I did a search, but didn't find the answer.

Looking for the best bullet type for hard cased LiPo. I've seen some local racers lose power in a crash as the bullet came out. On my son's car, one is a little loose and even bending the tabs out a little is a temp fix.

I've seen the smooth bullets which have 4-5 petals that you can expand a little. I have some Trinity ones that have a set screws so they can be adjusted.

I've also seen the ones that are called "serrated" bullets which might hold better.

ProTek RC 4mm Serrated Male Bullet Connector (3 Male) [PTK-5049] | Cars & Trucks - AMain Hobbies

The tradeoff is less surface area.

So, what is the best type of bullet to use in a racing situation?

I call those caged types as the cage is removeable.

They are fine for connections like chargers that don't constantly get removed/vibrated. Don't use them in your battery. They get loose even faster as you pull and push them many times a day. Its thin material and isn't that tough.

I've used the trinity ones and had one pair wear out as well. I just use the normal 4-6 segment bullets and replace them once or twice a year

Don't forget to clean your battery bullet connections everyonce in a while too
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The ones I have contain 4 petals/segments and are split so if they become loose, you can spread them apart with an exacto/knife.

Mine do too, but they don't stay tight for very long. Just thought I would see if there was a better solution. One pair is protek and the other pair is another name brand.

Makes me wish a little for the old days when we soldered silver bars to the batteries and soldered our ways to the silver bars.

If you have a 3D printer (or heck a bit of leftover Lexan and a heat gun could also work) you could probably make an addon for your battery holder that covers the bullets, that way they can't fall out during a race.

Depending on the lipo brand you are currently using(4mm or 5 mm tubes), I've had great success over the years with either size bullets with the TQ Wire low profile bullet connectors. Can't go wrong with those.

Look for #TQW 2501 or 02 or C07 depending on lipo tube size.

Serrated bullet types are better suited for charging purposes in my experience.

Just soldered a couple of the 5mm versions up tonight and was impressed by the fit. Yes they are brand new but have a good fit/feel. Don’t seem like they’d come loose for awhile.

the caged/serrated/eggshell ones are a little looser, and aren't used as much. The other style are all the same and probably made in the same factory, just get one with 6 parts and not 4. Low profile looks nicer and is easier to solder flat. Team Powers, Maclan, TQ, Protek (careful they have both the 4 and 6 part versions) , 1UP all have them. Most batteries include a pair (at least the team powers ones do) and I would if possible get them from your local hobby store to support them (ex: add to your next online order).

How much resistance do Deans ultra plugs offer/ how much of a performance difference is there to deal with bullet issues over Deans?

Probably not a lot of difference. But, if the battery has bullets it is just easier to use them instead of having another plug. Originally, when my kid got into buggy racing with LiPos, I had the plug in between. That became more of a hassle because of how the charger was set up. So we just ditched the plugs though we still use them for nimh at home.

Best 5mm bullet available, second to none.
There is a .050 set screw that you snug up after inserting into the battery, that doesn’t lose contact as it gets warm. They will not fall out in a crash either.

I agree with everything you say. Just curious how snug they get? You could still pull them out in an emergency right?

I have some of them. Wish they made them in a 4mm as we also run a spec class that requires a battery with 4mm bullets.

Dean's connection offers 0.4 ohms resistance (RCCA Apr2006) / applications on my race trucks are 4mm LiPo battery bullets (Gens Ace) and Dean's connectors battery-to-ESC. Caveat is 5mm-to-4mm reducers (ProTec) on LiPo HV connection to Dean's ESC connection.

No when tight they will rip your battery apart before they come out. They are unnecessary though, a nice regular plug works just fine. Its a HUGE pita to have a wrench on you when you go through tech to make sure you can connect your battery and have it snug. I had 3 pairs in different cars and just went back to regular bullets. Plus in a 2w buggy they will dent your body for most designs.

Regular bullets work just fine, the vast majority of racers do not have them and have no issues. Battery tubes get worn, but by then they aren't competitive anyway. So replace or spread out bullets as needed. No need to over complicate it.