more questions

[Rabbitz]

To paraphrase someone far smarter than I:


If a boat always points its bows to the current, why wouldnt a projectile to the wind?

Well I respectfully suggest that the boat in question isn't spinning about its axis at several thousand RPM and enjoying the gyroscopic stabilisation from the spin.

[mick_762]

To paraphrase someone far smarter than I:


If a boat always points its bows to the current, why wouldnt a projectile to the wind?

Well I respectfully suggest that the boat in question isn't spinning about its axis at several thousand RPM and enjoying the gyroscopic stabilisation from the spin.

You can only "force" so much change before physics and nature take over.

[The Raven]

To paraphrase someone far smarter than I:


If a boat always points its bows to the current, why wouldnt a projectile to the wind?

Well I respectfully suggest that the boat in question isn't spinning about its axis at several thousand RPM and enjoying the gyroscopic stabilisation from the spin.

You can only "force" so much change before physics and nature take over.

Sounds like the infamous Scotty quote: "Ye cannae change tha laws of physics"

[Tony Z]

Mick somewhere in an ealier post it was stated that the theory has the bullet turn into the breeze.

Dave i managed to find a few threads in the US about similar stuff but pertaining more to muzzle configuration to divert the gases away from an exiting bullet. Of interest was the laminar flow in regard to a sharp angled muzzle as opposed to a large radius that allows the gases to flow outward and not shear and follow the bore line.

Dave Tooley said that the gas envelope is travelling between 6 - 8000 fps and does over take the bullet briefly.
Another poster signed as WSnyder wrote this.....

"Harold Vaughn proposed that reducing muzzle gas pressure reduced group size. One of his experiments was to vent the barrel just before the muzzle. He bored what was similar to a radial brake with holes along the rifling grooves with no counter bore, chamber or baffles. The bullet is supported all the way to the muzzle and gasses are bled off before the bullet exits. His experiment claimed a 35% average group size reduction (from .350" to .230") in his 6mm Remington rail gun. I've never heard if anyone ever tried repeating his results."

Now how this differs from what i read of his initial attempt is that there is now no freebore, and as is clearly stated, the bullet is supported all the way to the muzzle. Now this changes things drastically. He pondered if the freebore would allow the bullet to release and set itself on a truer axis of symmetry while being further accelerated. Now it is fully supported and most likely loses a little velocity but the gas velocity most likely does not overtake the boat tail bullet. Those that have read about his intial experiment will recall the method he used to bore the bleed holes whilst leaving no burrs in the barrel grooves. The reverse angled holes would have to have the likes of the brake shields making headway into noiseless brakes recently. Otherwise the bleed holes contravene all sanctioned rules for brakes. The other area where this result is drastically altered is in accuracy. His initial results were very poor. Now at a later time there is a 35% improvement. Being Vaughn he would have altered nothing but the porting so as to not cloud the findings. At 35% reduction, that is astonishing.
For years and years i had talked about porting barrels. Now it looks like i will get to do it.

[kickinback]

Dave a while before i gave it away i built and trialled this devise because the issue of off center pin holes was really bugging me. I built it and fitted it to the old 30 cal HG. Shot it once and had very good results then sold the gun and use this as a paper weight now.

It has a parabolic cone to split the blast from the muzzle as the bullet slips though the bore which has around ten thou clearance on a 30 cal bullet. The cone sat clear of the muzzle by around a 100 thou and this in itself was to be a subject of trial and error to find working parameters. The cone diverts the blast through the vent holes and outward at 5 degrees and away from the bullet while it looks to depart its second muzzle. The vent holes are also angularly set at five degrees to minimize torque. The only gas, in theory, that is near the bullet is the gas trailing it. Vaughn talked about this theory of a bullet in free flight being accelerated without bore friction and also being free of disruption. He did it by boring the barrel and venting the gas sideways. That constitutes a brake where at the time of this experiment brakes were not legal for heavy guns in IBS rules.
Mine is not a brake but allows the bullet to be free of the gas envelope. It worked with 200 SMKs very well. Unfortunately i never got around to trialling it with a true slippery VLD. I know the concept works but unfortunately i no longer have the targets to show the result. Never got used in competition.
The other benefit was around a 100 fps velocity increase similar to Vaughn's experiment. That in itself was well worth the effort, but unlike his attempt i did see an accuracy gain and even looking bullet holes.

