How far off rifling to seat boolits?

[Charlie Horse]

My 9mm's are giving me fits. Loading data shows OAL for many recipes to be around 1.12". If I get anywhere near that, my Glock or Taurus won't chamber the round. I have to seat my boolits deeper.
So I try to seat the boolit as long as possible, but that puts it right up to the beginning of the rifling.

My question is, how far off the rifling do you keep the projectile? Do you ever seat boolits to where they lightly kiss the rifling? When I load cast for a rifle I make it so the boolit jams into the rifling. (Those are target loads.) That won't work with a semi-auto handgun.

What's your rule-of-thumb for OAL?

[Der Gebirgsjager]

OAL is just sort of a standard of average set by the NSSF and ammo makers. You're not rigidly held to that measurement and can make ammo customized to your personal firearm to any length that works for you. As an example, if you owned several firearms of the same model made by different manufacturers, such as the 1911 pistol, you might find your loads too long for some and too short for others. The OAL recommendation is supposed to be a happy medium, but not necessarily the best for each individual gun's performance. If the loaded bullets just kiss the rifling there is little harm, but they should not jam into the rifling to prevent elevated pressure. I usually, especially for cast bullets, seat a bullet loosely in a case, carefully close the slide, open it and take out the cartridge and then seat subsequent bullets at that OAL measurement minus .002". I pay little attention to what the manuals recommend the OAL to be.

DG

[BLAHUT]

Each gun has what it likes ? Some are 50 thousands off the rifling some are touching, I have one I have to bury the bullet 1/10 inch ( about the rim thickness ) into the riffling to get accuracy. Takes time to find, trial and ???, when you find what your guns likes, you will have a very accurate gun. The AOL is just a ammo makers standard and a starting point for you ?

[Randy Bohannon]

Send your barrels to DougGuy here on this forum and have them honed to a accept cast bullets. Your barrels are cut for jacketed bullets with zero free bore which raises cain with cast bullet and semi autos.

[Half Dog]

If you’re using cast bullets I second the motion of sending the barrel to DougGuy. Then shoot to determine the powder charge then fine tune using bullet depth.

[megasupermagnum]

The only semi auto handgun I have tried to get accuracy from I found seating .010" from the rifling worked really well. In that case it was a 45 ACP with a H&G #68 clone seated to a 1.250" OAL. It will chamber most of them up to 1.265", but it is leaving rifling marks, and I wouldn't trust jamming into rifling with a semi auto like this. I wouldn't get closer than .005" from the rifling.

I don't have a rule of thumb for this. Most bullets are limited to the magazine more than anything that I have found.

[porthos]

if i have my 45 acp and 9mm throated to shoot cast; will that affect the accuracy of jacketed bullets??

[mdi]

I own 2, 9mm pistols with "tight" chambers. My Masada and my Taurus G3 won't fully chamber Winchester147 gr Silvertips. My 3 other 9mm pistols have no problem. I just use the 147s in my revolver so not a big deal. I plunk every load (not every cartridge) in my Masada and Taurus to make sure all guns can use my handloads. I haven't measured ogive to rifling, just use longest OAL that will plunk test OK with a particular bullet...

[gwpercle]

Cast boolits must feed and extract (without leaving the boolit stuck in the barrel )
Cast lead have different nose profiles than J-word ...sometimes you can't go by the book dimensions ... so you deep seat your bullet untill they pass the "Plunk Test " search the term .
You may get close with book numbers but the final seating depth will depend on nose profile and the length of the gunbarrel's throat ... it's a test for fit thing , untill you get a seating depth that "plunks" in and out the chamber of your gun .
I've had trouble with this also and the Truncated Cone designs work best ... I bought several moulds to try differen't boolits , what worked best :
Lee 358 - 105 - SWC (more like truncated cone to me )
Lee 356 - 120 - TC
NOE 358 - 124 - TC

Round nose designs were the worse about jambing and sticking in the short throats of some modern 9 mm"s .... the Truncated Cone designs and especially the NOE design (it is improved so not to jamb as easily)was the easiest to achive proper cycling with .
Gary

[popper]

Pressure due to seating depth changes in 9mm can be critical. Best to start testing with mid range load.

[gwpercle]

Pressure due to seating depth changes in 9mm can be critical. Best to start testing with mid range load.

Excellent Advice !
Gary

[DougGuy]

Having a barrel throated for cast does not affect the accuracy or performance of j-words, in fact it ensures that pretty much ALL commercially made j-word ammunition will feed and fire reliably.

