JPH45's bullets

[Leftoverdj]

JPH45 kindly sent me a supply of bullets from his modified Lee mould. He milled off a Lee 429-310-RF GC mould to cast PB bullets of about 265 grains. I had two closely comparable bullets on hand,  a Lee 255 PB SWC and a Lyman 255 GC SWC.

I set up my measure to throw 11 grains of a surplus powder alleged to be equivalent to HS-7. That charge should have given about 1300 fps. The Lee PBs just sprayed. A five shot 50 yard group was roughly 6". Subbing the GC bullet with no other changes than a minor seating adjustment produced a 5 shot group just over an inch. Going to JPH45's bullet, the group was about 2". His bullet is slightly heavier and has a slightly wider base band than the Lee 255.

JPH's experiences are quite similar to mine. In pistol cartridges, accuracy with plain based bullets just goes to hell somewhere between 1200 and 1400 fps. The tipping point for a particular load/rifle combination may be as little as 50 fps. I have gotten good accuracy at far higher velocities with GC bullets and think the problem must have something to do with gases getting past the bullet.

If anyone is getting good accuracy with PB bullets in a microgroove barrel past 1400 fps, I would sure like to hear about it. There seem to be some variations that determine just where the breakdown takes place, but it sure seems that very minor changes can make a load go from good to foul accuracy.

If anyone missed the point, I ain't disparaging JPH's bullets in the least. They actually did a lot better than the Lee PB. I just used them to investigate the point where Marlin/NEF barrels quit working with PB bullets.

308, ain't you glad you got a GC mould by accident now?

And I am thinking on a GC mould for my .45-70s. That just might cut down on some of the crankiness.

[Haywire Haywood]

DJ, one of the bullets I'm sending you from Dan's molds is a 325gr Gas checked WFN sized 458.  I had better luck yesterday, should be in the mail early next week.  Mebbe they'll fit in with your experimentation.

Ian

[JPH45]

DJ, thanks for the compliment. I have been wondering these days if there is a crown problem, but I have no trouble getting exellent accuracy from jacketed bullets so I tend to think that rules a poor crown out. I have always read that 1600 fps seems to be about the limit of velocity/accuracy for PB boolits, I have also noticed that with the rifle length barrels, I have to use loadings UNDER anything I can find listed just to keep velocities to a working level. So I begin to think you may be headed in the right direction, we have some gas leak problems. Trouble is, the boolits I have been able to recover do not show any such signs. Note that I use pine logs for my backstop, and while it is fairly easy to recover a bullet, there is enough damage to the bullets that being able to make conclusive judgements about what is happening in the barrel is iffy. Perhaps a different backstop medium is required. So far, my experience with gas check designs has been just as miserable as with PB's. I am anxious to see just how much difference the throating can make. Judging by the pictures you posted, and a following response, it must be worth the effort.  Perhaps those of us with 44's may want to look at changing the leade angle in them too. Just so that others know have some extra info to keep in mind, driving PB's at full pressure/velocity I get pattens af about 8" diameter. They will stay on a paper plate at 75 yards but are completely unpredictable. With the Lyman 429421 (DJ sent me a sample of these last year) I can with H110 get 1700 fps without trouble, but the groups are about 4" diameter and again very unpredicable. The GC's do help, but I don't think in and of themselves are the total solution to the problem we are seeing. I am confident though that we will find a good answer to this.