starting loads dimensions for 375 Chey tac

Mag 300

Mag 300

Gunny Sergeant
Full Member
Minuteman
    • Dec 31, 2006
    1,891
    59
    67
    Downers Grove Illinois
    #1
    looking for a recommended load for a new "to me " 375 Cheytac.
    are you loading to the lands .010 off , jamming etc also a good load for a 600 yd zero
    I have 350 smk and the 333 leigh projectiles
    also two star Jammison brass
    Thanks Bill
     
    #2
    Re: starting loads dimensions for 375 Chey tac

    Loads .020 off of the lands.

    Start with 131.5 gr. RE25. With a 29.5" barrel, I yielded 3050 fps. Could easily get 3250 with 135.00 gr. RE-25, but too much heat, and not enough gain to justify that speed.

    Trigger
     
    #3
    Re: starting loads dimensions for 375 Chey tac

    Bill, jealous of your Kit.
    sick.gif

    Trig, jealous of your experience.
    cool.gif

    I know I will have to build a .375 one day. You guys should stop teasing me.
    frown.gif

    TAG.
     
    #4
    Re: starting loads dimensions for 375 Chey tac

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Triggerfifty</div><div class="ubbcode-body">Loads .020 off of the lands.

    Start with 131.5 gr. RE25. With a 29.5" barrel, I yielded 3050 fps. Could easily get 3250 with 135.00 gr. RE-25, but too much heat, and not enough gain to justify that speed.

    Trigger </div></div>

    What he said and if you use retumbo then add about 4 grains. The lehighs you will be able to push harder by about 3-4 grains as well.
     
    #5
    Re: starting loads dimensions for 375 Chey tac

    Hey Bill,

    I use 133 grains of R-25 behind the 330gr Lehigh's with 10 thou off the lands.

    I used 129gr of R-25 behind the 350SMK's with a 30 thou jump.

    Start low and work your way up.

    Steve
     
    #7
    Re: starting loads dimensions for 375 Chey tac

    Triggerfifty,

    Do you consider the .020 off the lands as optimum in your experience or a starting point? I would typically consider this a maximum freebore dimension and all things being equal I would rather run .005 to .010 off the lands and reduce the charge to keep pressures in line.

    I have to admit this is for other rifles I load (.223 Rem, 25-06, 300 Win, etc) and I am just getting off the ground with my .375 CT Imp and I am not looking to re-invent the wheel here. Improvement of the brass aside, I get a sense that you have a significant amount of Chey Tac specific experience and I would like to take advantage of that.

    As NotaGuru noted, I am shooting Retumbo and working north of 135 gr. on my loads but if there is a feeling that RL 25 is a better choice I will scrounge some up.

    I appreciate any light you can shed.
     
    #8
    Re: starting loads dimensions for 375 Chey tac

    RL25 has been the most common powder used for .408 and .375, from what I've seen (hence the several pounds of it I have in the garage). Yet recently Bobby pointed out that it can vary a little too much from lot to lot, while Retumbo seems more balanced.
     
    #11
    Re: starting loads dimensions for 375 Chey tac

    I imagine that they will all work well, just may be slight differences in loads.

    One issue I have had is that apprently the Rem 9 1/2 primers are a bit thicker and <span style="text-decoration: underline">may </span>require a stiffer firing pin mainspring for reliable detonation according to the Lawton folks. Conversely if you are getting good penetration on the 9 1/2's it is possible that <span style="text-decoration: underline">might</span> need to lighten your spring up on the 215's.

    I am going to some Fed 215's this weekend to test this very situation.
     
    #12
    Re: starting loads dimensions for 375 Chey tac

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: .375Mojave</div><div class="ubbcode-body">Triggerfifty,

    Do you consider the .020 off the lands as optimum in your experience or a starting point? I would typically consider this a maximum freebore dimension and all things being equal I would rather run .005 to .010 off the lands and reduce the charge to keep pressures in line.

