optimum Barrel spec for 215g hybrid.

[paulT]

Thinking of getting another bartlein 5R .308 barrel for next FTR season to shoot both the 215g and 200g Berger Hybrid bullets will be neck Turning Lapua brass, anyone shooting this combo with good results at 1000y and have info with neck clearance bore diameter etc etc sizes that best suited for this combo, thanks.

 

[paulT]

Anyone shooting this bullet for FTR able to share some info with barrel spec that suits the 215h, thanks.

 

[gsg5pk]

Steve has post this spec for his 215 ftr

337"nk , 281" freebore , 1-30


But if you gonna shoot unturn lapua brass, I would suggest 343" nk

 

[Marksman63]

Do you mean 1/10 TR?

 

[paulT]

Thanks for info gsg5pk, would that barrel spec for the 215H also suit the 200H.

 

[paulT]

Do you mean 1/10 TR?

Hi marksman, Barrel spec is for TR using 215H neck turned Lapua palma brass.

 

[Marksman63]

Do you mean 1/10 TR?

Hi marksman, Barrel spec is for TR using 215H neck turned Lapua palma brass.

I understand, but what does 1-30 mean? I think spec on twist rate is critical

 

[Jay Christopherson]

1-30 means "1.5º" and it's part of the chamber/reamer spec. I think it's the degree of entry into the lands, but I am not 100% sure that's the right description.

For twist, 1:9 was the original go-to, but I know that many have backed off to 1:10 twist, with the feeling that the 1:10 provides for slightly better accuracy, even with the slight loss in BC potential. I suppose it also depends somewhat on your barrel length and intended velocity.

 

[paulT]

Thanks for info Jay Christopherson, would quoted barrel spec for 215h also allow 200h to be used.

 

[Jay Christopherson]

IMO, 1:9 is probably too fast for the 200's. That might be a really good question for Bryan Litz on the Ballistics board. IIRC, he has previously chimed in on a thread about potential issues WRT using a twist rate that is too fast, but I might be mistaken. And I'm too lazy to double check.

I think that you could spec out a barrel that would work for 210's and 215's. To accommodate both 200's and 215's would be more difficult. I think that you would end up with a freebore that is slightly too long for 200's and slightly too short for 215's. In other words, you are compromising to both and ideal for neither.

If it were me, I would spec the freebore for 200's. Then buy a .30 uni-throater. And if you want to try the 215's, throat it out when you are ready. Throating out is dead simple and requires no special tools, other than the throating reamer. Of course, you can't go back, but on the other hand, you could move it out in increments and maybe you'll find a happy place that will accommodate both. My own barrel was custom throated by me using a .30 uni-throater for the 215's and it would not accommodate a 200 hybrid.

 

[Marksman63]

Jay, what do you mean for not accomodating a bullet? I could understand the issue for a too short throat (pressure rising, less powder, lower velocity) or a too long one (poor bullet hanging and concentricy issues) but if you get a little bit longer than ideal COAL is not so bad, isn't it?

 

[Jay Christopherson]

Jay, what do you mean for not accomodating a bullet? I could understand the issue for a too short throat (pressure rising, less powder, lower velocity) or a too long one (poor bullet hanging and concentricy issues) but if you get a little bit longer than ideal COAL is not so bad, isn't it?

It depends on what you mean by a little longer than ideal COAL and what your tolerance is for shank seating depth. I have my own opinions about how much shank seating depth I like. They are not based on any known scientific fact. Just my own personal preference.

I know some guys will chase a throat until the bullets are basically being held by a wing and prayer in the neck and if that is a case you are comfortable with, sure, you could make do. The freebore I am currently using for my 215's is too long to allow me to seat 200's, at least, to any useful length (according to my own needs).

 

[Marksman63]

Roger, thanks!