Air Gun Home :: View topic - First day with .25 cal Cast Bullets

rsterne · Moderator

I got a chance to shoot my .25 cal Disco today and test some .250" diam. cast bullets at 50 yards.... The gun is tuned for about 85 FPE depending on bullet weight.... I shot two 5 shot groups with each bullet from the bench.... My own cast bullets leave a lot to be desired, I was having problems with the sprue cutter bending the base of the bullet slightly, leaving one side of the base slightly rounded and the opposite with a sharp corner, so I didn't have a lot of hope for those, and sadly, they lived up to my expectations.... However, I had some (very expensive) Mr. HollowPoints, and while they shot better than my first effort, they weren't great either.... Here are the results for 5 shot groups, C-T-C, off the bench at 50 yards....

RCBS 57902 .25 ACP bullet, cast 0.251"-0.252" as 46.4 gr Hollowpoint shooting at about 900 fps, and 52.7 gr. Round Nose shooting at about 850 fps....

46.4 gr. HP Unsized: 2.25". 2.10"
46.4 gr. HP, Tumbled 10 min: 2.50", 2.15"
52.7 gr. Unsized: 1.85", 1.50"
52.7 gr. Sized to 0.250": 2.50", 2.20"

Mr. HollowPoint, 0.250", three different weights....

50.0 gr. @ ~880 fps: 1.45", 1.25"
52.0 gr.@ ~860 fps: 1.75", 1.00"
58.8 gr. @ ~810 fps: 2.75", 1.35"

Mr. Hollowpoint, 4 shot groups at 100 yards....

50.0 gr.: 2.25"
58.8 gr.: 2.90"

These results are significantly poorer than this gun delivers with JSB Kings, where it does nickle to quarter groups at 50 yards.... The barrel is a 0.470" OD Lothar Walther that I have had several years, I got it from Mountain Air and it's a good shooter.... I have three conclusions from todays testing....

1. If the base of your bullets doesn't look perfect, they won't be accurate....

2. Even if the base of your cast bullets looks "professionally done" they may not shoot as well as pellets....

3. I have a lot to learn about both casting boolits, and shooting them....

Bob

grizzlyadams · Member

that is why mr . hp's boolits are so expensive. they are a pain to get right, though i believe his are swaged. i have been wanting to try some from him, but just have not gotten around to it.i have an air force condor that will do in excess of 120fpe with cast. i have some of those same round nose that you cast and they were not cast very carefully, but ehh, they were a free sample. for right now, i guess i will stick to pellets until i get my own molds. swaging is out of the question for me right now as i have no extra organs to sell to get the dies!!! Laughing

rsterne · Moderator

I purchased 3 sizes of .25 cal Mr. Hollowpoints, 2 bags of 50 of each, plus he sent me a sample of another weight to try (nice addition on a $150 order).... They are definitely cast, not swaged, and the bases are pretty square, he does a nice job.... However, the best I got was 2 MOA at 50 yards (5 shots) and 2.25 MOA at 100 yards (4 shots).... That is acceptable "hunting accuracy" for large animals, but not for targets the size of ground squirrels, which I have taken with a .22 cal PCP at over 100 yards.... Virtually all of my airguns will put 5 shots under a quarter at 50 yards with the right pellet, and about half of them under a dime.... I'm getting to the point that if I can't cover a 5 shot 50 yard group off the bench with a quarter I haven't found the right bullet/pellet.... So far, I haven't found a single cast bullet that will pass that test in any caliber....

Bob

rsterne · Moderator

I tried some new things today.... I polished the Sprue Plate on the RCBS Mold for the .25 ACP bullets and made sure the hole was sharp, and adjusted it so that you can flick it open with your wrist.... Used the same 1% Tin I used last time, but this time I ran the temperature 750-780*F and I preheated the mold on a hotplate.... The biggest change in technique, however, was to open the sprue plate with a gloved hand instead of whacking it open with a wooden dowel.... Between the sharper, polished plate, looser fit, and more careful opening, the bases were a HUGE improvement.... Basically there was no more rounded edge on one side.... I think part of the problem was too tight an adjustment on the sprue plate pivot bolt accompanied by the violent opening.... The fillout on the mold was perfect, although I did get the occasional flash from not holding the mold closed tight enough....

After I had cast about 300 bullets, half of them hollowpoints, I sorted through and threw about 10% which had flaws back into the pot for next time.... The remaining bullets I ran through a Lee 0.250" Sizing Die which I had made from a 0.243" Die, and then I tumbled all the bullets in a rock tumbler for 10 minutes, just the bullets, no abrasive or water.... This eliminates any flash, and rounds the corner of the base very slightly, eliminating the sharp edge on the side that the sprue is cut towards.... I was VERY pleased with the results.... Here are 8 randomly selected bullets....

You can see the slightly rounded but very uniform base corner.... Here is a photo of the tumbler, and the rubber barrrel opened up with the bullets in it....

I ended up with 130 RN Solids and 140 Hollowpoints, and they are such an improvement over the previous bullets I can't believe it....

Virtually all of the previous bullets had one flattened side on the base from the drag of the (too tight) sprue cutter.... Not any more!....

Bob

rsterne · Moderator

I set up for some testing nearby at 100' and tried the new bullets in both the Disco with the choked LW barrel and my 2560 HPA with a TJ's .25 ACP liner.... The 2560 is normally set up to shoot JSB Kings at 960 fps (52 FPE) but by turning in the hammer spring preload 3 turns I got the 52.9 gr Solids up to 760 fps (68 FPE) and the 46.4 gr. Hollowpoints up to 805 fps (67 FPE).... The Disco is still shooting at 85 FPE the same as it was tuned when I got the disappointing results the other day that started this thread.... That testing was at 50 yards, but I don't have that much room where I was shooting today, so if you multiply these groups by about 1.5 you can compare them to the previous results for the .25 ACP bullets before I learned how to get better bases on them....

Results for the 2560:

52.9 gr. RN: 0.65", 0.90"
46.4 gr. HP: 0.90", 1.10"

Results for the Disco:

52.9 gr. RN: 0.95"
46.4 gr. HP: 0.80"

There is no question that getting square, symmetrical bases on the bullets has made a HUGE improvement in accuracy.... The groups for the Hollowpoint dropped from an average of 2.25" at 50 yards to 0.93" at 33 yards (the equivalent of about 1.4" at 50 yards).... For the 52.9 gr. Round Nose, the groups dropped from an average of 2.01" at 50 yards to 0.83" at 33 yards (the equivalent of about 1.25" at 50 yards).... In both cases, the groups are 62% the size they were before.... While these are still not stellar groups, they represent 2.5 - 2.8 MOA, which is a heck of a lot better than the 4 - 4.5 MOA I was getting before.... The best groups today you could cover with a quarter at 33 yards....

I ran out of air, and the guns haven't been tuned at all for these bullets.... so for preliminary results I'm a lot happier than I was the first day out.... On average, my cast bullets are shooting better than the Mr. Hollowpoints, so at least my casting technique has improved enough to accomplish that....

Bob