Nick93 said:
what about handgun cartridges ? In you reloading experience what did you find get the most accurate load?
For pistol loads - well, it depends ... as accuracy is the result of so many reloading/shooting variables.
In the simplest/fundamental sense, I consider accuracy directly related to consistent chamber pressures. If you are able to produce more consistent chamber pressures, it will translate to more consistent muzzle velocities and more consistent shot groups.
So, what factors contribute to consistent chamber pressures? A lot. Here are some factors I consider when trying to produce "accurate" loads:
- Barrel chamber/leade/rifling construction/dimensions - looser chambers with longer leade will tolerate greater bullet dimension variations, but will allow more high pressure gas to leak around the bullet as it jumps from the case neck/chamber to the start of rifling.
- Bullet construction - more on this below
- Consistent bullet weight - for me, this means less than 1 grain variance bullet-to-bullet.
- Consistent powder charge - for me, this means less than 1/10 of a grain variance charge-to-charge)
- Consistent primer ignition/flash size/duration (for me, Winchester)
- Longest OAL that will feed/chamber reliably so the bearing surface of the bullet will engage the start of rifling sooner to build chamber pressure faster
- Widest taper crimp that will pass the barrel drop test and feed/chamber reliably.
- etc.
Jacketed vs cast vs plated... Which is more accurate?
I consider FMJ bullets with exposed lead base more accurate than JHP bullets with solid copper/brass base. Why? During powder ignition, the exposed lead base will expand to seal with the barrel better, trapping more of the high pressure gas for more consistent chamber pressures. In my experience, I need to push JHP at near max/max load data for "very good" level of accuracy whereas I can achieve similar level of accuracy with mid-high range load data using FMJ bullets. For this reason, I have preferred to use FMJ for my "match grade" loads over the years.
What about plated bullets? I have done comparison tests between jacketed and plated bullets (Montana Gold/Winchester FMJ vs Rainier/Berry's/PowerBond/X-Treme) and found jacketed loads more accurate than plated. I attributed this to plated bullets leaking more high pressure gas around the bullet base than the FMJ bullets with exposed lead base. While most plated bullets are sized same as jacketed bullets, some plated bullets like Berry's are sized slightly larger (i.e. .355" vs .3555"/.356") to provide better bullet-to-barrel fit. Better bullet-to-barrel fit will decrease the high pressure gas leakage around the bullet base and provide more consistent chamber pressures.
Another factor to consider is oversized factory barrels that will leak more high pressure gas around the bullet, which will decrease the consistency of chamber pressures. You can replace oversized barrels with tighter aftermarket/match grade barrel to address this issue.
Berry's now offers hollow base bullets that will allow greater expansion of the base to increase the consistency of chamber pressures. I did some comparison tests of 9mm HBRN with my reference Winchester FMJ loads and I got increased accuracy with HBRN loads. So, this adds to my accuracy mantra of consistent chamber pressures = accuracy.
What about lead bullets? For those thinking jacketed and plated bullets may be more accurate than lead bullets, have I got a surprise for you. Unlike jacketed/plated bullets that may leak more high pressure gas around the bullet base (hence higher powder charges are needed to achieve the same average SAAMI max pressures), softer lead bullet base can expand/bump (obturate) to seal with the barrel and trap more high pressure gas. For 45ACP, I have yet to find a more accurate jacketed/plated load than 200 gr lead SWC load.
For me, accuracy is everything. Adjusting the reloading variables I have mentioned above, I have found very accurate pistol loads regardless whether the bullet was jacketed, plate or lead. For certain caliber, pistol, barrel, bullet type, bullet weight, powder and charge, one bullet type (jacketed vs plated vs lead) may be more accurate than another, but not for all.
I hope this helped.