**UPDATE** Is this Keyholing?

Andy

Andy

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Here's a pic of a target I shot up today. In a M1909 argentine (7.65x53) with the Frontier 230gr bullet. 36.0 grs of surplus powder equivalent to IMR 4064 for a MV of 1725 fps - very mild. I've seen keyholing, but not these spiral shapes. Load was accurate except for the horizontal stringing. Twist in the barrel is 1:10 which should stabilize it, but barrel slugs to 0.312" and bullets are 0.311".

Use a stiffer load? Abandon the bullet? Stick with it?

Target.jpg
 
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it is not keyholing.
the tears in the paper are from the target being loose against whatever the backstop was. If you make the paper tight against the plywood, you would not see the rips in the paper.
As far as your load appears; it could be much tighter, but there is nothing wrong with stabalization. I would suggest not abandoning the bullet, and continue on the "load". Change the amount of powder and see what happens.
Are you sure that your "point of aim" was the same for each of the shots?

look at my avatar; this was an actual playing card at 100 yards. I am not really impressed with the groups and have since imroved it to be a clover leaf, and sometimes it looks like a peanut ( 3 bullets in 2 holes). Your shots are all over the paper. I would suggest working with your COL and powder.

cheers,
 
I thought that the tears might be due to a poor backstop, and indeed it was in very ragged shape. What remains unexplained are the spiral "stains" that only this bullet left.

As for my POI, no it was not exactly the same for every shot - these are holes from two different strings, one at six o'clock, and one dead on. Not to get too defensive, but the shots were with iron sights on an old military rifle, with not so great eyes, and in fairly quick succession. I can't expect better than a 3" group under those circumstances. Cartridge OAL is set 0.050" off the lands, so I will stick with that.

Anyways, I intend to stay with the 230's, but will stiffen the load a bit and see where that takes me.
 
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I am guessing but the sprials look like a powder trail to me.

As for the vertical stringing. I've seen that before due to a loose stock. I've also seen that when I have rested a gun barrel at different points while bench shhoting, (i.e. by using the slng to stabilize, no sling for stabilizing, resting on forestock, resting on barrel)
 
Powder - hmmm interesting theory. The pressure was quite low on those loads, and the case neck was smoked up. Could that have soiled the bullet and it came off from the abrasion of the paper?
 
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Andy said:
. Not to get too defensive, but the shots were with iron sights on an old military rifle, with not so great eyes, and in fairly quick succession. .
Click to expand...

slow down between shots. this might make a difference.
 
That sure is odd.
Almost looks like the bullet is leaking lead. I've read of this with high speed, over stabilized bullets where the bullet is beginning to come apart. Not likely in this case.
Would be nice to get one of the bullets after firing but not sure how to do that. Anything that will stop a 230 grain FMJ bullet will probably damage it too much.

For fun, it would be interesting to setup a few targets say 6-12" ahead of each other, in line, and see if the spiral is on each one and it's location.
Don't know what it would prove but still interesting.
 
My guess also is that it is a "powder trail". The shock wave from the front of the bullet (plus the natural "drafting" area behind bullet base) is creating a low pressure area behind the bullet, pulling some powder residue and smoke along with it.

Spiral pattern is from rifling in barrel and helped to be maintained by rifling on bullet, causing the powder trail to rotate. The radial smear on the target indicates that the length of the powder trail behind the bullet is about 1/2 of the length of the rifling pitch.

For fun, it would be interesting to setup a few targets say 6-12" ahead of each other, in line, and see if the spiral is on each one and it's location.
Click to expand...

My thoughts exactly, I bet that moving target or rifle back/forth 1/2 the rifling pitch would cause the spiral location to shift 180 degrees.


Not quite like these but it gives you an idea. My guess is also that there is something about the velocity you are using to generate a "perfect" following shockwave.

bullet_shadowgraph.jpg



flow.jpg



sodacan.jpg
 
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Very interesting theory that makes sense. I've shot a lot, with many different of loads, and never seen this phenomenom before.

The pressure was quite low (I'm guessing 30K) and there was lots of powder residue on the empty cartridges and boltface, so it could well be that this powder was scrubbed off the bullet when it hit paper. The spiral pattern certainly is consistent with that.

