ORIGINAL: Underclocked
The flash hole could be either too large OR too small and cause those symptoms. Doesn't happen to have a domed breech plug does he?
He is swabbing the bore after each shot isn't he? I would think he is given his reported groups - but you know how that goes. Some T7 crud buildup can cause excessive pressure - this I experienced first hand right after the powder became available. I was shooting loose powder though.
UC, Thanks. No, he is not swabbing. I asked him to buy another spare breech plug and check the diameter of the hole. I also talked to him about swabing, saying that the crud ring at the last inch or two is giving the bullet a lot more resistence to get started causing the blow back, he said he puts a patch of bore butter down about the 5th shot, cause he can't load a bullet. So I think he has to go for swabbing to rid himself of this problem or shoot the .25ACP small primers. Chap Gleason