Natural Cast Accuracy Caliber - Does it exist?

[davidheart]

I had a thought go through my head that I'm hoping will be a relatively simple answer. ((Even now I'm laughing at myself.))

Is there a particular caliber (ie: boolit diameter & velocity combination) which lends itself exceedingly well to 300 yard accuracy.

I know we should be really happy with one inch at 100 yards from a cast boolit perspective... but is there a particular caliber or combination which will perform naturally well so half inch at 100 yards is not out of the question and velocity is not so hampered to make a 300 yard hunting shot (deer/eastern black bear) out of the question?

I know the answer is out there... and it very well may be "Whatever you have, no matter what caliber you have, if you have the right boolit and keep it under 2200 fps you'll be fine." But I'm curious in regards to ideals.

[smilie=p:

[Outpost75]

You need to go over to the "other" forum to catch Larry's current discussion on this, but here is a taste to whet your appetite.
You are welcome to join the discussion over there:

. I use the Applied Ballistics Calculator as received with Bryan Litz's book on Applied Ballistics For Long Range Shooting. It uses the Miller Formula and gives an SG of 1.4 as fully stabilized. Just noting the difference so you can compare the two. Using my cast (#2 alloy) 30 XCBs at .985 length at 1800 fps I get the following SGs;

10" twist: 3.84 SG
12" twist: 2.67 SG
14" twist: 1.96 SG
16" twist: 1.50 SG

I might have to just drop back to 1700 - 1900 fps with my 16" twist 30x57 XCB just for S&Gs to see what happens.....

http://www.castbulletassoc.org/forum/view_topic.php?id=12458&forum_id=63

[.22-10-45]

Looking at the question in a historical perspective...the Creedmoor match shooters considered 300to 500yds. Mid-range. The most popular calibers were the various .40's... Sharps had their .40-70 2 1/2" straight, & .40-70 2 1/4" B.N. Ballard had their .40-70 & .40-63 everlasting (same outside dim. thicker walls) & the .45-70. Probably any of the .30 cal. from .30-40 krag thru .30-06 will do well.

[Good Cheer]

Yeah, 40-ish is where it's at.

[jcren]

Seems like the big bores work best. Large bullets and slow twist/velocity seems less effected by casting variables.

[W.R.Buchanan]

I would second the examples from above. From my reading over the years the larger calibers seem to be the best performers with cast boolits. One big advantage they have is more resistance to external influences due to higher inertial retention over distance.

Venturino shoots a lot of Black Powder Cartridge Silhouette, his guns are normally 1MOA or he doesn't use them. His exact yardstick is 3" at 300 yards. if the gun won't shoot to that then he won't use it. But he will try everything he knows (which is a considerable amount on this topic) to make the gun shoot. If it won't shoot then down the road it goes.

Obviously he is casting his own boolits and is somewhat of an Authority on the subject. But the long and short of it is just like any other precise endeavor. IE; meticulous attention to detail, and relentless pursuit of perfection. He freely states that the reason he does as good as he does is because he makes better ammo than most everyone else. And that alone will make anyone perform better.

All the factors discussed on this site are relevant and contribute in one form or another to the ultimate goal of having boolits which are as close to identical as possible. Consistency is the name of the game were accuracy is the primary goal. No other way around it.

You have to make sure the bases are sharp and square, you have to weigh all the boolits and sort them into groups, and you have to assemble them into best cartridges you can make.

Only then will you realize the best performance from your guns,, Whatever they are.

Randy

[Bigslug]

Depends a lot on how flat a trajectory you demand from a hunting bullet and if you need a repeating rifle or not. Other projects slow the research, but if I had to put my finger on something at this point in my education, for just sheer accuracy potential, I would have to pick the 535 grain Postell bullet at 1100-1150fps out of a .45-70 using minimally sized brass:

1. It's basically a straightwall pistol case - minimal rocket science required there.
2. The bullet's got a stout nose to help center itself up and resist slump.
3. You avoid all those pesky transition through the sound barrier issues.

Think of it as a .22LR Eley TenEx match load with the bullet size increased by 14x.

If you want to flatten the trajectory a bit by increasing the speed, and need it to work in a repeater, switch the Postell for the RCBS 405 grain GCFP and increase the speed till it hurts.

[Artful]

I also concur that traditional straight or of slight taper in the case is the best -
45-70 or 38-55 are probably the most popular
- then look into a cast bullet with plenty of surface contacting the rifling
and keep the velocity under 2000 fps.
Do your ladder test and go forth to 300 yards.

[Scharfschuetze]

Inherent accuracy at 300 yards will depend not only on boolit quality (noted above) but also in ballistic uniformity from shot to shot. Black powder is very uniform, but smokeless can take some tweaking. Chronograph readings of a load matched with actual results at 200 or 300 yards can be very illuminating.

At 300 yards, atmospheric issues will also start to have an effect on your boolit, particularly wind, which can blow you right off of the target if you are not adept at reading it. To mitigate atmospheric effects as much as possible you'll want a boolit with a good ballistic coefficient, ie. long for calibre (heavy) and pointed. Cast boolits will never be Sierra Matchkings, but you can certainly select a design that affords you the best numbers with research.

Calibre? The 40 calibres do seem to hold some advantages. I've only used the 45/70 Trapdoor and a couple of different 30 calibre military rifles for shooting at 300 yards and farther so I can't comment on the 40s with any authority. I will note that most of the original long range rifles were black powder rounds and they needed the large bores for such work as they were limited to BP velocities. I believe the 40 was considered about minimum under those constraints.

Given that, shootable accuracy often depends on the marksman's ability to absorb recoil. That's probably another reason why the 40s are popular in the long rang game. They give a shooter a good ballistic coefficient with a boolit of about 400 grains. This will compete ballistically with the heavy 550 grain 45 calibre boolits used in the 45/70 and larger cartridges. Due to less recoil, they can simply be shot by a human longer and without flinching than the bigger diameters can be shot.

Were I to build a long range cast boolit BP rifle now (not for silhouette) I'd probably go with the 38/55 calibre.

Don't overlook the 30 calibres though. I have shot them to well over 600 yards with good success and accuracy. My favorite 30 calibres for such work? The 30/40 Krag, the 30/06 and the 7.65 Mauser. When loaded with 200 grain or heavier boolits like the Lyman 314299 or 311289, at velocities between 1,800 or 2,000 fps they will hit most of what you aim at (with capable sights of course) way out past 600 yards.

I note that you mention hunting in your OP; and for that I can't help as I've never shot even an antelope much past 125 yards. Still, I guess I'd recommend the 45/70 and advise you to know your load's trajectory and its wind deflection for 5 and 10 mps cross winds as well as being an excellent judge of range to compensate for its markedly high trajectory.

[M-Tecs]

The 30BR seems to be the favorite for the cast bullet benchrest crowd.

[MT Chambers]

yup, .30 br. is as accurate as you will find using cast boolits, a much better round then the Blackout/Whisper.