1000 yard QRA Queens scores.

[plumbs7]

Was just brushing my teeth and remembered more !
The day before Ipswich opm I took my rem , the same gun my Son shot a 90.7 in warmer conditions a month before , to Cannon hill to shoot 1000 yds club comp.
well the tune was way out! Was going with 155 hybreds about 2920 fps and got vertical and horizontal and a score of 50.1 Mark f beat me with his TR rifle 11 count!
I left the rounds in the sun and things did improve . But most defiantly need more 2208! So I think 2980 fps is the low end of the node for a .308 with 155's .
Ok good night!

[Longranger]

Thanks for your comments Graham:-).

Using the fullbore 155.5's on the weekend for the first time yielded a double possible with 120/14. I use BM8208 and the vertical was outstanding, about a third or less of the X ring. Admittedly, this was at 700m.

Using Hybrids in 300m testing shot outstanding groups but the wheels fall off after 500m in tricky conditions with wierd screwy shots that defy explanation. The Fullbore's are just more stable it seems. Maybe a faster twist barrel than a 1 in 12" would work better though I am not entirely convinced this is the full reason.

Pete

[Josh Cox]

Hi peter,

My findings are the same as yours regarding the Hybrids, I've extensively tested the hybridss in 11 and 12 twist have just purchased a 10 twist ( its only money........rids, for me, do not groups as well as any other bullet I've tested, believe it or not the nosler tested the best Tue ing,e definately have a BC advantage, less time of flight over distance which I hope reduces the effects of my subpar wind reading abilities


Sorry for the retarded sentence above, spell checker will not let le change.

[plumbs7]

Thanks for your comments Graham:-).

Using the fullbore 155.5's on the weekend for the first time yielded a double possible with 120/14. I use BM8208 and the vertical was outstanding, about a third or less of the X ring. Admittedly, this was at 700m.

Using Hybrids in 300m testing shot outstanding groups but the wheels fall off after 500m in tricky conditions with wierd screwy shots that defy explanation. The Fullbore's are just more stable it seems. Maybe a faster twist barrel than a 1 in 12" would work better though I am not entirely convinced this is the full reason.

Pete

Hi Pete , I've heard what ur are saying is exactly what others are saying bout 155 hybreds. I can only think that maybe the 3 groove barrel that I use may make some sort of a difference ???.
But I know there's plenty of hybreds around for sale . So it seems to support what u are saying. For what ever reason it works for me ? Another mystery for riflery !
Regards Graham.

[williada]

Good info on the 155 Hybrids. In the turbulent stuff, not necessarily the tricky stuff, I prefer the tangent ogive shape. You just get to know a bullet, and much has to be said for doing things in a consistent way. In an attempt to get the best of both worlds, i.e. using VLD's in stable conditions which can group tighter and the ability to get a bullet to hold its course better in turbulent conditions like a tangent pill, came the design of the hybrid which is a cross of the two ogive shapes. The design might not hold up in the field across all conditions either. The old tangent job might not be as pretty, but she sure is reliable. You can be seduced by the sirens but like Ulysses you need to be tied to the mast so you're not smashed on the rocks.

Any bullet shape's external performance depends how it sets up in the barrel. I think some bullets perform better due to bearing length subtleties and bore size which can explain why some bullets of lesser "name" just might suit your barrel's internal dimensions of which there are so many variables.

Plumbs you mentioned the 3 groover. They will work well. Did some experiments with a few barrels made in the 1980's with a manufacturer I was testing for with a land height of just 1.5 thou in 4 groove. Won a regional championship with it but it was toast because after getting past the hump we talk about, it wore out quickly. The 3 groover like the 5 groover has opposing lands with grooves. In theory it is meant to be better with the jacket and core balance. The core balance issue is why some tinker with slower twists than recommended gyroscopic stability rates of 1.5 but these are subject to strict atmospheric density parameters for use. Edit Could imagine a BRIGHT YOUNG MAN BEING PREPARED FOR THIS having a number of barrels to screw in and out for a Queens.

There is so much to screw you in this game if you want to travel on the edge. Me, I go for old reliable because by playing the percentages you will get your turn. David.

[Norm]

I think that the Hybrids are more VLD than Tangent in ogive design. With the hybrids, only the actual land contact zone has a tangent radius and then quickly revert to a larger secant radius for the remaining part of the ogive.

From my understanding they introduced the hybrid design because so many shooters in the USA found the VLD hard to tune and that the tangent ogive was known to be easier to tune for short range accuracy. So they came up with a compromise design that supposedly has a higher BC. This may have been more by accident than design.

