Triple 7 powder charge for a 300 grain sabot

[fast*eddie]

I was researching Hornaday 300 gr XTP sabots and saw in one spot where it was recomended to use 150 grains of powder . Is this necessary ? Any suggestions ? I was loading 100 gr of 777 but wasn't getting tight groups .

[Swift One]

Me and my buds over the years have used the 300gr XTP and SST bullets in out 50 cal MLs.  Both will run 150grs of 777 pellets with decent accuarcy.  However, I have found that in all of our MLs, only one shot great with 150grs- an Encore with a bergara barrel.  The others manitained tighter groups with 100grs of 777 pellets.

[flintlock]

I use 80grs FFF Goex behind a .429 Hornady XTP 300gr...Let your rifle tell you what it groups best...Anywhere from 70-120grs is plenty for whitetails out to 150 yards...
 
The 45/70 killed plenty of game...It used a .45 caliber bullet of about 405grs and 70grs FF black powder....

[omegahunter]

If you are shooting pellets, try 150 grain load and see if the groups improve.
 
If you are shooting loose powder, shoot some at 110 grains and 120 grains by volume to see if groups improve.  BTW- Hodgdon techs state that 127.5 grains (volume) is MAX load of loose 777.
 
Be sure you are cleaning between shots for best accuracy with 777.  If that still doesn't do it, try to shoot it fouled, but you likely won't be able to load more than a couple shots easily with the barrel fouled.
 
Next step would be to try a different bullet/sabot combination.  I get great groups with 250 and 300 grain SST's on top of 120 grains volume of 777 and cleaning between shots.  2 wet and 3 dry patches make a pretty much spotless bore between shots.
 
Good luck!

[sabotloader]

I was researching Hornaday 300 gr XTP sabots and saw in one spot where it was recomended to use 150 grains of powder . Is this necessary ? Any suggestions ? I was loading 100 gr of 777 but wasn't getting tight groups .

Powder charge... I think shooting 150 grains of pellets either T7 or Pyro Pellets would offer you reasonable accuracy.  Remember pellet power is based on real BP, so 150 grains of pellets is like 120 grains of loose t7-2f or 150 grains of Pyro RS/S.
 
I have used 100 grains of loose T7-2f for years with a 300 grain bullet, but I do go to 120 with a 300 grain bullet for Elk.
 
Also if I could suggest and I know that Hornady XTP's are and have been favorites for years, you migh look at a .452-300 grain Speer Deep Curl with a BC of .232 and the fact that it is a bonded bullet are well worth it.
 
The Deep Curl will expand with out separating the lead from the copper as an XTP can do especially if it were passing through bone at higher velocities.
 
Here is a picture of a tortured Deep Curls...
 

 
And the same test with XTP's
 

 
As I mentioned the copper is applied hot to the lead to form a tight bond.  A small brass dot found internally in the bullet shapes the mushrooming of the bullet and normally will not allow it to over expand or pancake....
 

 
This is a picture of a perfectly expanded Deep Curl - I wish I could say they always look like this...
 

 
Note: Gold Dot was the original name of the bullet but the name has been changed to Deep Curl