Fiftydriver
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Roygeterdone,
No offense to Walt as he has set more world record then I could even even dream of but the simple issue her is jumping those thin jacketed bullets into the lands.
In a fresh clean bore you may not see much issue with this. As the barrel gets dirtier, he is right you will get more bullet failures but not really beause of the dirty barrel. More because the bullets are weakened by the freebore jump and then the added friction between the bullet and dirty bore magnify the problem and bullets start dusting.
He is also correct in that the 30-378 Was used extensively as a 1000 yard BR rifle but I suspect there was less then 1% of all those rifles ever made that had freebore. Most are VERY short throated for best accuracy potential and the ability to chase the lands when they start to erode.
One other thing you may want to try is a powder switch. Retumbo is a great powder but you are really out of its useful range with the 30-378. It will work but its pretty quick buring for this size of a round and this bullet weight.
If you look at different load data, most leave out Retumbo once bullet weights get over 180 gr. Some go to 200 gr but those that offer pressure data as well, you will see that Retumbo produces alot of pressure to reach top pressures in this case and generally with a pretty light powder charge.
I would personally look at something like US869 or H-50BMG for this bullet weight. YOu may also want to try a heavier bullet if the rifle will stabilize it.
The heavier the bullet the better this big case will work performance wise. I would try some SMK 220 gr pills and see it they shoot well.
Again, I think your running a bit to fast burning a powder for this case. Were you shooting a 300 RUM I would say you are right on the money but you have another 15 to 18 grains of powder capacity, thats a significant jump.
Yes, if your barrel is worn and rough it will be much harder on the bullets so that is a consideration with the J-4 bullets, just the nature of the beast.
I generally do not recommend them for really high performance rounds. When used properly they work very well but there is a narrow performance window you need to keep them in. If you go over that they will let you down.
#1 key is you either need a stouter bullet or a shorter throat to get things to work consistantly well. Either one will probably solve most of your problems as long as the bore is not extremely rough.
Have you tried to reach the lands by seating the bullets out far. Would limit you to a single shot but for long range this is hardly a disadvantage. May want to try that. If you do I would certainly go to a slower burning powder because seating the bullet out farther will only increase your case capacity.
H-50BMG is very hard to beat in the 30-378 and the new H-US869 may be even better.
Good SHooting!!
Kirby Allen(50)
No offense to Walt as he has set more world record then I could even even dream of but the simple issue her is jumping those thin jacketed bullets into the lands.
In a fresh clean bore you may not see much issue with this. As the barrel gets dirtier, he is right you will get more bullet failures but not really beause of the dirty barrel. More because the bullets are weakened by the freebore jump and then the added friction between the bullet and dirty bore magnify the problem and bullets start dusting.
He is also correct in that the 30-378 Was used extensively as a 1000 yard BR rifle but I suspect there was less then 1% of all those rifles ever made that had freebore. Most are VERY short throated for best accuracy potential and the ability to chase the lands when they start to erode.
One other thing you may want to try is a powder switch. Retumbo is a great powder but you are really out of its useful range with the 30-378. It will work but its pretty quick buring for this size of a round and this bullet weight.
If you look at different load data, most leave out Retumbo once bullet weights get over 180 gr. Some go to 200 gr but those that offer pressure data as well, you will see that Retumbo produces alot of pressure to reach top pressures in this case and generally with a pretty light powder charge.
I would personally look at something like US869 or H-50BMG for this bullet weight. YOu may also want to try a heavier bullet if the rifle will stabilize it.
The heavier the bullet the better this big case will work performance wise. I would try some SMK 220 gr pills and see it they shoot well.
Again, I think your running a bit to fast burning a powder for this case. Were you shooting a 300 RUM I would say you are right on the money but you have another 15 to 18 grains of powder capacity, thats a significant jump.
Yes, if your barrel is worn and rough it will be much harder on the bullets so that is a consideration with the J-4 bullets, just the nature of the beast.
I generally do not recommend them for really high performance rounds. When used properly they work very well but there is a narrow performance window you need to keep them in. If you go over that they will let you down.
#1 key is you either need a stouter bullet or a shorter throat to get things to work consistantly well. Either one will probably solve most of your problems as long as the bore is not extremely rough.
Have you tried to reach the lands by seating the bullets out far. Would limit you to a single shot but for long range this is hardly a disadvantage. May want to try that. If you do I would certainly go to a slower burning powder because seating the bullet out farther will only increase your case capacity.
H-50BMG is very hard to beat in the 30-378 and the new H-US869 may be even better.
Good SHooting!!
Kirby Allen(50)