The interesting thing is that most target shooters in Aus. seem to find the VLD pills easy to tune. While in the USA a lot of hunters started using VLD's in factory rifles and had trouble with getting them to shoot. I think the larger tolerances of factory rifles had more to do with this than anything else.

Anyway, at least we now have a greater choice than ever before if we can only get them stocked onto the suppliers shelves.

[Longranger]

I have often wondered about the 3 groove barrels. I can see some merit in crosswind conditions but I'll bet they are a pain to manufacture especially with button type processes. The displacement of metal would be significant. Probably more amenable to a single point cut process but with finer cut increments. PacNor seem to get their 3 groovers working but how long they last I don't know. I haven't tried one yet being a cut barrel disciple.

[williada]

Yes, Longranger I have seen a couple buttons shatter in the experimental stuff. Usually the land groove displacement volume is worked out and of course you have to consider the depth in relation to bullet jacket hardness and depth which varies with military, target and hunting projectiles. But as far as rotating the bullet with a soft jacket it doesn’t take much depth. If the bullet is a tad harder it will strip. If the 3 grooves are not wide enough, they wear quicker.

I am a cut rifle fan, but that has downsides too unless the machinery is top notch or certified blanks don’t meet the certification of hardness. A problem that can be encountered is a variable land height more often than you think that a bore gauge doesn’t pick up. You need a groove gauge made like a star to pick that up, not like a cylinder which runs on top of the lands. Usually caused by hard and soft spots in the steel or a blunt scraper with the old methods.

Following up Norm’s comment, yes they are more like VLD than tangent and perhaps that exposes a bias weakness to the turbulent condition unless you can drive them a bit harder. It also demonstrates that BC is not everything in the turbulent condition of an atmosphere. Of course Norm is dead right in that VLDs in wider throats needed to be jammed for concentric alignment and efficient pressure development.

As every rifle is different the jam setup may not give you the best performance. Only a bullet jump test will reveal that. I think some doubting Thomas’s in recent testing in Qld saw the wisdom of that.

If you were to follow the aerodynamic models through, the circumference of the secant section of the hybrid ogive as measured by its radius does intersect the body of the bullet in a different place than compared to say a tangent ogive. This alters the effective length of the body and bearing surface for other internal purposes such as friction for timing bullet exit that relates to the angle produced for muzzle launch. It has a direct effect on gas seal and efficient use of ignition and alters the height, duration and distance that peak pressure occurs from the breach. If the powder is fully consumed quickly, the harmonics are also smoother. So slow burning powders with the big projectiles can waggle the muzzle more and that’s why IMO they often have a short node in which to operate, which makes them suspect to atmospheric irregularities. Great if all is smooth sailing. I tend to have better performance out of longer bodies in bigger bores (or if your bore enlarges through wear) and make the most of shorter nodes. I found in Project Penumbra, that with the old Sierra, it required a tighter bore to perform better in the .3075 x.298 configuration because of its shorter body length. If you were going with those longer heavy pills then I would prefer a .308 x.300 barrel configuration.

At long range, the angle and length of the boat tail largely determine the parasitic drag. There is a lot of focus by reloaders measuring the base to ogive, the bearing surface etc. We know how important that is. But the boat tail can screw you in two ways. Firstly, by way of varying parasitic drag, if the angle or length of the boat tail varies. This can also upset the relationship between the centre of pressure and the Magnus force with the centre of gravity to keep the bullet stable in flight as does any other length variable in body or nose as they can affect the overturning moment as Longranger has mentioned, and so lead to elevation problems as well.

If your throat is sloppy or your bullets are not loaded concentrically with the bore the gas flow can slap your bullet off centre because they impact on the side of the boat tail too. Within reason, the alignment difficulties can be offset with a tighter throat. Remember reamers cut bigger than they indicate. Your work has to be measured with a cast. This is not so much the case with flat based bullets which are pushed straight ahead. But flat based bullets are not as aerodynamic as boat tail bullets at long range because of a greater parasitic drag.

The prevailing conditions at a range mostly determine what will be effective. But you just have to be aware when they will not work. Setting up for a one day completion is really so different from being exposed to a range of conditions over 5 days in a State competition. Consistency is the key.

This is nearly the last of these contributions as my time will be taken with a train the trainer program to build the strength of the competition locally. Alan has asked me to report on the Bulleseye Camera System which according to my tracking number has reached Melbourne after some delays beyond the manufacturer’s control. If I get a chance, I will try to report but it might be later than sooner. Its been a pleasure. David.

[plumbs7]

Thanks David , I always enjoy your posts, even though sometimes don't quite understand them all. But learning all the time! Regards Graham.