445 sm powders and pressure issue

[bucco921]

I recently reamed one of my handis to 445 sm. Ive been trying to develop loads with h110 and hornady 240 & 300 xtp bullets. hornady lists 29.6 min to 32.8 max for the 240 and 24.6 min to 29.1 max for the 300. I loaded my 240s down to 30.0 and my 300s down to 26 and have gotten extremely flat primers with both. I have some room to go down with the 300s but im only .4 above minimum with the 240s and primers are as flat as they come. Brass was never fired starline and cci mag pistol primer. Has anyone else experienced this at loads not near book max? Ive been talking to another member here and we've been discussing the possible use of rifle powders such as rl7 or 4198 in the 445sm but wouldnt really know where to start for a minimum charge. Any ideas, suggestions or experience would be greatly appreciated. Im kind of confused on why I am seeing this issue when I see many members here claiming to use charges way above mine and not seeing any pressure signs.

[BCB]

 I don’t think you are going to have much success with powders any slower than SR-4759,
5744, 680, or 1680…
 
I have used them in my 445 SM and the 680 gave the best velocity…
 
As far as using slower powders, I have used known data for powders that are faster than a slower powder I wished to try when there was no data available…
 
That method is ENTIRELY UP TO YOU…
 
But, I suspect that you will not have enough case volume after seating a 300 grain slug to get much efficiency from slow burners—May be wrong on that…
 
I have found the 445 SM to be a strange cartridge.  I am shooting it from a Contender and I have never been sure of pressures…
 
Maybe that is why it really never caught on.  The only reason I have it is because the 44 Magnum Super 14” shot 3-4” groups at 100 yards and really didn’t do much better at 50 yards.  The 445 SM will shoot 2” groups at 100 yards if you can stand the recoil for a bunch of shots.  Definitely not a pleasure to shoot…
 
Good-luck…BCB
 
 

[quickdtoo]

I'd give 1680 a shot. 

Tim

[stimpylu32]

bucco921
 
What you may be seeing is not an over pressure but a under pressure , were the case is not griping the chamber tightly enough and allowing the case to slide back and flatten the primer against the breach face .
 
stimpy

[bucco921]

stimpy, what would cause that? the ream job was clean, no scores in the chamber. I read that somewhere else and the guy claimed it always happened to him with brand new brass but went away after the case basically fireformed to his chamber. Tim I just bought some 1680. thnx guys

[stimpylu32]

The 445 was desinged to be hot-rodded , you may not be building enough pressure to fully form the case to the chamber before the bullet starts down the barrel , that along with a very smooth chamber may be adding to the problem ( nothing for the case to bite to )
 
Another thing could be your sizing die may be on the low end of the spec and the case's can't expand quick enough to fill the chamber .
 
Just a couple ideas .
 
stimpy

[dpe.ahoy]

That cartridge is headspaced on the rim.  Could be the rim cut is just a bit too deep, allowing the firing pin to move the case forward.  Primer starts the powder burn, forcing the primer to start to back out of the pocket, case gets pushed back flattening the primer.  DP

[woods]

     You are useing large rifle primers? I'm shooting a 12" hunter contender mine flattens somewhat but not excessive. This is what my contender load manual states due to higher operating preasures.
     woods

[quickdtoo]

Brass was never fired starline and cci mag pistol primer.

[dave29]

bucco921
 
What you may be seeing is not an over pressure but a under pressure , were the case is not griping the chamber tightly enough and allowing the case to slide back and flatten the primer against the breach face .
 
stimpy

This.

H110 is a really finicky powder when it comes to pressure as well.