Hi guys, whats the likelihood of experiencing a SEE when using a reduced load of a slow powder and a cast bullet!

It seems from what I have read CB will not get stuck and result in a pressure spike! I am however still uneasy about loading up with a slow power in reduced loads!

Also can a reduced load of H4831 really produce the same velocity in a CB with 12 grains less than it takes to get a jacketed one there?

There really insn't much published data at all for slow powders and CBs!

I should outline what I mean by reduced load. The max load for H4350 and H4831 are 44 and 47 respectively! I am looking at loads of 30-33 and 35-38 respectively in the 6.5X55.

The thing is I do not need or want a slower velocity, I am chasing high velocity in the Swedish Mauser M96 6.5x55! I want an accurate load to a minumum of 2100fps if possible. The load data for cast bullets is limited.

For a 140 grain jacketed projectile the data suggests 39.5-44 grains of H4350 and 42.5-47 grains of H4831.

In order to achieve similar performance with cast bullets Quickload suggests 32-37 and 36-39 grains of each powder respectively. I have seen reference to loads used of both powders lower than those Quickload ranges.

A cast bullet does require a smaller powder charge as less resistance is needed to engrave the lead of the bullet.also it reduces the leading of the bore. I would recommend you use a Dacron wad over the powder. This will prevent a "Flash Over" and also give you much better constant velocities.
The problem with a slow powder is that with a light load that is safe to shoot, the primer can blow the powder forward moving the bullet into the rifling causing very poor velocities as the powder charge will not burn the same way twice. Years ago the shooters I learned from would raise the barrel straight up for a couple of seconds to "pack" the powder to the rear of the case to help offset the moving powder charge and prevent a Flash Over.
Dacron prevents this today.
Where shooters get into trouble is when they shoot a jacketed bullet with a light load and the primer blows the bullet into the rifling when fired. This can "plug the bore" and the pressure can spike to dangerous pressures as the light powder charge flashes over.
Cast bullets are less prone to this due to the bullet being softer.
The only real problem I have ever noticed using a slow powder with cast bullets in any center fire rifle is the case does not seal the chamber properly and you get gas blow back into your face. The warning signs will be powder fouling back behind the shoulder with streaks half way down the case towards the base.
If you see this you want to raise the charge one grain and see if it works better.
I have loaded the 6.5 Swede and other 6.5 calibers using surplus .50 BMG powders and have gotten very good down rage results.
I always use a gas check and Red-Rooster bullet lube.

Have you considered using 4895 ? It's not the slowest powder, but it isn't all that fast either. Hodgdon has a "60% formula" using H4895. I've used it with both cast and jacketed bullets with good results.

Data here: http://www.hodgdon.com/PDF/H48...%20Rifle%20Loads.pdf

I agree that H4895 is a better powder for reduced loads. (the best?)

When loading slow burning powders (they rely on pressure to burn properly) in reduced loads the problem is that the primer moves the bullet forward as the powder is ignited - the increase in chamber volume slows the burn rate and the powder burns too slowly to raise the pressure. The powder is burning on the exposed surface (like when you light powder in the open air) until the pressure builds. By that time most of the surface has burning powder and the rising pressure accelerates the burning causing all of the remaining powder to ignite at once. That causes the SEE and pressures generated are much higher than one would get with normal burning.

It doesn't matter if the bullet is a lead or a solid bronze bullet - the chamber volume increase is the problem. Using a hotter (magnum) primer can make matters worse due to the primer moving the bullet further into the bore creating a larger chamber space. Filling the extra volume with dacron or kapok is moderately effective when using very small charges of pistol powders but won't necessarily make much difference when using slower burning powders.

Most powder manufacturers caution about using reduced charges of slow burning powders. They do this because they like selling powder and if you blow your gun up you are unlikely to buy more powder.

Cast bullets and slow powders like 4831 are best loaded like black powder; a case full. Never use reduced loads with either cast or jacketed bullets with slow powders; there are plenty of alternatives. There is good reason why there is no published data for cast bullets and reduced loads with slow powders; it is dangerous except for full loads. There is plenty of data for cast bullets and slow powders; look in the Accurate Arms Powder manual. All of them are for a case full of powder.

quote:

Originally posted by PaulS:
I agree that H4895 is a better powder for reduced loads. (the best?)

When loading slow burning powders (they rely on pressure to burn properly) in reduced loads the problem is that the primer moves the bullet forward as the powder is ignited - the increase in chamber volume slows the burn rate and the powder burns too slowly to raise the pressure. The powder is burning on the exposed surface (like when you light powder in the open air) until the pressure builds. By that time most of the surface has burning powder and the rising pressure accelerates the burning causing all of the remaining powder to ignite at once. That causes the SEE and pressures generated are much higher than one would get with normal burning.

