Author Topic: PPB velocities? (Read 1242 times)

jpuke · « **on:** March 01, 2003, 02:33:22 PM »

Does anyone know what happens when you push a PPB too fast? Paul Matthews mentions that they can be loaded to around 2200 fps but he never mentions why that's the limit. He also mentions that harder alloys can be driven faster. Is the paper not able to withstand the friction of higher velocities? Does the bore lead horribly when they're pushed too fast? I'm trying to get my .308 bullets between 2300 and 2400 fps, but I still want them to expand on deer - am I asking too much of the patch?

Castaway · « **Reply #1 on:** March 02, 2003, 10:45:20 AM »

Above 2,200 f/s without the barrel around them, they spin themselevs to death. Found the threshold myself this past month when trying to patch my 303 with a 308 bullet. All of the bullet didn't disentegrate as I had downrange impacts but the bayonet stud was coated with "powdered" lead. Evidentally this was enough to disturb the flight characteristics of the bullet and destabalize/slow it down as the remaining protion of the bullet(s)missed the target frame at 50 yards. Impact on the 100 yard berm was consistently to the left when I could detect sand flying. Some hit below the frame and skidded into the 50 yard baffle, but some high. Even at 25 yards and a slower load (still at what I thought was less than the magic speed limit), I only got one of 5 on the frame and what hit was keyholed and again the exterior of the rifle was powdered.

jpuke · « **Reply #2 on:** March 02, 2003, 01:48:41 PM »

Thanks Castaway. I really need to get a chronograph. I'm guessing that I'd be getting 2300 fps out of a 24" barrel (like all the loads in the manuals are tested in) but I'm shooting a 20" Rem Model 7. I've been getting clean holes in the targets but I'll keep an eye out for what you mentioned. Thanks.

Castaway · « **Reply #3 on:** March 03, 2003, 01:08:31 AM »

As much as I want to see how fast the loads are I'm shoving through the barrel, I'm afraid a getting a keyhole in my crony. After I get it settled down and get consistent I may give it a try.

kbmoly · « **Reply #4 on:** July 18, 2003, 05:34:31 AM »

... it's VERY unlikely you are driving PPCB's too fast. Col Harrison's write-up in the Rifleman contained PPCB loads for the 300 Win Mag that fully equaled factory power and accuracy. In fact, one of his co-workers seriously offered to use them in long range rifle competitions.

More probably, you are just exceeding the velocity limits for your alloy. Col Harrison noted that for best results, the alloy and load should be ballanced, harder alloys for hotter loads. The trick is to get a little bit of base upset when fired, but not enough upset to make a blob out of the PPCB.

You can probably get a copy of his article for the trouble of a phone call to the NRA.

HTH

kbmoly

Castaway · « **Reply #5 on:** July 18, 2003, 12:04:59 PM »

I think we're speaking the same language. Pure lead has a limit of around 2,200 f/s. Harder alloys can go much faster. In fact, patched linotype or equivalent alloy can equal velocities of a jacketed bullet from a "magnum" caliber rifle.

Kragman71 · « **Reply #6 on:** July 20, 2003, 04:03:41 PM »

Jpuke,
That 'Rifleman' article was in the March 1977 issue,on page 28.
It is strictly for target shooting. He uses very hard alloys to get the high velocities.
If you have a 'smoothe'barrel,you should be able to get 2400 FPS with a moderatly hard bullet that will expand.
If I could get my Krag 30/40 to shoot patched bullets,I would be working on the right alloy,right now.
Frank