CB for various .308s

[aimlowsqueeze]

I own several milsurp rifles that shoot a .308 jacketed bullet. They include 3 k31's that mike out at .307 and a Springfield '03 that mikes at .308 and an Enfield 2A1 that mikes at .308. What do you guys think of sizing all my CBs to .309 and using them across the board or do you think it is worth the time and effort to size some at .309 and some at .310? I am new to CB shooting and really appreciate any help. Oh by the way, what is the rule of thumb for using Dacron (or any other fiber) filler?

[NVcurmudgeon]

aimlowsqueeze, what you are suggessting is a trick that has worked very well for me. I have a Lyman 314299 mould that I bought for my .303 British (groove diameter .3138".) I size it .314" for the Lee-Enfield. Then I tried it sized .310" in my .30/06 Springfield (groove diameter .3085".) It was unbelievably accurate there, too. Next up was my sporterized Krag (groove diameter .309", boolits sized .310") The .30/40 managed a ten-shot 100 yd. group of 2.14". My newly aquired 1891 Argentine Mauser (groove diameter .3105") will be next. Looks like the Argie will need a .312" sizing die. Because your rifles are closer together in groove diameter than mine, you may get good accuracy sizing the same for all three. BTW I am using the same load in all three rifles, C.E. Harris' go-to load for most milsurps of 16.0 gr. 2400. For your rifles the 311299 version of the same boolit may be a good one.

[Bass Ackward]

ALS,

I size everything in a .3095 sizer which was an outta round .309 Lee sizer prior to correction. It works (< MOA) in three 30-06s which one is an 03A3 sporter.

But "my" finest accuracy has always come from bore diameter bullets that were just hard enough to survive the chosen pressure range of operation. On bottle neck cases anyway. But if you have to jump a cast bullet for any reason, whether this is imposed on you by your throat or personal biases about exposing lube grooves etc., then a better throat fitting bullet is going to produce a wider range of positive results from which to choose an accurate load.

What does all that mean? Ya gotta try it, to see if you like it.

[Larry Gibson]

I own several milsurp rifles that shoot a .308 jacketed bullet. They include 3 k31's that mike out at .307 and a Springfield '03 that mikes at .308 and an Enfield 2A1 that mikes at .308. What do you guys think of sizing all my CBs to .309 and using them across the board or do you think it is worth the time and effort to size some at .309 and some at .310? I am new to CB shooting and really appreciate any help. Oh by the way, what is the rule of thumb for using Dacron (or any other fiber) filler?

You don't say which CB or what it's "as cast" size is. If they are "as cast" at .311 or .310 I'd use that size of sizer and just seat the GC and lube them. They will better fit the throats (more important than bore fit) of your .30 cals. If your cast bullet is "as cast" larger than .311 then I'd suggest .311 for sizing. Although I do shoot a lot of .312 and .314 sized bullets in .30-06 '03s with excellet accuracy.

I use a lot of dacron as a filler. I do not use any wads except in shotshells. With lighter than normal bullets I use a faster burning pistol powder. For heavier than normal bullets I use a medium powder with a dacron filler. I use the slow powders without filler for specialty loads.

Example in an '06; 90 to 150 gr cast bullets for velocities of 800 to 1900 fps I will use one of the fast burning pistol powders. Bullets of 160 - 220+ gr at 1700 through 2100 fps I use the medium burning powder with a dacron filler. Bullets of 150 - 220+ gr at 2100 - 2500 fps I use one of the slow burning powders with no filler.

My rule of thumb is; with fast burning pistol powders (Bullseye, Red Dot, Unique up through 4198, 5744 or 4759 I do not use a dacron filler. With medium burning rifle powders (mostly 4895) that occupy 80% or less of the case capacity to the bottom of the bullet I use a dacron filler of 1/2 to 1 1/2 gr (depends on case/cartridge). With slow burning powders (4350, RL19/22, 4831 or the slow milsurp powders) I use 90 - 100% loading density so no filler is required.

