Plain Based Boolits for High Velocity

[303Guy]

I want to shoot plain cast in one of my rifles (a 303 Brit) and I specifically want to shoot plain based boolits. So what is it that a gas check actually does and how can it be eliminated? I have driven plain base paper patched boolits fairly fast with no base distortion but paper patching seals the bore so there is no gas leakage.

Anyway, I going to make a mold to suit my purposes but need to know where to start. I'm thinking of a rebated base to bore diameter and a radiused trailing edge. Also a fibrous filler to form a sealing wad or perhaps just a card disc over the powder.

So any thoughts, suggestions and experiences on boolit design? Choices of powder and loads?

[Tatume]

Before you make a custom mold, try an ordinary plain based bullet and some Cream of Wheat as a filler. The compressed CoW will protect the base of the bullet.

[GhostHawk]

I have to wonder what you have against gas checks?

[44man]

My guess is the cost, I hate to see that myself.
The gas check halts boolit skid to keep the seal and that is all it does. The base needs no protection from heat or powder. Make the boolit tough enough to not skid and there is no need for a check.
Fillers do not stop skid either but some might plug skid grooves. Lube also does not plug over size rifling grooves. A wad might hold gas back even if the boolit has some skid. Low density polyethylene is good. Works like a shotgun wad.

[OuchHot!]

It just happens that last night I was reading a well done article by Ken Mollohan in FS #197 JanFeb '09. It was on base upset in high intensity loads. He was firing into (and sometimes in!) water and diving to recover the boolits. It pretty mush went along with what 44man said above. The principle failure mode was skidding where the groove impressed on the boolet was seen to get progressively wider with etching on the trailing edge. COW seemed to seal the trailing etched area from gas but otherwise the check didn't seem to affect base upset. He did a lot of work that looked pretty systematic to me.....and not what I was brought up to think about gas checks.

[303Guy]

Thanks. It's cost and effort but also just something I want to try. I plan on shooting as cast with pan lubing. My intention is to form the boolit to exactly fit the throat. This will give the boolit full length rifling engagement.

A benefit of the gas check may be that the as cast trailing edge is covered giving a well formed trailing edge. To provide the desired trailing edge I plan on a nose pour design. This will also give a wide meplat.

[MT Chambers]

Many have tried before you and have not had success as soon as pressures and vel. increase, there is a reason why CB benchrest shooters all use gc designs with the exception of breechseaters using soft pb bullets to shoot excellent groups but at reduced vel. prolly below 1400fps.

[Scharfschuetze]

Try Colorado Shooter's Supply for his Hoch style nose pour molds. I've been using them since he bought the operation from Richard Hoch in the late 70s. They are the cat's meow for quality.

Link: http://www.hochmoulds.com/

[1johnlb]

Paper patching, copper jackets, and gas checks all increase the capability of the lead to grip the rifling. With out grip you rip or skid through the rifling much faster which causes the bullet to yaw. Plain base can only be driven to a speed that your alloy can handle before giving ( skid). I shoot 100 gr lee 311 thru my 30 Cal's with 5gr titegroup or unique for a plinker with very good accuracy but at low velocity. This is extremely accurate in my no1mk3 isshy 308 1in12