Originally Posted by
Wilderness
I have recently been reminded of the occurrence of lubricated cast bullets setting up some sort of bond with the case neck after loaded cartridges have been standing for a time. The relevance of this is that it can affect velocity and POI, and probably group as well.
The outcome can be a very different POI when you come to use the ammo versus what was obtained when testing immediately following loading. I have an instance to relate.
With cast bullets, this adhesion may occur in as little as a week.
I have found extensive discussion of such “welding” as it relates to jacketed bullets, but nothing at all on cast bullets. Welding/gluing, whether of jacketed or cast, can be discovered when attempting to pull bullets that don’t want to be pulled, or by attempting a small increase in seating depth. I occasionally pull cast bullets soon after loading them, for all the usual reasons, and do not recall any difficulty pulling newly loaded ammo. Seemingly it happens only with “aged” ammo.
My reminder came from loading some .30-30s with 175 gn hard cast GC HP bullets and BAC lube.
Powder was BM2 ("Benchmark" in U.S.). Rifle is a 1949 Marlin 336A. Bullets are seated out to engage the rifling, and not crimped. My Remington cases have a light outside neck turn – removing high spots and leaving neck thickness of .010” max to accommodate .3125” bullets with neck clearance. Case necks are expanded with Lyman M Die 31.
With 24 gns of BM2, loaded the day before, I got 1830 fps for the clean barrel fouler, and 1782 average of 5 for the group, with SD 54. Next load was 26 gns, again loaded the day before - missed the velocity on the fouler, 1898 and 26 for the group. So far so good, about 50 fps per extra grain of powder, but still too much SD and vertical stringing (2” at 50 meters).
I then loaded 27 gns, expecting 1950 fps, and hoping for the velocities to tighten up. Shooting was delayed by a spell of windy weather, so ammo aged about 10 days.
When calmer conditions returned, the clean barrel fouler gave 2105 fps - up 200 fps for one grain, but extraction was fine. After some thought I then ran the group - average 2036 fps (138 fps extra for one grain, much too much), and SD 38.
Groups were all about 1" lateral at 50 m, but 4", 2" and 4" vertically for the three loads when shot fresh, in line with SD. Updated plot of individual shot POIs against velocities (now 23 non-fouler shots) indicates 2.2" displacement per 100 fps velocity, emphasising the need to reduce velocity spread. Good loads in this rifle group about 1” at 50 m for 5 shots.
I took the unfired 27 gn cartridges home and pulled them (collet). The first one tried WOULD NOT BUDGE. Then I bumped them in a few thou with the bullet seater. Each gave a distinct pop as the seal broke. After that they pulled normally. This looked like a message.
Next, I shot some 26 gn BM2 loads that had been “aged” five days. This load previously, when shot fresh, averaged 1898 fps and gave a 2” five shot group at 50 meters. The same load now “aged”, and refusing to pull, gave 1993 fps (clean barrel fouler) and 1939 (average of the three following – I wasted two of the intended five).
I repeated this part of the test later with 10 day old ammo with very similar results - clean barrel fouler 2035 fps, group 1943 fps. Combining the 8 non-fouler shots from the two tests gave 1942 fps and SD 18. POI comparing the eight aged rounds with the five fresh gave 4 minutes higher POI at 50 m, which would translate into about 5 minutes on the 200 m LAS rams. Groups at 50 meters for the two "aged" 26 gn tests were .59" (4) and 1.71" (5).
Incidentally, for the four groups for which I had clean barrel fouler velocities, the average increase over the "group" velocity was 66 fps.
I reread Larry Gibson’s report on his excellent lube test from 2014 (NOE site), but found no mention of when the shooting took place relative to when the cartridges were loaded.
I have answered some of my own previous question (which lubes do it and what to do about it) - I have demonstrated adhesion for five different lubes, and resolved that henceforth I shall do both my testing and my serious shooting with ammo that is at least a week old.
Edit April 29 and May 1 re testing:
Testing for adhesion by pulling bullets is complicated by collet slipping on cast bullets. A surer method seems to be applying pressure with seating die to test for "click" when the bullet moves. By this test, BAC (Beeswax, Alox, Carnauba) remains a front runner loud and clear, and ammo loaded a few months ago with LBT is "clicking". Another aged lot with 3:1 beeswax and synthetic two-stroke oil seems to be OK.
Dummies loaded by me and tested 8 days later clicked for BAC and LBT lubes, but not for Orange Magic. A different set of three dummies tested at 12 days gave definitive clicks for BAC and LBT, and a lesser sound for OM.
Alternative for home testing of a loading batch is to seat all bullets out a bit, then seat to full depth immediately before use to check for adhesion. A click will indicate adhesion at some level. I have no idea yet whether adhesion will set up again after once being broken - that is for the future.
If someone actually tests their ammo I would be REALLY interested to hear how different lubes respond.