Sorry for the cross post, but I thought I'd see if anyone here might be able to help.



M question is about erratic velocity that I got this weekend. My rifle is a Browning model 71 in 348 Winchester with a 20� barrel. The load was 61 grains of IMR 4350 under a Hornady 200 grain FP bullet. Each charge was weighed on a RCBS 5-0-5 scale. The primers were CCI 250s. Cases were all trimmed to a uniform length and bullets seated to the canelure and roll crimped.



Velocity for 6 rounds fired was 2654, 2639, 2451, 2747, 2363 and 2565. I quit after noting the erratic (and high) velocity of some of the rounds. I was expecting to get about 2450-2500 fps, and was very surprised by the high readings. I figured the load was safe since Lyman 48th edition lists a maximum load of 63 grains of IMR 4350 with 200 grain slugs. My brother also fired a few 22 magnum rounds over the chrony just for verification, and got around 1850 fps with one exception which went 2235 fps (10 shots total). The chronograph is a shooting chrony F-1.



Any suggestions as to the reason for the wide extreme velocity spread would be greatly appreciated. I�ve been using IMR 4350 in my 308 and 30-06 with 180-grain bullets for years, and though I�ve seen some extreme spreads in the 100+ fps before nothing like this.

See what happens with a few factory ctgs.

When I had a similar experience with my Whelen (though not as extreme), the technicians at Sierra suggested seating the bullet deeper. Presto, problem solved.

What I suspect is happening is that the primer discharge is dislodging the bullet on some cartridges, and this slows down the initial ignition rate of the powder. The bullet stops in the bore, and a pressure spike occurs.

Try either seating the bullet deeper, or add a slight crimp. You could also try to take out the expander ball, and load a few cases without expanding the neck. Anything to increase the bullet pull, and get a good solid burn going before the bullet starts moving.

Let us know what happens, Dutch.

Several potential culprits exist here but you will have to do the investigating. Since you say the case lengths are uniform the first place I would look is the quality of your crimp. If you are seating AND crimping at the same time, try adjusting your die to seat only, then back the seating stem back a bit and do the crimp as a separate step. You will have much more uniform neck tension for your efforts. Next issue regarding quality of crimp is just how much you're crimping. The roll should be very mild. Perceptable but not pronounced. Excessive crimping will screw hell out of neck tension, just as surely as work hardened cases. That brings up the next issue, namely, how many times have your cases been fired? They may need annealing around the neck area to soften the brass a bit. Again, the issue is neck tension.

Part and parcel with neck tension comes the powder you're using. Slow burners like 4350 benefit from consistant and firm neck tension, the penalty for lack of this is erratic velocities. You may find benefit from a faster powder such as 4895 regarding this, or perhaps a hotter primer such as Winchester or Federal, Magnum of course. I've never had success with 4350 in cases that generate pressures common with levergun cartridges.

Regarding your Chrony: I've used them for several years, and they are not fool proof. The "test" you did with the .22 Mag makes me arch an eyebrow as I'm doubtful that cartridge will actually generate velocities in the 2200 fps range. The Chrony will generate false readings due to bad lighting, weak batteries, and high readings if it is not folded out completely flat before use. Too, if you are shooting with less than 15' spacing between muzzle and skyscreen you can experience false readings from the muzzle blast when shooting high capacity cases. The question I have for you now is, how did it shoot for those 5 rounds you fired?

That's about 105% of what I'd be looking at, hope it helps.

what kind of group did it shoot?

Hi guys, thanks for the replies. I think the crimp is something I need to look at. I crimped the bullets with a tight crimp near the front of the canelure. When I ran some of the loaded rounds through the action to check function, some of the bullets had been pushed into the case past the canelure. I used a bullet puller (hammer type) to get the bullet seated in the correct location. Don't know if that may have some affect on the powder/velocity or not.



I have a lee factory crimp die on the way, and I'll be trying some faster powders. I've got some IMR 4064 and RL-15, which are both listed in various places as suitable for the 348. I'll change the battery in the chrony too.



Didn't get a chance to check accuracy as I stopped shooting before I wrecked something. I was shooting offhand from about 15 feet from the chrony. I'll let you know as things progress.

We would be interested to hear what you discover when you start using a heavier crimp. Please let us know what happens.

You may want to check the expander ball. Sounds like it is too big. On all my competition loads I never crimp my .30-30. I've never had a bullet move and the .30-30 case has much thinner brass in the neck than the .348 does.

I had a chance to get out and fire a few rounds through my chrony this afternoon and I think I have the 'problem' solved. I crimped my rounds with the lee factory crimp die and shot over the chrony with new batteries. Velocitis now are much more reasonable--and lower. I believe the battery was the issue. The load I was trying Sunday (61 grains of IMR 4350 w/200 grain hornady FPs) clocked at 2339 fps with an ES of 26 fps. Factory rounds were almost identical at 2342. I also chrony'ed some 220 barns originals with 57 grains of the 4350. They plugged along at 2158 fps with an ES of 41 fps.



So problem solved... sort of. Now I need to find a load that reaches my goal of 2450 fps. Maybe faster powder like RL-15 or H-4895.



Thanks for the help. I'll post an update when I get a chance to test some more powders.

Lee factory crimp dies are great. I use them on everything
that deserves or needs a good solid crimp. They don't make
one for the 450 Marlin, so I took the collet out of my
45/70 die chucked it in the lathe. and turned a relief
inside the mouth for the belt. Works great.
Lyle