Grease fittings

[70 longbed]

I finished getting the front end rebuilt, (new inners, outers, uppers, lowers, and even new upper and lower control arm shafts.) My dilema is; that when I went to lube everything, I could only get a seemingly small amount of grease into the new A-arm shaft assemblies. I got one, maybe two strokes of the grease gun, and no more. I couldn't force more grease in; I couldn't squeeze the handle again. It got tight (hard) or whatever, and I had troublr getting the gun off the grease fitting.

I am used to a grease fitting getting it's amount of grease, and then the boot lets some leak out, indicating that there is enough grease in there.

Can someone explain what is happening when you can no longer squeeze the handle of the grease gun? Should grease escape from these boots just like a ball joint boot?