Possibly the most interesting post I have ever read on here.


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[dg]

If i can organise it,for our 1000 on sunday i intend to position non backed thin paper and whack a few shots at it.

In terms of pin hole orientation this may or may not be interesting? ??

[Rabbitz]

Just thinking out loud here:

Would a second target, or paper sheet a few feet behind the scoring target offer any new data?

If the off centre point is wind pointing, then a case could be made that the offset should be the same as the corresponding hole on the scoring target.

If it is wobble, then it would be random as the projectile would have revolved many many times in between the cards.

Of course this all could be for nothing if the impact with the first target materially changes to attitude, spin or shape of the projectile.

[The Raven]

If i can organise it,for our 1000 on sunday i intend to position non backed thin paper and whack a few shots at it.

In terms of pin hole orientation this may or may not be interesting? ??

I generally shoot plain paper targets I print out. Generally I see no pin holes BUT if a backer (coreflute) is used it’s a slightly different story. I can occasionally see them on the coreflute (not that I usually look).

[Old Trev-39]

I have a couple of targets I have shot at about 150yds.doing load testing, that I will take to Townsville on the weekend. We can compare these with the various type of projectiles I will be shooting at 600.
Cheers,
Trevor.

[dg]

Hey trev

You show me yours
And I'll show ya mine ☺☺

[dg]

Raven

Not sure how you are not seeing pin holes in the target bullet holes ???

I think the pin holes are caused by the point of the projectile penetrating the paper

Unless you are using round nose or bluntish pills ??

[curan]

Dave a while before i gave it away i built and trialled this devise because the issue of off center pin holes was really bugging me. I built it and fitted it to the old 30 cal HG. Shot it once and had very good results then sold the gun and use this as a paper weight now.

It has a parabolic cone to split the blast from the muzzle as the bullet slips though the bore which has around ten thou clearance on a 30 cal bullet. The cone sat clear of the muzzle by around a 100 thou and this in itself was to be a subject of trial and error to find working parameters. The cone diverts the blast through the vent holes and outward at 5 degrees and away from the bullet while it looks to depart its second muzzle. The vent holes are also angularly set at five degrees to minimize torque. The only gas, in theory, that is near the bullet is the gas trailing it. Vaughn talked about this theory of a bullet in free flight being accelerated without bore friction and also being free of disruption. He did it by boring the barrel and venting the gas sideways. That constitutes a brake where at the time of this experiment brakes were not legal for heavy guns in IBS rules.
Mine is not a brake but allows the bullet to be free of the gas envelope. It worked with 200 SMKs very well. Unfortunately i never got around to trialling it with a true slippery VLD. I know the concept works but unfortunately i no longer have the targets to show the result. Never got used in competition.
The other benefit was around a 100 fps velocity increase similar to Vaughn's experiment. That in itself was well worth the effort, but unlike his attempt i did see an accuracy gain and even looking bullet holes.

Does anyone else think this sounds like the job an air stripper claims to do for air rifles?

[The Raven]

Raven

Not sure how you are not seeing pin holes in the target bullet holes ???

I think the pin holes are caused by the point of the projectile penetrating the paper

Unless you are using round nose or bluntish pills ??

I think the paper is too thin to register the pin hole, noting it's the generic 80GSM paper and not the (guessing) 200GSM paper stocks used for targets..

Looking at some 80GSM paper targets I've shot there are relatively clean holes rather than "petalled". No "pin" to identify, just a punched hole with a little bit of radial petalling.

[Tony Z]

This is one of JRs 1K targets from around 2003. 187 BIBs again. He dropped over around ten targets to pick from, all of which were centered in the blue which made the pin holes very difficult to see no matter how i took the photo. This one has them in the white square so are a bit easier to see. The targets are old and deteriorating with some of the petals missing, but you can see the pin holes are centered.

[trevort]

An argument for flat base bullets?


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