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MarkCO wrote:I think that you would have achieved better results with a fast rifle powder rather than a slow pistol powder. Accurate 1680 and maybe 2015 certainly look to be well suited to a bolt gun with a 24" barrel. More area under the curve but with a lower peak pressure.
260 S&W 8.37" bbl
Bullet Accurate No.9 Accurate 1680
--------------- ------------------ ------------------
wt Mfr type gr fps psi gr fps psi
--------------------------------------------------------
200 Barnes XPB 46.0 2409 56,690
240 Horndy XTP 38.0 2000 59,300 50.0 1985 53,300
260 Nosler PART 35.0 1895 59,000 46.0 1860 51,500
275 Barnes XPB 38.0 2006 57,750
300 sierra JSP 34.0 1790 61,000 45.0 1810 57,000
Mark-MarkCO wrote:Bob, you might hit the powder capacity wall, however your posted data is for a short barrel. 1680 will still have beneficial expansion occurring out to about 16" of barrel length whereas #9 is done at about 10" for a .45 caliber bore. I have also found that using the stab crimp does boost my velocities as well as provide better accuracy, so with a light bullet, I would definitely be using that.
pitted bore wrote:MarkCO wrote:I think that you would have achieved better results with a fast rifle powder rather than a slow pistol powder. Accurate 1680 and maybe 2015 certainly look to be well suited to a bolt gun with a 24" barrel. More area under the curve but with a lower peak pressure.
Mark-
Thank you for your interest. I'm assuming by "better results" you mean a higher velocity with less pressure.
I did consider 1680 when selecting powders for this work. It's in the powder locker, and I've used it with some trials of 300-grain bullets in the 450B. However, I decided against it for the work described above based on my interpretation of data in the Western Powder Manual. You're right, a pressure curve for 1680 will be flatter and longer. However, with this light bullet, the peak for 1680 is probably too low compared with No.9 to make up the pressure curve areal difference.
Here's what the Western manual shows for No. 9 and 1680 in the 460 S&W. The 460 S&W is a pretty good surrogate for the 450B for exploring powder/bullet behavior when 450B SAAMI pressure limits may be ignored:
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260 S&W 8.37" bbl
Bullet Accurate No.9 Accurate 1680
--------------- ------------------ ------------------
wt Mfr type gr fps psi gr fps psi
--------------------------------------------------------
200 Barnes XPB 46.0 2409 56,690
240 Horndy XTP 38.0 2000 59,300 50.0 1985 53,300
260 Nosler PART 35.0 1895 59,000 46.0 1860 51,500
275 Barnes XPB 38.0 2006 57,750
300 sierra JSP 34.0 1790 61,000 45.0 1810 57,000
In this table, looking at the 240 XTP bullet, it is obvious that 1680 runs out of powder room before it can get sufficient powder to boost pressures up to 59,000 psi level. (Even if the cartridges were stretched a half-inch to make more room, it is likely that the light bullet will not provide enough resistance to allow pressures to build to the point that 1680 can burn efficiently. With heavier bullets 1680 performs well, as shown by the data for the 300-grain JSP in the table, and in the experience of several forum members.
If you have the pressure curves to show that my interpretation is incorrect for 1680, I'll be really delighted to see them and revise my thinking. When I start playing with "suicide runs", I like to have my ducks in some semblance of order, if not in a nice row.
Meanwhile, as soon as I can get to the range, I'll try some max loads of 1680 behind the 200-grain XTP. I'll report the results in this thread, but I'm expecting 1680 to run up against the same limits that I found for Enforcer and 296; that is, the case will be full before the velocity equals No. 9's. The light bullet is part of the limiting factor.
Thanks again.
--Bob
pitted bore wrote:Mark-MarkCO wrote:Bob, you might hit the powder capacity wall, however your posted data is for a short barrel. 1680 will still have beneficial expansion occurring out to about 16" of barrel length whereas #9 is done at about 10" for a .45 caliber bore. I have also found that using the stab crimp does boost my velocities as well as provide better accuracy, so with a light bullet, I would definitely be using that.
As indicated in the description of procedure, I did use a side/stab crimp.
At your suggestion I checked 1680 powder today. The maximum amount of 1680 that I could fit in a Hornady 450B case under a 200-grain FTX was 50 grains. I loaded five cartridges with 50.0 grains of 1680; other procedures were as described in the second post of this thread. Over my chronograph at 10 feet from the muzzle, I found the following velocities in fps: 2216, 2237, 2187, and 2241. One shot failed to register. Average of the four shots was 2220; sd=24.7, es=54.
This is about 400 fps slower than VV N110, the powder with the lowest velocities of the five tested above. It is about 800 fps slower than No.9.
--Bob
Texas Sheepdawg wrote:Could unburned powder exiting the barrel and flying through the chrony be confusing its sensors? Was there excessive muzzle flash? Either way, the 1680 does not sound like a viable powder for this weight of bullet.
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