Boat tail slugs vs. Round nose bullets?
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"Bob and Lloyds Workshop"
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Boat tail slugs vs. Round nose bullets?
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Topic: Boat tail slugs vs. Round nose bullets? (Read 544 times))
Greg_E
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Real Name: Greg
Boat tail slugs vs. Round nose bullets?
«
on:
March 07, 2021, 11:47:10 PM »
Bob,
I'm reading up on your boat tail design to maybe start casting them for my Benjamin Bulldog, but had some questions. It is still frozen winter here but looking forward to getting out and shooting soon. So far I've used a few Benjamin Nosler and they proved to work very well for me. I've also used some Griffin boat tail slugs and they also proved to work very good.
The Griffin are much more "pointy" than the design you made. Is this an advantage or not in a subsonic airgun? Does this have to do with sectional density over "smoother" shape giving a better BC?
Since the Nosler worked so well, I bought a Lee 356-125-2R mold and made myself a few to try. Since Crosman told me that I should only use swaged soft lead, I'm concerned about hardness, the lead I had was dental xray backing and tested a bit harder. My thoughts on this issue is to powdercoat and size back down to either .358 or .357, not sure which size it will like better. Theory is that the powdercoat will squeeze down nicely in the rifling where the cast lead might be a small problem. Again, haven't fired any yet. Your thoughts on this would be welcome.
And finally, how is your .25 design doing? When it comes back from repair, I'll have a Kral Empire X in .25 and may want to get a mold for it. Maximum pointed round length is .450, flat nose is probably .430 or .420. There is a groove in the magazine for a pointed round and since I only had the rifle for a day before discovering some damage, I can't give more detail on projectile sizes yet. Hoping it wants either .249 or .251 since those are common Lee sizes in sizing dies.
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rsterne
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Re: Boat tail slugs vs. Round nose bullets?
«
Reply #1 on:
March 08, 2021, 01:17:47 AM »
This slug has proven to be a good one....
https://noebulletmolds.com/site/shop/251/250-50-fn-bb3/250-50-fn-bb3-2-cavity-rg2-bt/
It weighs 50.4 gr. as a FN and 47.5 gr. as a HP, cast with 40:1 lead/tin alloy.... The BC (G1) of the FN is 0.107 and the HP is 0.101, measured at 857 and 886 fps respectively.... They work fine in an 18" twist, and measure 0.417" long....
Bob
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Greg_E
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Real Name: Greg
Re: Boat tail slugs vs. Round nose bullets?
«
Reply #2 on:
March 08, 2021, 05:37:14 PM »
Bob,
Thanks for the reply. How big can the hollow point be made before it destabilizes the slug? With the power levels before mods., I think I'm going to need closer to 30-35 grains. The manufacturer rates this at under 40 foot pounds with some unknown weight of pellet which means that they either under rate it, or it needs better flow. And all that with only 50 shots out of a 600cc 3000psi air system. Nope, several things do not add up.
Would a "straight" sides and flat bottom hollow point affect flight performance? That's something that I might be able to machine myself. I'd like the longer length for better BC, the Empire X can take up to about .420 or .430 inch long.
I may need to risk some money to give this a try, I'll probably order the .357 after I try the Lee molded rounds since there is almost no risk for the Bulldog. Biggest risk is making sure I cast them properly for this rifle.
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Greg_E
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Real Name: Greg
Re: Boat tail slugs vs. Round nose bullets?
«
Reply #3 on:
March 08, 2021, 05:39:15 PM »
Ignore the above, changing the hollow point would change the center of gravity a lot.
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Boat tail slugs vs. Round nose bullets?