i recently bought a 375 cheytac from notaguru and have some quesions on loading. he gave me a load but said i might have to adj seating depth since load was when gun was new. gun has 300 rds down the tube. what has been every ones thought on the jamison solids? do they like to be touching the lands or have a jump? and with adj seating depth, at what increments should i work with .01, .005 or more? the charge he gave me was 137grs of retumbo if i work up a ladder would .2 grs make a difference or should it be a bigger jump? i just dont want to blow my self up... thanks!
375 chey tac load questions
- Thread starter blackwidow2912
- Start date
Re: 375 chey tac load questions
BW:
See link that has my load data in it.
http://www.longrangeresearchcenter.com/gpage9.html
Thanks
BW:
See link that has my load data in it.
http://www.longrangeresearchcenter.com/gpage9.html
Thanks
Re: 375 chey tac load questions
BlackWidow,
It has been my experience that full caliber solids like the 350 grain Jamison bullets like to have a run at the lands. You can have a significant pressure spike if the bullet is close to or touching the lands. Solids do not deform or swage like a copper jacketed lead core bullet, and must be treated differently.
Bobby has extensive experience with these, but 137 grains in my experience is a pretty stiff load. It wouldn't hurt to start a little lower, and work back up to that. You could also ask him what the COAL he was using with that load. That would help you a lot.
Scott.
BlackWidow,
It has been my experience that full caliber solids like the 350 grain Jamison bullets like to have a run at the lands. You can have a significant pressure spike if the bullet is close to or touching the lands. Solids do not deform or swage like a copper jacketed lead core bullet, and must be treated differently.
Bobby has extensive experience with these, but 137 grains in my experience is a pretty stiff load. It wouldn't hurt to start a little lower, and work back up to that. You could also ask him what the COAL he was using with that load. That would help you a lot.
Scott.
Re: 375 chey tac load questions
BW,
You can also try retumbo as per the Jamison website. Start low and work up as always. I started breaking mine in with 133grs. using Lehigh bullets and am up to 136grs. without issue although it is 42 degrees outside. I think that the brass will affect the accuracy more as it seems to need some work to get it up to par. So far, concentricity using the Lehigh solids and the virgin Jamison brass has a fair amount of runout. May need to work on the necks inside and out to get things in line. Regardless, you may want to change one variable at a time.
I'm going to try some VV N170 soon. I like VV powders since they seem to foul less although they are expensive. Anyone have N170 data?
Len
BW,
You can also try retumbo as per the Jamison website. Start low and work up as always. I started breaking mine in with 133grs. using Lehigh bullets and am up to 136grs. without issue although it is 42 degrees outside. I think that the brass will affect the accuracy more as it seems to need some work to get it up to par. So far, concentricity using the Lehigh solids and the virgin Jamison brass has a fair amount of runout. May need to work on the necks inside and out to get things in line. Regardless, you may want to change one variable at a time.
I'm going to try some VV N170 soon. I like VV powders since they seem to foul less although they are expensive. Anyone have N170 data?
Len
Re: 375 chey tac load questions
ok sounds good the overall he gave me was 4.49 i made a dummy round and that barly kisses the lands. i load a whole bunch up working up and down the ladder with the charges and seating depths will be taking her out today. ill post how she does
ok sounds good the overall he gave me was 4.49 i made a dummy round and that barly kisses the lands. i load a whole bunch up working up and down the ladder with the charges and seating depths will be taking her out today. ill post how she does
Re: 375 chey tac load questions
when out yesterday ended up wasting the first 12 rounds trying to get on the target fatherin law was the spotter he is not very good at that! from the ones i tested 139gr retumbo with an overall of 4.48 gave me a .971 moa 3 shot group with a velocity of 3295.6fps so im gonna load up those 12 since im on target now and see how they are.
when out yesterday ended up wasting the first 12 rounds trying to get on the target fatherin law was the spotter he is not very good at that! from the ones i tested 139gr retumbo with an overall of 4.48 gave me a .971 moa 3 shot group with a velocity of 3295.6fps so im gonna load up those 12 since im on target now and see how they are.
