I would be very happy with a group like that! The marginal stability is not necessarily a bad thing, from a terminal ballistic perspective. That bullet would probably tumble in the game animal, instead of just punching a pencil hole.
You could convert it to «flat base» by adding a gas check, as the boat tail accepts gc. I doubt it would help, but it could be an interesting experiment. Another interesting experiment, would be to shoot it at 200y. Would it yaw more, or less?
re-design the whole bullet, it's marginal to begin with.
I just powder coated a couple hundred of these things in an attempt to gain a little more diameter in some of the drive band area.
[as I understand it I have one of the larger casting molds already, but that's probably because I lapped it out]
I'm gonna have to re-work my loads now since I was on the edge to begin with even in a 7 twist barrel.
I didn't/don't much care because I'm just target poofing at 50-75 yds. and all I really care about is how close the holes are together.
Marginal, indeed. That 1-10" twist was designed around 220 grain RN FMJs in the 30/40 Krag running in the 2000 FPS ballpark. The 30-06 inherited the twist rate, and the 308 (the Krag's grandchild) campaigns on with that twist rate almost 130 years later. It works well, but 230 grain spitzers at lower speeds might be asking a bit too much of the pitch.
The extra weight of squaring the base might be enough based on my extensive reading and nil application of such . I have the NOE 2+2 or maybe it's a 5c ........ I know it won't shoot in the 308 available but it makes similar holes , bigger groups , in the 30-30 . The 06' it should be right at home but these 3 have 12,10, and 8.5 twists which tends to hold the 06' to about 1800 fps with cast so far .
I'm just miffed because double-coating before lapping did a lot better with the yawing, same everything else. Maybe it was just a fluke that time. I hadn't rechecked in a while because the bullets go where aimed. I was hoping for a tumble effect anyway as this is my varmint sniper rig.
They may settle down past 100 yards, seen that before with long, skinny bullets, but I'd rather they went to sleep within 5,000 caliber lengths like properly stabilized bullets do.
Can't speed up much, already going about 980 fps at the muzzle. Could probably take it up to 1030 or so before the bullet flight noise starts being too much.
the nose shape will see to it that the bullet tumbles whether it's stabilized or not. [unstable will just make it easier]
if it were something more like one of the RCBS silhouette designs then a punch through would be a lot more of a concern.
I have seen them punch straight through everything I have shot them with, from ground squirrels up through 16"s of dry pine.
most of the little stuff I shoot with them look like bad actors doing a hammed up death scene, grabbing their chest and staggering around.
I'd shoot them again but it's one of the most comical things I have ever seen and I can't.
I'm gonna try to find one of the GOOD targets, ten into less than an inch, and little if any yawing. This load has always been pretty good to excellent, and I want to get it back to what it used to be. Maybe I'll go back to large pistol primers again.
Since answers don't find themselves, i decided to take some Ace 230-grain flat base bullets and try them. Only problem is they're. 314" on the bands. Sio I sized them to .309" in two steps and then chucked them in the lathe to cut the bases flat again and remove flashing from the base edge. I turned a slight radius on the bases too. They're baking now.
Didn't get a chance to post before family activities, but I'm back.
First go with the Ace bullets, fresh and soft from the oven, answered the plain base vs boat tail question...still yawing horribly and not grouping at all.
Ok, so I buggared the neck tension on all these loads, was still using the .331" neck bushing for the soft military brass and my pig-getting loads, which outs these RP necks at .304" ID. Swapped to .337" to get about .3085" and just kiss the necks with my custom .3085" powder-thru die (thanks Waco for the stainless steel round bar scraps).
So after fixing that I loaded ten more just the same and got a noticeably better group, but still with wild flyers and yawing.
Thinking something was still amiss with the launch, I went back and changed two things for the last ten: Switched to CCI 300 primers and seated the bullets out about .025" more to engage the lands a little more. Much better group, down to 2" or so, and much reduced yawing. Then I was out of time. I wonder how the Lee bullets from the lapped mould will do with the pistol primers? I solved the mystery now of why the yawing showed up....I somehow forgot the pistol primer thing and started using large rifle again.
it can work both ways around too.
I got my 300 BO right on the edge with rifle primers but I have like 200-K pistol primers and only like 100-K rifle primers so I thought about a swap out.
that didn't work out quite as well as things did here in fact it went closer to exactly the opposite.
we are talking about 2 completely different situations though.
it was definitely something I noted, and when I switch my next batch over to trying powder coat I'm gonna go back to pistol primers and a slower more case filling powder,,, hopefully around the same velocity.
another situation I have dealt with when primer swapping is groups going weird until I adjusted the powder amount to bring things back in line.
that was in the 30-06 and I switched from rifle to pistol using 2400, I had to bump the load up a full grain of powder to see things come back around again.
I laid that one down to partially powder ignition characteristics, and went straight to Boyles law for an explanation of what was happening.