Another lesson learned

[Solus]

I don't have the experience to know how all the factors I'm listing below interact...or if I have the interactions correct...so I'll post what I "think" and learn where I'm wrong

I have heard that the way to determine optimal OAL for a firearm is to take a sized and expanded case start a bullet into it with your fingers, then gently push it into the chamber until it headspaces.  

This will produce rounds where the bullet is just touching the start of the lands in the barrel which is supposed to reduce "trauma" to the bullet as it enters the rifling.  Of course, this would need to be done for each firearm.

Shortening OAL will increase initial pressure inside the case and the initial velocity and the bullet will have some momentum when it hits the rifling.

I would expect the "slamming" into the rifling to cause a pressure spike and a reduction in the velocity...which the increased pressure might offset some?

With the max OAL determined above, the case will have the maximum powder capacity, which may or may not make any difference depending upon the powder used.  The bullet will start resting against the lands which will cause more resistance than bullet inertia along..so that should increase starting pressure.  I don't see a pressure spike in this.  

I have no idea which will produce the highest muzzle velocity.

A related issue.  

After loading for a Ruger Blackhawk, I tended to take the max powder load listed in the manuals as load to approach in small increments and with caution.  I always depended upon case examination to show indications that pressure was nearing the max...particularly flattened primers...or even cratered primers if I push to far to fast.

Is that procedure valid for all firearms?  Revolver, semi-auto, rifle, pistol, bolt action???

Thanks.

[Magoo541]

I have heard of rifle guys doing that but never thought about applying it to my pistol. I'll give it a try and see if my data backs it up.  Right now I seem  to have max velocity at 1.220" in my XDM with the three loads I ran across the chrono.  I'm still getting comfortable with the whole process and beginning to understand some of the parameters in play.

FWIW I've used to bullets in my 45 so far a RNFP from Badman bullets and a RN from Berry's that is moly coated both over Bullseye and CCI 300 primers. 

[Solus]

Yeah...in a rifle, it is probably done for bullet integrity and accuracy.  Variations of 100fps might not matter much when you are doing +2000fps.

Accuracy in SD handgun at 20ft probably won't care about a bruised bullet...but 100fps would make a significant difference.

[tombogan03884]

In a hand gun what works in a rifle may produce a cartridge that gives feeding problems because of the angle it approaches the chamber mouth.

[PegLeg45]

You do not want the bullet to start against the lands.....it will cause a pressure spike at the point of ignition. You will want to determine what the length is to touch the lands/grooves and then back off a few thousandths.

The Importance of Bullet Seating Depth
(Editors note: This article focuses on the importance of seating depth, and how it can be different for various rifles. To learn more about techniques on determining seating depth click on the below link to read an article from our March, 2009 “Reloading Press”) :

What is the proper seating depth for bullets? There is no definitive exact answer to this. However it is what makes the rifle shoot best. Over the years many bench rest shooters have said that the rifle won’t shoot unless the bullet is jammed into the rifling. I have two rifles in which jamming the bullet works, however on most of my rifles the bullets need some “jump”. The two rifles that like bullets jammed into the rifling are chambered in wildcat cartridges, and their barrels are worn. They each have about 500 rounds through their barrels. One of these rifles is chambered in “.22 Cheetah” which is a notorious barrel burner. I tried seating the bullet on the lands and worked off in 0.005” increments back to 0.020” and accuracy was 0.375-0.500” at 100 yards. I felt that I should be able to tighten the group. So not wanting to miss something I tried seating bullets into the rifling with a 0.005” jam. The group tightened up to 0.220” and when I tried a 0.010” jam, the group opened up to 0.270”. My other varmint rifles like the bullet’s ogive to be seated away from the rifling a bit.

(Note to reader: “jamming” or touching the rifling with a seated bullet will increase case pressure significantly! Use minimum published powder charges while working these loads up. Please approach with extreme caution!)

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more at link:

http://blog.sinclairintl.com/2010/12/15/the-importance-of-bullet-seating-depth/

Here is a thread on the Nosler forum about it.

http://www.noslerreloading.com/phpBB2/viewtopic.php?f=4&t=16847

[Sponsor]

[Solus]

Thanks, Peg.  Lots of good info in the comments too.

[les snyder]

ellis4538... WW452AA was the most accurate powder I ever shot in my 1911s...

[ellis4538]

les, Super Target is supposed to be the same or quite similar...give it a try.  A number of us have used it with great success since 452AA was discontinued.

Richard

[les snyder]

Richard... shot a lot of WST then later Clays when I was shooting only .45 and 12ga.  ... I turned to the Dark Side about 5 years ago, and retired the 1911s for Glock 34... now handload Precision Delta 147 fmj and Win Super Field at about 935fps

[tombogan03884]

Richard... shot a lot of WST then later Clays when I was shooting only .45 and 12ga.  ... I turned to the Dark Side about 5 years ago, and retired the 1911s for Glock 34... now handload Precision Delta 147 fmj and Win Super Field at about 935fps

Barbarian .