Sizing gas checked boolits

[Patthehandyman]

When sizing gas checked boolits for a high powered rifle, should I size them to the groove to groove diameter of the barrel, like a jacketed bullet, or .001 over, like a cast bullet?

[Tatume]

Over, and more than 0.001" is better. I use the largest diameter that will chamber easily.

[Patthehandyman]

So .003 over would be ok?

[Bookworm]

If it will chamber, it'll shoot.. Try it at .003 over. See if it will chamber. If it does, shoot it.

[JonB_in_Glencoe]

Patthehandyman,
welcome to the forum.

You need to be careful going too large, especially with bolt action rifles.
If it's difficult to chamber a cartridge, and if the added effort needed is due to a tight fit in the cartridge neck area of the chamber, you may get higher pressures during launch.

Actually, I think you can go as small as Groove diameter in bolt guns. But really the more important thing is to get a boolit nose design that "fits" the throat of your gun, for accuracy sake. Search "Pound cast" for more info about that

[243winxb]

This is good advice.-

You need to be careful going too large, especially with bolt action rifles.
If it's difficult to chamber a cartridge, and if the added effort needed is due to a tight fit in the cartridge neck area of the chamber, you may get higher pressures during launch.

[Jniedbalski]

My 308 win savage axis can go .311 .312,is tight on closing so I size at .311

[toallmy]

How about the if it fits in a fired brass from the particular rifle before sizing the brass you can shoot it out of that rifle . Although only you can figure out what your particular rifle will shoot the best , I think at least 1 - 2 thousands over is the general rule .

[osteodoc08]

When sizing gas checked boolits for a high powered rifle, should I size them to the groove to groove diameter of the barrel, like a jacketed bullet, or .001 over, like a cast bullet?

What rifle and caliber are you shooting? What is your goal? Plinking? Long distance high velocity accuracy? There is more to high velocity cast accuracy than plug and chug. When searching for jacketed like accuracy your castings, alloy, lubes, mold design, etc all can make a difference.

BTW, welcome to the CB site and welcome to the hobby and addiction of cast boolits. Please look up and read the excellent article by Glen Fryxell “From Ingot to Target”. An excellent primer into casting.!

[Patthehandyman]

This particular project is for an S.M.L.E. in .303 british. With jacketed projectiles, I get pretty good performance from both .311 and .312 diameter. The primers with the .312 bullets show more flattening. Slugged the barrel, got .311 groove to groove diameter. My goal is to be able to hit an 8" armor plate consistently, from up to 200 yards with iron sights, which I can do with jacketed bullets. The reason I posed this question in the first place, is that lee's standard sizer kits skip from .311 to .314. Also there is mould selection. I know I can order a custom sizer for slightly more money, but I want it to be the right size. Planning to do the same with 7.62x54r.

[Jackpine]

All good advice. The problem that I have found, is that my guns do not read these forums and often do not know what they are supposed to do with the "right" load. It usually comes down different bullet design, diameter and bullet shape. Sometimes the first theoretically best load works great, but more often than not, at least in my experience, something else, sometimes far from what "should" have worked the best, groups much better.

Logically, .312 or .313 would be the place to start, but if your first load does not make you happy, try different powders and powder weights, before jumping to a different bullet diameter.

Welcome to forum. Lots of good folks here.

[ShooterAZ]

While my Enfields and Mosins will shoot a .312 Hornady jacketed bullet just fine, they prefer the cast boolits sized at .314 and they shoot them very well. As long as a .314 will chamber, you should be good to go. Fat bore riders and loverin styles have worked well for me in those 31 cal milsurp rifles.

[R. Dupraz]

An easy simple technique to start with is to size the bullet just enough so that it will slide with some resistance into the mouth of a fired case and see how it will shoot. Generally, the best with cast bullets is to size to the throat diameter of the bore or maybe .001" over and not the groove. Any thing more is unnecessary in my experience.


If you want to go further, a pound cast of the throat and leade is the way to go. The spec's on these old military beasts can be all over the place.

[Hick]

What shooterAZ said. My Enfield slugs at .311, but it seems to like cast bullets that are at lest 0.313

[kungfustyle]

You can enlarge your Lee sizing die with a wooden dowel, sand paper and a drill. Chuck up the dowel and tape the sand paper onto it spin it inside the sizing die, size a boolit, repeat till you get the size you would like.

[mattw]

Good fit is the key... picking a random size often does not work out well. My old 303 really likes Loverin design bullets with hard'ish lube in all of the groves and yes some of the lubed grooves do show. It also likes the Lyman 311041 and mine actually drops .314 with my alloy. One other thing to consider, that is not cheap brass and if you are using it in the same rifle time after time you might want to consider neck sizing. Once the shoulder is pushed forward to the chamber in your gun, it will save a lot of brass wear by not pushing the shoulder back and not working the brass right above the web of the cartridge.

[Patthehandyman]

Great idea. I think I'll try that. Thanks.

[Eutectic45]

Take a factory load case fired in your rifle. If the bullet slips easily into the case, the bullet diameter is OK for those cases. You always want at least 0.001 over groove diameter but even bullets much larger may shoot great. Many times the unsized as cast boolet can be used which saves a lot of work.