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338 Jarrett
- Thread starter comen
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Elkhunter007
Well-Known Member
If your rifle was built by Jarrett Rifles you can call the office and they will give you the information from the original load development. Some of this information may help you with your new load development.
The gun in my Avatar is a Jarrett 338.
The gun in my Avatar is a Jarrett 338.
Mine is a custom with a 28" McGowen custom contoured Barrel
You can use .340 WBY as a baseline. I have a .30 LARA, which is an improved .300 Jarrett.
Weatherby charges are too hot. I max out at 84 Gr of RL 22, and that gets me 3200 FPS from my 28" barrel, according to my magnetospeed. I'm wondering if I need to reduce my load more given the velocity. I don't have much freebore; Seating at 3.6" I'm jumping .045"
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I have a .125" freebore on my .30 LARA, and I can shoot the .300 WBY (freebore .361") ammo. I also used the .300 WBY as my baseline without any issues. As with anything else, you need to work your way up slowly. If you are pushing the 225 TTSX at 3200 FPS, then you are doing better than what Barnes has published with 225 TTSX .340 WBY.
Lyman #50 shows a starting load of 83 gr and a max of 87 gr RL 22, but a much shorter barrel than mine. My old Barnes book shows the same with the ungrooved x bullet. My action is a Remington M1917 action, fully blueprinted. I don't have any pressure sign other than slight cratering from a slightly large firing pin hole in the bolt face, and I get this with 78 grains, The action opens very easily, and the edges of the primers are still round. Still, my velocity seems high. I chrongraphed at 30 rounds, and this same load gave 3110 fps while fireforming. I am about 80 rounds now, and Chronoed 6 fireformed rounds today:
1. 3228
2. 3230
3. 3235
4. 3224
5. 3237
6. 3245
ES was 21 fps and SD was 7
Should I reduce further, or is my barrel just fast? Could my magneto speed be giving bad velocities?
1. 3228
2. 3230
3. 3235
4. 3224
5. 3237
6. 3245
ES was 21 fps and SD was 7
Should I reduce further, or is my barrel just fast? Could my magneto speed be giving bad velocities?
I f anyone is watching. I shot 3 fire formed Remington cases, and 3 new unformed Quality cases, at 100 meters. All with CCI Magnums. I dropped the powder charge down to 82.5 gr RL22; the firefomed cases chrongraphed 3207 fps, 3220 and 3237, the unformed cases did 3192, 3173 and 3212. The formed cases made a large single hole about 5/8" outside measure. the unformed cases had 2 touching and one an inch and an 8th higher. All still 225 gr TTSX
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FYI if you want some 7828 data:
my 338 jarrett shoots a 225 partition at 3200fps over 92 grains of compressed 7828 from a 26" tube with FF 8RM brass.
225 grain accubonds at 3.66 coal take up more case capacity and puts me beyond where im comfortable compressing.
last week Jay Jarrett said my other 338 jarrett should be shipping out any day now.
who has 250 grain (accubond) load data for H1000?
my 338 jarrett shoots a 225 partition at 3200fps over 92 grains of compressed 7828 from a 26" tube with FF 8RM brass.
225 grain accubonds at 3.66 coal take up more case capacity and puts me beyond where im comfortable compressing.
last week Jay Jarrett said my other 338 jarrett should be shipping out any day now.
who has 250 grain (accubond) load data for H1000?
I backed all the way back down to 80 gr of RL 22, and got 3116 FPS from my 28" barrel with the TTSX. Shot a 3 shot group at 100 meters and got .621" outside edge to outside edge. I shot another 3 shot group at 200 meters and got 1.214" outside edge to outside edge. Center to center both groups are well under 1/2 MOA. I cut the two groups out and glued them into the load book, as I probably won't shoot that well again!
I have a little IMR7977, but I'm saving that for my 8mm Mag!
I know :-( ... I shoot 83 gr. with the Sierra 220 BT and have 50 loaded and enough powder for about 35 more. This is another '17 Enfield action, with a Green Mt 1.2" bull barrel. It is my steel banging special for 800-1000 yds. I will try to find 7828, or H1000 when that's gone. The Barrel weighs 8.5 lbs. so not a backpacking rifle.
