Does this seem a little slow?

[Cowboy2]

I took my chronograph out today and see how fast my new GPR was throwing round balls, and at 70grs 3F of Goex, it was only 1460fps (measured at about 30ft). Does that seem a little slow? My rifle loves this load, but I'm not sure I feel its enough for a whitetail at 100yds. The manual lists 90gr 3F as the max- so I had previously only shot up to 80gr. Is the manual low-balling it?

Thoughts?

 

[paulvallandigham]

Mind telling us what caliber? For a .50 caliber, that is not too low. For a .54 it is. What ball diameter, patch thickness, and lube are you using? What bore diameter is your barrel-- EXACTLY- to the thousandth of an inch, please?

What are the spent patches telling you?

I wish I had a crystal ball, but that didn't come with my diapers! I can't help you without more information. :shocked2: :idunno: Sorry. :surrender: :hatsoff:

 

[longcruise]

Hard to say with the info provided. Try setting your chrono at about ten feet. Get as close as you can without the ejecta interfering with the readings.

My GPR .54 shoots 1668 fps with 80 grains of scheutzen 3f. Thats with a green mountain replacement barrel. The Lyman barrel shot a bit faster.

My .50 Traditions Deerhunter (24" barrel) shoots 1551 with 70 grains of schuetzen 3f. This gun shoots faster with scheutzen 3f than with goex 3f.

There are many variables that can effect your results here's a few that come to mind.

Patch thickness (tighter loads shoot faster)

Bore condition (rougher bores shoot faster, and no, that is not a type )

Slicker lubes shoot slower.

Various granulations (ff, fff) shoot a different speeds.

Various brands of powder can make a rather large difference in velocity. My tests show differences of hundreds of fps! :shocked2:

Powder lots from the same powder maker can vary a bit too.

 

[Cowboy2]

Sorry, thought I had put the load in there. Its a .50 cal. .495 ball with .15 Ox-Yoke patch with whatever lubricant they use on them. Spent patches look just like the manual says they are supposed to- no cuts or burns. The .15s aren't difficult to load, the .18s I've tried are, plus they aren't giving me the groups the .15s are. The .20's would have to be pounded in.

But from what you've both indicated so far, that velocity from that much powder isn't out of line for a .50.

 

[hanshi]

Velocity per grain weight of powder is not a straight line. I've had a 5 grain increase give me an extra 275fps; more that the previous 10 grains. Use a good, snug load, at least a .015" patch and go for your most accurate load. Your speed is not necessarily that slow and will kill any deer you can hit with it at any range. YOU are the variable, not the load.

 

[ApprenticeBuilder]

My rifle loves this load, but I'm not sure I feel its enough for a whitetail

Thoughts?

If its accurate and you can put the ball where you point out to 100yds then I am thinking your over thinking this, doesn't matter the caliber if it goes where you need it to.

Does not take magnum velocity to kill a soft skinned animal, a .50 call ball is larger going in than most whiz bangs going out.

Once the ball exits the off side of the animal all of the energy at that point is wasted, just a thought.

 

[Zonie]

The Lyman "BLACK POWDER HANDBOOK" says your muzzle velocity in a .50 caliber X 32" long barreled gun with a 70 grain powder load of GOEX 3Fg under the roundball will be about 1655 FPS.

The roundball ballistics calculator says that velocity will be reduced to about 1540 fps at 10 yards (30 feet) downrange.

Then again, different barrels and different lots of powder will shoot the same loads differently.

 

[Trench]

There's really not to much to fret over here. My round ball ballistic calculator shows your ball starting out at 1490fps is going 926fps at 100yds. If you were getting 1590fps at the muzzle you would have 951fps at 100yds.

Using this calculator, I found out that the round ball just bleeds too much velocity to worry about trying to increase power down range. So, even if you did get more velocity at the muzzle, id doesn't make that big of a difference that far down range.

 

[ebiggs1]

Does that seem a little slow?

Yes, it does.
Are you sure your chronograph is accurate? They can be finicky if not set up properly.

Does 1460fps really matter? Probably not. :hmm:

 

[mmahlock]

Personally I don't think it too slow. If you are getting consistent tight groups at 100 yds then you can be sure of hitting your target. If you are concerned about penetrating power, make up a wood target 2 inches think and shoot at it from 100 yds. If you go all the way though it your shot will kill just about anything you can hit.

 

[Cowboy2]

ebiggs, I wouldn't trust any of them down to the fps, but going by some other things I measured with it that day, I'd say its certainly ballpark accurate.

Well, I took the rifle out again yesterday and tried some heavier loads. 85gr 3F with the same patch/ball combo was giving me groups almost as tight as the 70gr, say 2.5-3", as opposed to 1-1.5". It was too windy to use the chronograph, so I'll have to check the velocity later, but obviously, there was noticeably more recoil. Sometime when the wind has calmed this week I'll take it out and measure it at 30yds, then both at 100, and see if they're so close at distance, as Trench was noting, to make the heavier load worth the effort- or if the POI tracks close enough to just use one for targets and one for critters.

I appreciate everyone's help.

 

[Many Klatch]

Cowboy, try piling a few phone books back to back at 50 yards, then shoot a ball or two into them. If you penetrate two or three or five phone books that should show you how your load is doing.

Many Klatch