Tom G
posted this
27 February 2020
We can blame poor accuracy on all kinds of different reasons but my experience has shown that cast bullets just don't shoot as well in a particular rifle as match grade or even so so jacketed bullets. This tells me that it's something to do with the bullets and not the guns or the shooting technique or the guy behind the trigger.
Sure, none of us have exactly the same level of skill as the others when it comes to shooting. But, when you build a first class benchrest rifle, put a 36 power scope on it., shoot it on a first class bench in good shooting conditions, if you get poor groups, it pretty much boils down to something to do with the bullets we shoot. Shooting off the bench with a flat fore end rifle on a front rest with proper bags and a 2 oz. trigger takes a lot of the personal skill out of the reason why cast bullets don't shoot much better than a half minute of angle.
I've shot thousands of rounds with cast bullets over 30 years and they never shoot as good as good jacketed bullets in the same gun. I have a Rem. 788 in 30-30 that shoots 7/8 moa consistently with cast bullets. One day I shot a bunch of 150 gr. jacketed bullets and worked up a good load. This gun shot half inch groups with just run of the mill production hollow point jacketed bullets. I have no doubt that it can shoot even better with match grade bullets. Before I shot the jacketed bullets I shot a series of groups with cast bullets that averaged just under one MOA.
I was using the exact same equipment on the same range under the same conditions for this test. Nothing changed but the load. The results were consistent and repeatable. I shot lots of groups so it wasn't any kind of an abberation or fluke.
The cast bullets I shot were all very good quality. The were very uniform and weighed just as close to each other as the jacketed bullets. They fit the barrel properly and were bumped in a taper die that fit the taper of the throat of the gun. The bases were gas checked and bumped perfectly square to the c/l of the bullets. They should have shot into .3 moa in my estimation. But they didn't, while so so jacketed bullets did shoot way under a half inch. groups.
I've come to believe after many years of shooting cast bullets that the reason cast bullets are not as consistent as jacketed is a lack of a consistent barrel condition. By that I don't mean that this is caused by leading because my loads didn't lead at all. After a lot of soul searching and some more testing, I came to the conclusion that the lubricants that we use are the reason we can't shoot as good with cast as jacketed.
In other words, the friction in the barrel and possible the gas blow by varies from one shot to the next and this caused the bullet to emit from the barrel at a different time during the barrel vibration cycles. I know from testing and have confirmed to my own satisfaction that the amount of lube on the bullet greatly effects what we call fliers. I also know from testing that the actual lube formula has a great effect on accuracy. By "great effect" I mean adding a quarter of an inch to a half inch to the group sizes. To some, that amount may be inconsiquential but for a benchrest shooter it is a lot.
Lube is the one variable in our loads that we have never really gotten a real hold on. If we ever get one that works perfectly, I think we can shoot cast bullets just as good and probably even better than jacketed bullets.
In the past I've identified the fact that lube causes fliers. It's a necessary evil at this point in time if we want to shoot cast bullets without leading at any kind of higher velocity. So far, I've never been able to lick the flier problem but I've been able to reduce the fliers by playing around with the lube formula and the amount of lube on the bullets to get rid of about 90% of them. My theory, and it's only a theory since we can't see whats going on inside our barrels with each shot, is that the problem is that we cannot maintain a consistent level of lube and thus, friction and sealing over a long period of time. That the lube builds up in the barrel and every once in a while, it purges it out and the barrel goes back to a steady state for a few shots before the lube builds up again and gets to the point of causing bullets to fly out of the groups.
I can cite examples of this happening. but this is already a long post. I can say that my suppositions are based on real observations of cause and effect. Not being able to monitor bore conditions as well as we would like, that's about all we can use to try to rationalize why we get fliers with cast bullets and don't with jacketed.
It just snowed 6 inches last night and the wind is blowing so that the wind chill here is 8 degrees. I figured that this is a good time to throw out this theory and see how others feel about it. I think that the next big leap forward in cast bullet accuracy will undoubtebly be tied to finding or eliminating the use of converntional lubes as we know them. Flame on!!
Tom Gray in snowy Michigan