Having the barrel throated properly will put a ring of smooth freebore before the leade ins, this will serve to align the boolit as it leaves the case to the centerline of the bore, and hold it squared up as it prepares to engage the rifling. It's like the front half of a Taylor Throat for a revolver, it enhances accuracy in most cases, and some shoot well enough that you may not notice a drastic improvement but most will definitely improve groups fired with cast.

There is also less initial pressure as there is less resistance to boolit movement, and therefore the pressure curve is somewhat softer in the initial firing sequence. You can usually compensate with the load data to adjust any loss of velocity due to the softer pressure curve.

[Winger Ed.]

Pressure due to seating depth changes in 9mm can be critical. Best to start testing with mid range load.

^^
I'd do this as I eased the OAL down to what works for that gun.

[DougGuy]

I copied this from replies on another forum, but here's a comment worth it's weight in GOLD, from the man himself, Jerry Keefer:

1911 9mm Softball Accuracy Empty Re: 1911 9mm Softball Accuracy

Post by Jerry Keefer Fri Feb 27, 2015 10:52 am
I don't like or want the rifling leade to dictate the seating depth.. An auto pistol will eventually have cycling issue. I have all my reamers ground with some freebore.. I believe accuracy is improved, much of the abrupt, peak, ignition shock is reduced, as the projectile gets a running start into a 1-1/2 degree leade.

I might add, that leading is also greatly reduced, since the bullet is gently introduced to the lands and grooves, as opposed to the higher pressure required to engrave the usual 5 degree leade. The less the projectile is distorted or deformed the less lead transfer, and better accuracy.
More..

HenryA wrote:
Jerry, thanks for your helpful response.

Would you think a .030" X .359 or .360" free bore transitioning into a 1.5 degree throat is about right? (I'm thinking about .358" lead bullets but have not slugged the bore yet, so maybe smaller) Is that in the neighborhood? Would you mind sharing your reamer print?

I run more than that.. .075/.100 is not excessive. A revolver Taylor Throat freebore section is the length of the 148 HBWC projectile..which is about .625 It's best to determine exactly what projectile you are going to use, and make the diameter to compliment that diameter.. For example: In 45 we only use PENN Bullets @.452 and that is the freebore diameter. The expanding gas pressure speed is much faster than the projectile ever reaches, and passes the projectile for a nano second, before the bullet actually moves into and seals the bore.. Some theorize that the expanding gases, which exert forces equal in all directions, tend to center the projectile as it enters the freebore and leade during the internal ballistic period. One ballistic scientist once wrote, " We know a great deal, about what actually takes place internally, during the ignition event, but we don't know everything exactly."

[Bigslug]

If it fits the magazine, feeds, and can be manually extracted without a hangup (i.e. engraving from the rifling) I'm happy. Getting snug up to the lands is something I only REALLY worry about with match rifle ammo - for anything else, I want the gun to WORK (period, paragraph), and not give me grief with an action that won't close. As long as there's still a little bullet base left in the case handing off "centering duties" when the lands are finally contacted, there's little reason to doubt that decent grouping can be achieved.

My preferred auto bullet profile is the LFN/WFN style, which, when blueprinted out for a specific cartridge, gives you a functional overall length when seated to where the full diameter stops and the nose taper starts right at the case mouth. If done right, that taper won't hit the throat.

The LBT 45/230/LFN is my gold standard for this - it feeds slick as greased eel boogers.



The NOE TL357-135RF / Accurate Molds 35-135D is one of Ranch Dog's designs and runs well on the same concept for 9mm. There are a ton of truncated cone designs that do the same thing



That one needed a little experimentation - we ultimately used a tightly chambered Springfield 1911 to set the seating depth for the final load; the Glocks, BHP, and Ruger P-85 are practically cavernous in comparision.

There are a few designs out there with an obvious step that you would seat to, or almost to. The Accurate 35-125B and 35-128N would be examples of this. My understanding in talking with Tom years ago about the 45-230F is that this is often done to provide clearance for the slide stop lever in 1911's and other autos, but it has the side benefit of giving more clearance for a tight throat.

[243winxb]

.010" or less off on my short throat Taurus 9mm G3C. Runs fine. https://www.thehighroad.org/index.ph...9mm-luger.317/

For 45acp, slow fire at 50 yards, the 200 gr lswc is more accurate lightly into the rifling. Not for timed or rapid fire.

Does not work on long chambers. This is touching for my Colt 45 acp GC.