I'm going to up the charge to a higher pressure and see what happens, and will report back.
 
Powder burn effiiciency seems to be affected by pressure - I've seen low pressure loads look very "sooty". Bumping up the pressure may be beneficial on several fronts...
 
The Quickload program doesn't have the exact bullet you were using but peak pressure should be in the neighborhood of 35,000 psi.

I don't think it is powder scrubbed off the bullet, but it is powder and smoke following the bullet. This trail would look like a spiral, wider than the bullet, therefore when this trail it hits the paper it is deposited in a spiral pattern, much like a moving drill against the target. I would guess the one hole without the powder marks was one where the brass sealed against the chamber, raising pressure and velocity to change the shockwave characteristics.

These are just observations and a guesses, but still very interesting.
 
The ink on your targets is getting blasted off when the paper rips. Nothing to worry about.
"...surplus powder equivalent to IMR 4064..." There's no such thing. IMR4064 was never used by any military. You using a .311" or .312" bullet? You'll likely find a 180 grain bullet gives better performance. Try 40.0 to 44.0 of IMR4895 with a 180 grain jacketed bullet. That's the powder given in my old Lyman manual for the accuracy load in the 7.65 Argentine. Mind you, the original military bullet was a 215 grain FMJ. .311 to .313" bullets of that weight are difficult to come by these days. The heaviest cast data I have is for a 214 grain bullet. Shoot me an E-mail if you want it.
I suspect your 230 grain bullet may be too heavy to stabilize.
The Hodgdon site has data for a 150 and 174 grain jacketed bullet. There doesn't seem to be much else for that cartridge.
 
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He did not say it was 4064, he said it was equivilent. Sheeesh!

The pattern could also be caused by bullet yaw, or, the bullet wasn't tumbling, but rather wobbling slightly in flight.
Keyholing typically gives a nice sideways impression of the bullet.
For larger diameter bullets visit 303british.com. Steve has custom .313's, and i think even .314's, should your barrel require a larger size.
I suggest you slug your bore, and find out.
 
Mystery comet

Funny how the "comet tail" always originate at the tear in the paper...
I guess there is a combination of many things: very soft bullet, not enough pressure to get a clean powder combustion, not enough pressure to make the case mouth stick to the walls of the chamber, bullet barely stabilized (perhaps still yawing) which would explain why there's a tear on one side.
Now why that grey mark begins at the tear is beyond my comprehension. We need ultra-fast cameras!
BTW, do you use gas-checks on these bullets?
PP.:)
 
I guess I should restate and clarify a few things:

- the bullets are the Frontier 0.311" 230gr Copper Washed fully jacketed (I'll call them FMJ) bullets sold by Marstar. There's a thread on them here: www.canadiangunnutz.com/forum/showthread.php?t=124285
- my barrel slugs to 0.312"
- my barrel twist is 1:10 which theoretically should stabilize the bullet
- I am using pulled down Marstar Swedish 8x63mm powder which has a burn rate very close to IMR4064
- the load I used was very mild given the low velocities (~1725 fps) and smoking of the case and boltface. I agree that it's likely about 35K psi. My next load will be a full case (40.0grs) which should result in about 45K psi. I use this powder extensively and it is very versatile indeed. A full case (40.0 grs) should be a great load for the 303 British, but is well below what would be a Max load for the 7.65x53 in the M1909 Argentine Mauser.
- the target backing was a mess with very little support behind the paper. That can probably explain the tears.
- I have to think that the spiral pattern is from powder being blown off the bullet. I have shot many low pressure "dirty" rounds before, and never seen that, granted those were with lead, not FMJ bullets. I find it hard to believe that there could be a 100yd trail of powder following the bullet and still be enough to stain like that, hence my theory that the rubbing against the paper as the bullet penetrates it is what is removing it.
 
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Hi Andy.
Does the spiral pattern rub off? If not, then I'd more than likely agree with Sunray and suspect it is just the print being altered due to shock or slight stretching of the paper when the bullet strikes it.
Cheers
The County
ps I have some beautiful examples of keyholing with my slow twist snider.:rolleyes:
 
Tried 40.0 grs (full case) today. Very little neck smoking, spiral stains went away, consistent 2050 fps MV. Still not a max load (I would say that would be a full case of H4895), but an accurate one.
 
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