PRB vs PA Conical test

[Don Steele]

In a thread in the Percussion Rifles section there's a discussion of the Hornady "PA Conical" bullets going on. Thanks to Mole Eyes generosity, I had an opportunity to run a direct comparison between the PA conical and my personal choice PRB hunting load. I'm posting here for general information.
The rifle: For this test I'm shooting a 50 caliber T/C hawken style rifle with a 32" Green Mountain "drop-in" bbl.
Conditions: Bright sun, some shade on the targets. Blustery winds running 15-20 mph. Temp. was mid 60's.
All shots from sandbags at 50 yds. I alternated shots, first a PRB, then a conical. Back and forth until I had 5 shots on each target. All 10 shots "felt good". None were called flyers. The powder charge for each shot is 90 gns.(by volume measure...not weighed) Goex 2f.
My PRB combination is a .500 lead ball in a .021 patch dry lubed with 7:1 Water/Ballistol.
Here's the PA conical target:


For comparison, the PRB target:


Based on the comments from Galamb in the other thread, I find myself wondering if 3f might not be a better choice when shooting HB conicals. I use 3f with Hornady's 385 HP/HB Great Plains bullet with excellent results. For this first test however, I wasn't so much looking for a BEST load as wanting to simply do a DIRECT comparison.

 

[Vaino]

What is the "twist" and depth of rifling of the "drop in" bbl? If it's deep rifled, it's unsuitable for a conical....irrespective of "twist". The blowby would be tremendous.

Surprising that the conicals shot that small a group if they're being shot out of a PRB bbl.....and the PRB group is excellent......Fred

 

[coloradoclyde]

I find myself wondering if 3f might not be a better choice when shooting HB conicals.

And round balls too..... :thumbsup:

 

[jamesthomas]

I'm wondering how you got a .500 Rb. with a .21 patch down the barrel :idunno: :shocked2: . Good group though for the Rb. and the conical also. How was the recoil with the conical?.

 

[Stumpkiller]

I look at those two targets and the answer jumps out at me. Like Occam said: the simplest answer is the best.

I take it Green Mountain bores run a little larger than T/C. I'd need a hydraulic ram press to get a .500" ball and .021" patch into my .50 cal T/C rifle.

 

[mooman76]

One is obviously better than the other but neither one is all that bad. Certainly good enough for hunting loads. Starting out at 90gr are pretty heavy loads and dropping them down some could make your results even better.

 

[Don Steele]

Start it with one of those little Delrin starters and a mallet to get the ball below the muzzle crown. Cut off the excess patching. Then a conventional short starter and ram home with a 3/8's in. solid brass range rod.
I believe the twist in the Green Mountain bbl is 1:70. The PA conicals started a LOT easier in the Grn Mtn. bbl than they did in the original T/C bbl. I found them almost too difficult to start in the T/C bbl. Wound up using a mallet to tap on my short starter.
Once started they went down pretty easy in both bbls. btw: I wipe between shots with a single patch, just damp with moosemilk. I'm of the opinion they went down too easy in the Grn Mtn. bbl. Were I to take them in the field to hunt, I'd put a wad on top of the conical to hold it in place.
The 90 gn charge of 2f was used because that is what has proven to be the best choice for the Grn Mtn. bbl with PRB. My intention wasn't to find the BEST load for the PA conical. All I wanted to do was compare it's performance against my PRB hunting load.
Thanks for the comments folks. :thumbsup:

 

[Larry Pletcher]

Don,
My complements on the test and your shooting. I like your attention to details. Conventional wisdom would suggest that PRB would shoot better in a slow twist barrel, but few of us take the time to to confirm this. Without testing, my gut would have expected the conical to not perform even this well. I have to revise my thinking - I would have expected the conicals to key-hole. Thank you for taking the time.

Regards,
Pletch

 

[rodwha]

The PA conicals are short and were designed for use in slow twist barrels.