It doesn't matter if the bullet is a lead or a solid bronze bullet - the chamber volume increase is the problem. Using a hotter (magnum) primer can make matters worse due to the primer moving the bullet further into the bore creating a larger chamber space. Filling the extra volume with dacron or kapok is moderately effective when using very small charges of pistol powders but won't necessarily make much difference when using slower burning powders.

Most powder manufacturers caution about using reduced charges of slow burning powders. They do this because they like selling powder and if you blow your gun up you are unlikely to buy more powder.

I would agree here with Paul. One of the first indications you will get if loading lighter charges of slow powder is delayed ignition, sometimes this can be only a very slight but noticeably differant sound to the shot right up to a "click bang". Dacron filler will help where the delay is only slight but as the powder charge is reduced further even dacron won't prevent this.

Other factors such as neck tension on the bullet and amount of free bore in the barrel can influence just how a cartridge performs with lighter charges of slow powder.

I have experienced this phenomenum in my early days of trying to get an accurate load in my 404 using a plain based cast bullet and in three other rifles belonging to friends who were trying to develop loads for their odd ball European cartridges, a 10.75x63, a 10.75x47 in a double using swaged down 44 cal pistol projectiles, and an 8x75 with cast.

I was trying a range of fast burner powders in my 404 with a 400gr cast bullet but got no accuracy until I tried some H4831 which gave a semblence of grouping. Grouping became quite satisfactory as I got down to around a 65% loading density. Any lower produced click bang delayed ignition, although I did fire off quite a few using this powder taking some game with the cast bullets. I eventually backed out after advice from a reknown writer and shooter. In saying this I did not see any signs of high pressure in any of the instances of delayed ignition, perhaps this could have come at anytime.

Years later using a powder (4350 equivalent) and charge recommended by Von Gruff who posts here, I did noticed a very slight change in ignition if I did not use a wad over the reduced load of powder with cast bullets while VG did not use a wad in his 404 with the same load and bullet. My 404 does have quite a bit of freebore while his was chambered to correct dimensions.

It is really a matter of experimenting in differant rifles but like many, I would add my caution about light charges of slow powder.

On a slightly off topic Lees manual lists a lot of reduced loads for the 30-06 whilst not similar in its over bore characteristic of the 6.5x55 is serves to demonstrate that loading down even of slow powder can be done, depending on the projectile weight to bore ratio!

For example Lee lists reduced loads of Varget down to as low as 26 grains in the small for bore 130GN projectile. (For jacketed its 49+)

H4350 is first listed for the medium to bore projectile of 165GN and goes as low as 29 grains. (For jacketed its 51.8+)

H4831 is first mentioned at the medium-heavy for bore 180GN projectile, but it does go down as low as 29 grains and list a low 15000psi. (For jacketed its 51.8+)

The super slow H1000 is first mentioned at a heavy for bore 200GN projectile and goes down as low as 39 grains. (For jacketed its not listed)

On that principle then in the 6.5x55, Varget is suitable for all but the smallest projectiles. H4350 should be suitable from 129 grains upward, H4831 for 140 grains upward and H1000 only for the biggest projectiles 160GN +.

Lee suggests
"The slowest burning powder should not be reduced more than
20%. Each preceding powder may be reduced 1% more.
Example: 20%, 21%, 22%, 23%, 24%, etc."

If I apply this principle to the 6.5x55, and only to Hodgdon (ADI) powders due to availability.

For a 139-144GN projectile.
H870 - 20% (53x.8=42.4)
H1000 - 21%(50x.79=39.5)
H4831 - 22% (47x.78=36.7)
H4350 - 23% (44x.77=33.9)
Varget - 26% (36x.74=26.6)
H4895 - 27% (35.8x.73=26)

These figures of course would relate to a hypothetical load without a filler and in theory with a filler to reduce case capacity could probably be a bit lower.

While many have used fluffy fillers with success (myself included) current thinking is to avoid them with smokeless powders. Lyman was so concerned that they re-shot all of their cast data which previously used Dacron fillers not using fillers. This was done for Manual Number 48.

Not all powders will "flash over" or whatever term some want to use. The old skool solution for reduced cast loads was to use fast burning powders, but depending on the powder and the velocity desired they can cause leading. I would never reduce a slow powder like H870 by 20 percent, Lee is not a loading data company. But H4895 or IMR4198 can safely be reduced far more than that.


.