    I have to admit this is for other rifles I load (.223 Rem, 25-06, 300 Win, etc) and I am just getting off the ground with my .375 CT Imp and I am not looking to re-invent the wheel here. Improvement of the brass aside, I get a sense that you have a significant amount of Chey Tac specific experience and I would like to take advantage of that.

    As NotaGuru noted, I am shooting Retumbo and working north of 135 gr. on my loads but if there is a feeling that RL 25 is a better choice I will scrounge some up.

    I appreciate any light you can shed. </div></div>

    Mojave,

    myself and a couple of buddies each have the improved version of the .375 CT, My load is 135 gr of AR2225 (Retumbo) behind the 350 SMK. I am just off the lands my Chrony average is 3140 fps. My friend has gone as high as 146 gr Retumbo behind the 350 SMK and primers were flat and the load was not as accurate as the 136 gr load with smk's he has settled on. With Lathe Turned Pills Aussie made Preadtors 350gr weight I have a load that shoots better than the smk's in a formed case same powder charge 135gr Shoots very well but have not tried that pill at distance YET. My friend's Formed case load using the same predator pill is 140gr and he is averaging a little over 3260 fps.

    Shot my unformed case load at 1368 yards on the weekend 350 smk behind 135gr Retumbo wind blowing 16mph at our spot, took 9mil elevation and 2.5 mil for wind and I hit my steel gong after missing first couple and putting a couple through my target frame. This is the furtherest I have shot my improved .375 to date (1079 Yards previously) and I plan to keep moving further out each time. Im hooked have a couple of smaller guns on the way to practice a little more cheaply
    laugh.gif
     
    #13
    Re: starting loads dimensions for 375 Chey tac

    pc3,

    I really appreciate the info. There seems to be very little info available on an improved .375 CT. I have run mine up to 144 gr. but was having primer problems and did not get much grouping info. Just slightly reduced the radius on the primers at that point so it is close to a max but I am probably a couple grains away from the absolute max.

    I got a great group (1/4 MOA) out of 136 gr of Retumbo over the weekend with the bullets about .020 off the lands. I am waiting on dies so I am at a standstill for a couple weeks. I stopped fire forming cases using a 350 SMK as the forming happens quite differently (possibly not good) than using a reduced charge, filler and a tissue plug.

    How does the accuracy of the Predator/140gr loading compare to your 136 gr load and, in general, how does the Predator perform when compared to the SMK's? Also, have you done enough testing to determine which is trending more accurate, lower loads just off the lands versus slightly heavier loads held back a bit?

    As soon as my dies arrive I am going to put together some 3 round, 1 gr increment loads holding them .015 off the lands and starting at 136 through 144 gr and see if I can start to zero in on the most accurate load for my gun. I will post the results here in a couple weeks.

    I really appreciate hearing from some of the other guys with similar rifles. Keep me abreast of your adventures, thanks.
     
    #14
    Re: starting loads dimensions for 375 Chey tac

    Mojave,

    the 140 gr load with Predator bullet and 136gr load with SMK is out of my friends .375 IMP. Very windy when he tested but I think the Predator load shows more accuracy potential.

    My loads are 135 gr for both bullets and the Predator is proving to be more accurate.

    Where my loading knowledge falls down is the fact I am unsure how far I actually am off the lands, I just seta slight deeper until it just chambers and then go a tiny bit more than that. Not great for making ELR ammo I know.

    On Game the Predator performs well for a lathe turned bullet although it does not open up as does the 350 SMK
     
    #15
    Re: starting loads dimensions for 375 Chey tac

    pc3... What you need to do is grap a piece of 000 steel wool and scuff the bullet up. Take the firing pin out and make sure the bullet is seated long enough to hit the lands. Then keep bumping it back about .005-.01" at a time until the lands barely make a mark on the bullet. That sets your seating depth for now. I always keep that first one to compare to later seating depths to check how much the throat is moving with a ogive tool and calipers. Good luck and good shooting!
     
    #16
    Re: starting loads dimensions for 375 Chey tac

    Good info. The starting point is a comparator and calipers so you can get a reading on the bullet ogive.

