8 twist?
30 sherman magnum
- Thread starter elkaholic
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snox801
Well-Known Member
Yup 8 twist. It's very cool and very light. Can't wait to break in barrel while fireforming then get to the real fun.
Copper Basin
Well-Known Member
Time to admit the error in my hopes. I thought I might get a lot longer barrel life out of my 28 Sherman mag than the 28 Noslers I have built. I have been using N570 with the 195 Bergers with great results as far as accuracy. I am at 250 rounds down the pipe and my throat has moved .018 and has some minor fire cracking started per my bore scope. My throat looks very similar to the last 28 Nosler I built and I would expect, at this point, to get 800 rounds out of this barrel. It is a 26" wilson. I have about the same amount of rounds out of my 30 SM that shoots the 245 Bergers and my throat is in great shape and it has only moved .003. As RRhovee said, I would not get twice the life of a 28. He was right. I still like the performance of the 28 SM over the 28 Nosler but the 30's hold up better. Thank you all for your comments. I think that the N570 is harder on throats than Retumbo. I am not sure if RL 33 is better in that regard. Unfortunately, finding Retumbo for me has proven difficult or just crazy expensive. Any thoughts on powder is always appreciated. Good shooting to all.
My 7-300prc is about done, and I'll run Retumbo or H1000 for that reason, N570 burns freaking hot, hard as he!! on throats. What is your velocity in the 30SM with N570 and 245s? I see guys with +P throated standard 300prc are getting 3k with em from 26" pipes.
Copper Basin
Well-Known Member
Running 2970fps. The 30SM is looking great and I have about 200 rounds down the pipe. A couple of my customers have about the same and they are looking good with negligible throat movement. We are all using N570. Speeds are close to each other. The 28 SM just is getting whipped by N570. Retumbo is nowhere to be found and LRT and RL33 are double based as well. Not sure what my alternative is.
Can you quantify why you like the performance of your 28 sherman over the 28 nosler? Thanks
Rhovee
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- Jun 29, 2017
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That's the problem I see with the really large 7mm. You have 2 maybe three powders that will work very well. I just realized that I don't care for chasing throats very much. If you get it dialed and don't shoot much then it's a great caliber. Same with 28 Nosler. The 30's and even more so, the 338's don't move much.
Copper Basin
Well-Known Member
I get 3038fps with the 195g Berger EH and very good accuracy with it in the 28 Nosler. My one customer shoots around .3 moa with it all the time. He shoots better than I do. And he does real well out to 1055 at the range. My 28 SM goes 3167fps with the same bullet and shoots under a .5 moa. I do like the extra speed with the same barrel wear. I guess that is how best to quantify it. I have heard of worn out barrels fragmenting the 195's down range. I have not experienced that yet.
Copper Basin
Well-Known Member
I agree with you there. I have much less throat erosion in my 30's than the 28's. I have only done a few 338's for people so I don't have a good sample size to go off of.
The 28N holds 5-6gr more powder than a 28SM. so if you're running 130fps faster with the smaller case, I'd likely say you're running 10-15k psi higher pressure(assuming same powder). 3030 in a 28N is a pretty low psi load.
Copper Basin
Well-Known Member
I am running 79g of N570 in the 28 Nosler with ADG brass. Pressure signs started at 80g of N570. In the 28 SM I am running 80g of N570 in ADG brass. I was hoping the 28 Nosler would run a little faster but I do not have any Retumbo to test. This is just what I am experiencing at the range. The 28 SM was having pressure issues at 81g of N570. I have used H1000 but have been unable to get to those speeds.
N570 will outperform Retumbo by 100+ fps. I suspect you have a tight bore on the 28N. My shooting partner runs 78gr Retumbo for 3080 fps in his rifle with 195s. 83gr N570 was 3170 but he wanted to use the cooler burning Retumbo.
