357 Mag went from 6" group at 200 to 15" at 100 ???????

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"How long of an interval between shooting the 2400 and the Blue Dot? (24 Hours) What kind of sights or scope was being used? (Redfield/Lyman Iron sights) What was holding the gun? (utilized a Beecher Best Rest support)

Sights can come loose,(THEY DIDN'T) scopes can come loose (both internally and externally) , eyesight get worse over time,(20-15 vision then in 30s and now at 70) shooting from a rest vs standing (was not standing but can shoot much better than that if I was standing) maybe the barrel was fouled up and full of lead (never shot a lead bullet in that rifle, all JSP or JHP) when shooting the Blue Dot, maybe the sun was in your eyes,(sun was same place both days) maybe you didn't drink your morning coffee...."(didn't drink coffee at all for years due to it was not consumed by competition shooters)
 
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Not enough crimp. Not enough powder. BlueDot works best at or near max charges and requires a good consistent crimp. And that’s also what it needs to burn cleanly and achieve proper, consistent pressures which will result in at least a more consistent group. “A book load” doesn’t mean anything. What book? What edition? Were you at a starting load or near max?
 
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It as top end. Don't remember what manual I used, probably Lyman or Sierra. Whatever it was it was 30+ years old. I used the same crimp, same cases, same bullets etc.
 
Hummer70 said:
"How long of an interval between shooting the 2400 and the Blue Dot? (24 Hours) What kind of sights or scope was being used? (Redfield/Lyman Iron sights) What was holding the gun? (utilized a Beecher Best Rest support)

Sights can come loose,(THEY DIDN'T) scopes can come loose (both internally and externally) , eyesight get worse over time,(20-15 vision then in 30s and now at 70) shooting from a rest vs standing (was not standing but can shoot much better than that if I was standing) maybe the barrel was fouled up and full of lead (never shot a lead bullet in that rifle, all JSP or JHP) when shooting the Blue Dot, maybe the sun was in your eyes,(sun was same place both days) maybe you didn't drink your morning coffee...."(didn't drink coffee at all for years due to it was not consumed by competition shooters)
Click to expand...
The only thing you didn't answer which I asked back in Post #17 was if there was any leading in the barrel after the first range trip? Is it possible the ammo loaded with 2400 leaded the barrel so that when you shot the ammo made with Blue Dot the groups opened up that much.
 
That rifle never saw anything but JSP and JHP ammo factory or handload. I will shoot cast bullets in revolvers only exactly for the reason you stated.

Post 18 is the closest yet.
 
Case fill? Orientation of the blue dot powder in the case whether against the back of the bullet (lowest pressure), at the base of the cartridge (highest pressure) or equally distributed on the earth side of the cartridge (middle pressure).

Other than above I would have to say it has to do with the pressure spike difference in relation to where the bullet is in the barrel when it occurs between the two powders. However, I wouldn't think that wouldn't explain a shotgun pattern more of a POI change.

I'm intrigued...I know less than most people on this forum have forgotten.
 
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My guess is too much initial pressure and the bullet blew through the rifling without imparting any spin, and the only way to prove it was the soft recovery.
 
I'll guess the bore diameter on the marlin was oversize and the blue dot load did not obturate to fill the groove diameter
 
Interesting read. Thanks for posting.

My guess is some flame cutting of the bullet.
 
Here's my secondary guess..
I have read Blue dot can have pressure spikes....also read it could be from cold temperatures....I don't know what temperatures you had at the range

So, let's say the initial push is sending the bullet down the barrel
Then there is another smack on the bullet from a pressure spike, when the bullet is farther down the barrel

It swells up and the base of the bullet is deformed asymmetrically ......as the bullet is leaving the muzzle... it's given a nudge in who knows what direction!

Since the base steers the bullet and it's wobbling.....your group opens up compared to the 2400 load

If this is the case....would the bullet stabilize by the time it hit the 200 yard target?
 
BINGO WE HAVE A WINNER ! ! ! !
Bill Davis surmised that the Blue Dot gave a faster pressure spike on initial ignition and the base of the bullet deformed and center caved in and looked like a bowl. The base of the bullet retaining integrity is critical to maintaining accuracy. The 2400 had a more gentle pressure spike did not deform the base of the bullet.

Subsequently I was at the Secret Service facility Beltsville talking to my friends in the gun shop and told them I had just purchased a thousand 7MM FMJ boat tails of "foreign manufacture" at Camp Perry. The ammo tech worked for Larry Moore at Frankford Arsenal and he took one look at them and said, "they won't shoot". The techs at FA could look at bullets and tell you if they were good or not. He was going through them on a looksee and saying, "good, crap, crap, good etc" He told me when I returned home segregate the bullets just as he had and he showed me what to look for. Then I was to shoot a group with bad bullets, then go to a different aiming point and shoot the good bullets.

I did as he said, shot 10 round group and it went about 3" at 100 yards, then I shot the bullets he said were good and 10 rounds in an inch! ! ! ! !

It is like Yogi Berra said, "you don't know what you don't know till you know what you don't know.
 
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as i said earlier
its an open book question

I had to read a bunch of posts this week by unclenick and this guy Humpy:D

there's alot of wisdom stored in these forums
 
Pressure spikes with BlueDot in .357 is what led to Alliant's warning about not using it with 125gr pills. I always wondered why there was no concern at all with other projectile weights in .357.
 
I had not heard that but seems so likely it might happen. I think the reason I got it was to load 9MM and never got around to it. It stopped everyone but Bill Davis and it took him about 3 seconds to come with that answer.
 
I had a possibly similar experience last year with some plated bullets in .44 Mag: With Nosler 240 grain JHP bullets, max charge of 4227 and near-max charge of Longshot both shot well. Plated 240 grain HP bullets with the same charge of 4227 worked fine, but when placed in front of Longshot, they started scattering like buckshot. Don't have chrono data in front of me, but I believe the velocities of all were roughly the same. Can't recover bullets but my assumption was that the more abrupt kick in the butt from faster-burning Longshot mangled the bullet in some way.
 
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