Position sensitivity of 2400 in 303 British

[greenwart]

My son and I were out shooting taking turns of shooting groups of 5 shots with some new cast bullets. So I loaded the universal load of 16gs 2400. I brought the rifle to a vertical position and ejected and chambered my rounds, Will kept the gun horizontal and never tilted it up. these are the results.

67358

I am going to rerun these numbers again to see if I can create the same results again. I know the data set is not that large but it seems to be a significant difference. We also shot groups of Unique and Red Dot which I had him tilt up the charge and saw no difference.

P.S. The Red Dot shot the most consistent groups. I picked up 8lbs on a whim recently now I know what I will be able to use it for.

Bob

[mpmarty]

You are positioning the powder to the front of the case when you work the action in a horizontal mode.

[greenwart]

I was swallowing the kool aid about 2400 being position insensitive until I saw these numbers. I have been casting for about 2 years and finally got a chronograph in February. It takes alot of the guess work out of developing a good load.

Bob

[Bigslug]

Saw an article yeeeeears ago in Precision Shooting Magazine that discussed a similar experiment. The guy shot two groups with identical ammo - one by first pointing the rifle in the air before benching for the shot, and the other by pointing it at the dirt. As I recall, he got two essentially identical-sized groups at two significantly differing points of impact.

This is a part of why I keep Nosler's loading manual around - it lists load density figures, and generally the powders with the higher figures are also their accuracy loads. This is largely down to a more full case burning more consistently.

I've yet to delve into cast for serious rifle accuracy, but I'm glad I saw this thread to get me thinking about powder bulk again.:drinks:

[williamwaco]

I have run quite a few tests with Unique and I agree that powder rear, powder front or powder shaken along the bottom of the case makes absolutely no difference.

[PS Paul]

I have run quite a few tests with Unique and I agree that powder rear, powder front or powder shaken along the bottom of the case makes absolutely no difference.

Is that right? So this would dispel ANOTHER wives' tale, I guess, eh?

[HangFireW8]

Next time have the same shooter do both tests.

[BruceB]

On a very-much-related subject, for many years now I've been using dacron in MANY different rifle cartridges simply to eliminate the POSSIBILITY of differing powder performance due to varying powder position in the cases.

To my own satisfaction, I've determined that ignition is somewhat improved, as direct comparisons with same charge/same case/same bullet/ same DAY etc etc with/without dacron have consistently shown slightly-higher velocity and slightly-lower extreme spreads and standard deviations WITH the fluff.

So.... when using smallish charges of quick-burning powder, I add dacron and just don't concern myself with powder positioning.

[Catshooter]

I have read that some powders are position sensitive.

I've never read (from anyone that I respected) that 2400 is anything but.


Cat

[felix]

It depends on the ignition of the powder, and that depends upon case size and form, and of course, the primer selected for that specific case and powder. Not to mention the pull friction which includes boolit mass, and where the projectile itself contacts the lands. All powders are position sensitive until proven otherwise by the said parameters. Therefore, BruceB is correct in his statement(s) by default. An ES of 20 or less more or less proves there is no powder position difference for that load-gun-person-application combo. ... felix

[btroj]

I did some chrono testing last year with my 45-70 and 2400. A bit of Dacron not only improved consistency it also increased velocity, and therefore pressure.

I now prefer to use Dacron when I load reduced charges of 2400. I think 2400 is one of the most versatile cast bullet powders in rifles, it just needs to be positioned to the rear of the case.

[geargnasher]

All powders are "position sensitive". To what degree depends on the factors Felix outlined. Even Unique is position sensitive in .30-30 and up rifle cases if you carefully check via chronograph and target, although it's very slight and not comparable to 2400 at the pressures to which most cast boolit shooters are loading.

Even when shooting rifle powders in rifles with cast, measures to improve combustion consistency usually improve accuracy, although the approach is different. It isn't the position that matters so much with something like 4350 or 3031 since they already take up a lot of the space in the case, it's the boolit pull, engraving resistance, and a multitude of other factors affecting the consistency of the combustion wave which in turn affects barrel time that causes variations in impact points on the target.

Gear

[runfiverun]

it's the consistency of the powder position that matters.
I taught this lesson to the wife on Friday [apparently her retention period is exactly 6 months] again.
she was showing a little stringing on her targets compared to mine with the same gun and loads.
I finally told her how to load her rifle and she showed an immediate improvement in her group size.
I will poke Dacron in a hundred cases for stuff that matters but I am not gonna poke it into 800 of them for general stuff.
she can tip a case or carry the rifle muzzle up. [or load her own boolits]

[303Guy]

Just one suggestion, do the repeat tests with same brand and weight cases. Segregate them by weight as that controls the internal volume. But first make sure they are the same length. Neck tension could cloud the results too as could variances in boolit weight and so on.

[JeffinNZ]

From the first day I loaded 2400 in my .303 Brit I used a wool wad to hold it down. I get ridiculously good accuarcy and consistency doing so.

[Catshooter]

After reading some of the replies in this thread I can see that I think I am mistaken. Sounds like position does matter, or it can anyway.

Learn something every day, especially here.


Cat

[quilbilly]

I wonder what the load density has to be before load density ceases to be a factor. I have theorized that it might be around 40 per cent but never did the test. I sense a new project coming with my light loads in the 222.

[geargnasher]

I wonder what the load density has to be before load density ceases to be a factor. I have theorized that it might be around 40 per cent but never did the test. I sense a new project coming with my light loads in the 222.

100 percent pretty much takes care of any position sensitivity issues, whether the sum total volume is all powder, powder plus filler, or powder plus buffer.

Gear

[runfiverun]

grr that reminds me I still need some puflon for the 308.

[Larry Gibson]

"it's the consistency of the powder position that matters."

That is exactly correct. Reading more than that into it is is simply seeking an answer to a non question. Dacron with 2400, 4227, 4198, 5744 and 4759 is often recomended with certain bullet weights in certain cartridges, especially when load density is less than 80%. Several of us were scoffed at for recommending such numerous times in the past but the OP has demonstrated the correctness of when to use the dacron filler.

Larry Gibson

[uscra112]

Not quite so rigorous in my data presentation, but my notes from years ago when I learning on the .35 Rem cartridge say that I gave up on 2400 because it was acting position sensitive, and finally settled on XMP5744 because it was not.

[303Guy]

I did some chrono testing last year with my 45-70 and 2400. A bit of Dacron not only improved consistency it also increased velocity, and therefore pressure.

Thinking about it, if the powder is up against the boolit as in when pointing the gun down, the primer flash is going to light the exposed powder surface while if the powder is held against the primer with a tuft of Dacron the primer flash is going to blow the powder away, spreading it and lighting it from within, i.e. lighting a larger area of powder so it should burn faster and produce more pressure.

Similarly a compressed powder charge might have a smaller ignition area to a slightly loose powder charge which may help reduce pressure by slowing the ignition slightly. This effect I've seen with Lil'Gun in my hornet or should I say it appears to be so.