Re: 375 chey tac load questions
blackwidow,
I own a 375CT.I'm not an expert by any stretch of the imagination but I've picked up few things by reading here on the hide and finding out the hard way over the last couple of years.
Your velocity seems too high ??? You might want to back the chrono away to 15 or 20 feet.Too close and it will give you false readings from the huge blast.
IMO,There are some advantages to slowing down the speed some.
The barrel doesn't heat up so fast,doesn't foul up as fast and doesn't where out as fast.The brass will last longer too.Go for pure accuracy foremost.
Trigger50 an ELR expert said "something to the effect,that" the faster a projectile starts out,the faster that it will slow down near the end of it's trajectory.
Someone who understands this better than I hopefully can chime in and explain this phenomenon.
One of the most important and "expensive" lessons I learned was to test groups at 300 to 400 yards instead of up close at 100 or 200 yards.Those long solids usually aren't quite stabilized till farther out.
It's not a bad idea to do a ladder test and let your gun tell you what it likes best.
Steve
blackwidow,
I own a 375CT.I'm not an expert by any stretch of the imagination but I've picked up few things by reading here on the hide and finding out the hard way over the last couple of years.
Your velocity seems too high ??? You might want to back the chrono away to 15 or 20 feet.Too close and it will give you false readings from the huge blast.
IMO,There are some advantages to slowing down the speed some.
The barrel doesn't heat up so fast,doesn't foul up as fast and doesn't where out as fast.The brass will last longer too.Go for pure accuracy foremost.
Trigger50 an ELR expert said "something to the effect,that" the faster a projectile starts out,the faster that it will slow down near the end of it's trajectory.
Someone who understands this better than I hopefully can chime in and explain this phenomenon.
One of the most important and "expensive" lessons I learned was to test groups at 300 to 400 yards instead of up close at 100 or 200 yards.Those long solids usually aren't quite stabilized till farther out.
It's not a bad idea to do a ladder test and let your gun tell you what it likes best.
Steve
Re: 375 chey tac load questions
my crony was 15 feet away. i started with the load nag gave me but i was still finding the target at that point. i have to test those again. my gun also has a 32 in barrel i think that might be the reason for some of the added velocity. jamisons load was 139 gr with a overall of 4.303 and claimed to be 3200 but thats out of a 29" barrel. that would have easily been 3400 in my gun. i was also testing at 400 yds. nag told me to shoot for 1 moa group at 400.
my crony was 15 feet away. i started with the load nag gave me but i was still finding the target at that point. i have to test those again. my gun also has a 32 in barrel i think that might be the reason for some of the added velocity. jamisons load was 139 gr with a overall of 4.303 and claimed to be 3200 but thats out of a 29" barrel. that would have easily been 3400 in my gun. i was also testing at 400 yds. nag told me to shoot for 1 moa group at 400.
Re: 375 chey tac load questions
Sounds like you are on the right track then.You've got a fast barrel!
On a large capacity case like the 375CT a ladder done in .5 grain increments would be fine.It's not a bad idea to let the barrel cool down a few minutes between shots also.
Steve
Sounds like you are on the right track then.You've got a fast barrel!
On a large capacity case like the 375CT a ladder done in .5 grain increments would be fine.It's not a bad idea to let the barrel cool down a few minutes between shots also.
Steve
Re: 375 chey tac load questions
BW,
I agree with Steve and your MV seems high.
The Jamison load runs 3150 in all 4 of mine and after 6 rounds of normal pace firing the bolt starts to stick. And you are incorrect in regards to assuming that load will run 3400 in your gun.
REASON why: That back in the testing phases of the 375 it was noted that from 32" down to 29" barrel there was only approximately 75-90fps decrease.
ALSO NOTE: The 32" barrels developed a "fouling ring" about 4" from the muzzle.