    Another pretty simple method I have used is just get a casing with a very light grip on the bullet and fully seat the round. I do it on several and measure them. You typically need to back them off a couple thou to get them completely out of contact with the lands, and every now and then one will extract slightly as you remove it from the throat gripping it, but if you jot down the results of several you will quickly see the pattern on the dimension.

    I will have to give the steel wool technique a try (I think blueing would work too) and see how the dimensions compare.
     
    #17
    Re: starting loads dimensions for 375 Chey tac

    I was told to never use anything foreign in the barrel or die like magic marker. The reason was it can cause eroding and pitting like after you fire it and deposit that stuff down the barrel. Maybe changing the chemical composition of it. Maybe my buddy will chime in here.....
     
    #18
    Re: starting loads dimensions for 375 Chey tac

    I have a standard .375CT which I built on a Barnard P-Chey action, and my standard load is 132gr of AR2225 behind the 350gr Predator for 3150ft/s. This is in a 32" Lawton barrel with specs for the LRBT bullet, but I have 2 Krieger barrels coming in for when this barrel is shot out. I am seating 0.020" off the lands, and I use a Stoney Point gauge to determine this. I have found this projectile to be at least as accurate as any other .375" bullet I can find, including the 350grSMK and 350grLRBT.
    I shot my rifle along side PC a few weeks ago, and both really perform at long range. Has anyone tried the Rocky Mountain bullets on larger game at long range? Im looking for a bullet that will do the job a bit better than a solid on Sambar deer sized animals once the velocities are down a bit.
     
    #20
    Re: starting loads dimensions for 375 Chey tac

    Thanks for the Tips NAG. There are also the Henson Aluminium Tipped Pills are these the same as the Rock Mountains ? the .338 Pill in these is said to be a .9BC, so the .375 Pill would be as good I suspect, have the same BC as the Solids and perform better on game.
     
    #23
    Re: starting loads dimensions for 375 Chey tac

    We shot this past weekend at 1400 yard with the Rocky mountain hunting bullet. This is the only bullet i have shot at this time, I have a box of the Lehigh and a box of the Hooker Tacticle bullets. With the 375 grain Rocky moiuntain and 133 grains Retumbo i am running right at 3100 fps with my 11.5 LRB barrel. We will keep moving back as we can move to right around .1700 to shoot. I have alot to learn in this game.The gun shoots better than I do.
     
    #25
    Re: starting loads dimensions for 375 Chey tac

    <div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">When i did the predators they came out to be about 1.03 bc. So they came close to the LR solids at 1.13.</div></div>
    NAG,

    Did you use MV to work out the BC?.

    Thanks.
     
    #31
    Re: starting loads dimensions for 375 Chey tac

    Thanks to all
    Greatly appreciate it .
    Just got the two premier 5 x 25 mil mil gen 2 XR reticle for the 338 and the 375
    Shooting next week cannot wait!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
     
    #33
    Re: starting loads dimensions for 375 Chey tac

    well took a chrono with to the range and its the first time shooting the new beast for me . took the load from the hide here but it was 80 degrees and the rifle has a 32" barrel.

    loaded them .010 off the lands 135 gr retumbo fed 215M primer and a smk 350gr jammison brass

    3402 FPS 8 in a row all read within 30 fps
    checked the chrono with a 6 cm load that shows 3000 and it was 3021fps?
    is the chrono off?? rechecked the center of the two ohler sensors and there 24" apart exactly

    thanks Bill
     
    #36
    Re: starting loads dimensions for 375 Chey tac

    Bill, I was getting 3240-3250 from the same load combination except I was using a 139 gr charge of Retumbo, out of that rifle. I had the chrono 15 feet from the muzzle though. PM sent.
     
    #37
    Re: starting loads dimensions for 375 Chey tac

    Well,
    sometimes its hard to admit your an IDIOT but thinking abouot it I was only 5 feet away from the muzzle and also not used to burning 135 gr of powder in one shot.
    Thanks guys as usual you helped me out.
    Bill
     
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