308 Winchester Load for CB

[Sendaro]

Have bought a Lyman mold 311332 GC two cavaty mold. It throws a bullet that when lubed and the GC applied weighs in at 194.5 grains. Lyman states it is a 180 grain bullet, but they also used to produce a 311334 that is nearly a dead ringer for the 311332. I really don't have a problem with the finial weight but would like to start out with a powder that is suitable for accuracy with this bullet in a 308 Winchester ( 1 in 12 twist barrel). To start with I tried the Lyman hand book accuracy load of 5744 at 21.0 grains. This produce 4 1/2" groups at 100 yards. The rifle that this is being test fired in has a Hart barrel and will shoot sub 1/2 MOA all day with jacketed bullets. The cast boolits test fired are inspected by eye and weighed to within + or - 0.2 grains, and sized to .309. The next powder I tried was Unique at 11.0, 12.0, 13.0, 13.5, and 14.5 grains. The 13.0 and 13.5 grain loads produed the smallest groups, but there was vertical in them. The avg. was about 1.5 to 2.0 inchs at 100 yds. However at 200 yards there was clearly two grouping to the same load that were vertical. I'd get 2 shots touching high and three shots touching about 3" lower. The chronograph showed this in the spread of velocity. So I'm looking for a powder that has proved to be of the best burning rate for CB with GC at around 1400 to 1600 fps. Anyone have any suggestions based on their first hand experince with a powder that should burn clean and have a low shot to shot spread in velocity?
Thanks, Sendaro

[cbrick]

I use SR4759 in my single shot 308 1 in 12 twist,

19 gr
Standard rifle primer
RCBS 180 @183 gr

ES 28
AV 1800
SD 9

Air cooled CWW +2% Sn.

Powder Valley currently has 1 pounders of SR4759 in stock.

Rick

[Sendaro]

cbrick,
Thanks! I have some SR4759 and I'll give it a try. Have used it with CB breech seating in my Stevens 44 and 44 1/2 in 32-40. I hear that they are going to stop making it.
Sendaro

[cbrick]

That's what Hodgdon says. I use that powder in about 6 different cartridges, was down to about 4 pounds of it so I bought two more 8 pounders. I'll be good for quite some time but if you like it get it while the getting is good.

Rick

[kweidner]

I like the h335 myself.

[Sendaro]

kweidner, What do you like about it and what boolit/ charge are you using? What kind of accuracy/velocity are you getting?
Sendaro

[Larry Gibson]

Sendaro

What alloy are you using? AC'd, WQ'd or HT'd?

Are you looking just for best accuracy or do you have a velocity level in mind also?

Larry Gibson

[Sendaro]

Larry,

I have two goals for the load that I seek. #1 is accuracy and #2 is to maintain it at distances 200 yards and beyond. I do believe that it should be above 1500 fps though. It is not for hunting but rather for the enjoyment of shooting at distance. I also know that there are boolits that heavier and maybe better for that than what I have at present, but this is what I have to work with at this point.

Thanks, Sendaro

[AZ-JIM]

Not to be a party pooper, I would suggest skipping the 4759 as it is being discontinued along with some other IMR powders. I would look at a burn rate chart and pick one either side of the 4759 and work up carefully from there, that is assuming thats the powder you are set on.

az-jim

[sundog]

My best CB accuracy in a 12 twist .308 bolt gun has been with the RCBS 30-180-SP and 5744.

[Larry Gibson]

Is a shame about 4759 as it is an excellent powder but AZ-JIM is correct. I'm going to suggest 3031, RL7 or H4895 powders. Start at 22 gr with the 3031 and RL7 and 24 gr with the H4895. Use a Dacron filler.

That bullet should work quite well. Assuming a good alloy of at least 15 BHN. I suggest the bullets be sized to .311(I've found .311 to be the best sizing for most .30 cals if the bullet drops that size or larger) unless your rifle has a very tight match chamber and throat? A good softer lube is also suggested with GCs being firmly seated prior to crimping. You probably know all this but I'm just throwing it out.