Solids..especially the Warren Jensen designs like the MV to be from 2800-3200. Slower than that and the 408s dont like it, faster than that and the 375s dont like it.
Thanks
BW,
I agree with Steve and your MV seems high.
The Jamison load runs 3150 in all 4 of mine and after 6 rounds of normal pace firing the bolt starts to stick. And you are incorrect in regards to assuming that load will run 3400 in your gun.
REASON why: That back in the testing phases of the 375 it was noted that from 32" down to 29" barrel there was only approximately 75-90fps decrease.
ALSO NOTE: The 32" barrels developed a "fouling ring" about 4" from the muzzle.
Solids..especially the Warren Jensen designs like the MV to be from 2800-3200. Slower than that and the 408s dont like it, faster than that and the 375s dont like it.
Thanks
Re: 375 chey tac load questions
His chrono was right in line with my 35p. I would warn ya not to run the CT loads that are seated that deep. It will cause excessive pressure and may stick in the chamber. Those would need pulled out out 4.48 or more if you would want to run them.
His chrono was right in line with my 35p. I would warn ya not to run the CT loads that are seated that deep. It will cause excessive pressure and may stick in the chamber. Those would need pulled out out 4.48 or more if you would want to run them.
Re: 375 chey tac load questions
only reason i stated it would run 3400 was one of my test loads was 139gr 4.46 overal and i was getting 3330 fps now if i seat that to 4.303 wouldn't that increase the pressure to the point of boasting the velocity 70 fps? just from going from 4.48 to 4.46 boasted 35 fps. my loads seem to be consistant 4.48 with 139gr gave me 3293,3297,3297. all the ones i cronyed were all within at max 10-15 fps some much closer like the 4.48. i just have alot of questions and want to learn more about ELR.
only reason i stated it would run 3400 was one of my test loads was 139gr 4.46 overal and i was getting 3330 fps now if i seat that to 4.303 wouldn't that increase the pressure to the point of boasting the velocity 70 fps? just from going from 4.48 to 4.46 boasted 35 fps. my loads seem to be consistant 4.48 with 139gr gave me 3293,3297,3297. all the ones i cronyed were all within at max 10-15 fps some much closer like the 4.48. i just have alot of questions and want to learn more about ELR.
Re: 375 chey tac load questions
Get it down to 3150 and work back up a little. I bet it will come around right in that area.
Get it down to 3150 and work back up a little. I bet it will come around right in that area.
Re: 375 chey tac load questions
There are 2 issues at play here regarding pressure. Seating the bullet deeper in the case reduces the case volume, which can increase pressure. However, with full caliber solid bullets, if they are started touching or close to the lands it can cause a sharp increase in pressure. They need to have a bit of a jump to keep the pressure under control. The key here is finding that sweet spot between the two variables..... just my two cents....
There are 2 issues at play here regarding pressure. Seating the bullet deeper in the case reduces the case volume, which can increase pressure. However, with full caliber solid bullets, if they are started touching or close to the lands it can cause a sharp increase in pressure. They need to have a bit of a jump to keep the pressure under control. The key here is finding that sweet spot between the two variables..... just my two cents....
Re: 375 chey tac load questions
going out again today with more test loads 4.48 seems to be the best seating depth for the gun. last bunch of test loads all of the 4.48's seemed to be all tighter and more consistant. but i have backed the charges down to see if the slower velocity will tighten up my groups. just takes time and bullets.
going out again today with more test loads 4.48 seems to be the best seating depth for the gun. last bunch of test loads all of the 4.48's seemed to be all tighter and more consistant. but i have backed the charges down to see if the slower velocity will tighten up my groups. just takes time and bullets.
Re: 375 chey tac load questions
slowed them up a bit, 133gr 4.48 gave me a 1.14 outside to outside group. didn't crony them but should be around 3170fps.
slowed them up a bit, 133gr 4.48 gave me a 1.14 outside to outside group. didn't crony them but should be around 3170fps.
