OzFclass

Hi all,
I'm a fullbore shooter just using very basic reloading gear for my 308.
Standard die sets and a beam scale for weighing each charge that is.
I have a bullet runout gauge which tells me most of my reloads are under 3 thou runout. My reloads will group 1/4 moA from a rest at 300 yards.
Now if I was to use a competition seater, would I expect to reduce this runout, in so reducing the group or has bullet run-out got more to do with the sizing process.
Good shooting,
Bill

Billy,

For F-Class 1/4 MOA is plenty good enough for the shorts, but 300yd groups don't always tell you what's going to happen at the longs. That's when things like variable neck tension and variations in bullet BC will start to affect vertical spread.

I have a set of Redding competition dies, but don't think the seater is anything special for minimising bullet runout. It's very good for making tiny adjustments to seating depth. IMHO a Wilson inline type seater is best for controlling runout, particularly if it is chambered with the same reamer as your rifle. However .003 runout, while not as good as what many achieve, shouldn't cause inaccuracy. I saw some testing done, and the conclusion was that runout had to be at least 0.006 before it should be a concern.

Hope this helps.

Alan

Thanks Alan,
Yes there are alot of guys using the Redding competition dies in S.Aust. What do you think of their neck bushing die? What are the main causes of variation in neck tension?
Bill

Billy,

You're probably better asking that question on a BR forum, as they have it all down to a fine art. FWIW, my opinion is that consistent neck tension requires consistency of the necks in relation to wall thickness, and elastic properties. To keep them consistent, neck turning helps a lot, and having a tight neck chambering means the brass is not over-worked every time it is resized, so it doesn't lose its elastic properties. Some reloaders anneal the necks to revive their elastic properties. If you want find to out whether you may have inconsistent neck tension, you can use a chronograph to measure velocity variations. Of course there are several reasons other than neck tension why velocity variation might be high e.g. inconsistent primer ignition, inaccurate charge measurement etc., but if you do have low velocity variation, then its safe to say that neck tension is not a problem.

Alan

Alan,
On the limited chronograph testing I have done which has been mainly to get a load which will be fast enough for 1000yards (over 2950fps), my extreme spread is 23fps. But I have not tried different brands of primers or any neck turning.
I'm using Lapua cases and weighing them. Also using Sierra 155 HPBT's which I use straight from the box.
Bill

Billy,

By my calculations a 23fps variation in muzzle velocity using a .308, 155gn projectile at around 2950fps will cause a 10 inch spread in elevation at 1000 yds. And to reinforce what I said earlier about the dangers of using short ranges for testing loads, the same 23fps causes only 1/3 inch spread in elevation at 300yds!

Now before I get shot down in flames by those who say they get high ES AND good elevation at the longs, yes I agree that's quite common. And the reason is that the load (or the tuner) can be tuned to a "sweet spot" in the barrel's harmonics. If you do this then muzzle velocity variations become less important. However most precision long range shooters try to cover all bases by both tuning their loads (or tuners) AND minimising velocity variation. If you have zero ES, then theoretically there is no need to tune.

But don't take my word for it. There are several forums listed on the ozfclass.com Links page with some of the top long range shooters from around the world - put the same questions to them, and you'll get some good information.

Alan

Alan,
Yes I have always felt that a good load for 300 doesn't mean it will work at 1000.
As well as Fullbore target shooting, I have done a bit of match rifle shooting with scopes and heavier projectiles at 1000 - 1200 yards and that made me realise if you were brewing your own ammo, make sure the time reloading is well spent and it works!
Bill

Ps. The same could be said for home brewed beer!!

Hi Billy.
I was just curious to know if you uniform your primer pockets and flash holes before you weigh your Lapua cases.
I was amazed at the amount of brass shavings left on my reloading bench after I had completed this process with only 50 cartridges.

Hi Foxy,
I do uniform the primer pocket of my Lapua cases with a sinclair cutter (I think it's tungsten and stays sharp) that goes in my cordless drill. The first time I do it with a fired case, yes there is quite a bit of brass removed. From then on it's mainly used to quickly remove the soot.
No as yet I haven't used a flash hole uniformer, but I do intend buying one soon. I have lashed out on some the Redding competition die set for my fullbore rifle (.308). They are being shipped (as the Americans say) as we speak.

Bill Naismith

My feeling is that if you keep measuring runout and 'feel' for consistent neck tension whatever dies you are using are giving good ammo. BUT any loss of precision here will soon end up on the target.

I also think that runout tolerances have to relate to neck clearance rather than be an absolute. Like I dont think a runout or 6 thou is good enoug in a tighter neck situation but it may be in other cases. I aim for better than 2 thou which may be overkill. Who knows !!!

Peter Smith.

e]

Ajr,

how do u straighten em?

Cheers,

Simon

Thanks, Jeff, your comments on runout are interesting and don't surprise me. What neck clearance are you running ?

Someone originally mentioned 6 thou runout which is why I referred to it and tried to relate it to chamber tolerances which is in my opinion a key factor often forgotten. For some it may be OK but with tighter chambers and necks is not good enough.

Not sure if the following is totally relevant but I will relate it.

In conjunction with a poor batch of Lapua brass which have cost me a lot of heartache and 1/3 of the life of a barrel to sort out, I have returned to basics and experimented with runout among other things and 6 thou runout would not chamber easily with my rifle and will regularly show up on chronograph tests as higher velocities. Of course it may introduce other yaw errors as well giving greater errors on a target.

I now use an 'acceptance test' for my ammo which consists of inserting it in a dummy chamber (a fist sized piece of chambered barrel) and twisting it as it is inserted by hand. If It does not fully seat, and I can feel any more than the very slightest difference in resistance when turned its suspect.

Why did I do this. Well, at the NQ Queens I loaded in a tent which is definitely not recommended and this is a quick and convenient test and good insurance against stuck rounds. The bullets are seated using an inline set of dies I made about 1 week before the Queens. With the less than perfect brass there is still some runout even with this. Its neck turned minimally for uniformity now. This 'chamber gauge' was on hand and my runout gauge is makeshift and not portable.

I was chronographing and could experiment with effect on speed and it was definitely there if the round was tight in the dummy chamber. It is a bit hard to testfire on a target at home but the end result of reducing runout over all the shooting I did in the NQ Queens week showed an almost total lack of unexpected fliers.

Incidently, I found that straightening rounds with huge runout often resulted in them not feeling good in the dummy chamber. I think there was some distortion. But straightening ones with small runout was quite OK.

Peter Smith.

Peter,

On the subject of the NQ Queens. what happened? And who could supply full results for our Results pages?

Alan

te]