa Fe]

Thanks for sharing this info. I've been wondering what the velocities are for PRBs. I know when I shoot the 1/2" thick AR500 steel plate on my home range here the .530" prb hits it plenty hard.

That Speer .530 RB weights 226 grn. At 1600-1700 FPS that’s serious thump. It’ll knock a white tail stiff

 

[Cattywompuss]

Is the GPR rated to 120gr of 2f? Seems like 90 of 3f is knocking on the door, as the late great Larry Munson would say.

 

[Phil Coffins]

Good data. To add to your findings my GM barreled rifle is 32” and shooting a .535” ball with 110 grains of 2fg GOEX I get 1818.5 average FPS extreme spread 42.6 FPS . Groups for five shots are about 1 1/2” by 2” at 50 yards. Patch lub can make a difference I use spit.

 

[deerstalkert]

seems yesterday was the day for Chronographing muzzleloaders.
i ran 5 shots from my Hawken.
average for the five was 1630.
95g homemade ffg
.530 ball
.016 patch
28 inch barrel swabbed between each shot with spit patch.
high 1710 fps, low 1600.

 

[deermanok]

What about shorter barrel rifles?
I have a 24 inch barrel, shooting a 490 ball with 80 grains of 3f Old Ensyford.

 

[Notchy Bob]

So I never shot any muzzleloader over a cronygraph so today I fired 5 round balls from my Lyman GPR .54 caliber thru my crony it was most interesting. Each round fired got a little faster. The load was Speer .530 RB .18 patch 90 grains of 3F Goex powder first shot was 1610 FPS
1660 FPS
1683 FPS
1707 FPS
1739 FPS
I also fired 4 of the same loads thru my T/C renegade .54 26” barrel
1550 FPS
1636 FPS
1682 FPS
1537 FPS
I fired 5 rounds but the sun was getting low so last shot didn’t read on the crony extreme spread was a lot more than the Lyman. The longer barrel makes a difference

This is good information! Thank you for posting!

With the discussion of the effect of fouling on pressure and velocity, I would be interested in seeing the same test duplicated, except for wiping the bore in between shots. I would like to see what difference that makes for you, and if there would be a reduction in the difference between highest and lowest velocities.

Thanks!

Notchy Bob

 

[Santa Fe]

This is good information! Thank you for posting!

With the discussion of the effect of fouling on pressure and velocity, I would be interested in seeing the same test duplicated, except for wiping the bore in between shots. I would like to see what difference that makes for you, and if there would be a reduction in the difference between highest and lowest velocities.

Thanks!

Notchy Bob

Ok when I get some spare time this week I’ll do it. Wiping the bore with a damp patch?

 

[Grenadier1758]

A barely damp thin patch to ride over the fouling on the down stroke and bunch up and pull the fouling out on the way out.

 

[Notchy Bob]

Ok when I get some spare time this week I’ll do it. Wiping the bore with a damp patch?

A barely damp thin patch to ride over the fouling on the down stroke and bunch up and pull the fouling out on the way out.

What @Grenadier1758 said. Thank you! I believe a number of people will be interested in what you find.

Notchy Bob

 

[deerstalkert]

I don't want to walk on the OP's thread but i did some testing,(burning powder) and thought when Sante Fe does his we can compare results. I didn't shoot for accuracy, but at 30 yards the 6 inch shoot-n-see was all yellow when i finished.
TC Hawken 28 inch barrel
started with homemade ffg.
95g for 4 shots. spit swabbed barrel between each shot . O10 wonder lubed patch cut from bed sheet, with Honady swaged round ball
1.1020 fps
2. 1011 fps
3.1072 fps
4. 1045 fps
average fps= 1037 extreme spread=61 fps

Next tried .016 pillow ticking as the only change

95g homemade ffg. spit swabbed between shots. .016 wonder lubed pillow ticking.
1.1344 fps
2. 1336 fps
3. 1371 fps
4.1449 fps ( misfire with flash channel primed with ffffg) too much spit

average fps= 1375 fps. extreme spread = 35 fps if we throw out the 1449.
the above showed in my gun the patch thickness made a great difference. other then being harder to seat!

next i switched to Goex ffg with all other variables the same as test 2.
the ticking sure makes me work seating the ball.
1. 1612 fps
2. 1628 fps
3. 1640 fps
4. 1638 fps
average fps.=1629.5 fps extreme spread=28 fps.
think this is going to be my hunting load.

next up is my 22 inch investarms.
still using the ticking and 95g of Goex ffg
swabbed between shots.(less spit) except for shot's 2 and 4
1. 1494 fps swabbed
2. 1547 fps no swabbing between 1 and 2
3. 1489 fps . swabbed between 2 and 3
4. 1556 fps . not swabbed between 3 and 4.
Momma called lunch so had to quit.

looks from this small sample as if swabbing lowers velocity 50 to 60 fps in my gun.

I think next I will shoot as above but for accuracy. by the way that can of Goex is at least 30 years old. found it on a shelf in the canning shed where I put it when i built the shed in '91

 

[hanshi]

Patch thickness/material can make a major difference in both accuracy and especially velocity. Some years back I chronographed a .40 X 38" barrel. My standard load of 60 grns of 3F gave, with a .015" pillow ticking patch, a velocity of about 1850 fps (sd 17). But when MATTRESS ticking (.018") was substituted the velocity went to 2137 fps with an es (sd 16) of 44 fps. Tighter loads generally give higher velocities and better accuracy.