 

[Larry Pletcher]

THanks. For a better understanding, are they less than 2 calibers long? My long range bullet gun uses a PP bullet that is almost 3 calibers long, but that is with a 1x18 twist.
Regards,
Pletch

 

[Don Steele]

Thank You Pletch.
I've been reading your excellent T&E reports over the years...I admit I was modelling this modest effort after your style.
For those not familiar with them, here's the Dimensions on the PA conical:
dia. .509" nominal, length .562".
In my opinion, the shooting would have been better(more precise in both cases) if I used a 6 o'clock hold on the bull rather than center hold. At this time however...since we're in the middle of hunting season, my PRB bbl. is dialed in for hunting, i.e.: center hold. I know, I could have shot 6 o'clock anyhow and not care where the group went, but I didn't. Maybe next time.
At this point, I find myself wondering if the same charge (90 gns.)of 3f would show some tightening. I noted in my last response that the PA conical was almost too loose in the Grn Mtn bbl. Perhaps that is telling us is that more force is necessary to expand the skirt into the rifling...?? That said, would 3f provide an increase vs. 2f..???
Once again Pletch thank you for the kind words. You're work is the Gold standard for testing. :bow:

 

[Walks with fire]

One wrap of paper patch on the PA conical may tighten your groups and load more snugly and 3f may indeed expand the base into the grooves a little more effectively. That may provide a better seal in the bore; better horizontal grouping and less vertical variation. Mostly theory though and testing would verify. Just my opinion but if you tested both at 100 yards I think the ball would clearly show an advantage.

Several in my deer hunting group use the PA conical and it does work quite well. IMO it does seem to produce a better blood trail than ball does. I still stick to ball for my deer hunting.

GM recommends .495 ball for hunting and .500 for target and doesn't recommend conical of any kind in this barrel. If I get a chance in the next few weeks I will mold my GM .50 barrel and look at it on the comparator to see what size bore it is. Not that all GM .50 will be that size but just for a reference; I don't own a TC Hawken barrel anymore.

The .500 ball group looks great and a good choice for hunting if it loads well for you in the field. Thanks for posting your test.

 

[galamb]

If you don't have any FFF kicking around maybe just up your charge of FF to 95 grains (or even drop to 85 - you will still have a ton of thump).

That (95 grains of FF) should give you about (kinda/sorta) the same pressure as 90/FFF, just the pressure curve will be a little different.

Worth a try to see if it tightens up.

(final though, perhaps the FFF pressure spike helps flare the base a little better than FF giving it a better gas seal ???)

 

[Don Steele]

Thanks for that suggestion.
I do have plenty of 3f and may give that a try. I've wondered the same thing ( about the pressure spike). Moleeyes tells me that Hornady emphasizes the use of a HUNTING load for this product.
I'm pretty satisfied with my PRB hunting load. I've killed 2 deer with that combination, both dropped in their tracks so I can't comment on the quality of the blood trail :wink: . That said, I also really enjoy playing with new toys when I have the chance !!! :thumbsup:

 

[zimmerstutzen]

Did I miss the depth of rifling.
Starting a ball with a mallet? Deforming the ball when starting may account for the large size of the group.

The pa conical in a barrel of sufficiently shallow rifling will shoot one hole groups at 50 yards. But the round ball can be made to do the same..

The conclusion I see from the comparison is that the drop in barrel is not fit for either projectile.

 

[nkbj]

The initial pressure spike with faster granulation might help to seal the bore with less powder. That seems to be the case when shooting the heavy skirted Lyman .54 minie in a GPR.

 

[jamesthomas]

Sir, have you tried .495 or .490's Rbs in the rifle with maybe a .024 patch? it would probably be easier to load (no mallet) and shoot just as good. Just a thought.

 

[Don Steele]

Good idea.
As we all know, there's a lot of ways to skin this cat(i.e. : small groups).
When I bought the bbl, the fellow I got it from recommended .500 rb's. And a tight combination. I also have some thicker patch material, almost a "light canvas" that might go up in the mid 20's or more. Also have .490 balls.
Perhaps I'll run those side by side sometime against my current combination just for fun.
Surely SOMETHING can be found to work since It's been pointed out that this bbl isn't fit for either of the loads tested.

 

[Walks with fire]

The ball group looks pretty darn good to me. The more you shoot it the better it will get.

I bet if it were fired from a vice it would be one big hole; none of us hold perfectly steady and have the exact same position viewing the sights. Looks like a fine barrel to me.