Jacketed showing cast won't shoot well

[Wolfdog91]

So another question. Was thinking about this while doing some load testing. Not gonna say any specifics but I'm curious . Has anyone ever shot jacketed bullets a certain velocity that you would also shoot cast at see them preform poorly at those speeds and a cast bullet of a similar weight and design do the same ?

[Rcmaveric]

Similar weight and length, yes, they perform about the same. My pistol bullets are similar. My rifle bullets are different, though, in weight and length. Specially my 6.5m bullets where jacketed bullets tend to be long and pointy. So, the jacketed bullets won't stabilize at my cast speads. I never tried my 270-win jacketed bullets at cast. 30/30 well, everything works at whatever speed. I feel like sending it cast or jacketed, but I don't have jacketed ammo at plinker speeds.

I am a small minority that believes in the rpm threshold. Castbullets aren't perfectly balanced, like say a swaged or jacketed bullet (which also isn't perfect but better) . So when you start hitting certain bullet rpms, the bullet transitions from revolving around center of axis (would be inline with barrel) to center of mass (which would be erratic and cause wobbling or even orbiting).

I have taken a 6.5 Grendel 1 in 9 and shot really impressive groups at 2050fps. The same round shot in my 1 in 8 barrel groups is about 5 inches. I had to back the velocity down to 1450. Finally, I got a load 5744 that would give me 1500fps and cycle the bolt for an MoA group. I have other comparisons also that further drive my beleive. I want 1 in 10 twist barrels. Now, my hope is to hit 2400fps one day with cast. Till then, I am stuck with 1450 in my 1in8 twist bolt guns and 2000 fps in my 1in9 twist barrels. But those guns perform exceptionally well, all sub moa with jacketed at 100 yards.

So with pistols. I say I am too close to the target to judge. All bullet weight and profiles perform the same, whether jacket or cast at equal velocities. Riffles are a different story for what I believe is the rpm threshold.

Now, guns with jacket bullet loads at around 2000fps are another story. My 30/30 perform the same with jacket and lead 1600 to 2100 fps. But launching 180g of lead at 2000fps hurts after 6 shots. 1400 to 1600 will get the job done and is much funner to shoot all day. I am killing deer and hogs, not tanks or T-Rex. I want to get my hands on 35 Whelen, which also has similar lead vs. jacketed loads.

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[charlie b]

Yes, the rpm limit is key. That limit is dependent on bullet dia, alloy and the quality of the cast bullet. Smaller dia can go to higher spin rates. Powder coating does affect that limit as well.

I come close to max loads with my .308 and 210gn bullets. Accuracy is slightly less, but, the big difference is at range. Jacketed bullet ballistics are so much better at longer ranges.

[Thumbcocker]

I have one .30-30 that groups Federal factory 170 grain j words into less that 2" at 100. Doesn't shoot cast for beans so far but I ain't done yet. No real rush though 2 other 30-30s shoot cast very well.

[GhostHawk]

Size is the first key, Cast needs to be big enough to seal that bore.

After that a whole slew of variables come into play including speed, twist rate. Too much speed & twist can have cast boolits selfdestructing before they reach target. Lube comes into it. Exact alloy of cast. It is not rocket science but that don't mean its easy.

[dverna]

It is not a simple question. You can get .224 barrels in twist rates from 6.5 to 14 from Krieger. I doubt anyone shooting cast bullets would order a 6.5 twist barrel. And what happens with an AR using 1-7 twist will differ from a bolt action with 1-9 twist or an older one with 1-12.

A shorter bullet has a different "optimum" twist than a longer bullet. Factory barrels have a twist rate that works well in the range of commercially available loads in that caliber. If you download below that velocity, that changes the optimum twist rate.

The question is "What are you trying to accomplish?" There are twist rate calculators on line that can help you.
This one allows you to change the SG (Specific Gravity) of the bullet (lead, jacketed, copper).

https://thebarreloutlet.com/twist-calculator/

[MT Gianni]

I have cast pistol carbines and shot jacketed at about the same speed. Jacketed are usually more accurate but not by much. If a new gun won't seem to shoot cast well I believe you should try a box of factory loads. If they won't shoot factory it's better to find out why or sale rather than going further. I think that is the same as what you're saying while approaching it from a different angle.

[megasupermagnum]

I had to think about this a while since I'm not 100% sure of the question. I'm assuming you are asking as far as an accuracy potential sub 2000 fps. I'm also going to assume you are talking about cartridges that are capable of shooting well past 2000 fps, say a 308 winchester, 223 Remington, or 338 Lapua or something like those. As far as accuracy, it really comes down to stability. A fun load many use in 308 is a 125gr jacketed bullet downloaded to essentially be a weak 30-30. It's a great kids load, plenty deadly too. If you then tried to shoot say a 175 gr Sierra match king at 1700 fps, you may not even hit paper if you have a 1:12 twist rifle. Put a 1:10 twist barrel in there, and you would probably be ok. I've tried that specific bullet in a 1:11 twist 18.5" barrel, and I started very low, likely only 2100 fps. It was not very good.

The other way of thinking about this is effectiveness. I wouldn't count on too many bullets made for the fast rounds, say a Sierra 180gr gameking, to work that well below about 1800 fps impact velocity. You could use a bullet made for a slower round like a 30-30, but then you are usually talking about a bullet with the same or lower BC than a cast bullet. By comparison, you can make a cast bullet do pretty much anything you want down to some really low velocities. A hollow point cast bullet is likely to perform well down to 1000 fps depending on the alloy. You get to choose. In this case the way your question is worded, If I fired a Sierra gameking with a MV of less than 2000 fps, I would not expect good things beyond close range. A cast bullet is superior at the lower velocities, or at least it can be. If you don't do your homework, it could be bad. Or you can take option #3 like some do, and stick to overly large calibers like 45-70 where you really can't make it ineffective, but at the cost of range or recoil.