Larry Gibson

[Bullshop]

In a 308 Win and several rifle cartridges I have found favor with Alliant Steel. The reason is that Alliant Steel is about the same burn rate as Alliant 2400 which is widely accepted for use with cast in rifle loads.
The shortfall with 2400 is that its small kernel extruded type powder takes up too little case volume so may have position ignition issues.
The Alliant Steel is a very lofty flake type powder so gives a much better load density with the same charge weight. As a rule flake powders are easier to ignite than extruded powders especially at the reduced pressures we normally work at with cast boolits.
On the negative side Alliant Steel powder must be weighed for each charge and not just thrown. Because it it such a lofty flake powder it meters poorly so can have too large a variation from charge to charge.
In the 308 a load I am using is 20 gn weighed with cast boolits from about 200 to 220gn. Velocities depending on boolit weight are very consistent at about 2000 fps with extreme spreads in the mid teens.
Until recently I had only shot this load to 500 yards. Accuracy at that range was in the 2MOA area.
More recently I have been shooting even farther and accuracy seems to hold up. I say seems to hold up because I haven't yet set targets at the longer ranges 800 to 1000 to record actual groups just informal plinking at rocks and such. Still once the range is found and dialed in the load seems to stay right with the program. At 850 yards shooting over my PU hood a bowling ball size target is well in the game.
Not being a formal target shooter or competitor I don't know if that is good enough for formal target shooting but it sure keeps me amused. It also keeps the feathered chicken thieves that haunt the rock bluffs at that range from my house at bay as well.

[tygar]

Sendaro

What alloy are you using? AC'd, WQ'd or HT'd?

Are you looking just for best accuracy or do you have a velocity level in mind also?

Larry Gibson

Larry, would a even slower twist (e.g. 14) provide even better long range accuracy than the 12 & would it allow more speed?
Thanks
Tom

[Larry Gibson]

Larry, would a even slower twist (e.g. 14) provide even better long range accuracy than the 12 & would it allow more speed?
Thanks
Tom

Yes it would. I'm pushing naked cast bullets of 124 - 180 gr to 2500 - 2750 fps with at least 2 moa or less consistent accuracy (10 shot groups at 100, 200 and 300 yards) out of my 27.5" barreled .308W with 14" twist. In very limited testing the 311299 was shooting 2 moa at 2400+ fps.

Larry Gibson

[popper]

H4895 or 2400 (filler) has worked for me at that fps in 30/30 1:10. Unique did the same for me, funny groups.

[Sendaro]

Thanks to all that have responded to my questions. There is much information there for me to ponder over, and I will.
I have not been using a GC seater. I have one but it did appear to be necessary to use it as I could apply the GC by hand and just give the boolit a sharp rap on the bench before running it into the luber/sizer. To be honest I was a little worride about distorting the boolit using the GC seater with too much pressure. I have the cast the boolits a little softer than #2 alloy.

Thanks, Sendaro

[frnkeore]

Sendro,

The following is the top, 2013 National CBA, finishers loading data for 308's in Production (rethroating allowed) and Hunter (no throating). For production, they still use the factory .310 diameter Ball seat but, the leade angle can be changed. So note that the bands on the bullets fit the ball seat in both classes at size for size. NO fillers are used in any of these loads, CBA allows them but, Lyman does not think they are safe! (for Larry ) Also, note that they all are using straight Lino. Personally, I don't think the bullets need to be that hard but, that's is the 1st and second place data. Since yours is a custom barrel, you need to find out what size the ball seat or freebore is and size to it.


Production Class

Lino, Eagan MX4ARD 217 gr

.3008/.310, nose/base

26.0, N 130, 1725 fps

210m

.9, 100 yd, 1.62, 200 yd, ave of four, 5 shot groups
------------------------------------------

.301/.310, nose/base

Lino, 311299, 192 gr

28.5, Varget , 1900 fps

Primer F210m

1.3, 100 yd, 1.55, 200 yd, ave of four, 5 shot groups

-----------------------------------------------

Hunter Class

Lino, RCBS,180 SP, 178 gr

.302/.310, nose/base

4227, 21.0 gr, 1740 fps

Primer, F210m

1.3, 100 yd, 2.8, 200 yd, Ave of four, 5 shot groups

[Sendaro]

SUNDOG,

How much 5744 are you using and what primer?

Thanks, Sendaro

[GabbyM]

21 grains of 5744 is a pretty light load. Bout four to six more grains may get things going. I have run 27.0 under a 180 grain similar bullet in my 30-06. If you move to the slower powders and more of it your recoil will increase for any given velocity. 5744 in my 06 is very soft shooting.

[Sendaro]

Larry,
I believe it is near a #2 on the soft side. I guess that you may call it Scrapalloy.

What do you recommend for lube at the speeds you are shooting at?

Sendaro