bullet question

[hawkeye]

I have a custom build, with custom made .38 caliber fast twist barrel in 1-16 twist.
shooting a long elongated pope style bullet made by BACO
according greenhill formula  this barrel could stabilize a bullet up to 1.350 inch , my bullet is 1.340 length and 360 grains
bullet enters muzzle by thumb push, shooting like 3 inch groups prone with sling on a 220 yards distance, wich I guess is not bad for my 63 year old eyes.
butt I noticed that the bullet holes on target look like bullet is  slightly tipping, no clean round hole.
what could cause this is my question??

[alacran]

The bullet is yawing. It may not have completely stabilized at that distance.

[Bill Raby]

At that distance it is probably slowed down to where it is no longer spinning fast enough to stabilize. You have to get it moving a bit faster. Heavier powder charge should solve the problem.

[Standing Bear]

The bullet velocity may be dropping below super sonic before reaching the target.  In the Bell X-1, Then Col. Chuck Yeager experienced extreme turbulence as he went super sonic and again going sub sonic.

[Bob Roller]

At that distance it is probably slowed down to where it is no longer spinning fast enough to stabilize. You have to get it moving a bit faster. Heavier powder charge should solve the problem.

I also fully agree with Bill Raby. My Alex Henry barreled Whitworth .451 shot
best at 200 yards with 75 grains of DuPont 3fg with the Ideal 451112,full weight
of 485 grains.Any less and it lost stability.I think that an increase,incrementally
of 4 or 5 grains of powder will make a noticeable difference.
Please keep us posted,these rifles and the other extreme,Southern Mountain rifles
are my favorite muzzle loaders.

Bob Roller

[shifty]

    The powder charge does need tweeking i build and shoot some rimfire i do not compete ,the bullet velocity is really important at longer range,with rimfire you can't change the charge so you change the ammo test until you get the right combo faster ammo is not what usually is the best. when you go above the sound barrier which varies  some and drop back down through it again you create turbulence which is what you don't want. I didn't see what powder charge and what velocity the OP has with his rifle. 
.

[bob in the woods]

This may sound a bit weird, but my .45 would shoot donuts at 200 yards with 540 gr bullets, and the holes showed evidence of yawing.  At 400 yards and out, it was fine . For 200 to 300 yards, I went with a lighter bullet and that solved the problem. Your bullet may be just settling down at 300 yards .   Try it at 200 and see what you get. Or increase the charge and try that , but I found the heavier for cal bullets were better for longer ranges than shorter. 

[hawkeye]

I load 55 grains Swiss 2f powder as charge and yesterday even with 60 grain it did yawning a little. Could it be hardness of bullets.
Shoot now 1-17

[D. Taylor Sapergia]

No your bullet alloy is just about right.  Your bullets will obturate at that hardness just fine.  But Your rifle will likely enjoy a heavier bullet, just as your formula suggests.  You should be pretty happy with 3" groups at 200 yards though.  I have a .50 cal bullet rifle that likes a BACO 600 gr. bullet, and it shoots the same sized (3") groups at 300 as it does at 200.  I'll bet yours will too.

[Daryl]

 350gr. bullets shoot well in my .38, but it has a 12" twist.  I would not expect it to shoot as well with a 360gr. bullet as the 350gr. are deemed to be at that edge. In a 16" twist .38,
I think you will have better results with a 300gr. bullet.
Greenhills formula ("for cannon") as originally presented, shows the LONGEST projectile that will shoot in THAT rate of twist. With a difference of only 10 thousandths of an inch between
the longest possible and yours, you are on the edge of instability right off the bat. 
A shorter bullet - 280gr. to 300gr. - about 1" even would be a nice weight and much better length for a 16" twist.
 
Transonic speed zones (just above and just below SpeedOSound as Yeager found out) cause instability in EVERYTHING.  Flat bases projectiles are most stable

on the average when passing through these zones.

The slight yaw or tipping means that the bullets are not completely stable - YET - OR they may be becoming unstable due to the velocity loss and never will be stable. Thus, a shorter

 bullet is needed.  A shorter bullet will certainly help & by being lighter, will have higher vel. which will improve stability instantly in this slow twist (as far as .38 cal rifles are concerned).

This one would likely work better.  Trying the longer, heavier bullet first- at 300 or 400yards might be a good test. My guess, is by 400, they are going sideways.

https://www.buffaloarms.com/381-300-grain-money-1-cavity-bullet-mould-jim381300m3

[snapper]

Do you have a good solid target backing?  Making sure that the paper is not tearing?

Have you tried shooting it beyond 200 yards to see what is happening?

Fleener

[hawkeye]

I shot it already with the 55 grains load on 330 yards and the yawing was a little more then on the 220 yards. But tryed it only one time. Grouping was also little less. Shot it before with the Lyman 330 grain bullet which did better on 330 yards

[hawkeye]

I have also a.38 rifle with a 1-12 twist shooting a. 365 grain bullet very well on any distance, except 100 yards, for that distance I shoot the 330 grain bullet  by Lyman

[Bob Roller]

Are these bullets grooved/lubed or wrapped patched with paper or cross patched
with cloth or paper?Who makes a GOOD barrel for these 38's?

Bob Roller

[snapper]

Well, you have some different ideas on things to play with. 

You might also try a softer bullet, just to see what happens. 

Also try changing up your wads with veg fiber and wool and or combination of the two.

These things might not make any difference, but they are quick easy things you can try and eliminate if they dont work.

Fleener

[hawkeye]

Hello Bob,
I'm not American, butt from Belgium.
The barrel is made by a Swiss barrel manufacturer names: Eichelberger ueli
Makes muzzleloader and breech loading barrels. I shoot grease / lubed bullets

Hugo

[Bob Roller]

Hello Bob,
I'm not American, butt from Belgium.
The barrel is made by a Swiss barrel manufacturer names: Eichelberger ueli
Makes muzzleloader and breech loading barrels. I shoot grease / lubed bullets

Hugo

Hello Hugo,
I know of Uli Eichelberger from Guenter Stifter in Germany and heard good things about him.
Thank you for the additional information.I would like to see a revival of the old 200 meter
offhand matches of years long into the past but so far few are even aware of such things here.
The Freistand Schuetzen matches all but vanished during WW1 when all things German were
condemned,even small Dachshund dogs.Narrow minded,pathetic people killed it.
Good luck and good shooting.You have a fine barrel but it may be very particular about loads
and LUBE.
Bob Roller

[Hungry Horse]

You are so right Bob, about schutzen style matches before WW1. Northern California was a hot bed of these type matches. Shooters from Lake County spent a couple of day traveling to the matches in the San Francisco Bay Area. Remnants of old shooting gear still turn up every so often in yard sales, and junk stores. Amber lensed, wire rim, shooting glasses are in several local collections, including mine.

  Hungry Horse