Larry Gibson

[aimlowsqueeze]

An acquaintenace and shooting friend of mine has cast "a bunch" of 30 caliber boolits for me and is waiting to size them depending on the bore measurement from my various rifles. I would prefer to have him size them all to the same size and shoot them in my K31s and the '03 and 2A1. That way I don't have 2 or 3 different sizes of 30 caliber bullets laying around. Would it be feasible to size them all to .310 and shoot them in all five of the rifles or is the .003" oversize too large? As far as powders go, I will probably stick to Red Dot or Blue Dot if that is recommended.

[versifier]

Any way you look at it, you're still going to have to experiment first to see what works best in which. You might be able to get by with one size, but you won't know without trying different sizes to see what actually happens in your rifles. There is no definitive answer to your question that can be arrived at by speculation. Every rifle is different. You have to do the tests.
Start with .309, load at least 20rds for each different rifle, and then shoot them slowly and carefully from a solid rest. Don't let the barrel heat up too much. Try four 5-shot groups first at 50yds with each. Label the targets and save them for comparison at home. Then test the same loads with the only difference being the boolits sized to .310 the same way. You might even need to go up to .311 with the -06's.
Neck size your brass and keep the cases separated for each rifle in the same chambering. The more carefully you eliminate the variables, the better your test results will be. When the shooting is done, measure all the group sizes, list them, and average each set of four. Comparing the numbers will tell you which size boolit each rifle likes best. You might find that they will all shoot the same size acceptably, or you might find that the K31's prefer one size and the -06's a larger one. Maybe all the K31's will shoot the same loads interchangably. Yes, it means a lot of loading and shooting and measuring and calculating and comparing. No, you won't get all your answers quick and easy in an afternoon. We do it to keep us out of other kinds of trouble.[smilie=1:

[Larry Gibson]

...... Would it be feasible to size them all to .310 and shoot them in all five of the rifles or is the .003" oversize too large? .

That's what I'd do in your situation. If the .003" oversize bullets slip into the neck of a fired case they are not too large and will probably provide the best accuracy anyway.

If you use Red Dot or Blue Dot I'd not use a filler (or wad).

Larry Gibson

[Char-Gar]

I don't think much of your idea. Here is why. Bore diameter is important, but as long as bullets are .001 or more larger than groove diameter you have that base covered. If you are using a bullet with a bore riding nose, it needs to fit well on the lands, but that is not a sizing issue.

All things being equal (which they never are) the best accuracy will be had with bullets that enter the barrel dead straight. They are many factors that enter into straight ammo, but when it comes to cast bullet size, a bullet that is an exact fit to the barrel throat will be held in place and has a better chance to enter the barrel straight.

I hold very strongly to the notion that a cast bullet should be a big as it can be and still enter the throat without shaving lead or otherwise deforming.

Throat size will vary from rifle to rifle. My Krags with throats worn from use, do their best with .313-314. My 03A3 and 1917 Enfield will take bullets of .312 but no larger. My Marlin and Winchester 30-30s want .311. My Savage, Remington and Winchester .308 Wins. want .310 bullets as well as my Browing 1895 levergun in 30-40. The only rifle I own that won't handle bullet larger than .309 is my 1954 vintage Model 70 in 30-06. All of these rifles have a nominal .308 groove diameter, although the Krags run bigger.

You can indeed shoot all 30 cal bullets .309 or .310 and they will all land point on in some kind of a group. Some groups with be good, some will be excellent and some will be just so-so. It all depends on the rifle.

If you want the best accuracy each rifle can deliver you will need to fit the bullet to the individual rifle. IMHO, that is what it is all about. If I just want something to go bang, I will buy a string of firecrackers. I am not interesting in anything but optimum accuracy. Folks who can deal with just hitting the target may not worry about all of this stuff.