OAL and seating against the lands

[ciPeterF]

The consensus is that for best accuracy (especially with cast) that the bullet should rest against the lands (or have very small jump .005").. so I measured a couple of 9mm's I have. With one bullet the CZ85 produced an OAL of 1.124".. my S&W PPC9 is a full .060" longer and the bullet is barely in the case.

So "if" resting against the lands is the right choice, I can't get there with the PPC9.. something is not making a bunch of sense..?

Added: The goal is 1.5-2.0" groups at 50 yds.

Comments, info, other opinions... all welcomed!

thks

 

[john traveler]

It's not a concensus at all.

The rule of seating just short of touching the rifling lands is NOT correct, at least not in semiauto pistols. It is true for single shot high velocity pistols and benchrest quality rifles, but not for your typical service/sporting caliber 9mm, .40, 10 mm, or .45 ACP pistols.

It's more important to have a bullet seating depth strong enough for reliable magazine feeding and resist impacts against the feed ramp. Increased theoretical accuracy at the price of decreased reliability and functioning is no bargain at all.

 

[Skip Sackett]

Consensus, hum.

For some rifles and benchrest shooters maybe. Not really in a handgun and much less a semi-auto.

Two schools of thought about that in a rifle too. Against the lands is a sure way to increase pressure and that isn't always a good thing so some folks back their bullets off a bit. Others make adjustments to the powder charge to compensate for theirs touching the lands. It is a trial and error by gun/caliber/shooter rather than a general consensus.

The likelihood of having other problems with chambering in a semi-auto pistols with too long an OAL, 'cause even the best equipment will produce .005" or more in variance bullet to bullet, would keep me from seating too long. Use a cartridge gage. Make consistent batch to batch bullets, hone your shooting skills and you will get closer to those group sizes you want.

As for the difference in chambers, welcome to the real world, where men make things and standards have tolerances built into them.
One could be at the bottom while the other is at the top, both could be in tolerance.

Let's say you load a bunch of rounds for the longer chamber. What is going to happen when you grab them, run to a competition or the range and try to run them in the other firearm?

Not good. Make the rounds to caliber specs especially for a semi-auto.

 

[lafayne]

I agree. This is an issue with bolt actions and single shot rifles, but not pistols or revolvers. With a different bullet, I load dummy rounds and drop them in the barrel removed from the pistol. If all looks ok, I assemble the gun and see if they cycle by working the action by hand. I do not want my pistol ammo in contact with the rifling as a slightly long bullet can wedge on chambering and be left in the barrel if you extract by retracting the slide. Reliable function then accuracy are my criteria.

Ken

 

[Kirmdog]

For what it's worth.

1.5" to 2" @ 50 yards is THE dream pistol for Bullseye shooters. While there are some Bullseye shooters that shoot the 9mm most are shooting the 45 and to get that kind of accuracy out of their pistols they are spending a couple thousand dollars and up for custom hand fit pistols. Unless you're shooting skills rival Brian Zinn's the seating depth wont make that much differance in the accuracy for the average person. Or if you really need that kind of accuracy out of a 9mm then get a Beretta 92 and send it off for some tightening, new barrel, trigger work and some new sights. Some of the 92's that are showing up at matches are coming close in rivaling the best custom made 1911's accuracy wise.


If you need a dedicated target gun there are a few making good accurate 9mm's (mostly Beretta's), just bring your wallet with you, they are expensive. If your shooting/reloading for self defense or fun then load OAL for reliability like others have said.

Kirmdog

 

[OKFC05]

So "if" resting against the lands is the right choice, I can't get there with the PPC9.. something is not making a bunch of sense..?

No it really won't make sense trying to apply rifle loading ideas to straight-walled pistol cartridges. If I had a dolar for every time I've gone through this routine teaching somebody how to load pistol match ammunition......well, you're not unique in this.

I've found my TAC Five 9mm to give me better accuracy with a Montana Gold 124gr than the Lee mold 124gr lead bullet I tried. Still, my old 8" model 14 is more accurate for bullseye than any semi-auto centerfire I've ever fired. Ironically, the most accurate 9mm I've ever fired was a custom built K frame revolver!

 

[Jim Watson]

The only way I know of to get a pistol bullet against the lands is to load semiwadcutters. We have been headspacing .45 ACPs off the shoulder of a SWC for decades now, with excellent accuracy. 9mm SWCs are pretty scarce and I have not seriously tested it in the smallbore. My only source went out of business just about the time I got interested in trying them.

 

[OKFC05]

We have been headspacing .45 ACPs off the shoulder of a SWC for decades now, with excellent accuracy. 9mm SWCs are pretty scarce and I have not seriously tested it in the smallbore. My only source went out of business just about the time I got interested in trying them.

+1 on the .45 ACP SWC. When I started seating them long it solved a couple of problems for me.

I tried sizing down a cast .38 WC TL bullet to .357 and shooting it in a 9mm semi-auto: boy, was that a bust! No stability, so no accuracy. I have essentially quit shooting anything but jacketed bulets in 9mm, and I don't use 9mm for bullseye.

 

[fredj338]

Like the other guys said, that thought process really has no place in handgun reloading. A bullet that wedges into the rifling can & will cause reliability problems. I've seen very few 9mm that will hold 2" @ 50yds regardless of how perfect the ammo is. Load a 147gr bullet to a reliable OAL, try several powders, you may find a load that will go 2" @ 25yds.

 

[Forester]

Seems there is consensus after all.

 

[ciPeterF]

Thanks for the info,, I'll be doing some testing over Xmas holiday, and I'll try to post the results...

 

[tdan]

I'm in Skip's and others camp on this one. You would be better off spending your time on making sure your cases are all trimmed to the same length. This insures more uniformity in the crimp. That said, if you do all that, have a cartridge that feeds reliably through your mag, and produces tighter groups.........let us know!

 

[WILDCATT]

OAL

if the cartridge is so long it wont fit the mag what do you do then.I do what jim does.rollcrimp in the top band of a SWC in my 45,I dont have a custom gun but it will shoot nearly as good as the best.and cost me very little under a 100.my mod 10 bull will shot with the best and is stock except for a Bomar rib.I load SW to first crimp groove and flush if going in my Smith 52.
forget the OAL,fit the cart to the gun.

 

[ciPeterF]

First set of results

These were shot at 30 yds from Ransom rest with a CZ85 (4.72" barrel).. Will get the Smith PPC-9 (5") out soon, it's slide\bushing are noticibly tighter.

 

[ciPeterF]

2nd set of results

These were shot at 30 yds from Ransom rest with a S&W PPC9 (5.00" barrel).. I think I'm done for now.....

 

[flat top]

ciPeterF; Sweet!!!! Nice groups!!! That is some great load work, thanks for showing it off!!!