30 Sherman Magnum 20” Build

CA48

Well-Known Member
Joined
Nov 18, 2009
Messages
1,200
Location
Texas
If I get time Il do it today. Luckily the range is my front porch so I don’t have far to go. Surely if I load some up and leave them in the freezer for an hour then take them out and shoot them immediately that should suffice?
 

phorwath

Well-Known Member
Joined
Apr 4, 2005
Messages
7,284
Location
Alaska
If I get time Il do it today. Luckily the range is my front porch so I don’t have far to go. Surely if I load some up and leave them in the freezer for an hour then take them out and shoot them immediately that should suffice?
I put my rifle in the freezer also. But I can be nerdy. OCD afflicted. 🙂
 

CA48

Well-Known Member
Joined
Nov 18, 2009
Messages
1,200
Location
Texas
I would if I didn’t have to take off the stock. But I was thinking I’ll just mount the muzzle a few inches away from the a/c vent to get the chamber in the high 50s.
 

phorwath

Well-Known Member
Joined
Apr 4, 2005
Messages
7,284
Location
Alaska
I see. I had a 25cu ft chest freezer. Just had to make sure my wife didn't find out what I had placed in there!
 

CA48

Well-Known Member
Joined
Nov 18, 2009
Messages
1,200
Location
Texas
I put 2 rounds in the freezer at 28* for 1.5 hours loaded with 92.5gr of LRT. Had the rifle muzzle set up in the A/C vent to cool the barrel down as well. Also it’s 83* degrees today compared to 96* yesterday. Took the first round out of the freezer picked up the rifle and went outside and shot it within about 15 sec or less of pulling the round out of the freezer. Went back in and put the muzzle of the rifle in the ac vent for about 20-25 min then pulled the other round out of the freezer and repeated the process.

shot 1 2821
shot 2 2834

I’m going to estimate I was replicating shooting conditions of around 40* today compared to yesterday at 96*

That’s a 56* drop in temp and a 133 drop in fps with the same load. Which comes out to 2.37 fps/ degree.

This is a small sample and vague test but enough to show that LRT is Temp Sensitive and loads should be adjusted between summer and winter temperatures.

Just for the heck of it I have 6 more rounds loaded with 92.5gr to test for accuracy at some point in the next few days.
 
Last edited:

CA48

Well-Known Member
Joined
Nov 18, 2009
Messages
1,200
Location
Texas
Shot 92.5 of LRT at +.005” this evening, first 2 shots landed 0.8” at 100 yards. I stopped there and seated the next 2 at +.010” same charge. They grouped 1.0”. Loaded up the last 2 at +.025 and they grouped 1.3”. So nothing to good for the first 6 shots with LRT but it would need more testing. As I said earlier I’m sticking with the N570 load. Just had 6 pieces of 5x fired brass laying around that were ready to load so I gave it a quick try.
 

CA48

Well-Known Member
Joined
Nov 18, 2009
Messages
1,200
Location
Texas
Glad to help get some data on LRT. Ive been curious about it myself for awhile now as I heard it was supposed to be less temp sensitive than other ball powders. I’m thinking I might try a few more loads closer to the lands before I put it back in the cabinet to see if I can tighten up groups.
 

phorwath

Well-Known Member
Joined
Apr 4, 2005
Messages
7,284
Location
Alaska
A friend has a 338 LAI that groups very nicely with LRT. He's only shot his over a 20F temp change and no big temp issues within that much narrower temperature band.
 

CA48

Well-Known Member
Joined
Nov 18, 2009
Messages
1,200
Location
Texas
I’m pretty sure Kirby was having good luck with LRT in his AX lapua based wildcats as well. Seeing a big gain in velocity over retumbo.
 

CA48

Well-Known Member
Joined
Nov 18, 2009
Messages
1,200
Location
Texas
We had a storm roll through Thursday so that evening things were pretty calm. Right about dark I decided to pull the rifle out and put three rounds down range on one of my steel plates. Distance was 1308 yards and the wind was 1mph @ 3cl. I dialed up 34.5 Moa and left the windage at 0. Fired 3 as fast as I could accurately as it was getting dark quick. The road to my target was a little wet still so I waited until the next day to go check it. In the pic my the bulleye looks strange because my target is one of those old school giant gooseneck hitches mounted on a 3x3 plate. The first 2 shots were 1.8” apart and landed on the edge of the ball at 5cl. The last shot hit on the center of the ball.
As pictured minus the bi-pod weight is 11.5lbs Although when I shot the group the rifle had a Terminator t-3 muzzle brake on. In that configuration the rifle weighs 10.4 lbs

F6D395E8-9AAF-4352-8CBA-DFDB24FFDCEE.jpeg

EEEAE821-65E1-491F-8849-D3DB5CE2CA47.jpeg

7D5C25C9-F868-41A5-9BEC-F5A9F6278371.jpeg
 

highdrum

Well-Known Member
Joined
Nov 30, 2008
Messages
2,741
Location
Montana
We had a storm roll through Thursday so that evening things were pretty calm. Right about dark I decided to pull the rifle out and put three rounds down range on one of my steel plates. Distance was 1308 yards and the wind was 1mph @ 3cl. I dialed up 34.5 Moa and left the windage at 0. Fired 3 as fast as I could accurately as it was getting dark quick. The road to my target was a little wet still so I waited until the next day to go check it. In the pic my the bulleye looks strange because my target is one of those old school giant gooseneck hitches mounted on a 3x3 plate. The first 2 shots were 1.8” apart and landed on the edge of the ball at 5cl. The last shot hit on the center of the ball.
As pictured minus the bi-pod weight is 11.5lbs Although when I shot the group the rifle had a Terminator t-3 muzzle brake on. In that configuration the rifle weighs 10.4 lbs

View attachment 289843
View attachment 289841
View attachment 289842
Excellent shooting! How does your accuracy fair going from the terminator brake to the supressor?
 
Top