Bullet yaw at target,why?

[Tedly]

I've been shooting a 6.5mm Dutch Hembrug lately with Swedish Cruise Missle. 6.5x53R is the rimmed version of the Mannlicher cartridge. Basic load has been 19.6gr 4895 and Remington primers...at 50 yds. either IMR or Hogdon shoot the same groups... about 2" or so...pretty much shot as cast diameter cause the mould drops 'em @ .2695 about .0005 smaller than bore and I seat a Hornady GC with a homemade "sizer" that has several diameters inside, how deep I push'em in varies for size/application...@ 100 yds. I've noticed that the H4895 shoots a smaller group and the projectiles enter the target "squarely"...if I use IMR 4895 there is consistantly evidence the bullets are tumbling alittle when they hit...Is this destabilization ? Is this related to velocity ? The choice between these @ powders clearly has demonstrated this occurence to me several times...what do you think?

[excess650]

I suspect that you're on the ragged edge of velocity limit and the IMR powder is producing just enough added velocity that you see the oval holes. Drop the powder charge back on the IMR and see if the results on the target change. A chrono would also give a clue.

My 8x57 Turk shoots smallish groups with various powders, but as I increase the charge so as to increase velocity, group size opens and the holes become oval.

[MtGun44]

Smaller than bore (I will assume you meant groove diameter) is not a good place to be.
Possibly the velocity is too low by a touch, but it may also be that the pressure curve is
different enough that one powder bumps up the boolit diam just a touch and the other
may be a bit gentler and not do it. I find that .002 or even .003 over groove diameter
works well in rifles. That cruise missile is one long boolit, so it may be just on the edge
of being spun fast enough - so the velocity may be the only thing, but maybe the diameter,
too.

Bill

[badbob454]

think i read that the 6.5 cruize missle is partial to a particular twist as its so long cant remember what its preference is as i dont understand the twist to bullet length thing..just faster twist rates 1/9 will stabilize 223 bullets that are too long , (heavy ) than say a 1/14 so your rifle may be just on the edge , i would stick to the powder that works .. also what mity gun says need a wider bullet try adding some linotype to the mix and your bullets should cast bigger ,,, or try to lee-ment as ive read on this forum (cast a bullet drill the base dip it in fine valve grind compound and put a screw in the bullet base and give it a spin in a drill to lap open the bullet mold )

[Bret4207]

Boolit size or velocity or a combo of both. The guys gave the best answers I can think of.

Any pics of the rifle? Sounds interesting.

[Larry Gibson]

Boolit size or velocity or a combo of both. The guys gave the best answers I can think of.

Any pics of the rifle? Sounds interesting.

Concur; as mentioned suggest you drop the load of IMR4895 a bit a see. If that isn't it then you might try increasing it slightly as the IMR may also not be obturatiing the bullet to bore size. Chronographing both loads would give an answer; If the IMR velocity was higher then it is too much powder. If the IMR velocity was lower then not enough powder. With that long bullet in a fast twist it doesn't take much either way. Do you use a dacron filler with either load?

Larry Gibson

[Good Cheer]

Tedly, if you would sir please share any experiences, observations, reload sources and data you come across. I'm in the midst of trying to get mine percolating. About to see if some paper patches get shredded. If it looks like a #4 buck pattern I'll use these dipped in J&B to keep slicking things up.

[Wayne S]

[URL="http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi"]http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi[/URL
There are other stability programs posted in the 311-247 mold discussion. This one will give you something to "play" around with, mainly by varying the speed. BUT as others have pointed out, that is a long bullet and if the nose in not supported by the riflings, and or they are undersized to your throats Dia. all sorts of problems will start showing up at 50 yds and beyond

[frnkeore]

W/o a chronograph, it's hard to tell where your problem lies. I doubt, very much that the tipping is from to much velocity. It almost always comes from to low a velocity and transonic flight. Sever tipping can come from gas cutting.

H4895 and IMR4895 are not the same. The H can burn different in different cartridges. Depending on the application, H can burn as fast as 3031. If that is so in your case, then IMR is giving lower velocity causing the tipping. Try 1 gr more IMR.

Tipping can also be caused by the bullet going through the transonic range. Buffeting causing the tipping, again, speed it up but, in this case you can also slow it down to keep it out of the transonic range ( about 1050 - 1200 fps) at the target.

The under size bullet, I don't think is the problem. Undersize bullets can lead to a unstable bullet but, that's because of gas cutting on the base of the bullet. So, if the H loads are stable, I don't think that can be the case.

There is not much data out there for your cartridge but, I think your about 4 gr off on your powder charge from being optimum for the burn rate for either powder. A faster powder like 4227 might give better overall results and more complete burning.

Frank