Ballistic Coefficient Question

[Broz]

Greg, Respectfully,I have a different opinion about a radial not blowing more dust than a side discharge and also directed at the shooter. That opinion comes from using many brakes with some pretty like comparisons. An example would be one time we had two 300 wins, one wearing a vias the other a JP while shooting prone. The Vais not only blew dirt all over the shooter but also put more dirt in the scope bell and made a mess. The JP was noticably better and created no issues. I realize some of this difference of opinion could also be related to the dry climate I shoot in and the dusty Montana summers. Not saying a side discharge does not blow some dirt, you are correct, they all do, even non braked rifles will. It has just been my experience that the amount that gets on the shooter, scope or rifle is measurably less with a side discharge.

Now I do not doubt your pressure data and I have no way to measure except visual inspection and measureable condition of brass. But would you not agree that when comparing velocities of bullets of, or close to equal weight that one should consider the length of bearing surface? That was my point when comparing the 210 Berger to the 215. When the same rifle, same powder lot, same brass, same seating depth used with both bullets and 215 with shorter bearing surface proves to be faster by 40 fps , with a lower charge by 1 gr. I would have to assume the 215 has less drag in the barrel and at least is at equal pressure if not less from a 1 gr reduction. Not looking for debate just offering my experience of what I saw in what I feel was a well documented test conducted inside safe pressures.

One also might note the brass for this load is Lapua 300 win which was made by Norma and I think we all would agree that using knowingly soft Norma brass makes the first sign of pressure easily detected.

Jeff

 

[NZ Longranger]

Jeff,
I'm not disagreeing with you about radials verses directionals in most circumstances. Especially on flat dusty ground. Maybe I didn't make myself clear, because I know we agree in general. Its just some seem to suggest radials are impossible to shoot with because of this, and that their directionals don't blow dust back at the shooter at all, which is BS. The dust disadvantage with a radial is that some of the ports are always facing downwards. If shooting on a flat dusty plain or desert all the time, a radial has more downsides than positives, and will blow more dust up some of which will certainly settle on the front lens especially in a head wind.

You can minimize the downwards dust affects of radials to some extent by poking the muzzle out over a rock lip or similar. Most of our hunting lookouts are like this, shooting from a ledge across a deep valley, and judging by Shawn's videos a lot of yours are too. In this case the more widely dispersed all around 90 degree discharge from a radial is far less obvious than the concentrated backwards discharge from one of our rearward angled directionals. No matter where you put one of these, they do direct blast and debris back towards the shooter and especially his spotter. This is simply why they are the best at reducing recoil. With specialist heavy long range rifles where we want the maximum recoil reduction, we always fit directionals, but make no mistake, there are some disadvantages with these too. Especially if shooting out through a narrow opening in the bush, they can really direct blast and debris back into the general shooting area.

Everything is a compromise in some form, and there are some reasons where the advantages of a radial are more important than the disadvantages, as in walkabout rifles where you want to stalk with the brake off, but then wind it on by hand when you reach a lookout. Doing this continually with a directional will eventually end up with it getting out of index as they creep a little over time on the shoulder. For your situation where you said you never take your brakes off and want maximum recoil reduction, there is no reason why you would use a radial.
But mrb specifically asked this question about taking brakes on and off and using thread protectors, and I was explaining how we do exactly that in some situations with all purpose rifles that might be shot spook and shoot, and also long range. The majority of our rifle builds are lightweight hunting rifles that are used just like this, and a radial fits this application best. Clients want to hunt with them without earplugs in the bush, then screw the brake on and put their plugs in for a long shot when they get to a long range lookout.


And I don't try to guess pressures from visual pressure signs closely enough for this sort of caliber debate comparing velocities. Pressure testing gear is a real revelation, and its a shame its not more readily available. The bearing surface of the 215 is commensurately longer than the 208, and the velocity for the same pressure also drops commensurately. This is due to the longer bearing surface and the heavier weight. There is no magic bullet yet invented that defies the laws of physics. A longer bearing surface and more weight means less velocity for the same pressure. As I said, the lower velocity for the 215 I used from Hodgdon's 208 data matches the differential we've actually got across the Oehler 43 Ballistic Lab.

The problem I feel with most internet debates is they are often portrayed far too black and white, and life is rarely like that. And people can make flippant generalizations to make a point that on reflection they don't actually quite mean to that extent, and I can be just as bad at this as anyone.
None the less there is some really good information in this thread from some really experienced guys like you Jeff, and the info I've posted compliments what you're saying and fills in a more complete picture. Which is all good for those asking the questions and wanting information to help them make decisions, before they shell out what can often be quite large sums of cash!
Greg

 

[WildRose]

When you are set up in a hide one thing you can do to make a 360 deg radial discharge brake much more tolerable is to lay out a shooting mat starting at about the end of your forearm/just beyond the bipod which is a yard or so square.

Not very practical for spot and stalk hunts though.

 

[Shane1]

Use electronic hearing protection and leave them in. You can hear just fine and still be protected or my preference if you live in a free state, SUPPRESSOR. Recoil reduction and hearing protection in one package

 

[MMERSS]

When you are set up in a hide one thing you can do to make a 360 deg radial discharge brake much more tolerable is to lay out a shooting mat starting at about the end of your forearm/just beyond the bipod which is a yard or so square.

All of my LR hunting rifles utilize a brake either radial or directional. Blast debris be it dirt, vegetation or the combination caused from a 4 to 8 directional wind can be detrimental with follow on shots, spotting your initial shot and so on. You've nailed this problem, place something under your blast area. For practice sessions what's wrong with bringing along a couple of extra gallons of water? Soak the area where your brake blast will contact the dry ground. As stated a shooting mat works great. For hunting from a hide you can take that extra layer of clothing out of your backpack and place it under your radial or to the upwind side of your directional. Use your backpack if you don't have other material to help suppress the debris blast. Most of us have been there before and it's not fun having your face and scope filled with debris making spotting and that follow on shot much more difficult. Same concept applies with a non-braked barrel. If you have the time and can control your shooting location reduce or eliminate that debris blast area. Happy shooters make happy shots!

 

[idaho elk hunter]

The 7mm with all things equal will out pound a 30 cal all the time! Lets see who's feathers this ruffles. I bet I can guess! Some just are ostriches with their head in the sand.

 

[Michael Eichele]

The 7mm with all things equal will out pound a 30 cal all the time! Lets see who's feathers this ruffles. I bet I can guess! Some just are ostriches with their head in the sand.

That's hilarious!!

 

[MontanaRifleman]

The 7mm with all things equal will out pound a 30 cal all the time! Lets see who's feathers this ruffles. I bet I can guess! Some just are ostriches with their head in the sand.

You have nothing better to do than troll around making childish posts like that?