Minimum cartridge OAL?

[arizona hunter]

I read and hear folks talk about MAX OAL , but is there such a thing (within reason of course) as MIN OAL?

For example with my 6.5 X 55 Swede, the max OAL is 3.15, however if I load some Barnes XLC 120's at 2.89" and Rem CoreLok 120's also to 2.89 which is well below the cannelure, both loads shoot very nicely.

I guess what I'm asking is, could I be damaging the rifle by (although I do not see any primer problems or case expansion) making cartridges of this length rather than about 3.00" or more?

When I began loading the Barnes XLC several years ago I also used their #3 manual. In it they spoke of "smoking" a dummy load and chambering it to help determine OAL, that is how I arrived at 2.89 to 2.90. And although these are accurate in this rifle, it seems that everyone loads 120's out to about 3.00 to 3.12, makes me thing I'm doing something wrong and in the long run might suffer for it.

Your comments are appreciated.

 

[Scorch]

No mimum OAL, but the farther you seat the bullet from the rifling, the more the accuracy will suffer. That said, if your rifle is a sub-MOA weapon, it will still shoot well. I used to shoot Hornady 100 gr 7mm bullets out of my 7X57, and the groups would open up from 1-1/4" to about 1-3/4", but still reasonable.

The difference in OAL with different bullets has to do with different ogive shapes. Don't sweat it.

 

[arizona hunter]

Thanks Scorch. I appreciated your prompt feedback.

 

[Bullet94]

I’m no expert but I tend to believe what William C. Davis, Jr. says here –

“It is obviously possible also to increase the free run simply by seating the bullet more deeply in the case. That has two effects on chamber pressure, which are in opposite directions. The increased free run tends to decrease pressure, but the decrease in powder space increases the loading density, which tends to increase pressure. Which effect will predominate depends on the characteristics of the particular load and gun. In most full-charge loads, it is found that the pressure decreases at first as the bullet is seated farther away from the lands, but beyond some particular seating depth, the pressure begins to rise again as the powder space is further reduced. In revolvers, the free run through the cylinder is always relatively great, and increased seating depth always increases the chamber pressures.”

 

[Gbro]

I use the smoked dummy for OAL, but some of the rounds produced this way result in single loading the rifle, which i do anyway until i took some hunting and found the OAL was too long for the magazine.
I fixed that problem when i bought my .54 Hawkins flintlock. Now i know where i stand when a second shot is required,desired,necessary,needed,wanted,wished for, etc.
The 30WCF would shorten some of the cartridges in the T-Mag if it was loaded with more than 3-4. Never could get the crimp just right on jacketed bullets.

 

[Unclenick]

Accuracy is complex. In some guns better neck grip and higher start pressure from deeper seating improves accuracy. Sometimes a rifle and bullet will have more than one seating depth sweet spot. If you read a bit, you'll uncover a number of people who've been unable to achieve top accuracy in the usual just-off-the-lands configuration, and could only do better with deeper seating. I'm not clear why this occurs, but it does from time to time.

In any event, be aware that just as there is no minimum COL(OAL, COAL) for ballistic purposes, there is also no maximum COL for ballisitic purposes other than as dictated by your chamber and throat dimensions and the length of your bullet. The only reason for the maximum length you see published in manuals is to assure fitting in magazines that are compliant with SAMMI standards. Much longer than that published maximum, and cartridges will not fit in the magazine. You can still seat the bullets out and chamber them singly, though, as long as they're not sticking out so far they jam in the throat.

 

[arizona hunter]

Thanks guys for your feedback.
Bullet, your quote of Mr. Davis mentions pressure at both ends...I did recently read something similar in the new Hornady manual. For my loads, I'm using the starting charge to a middle of the road charge-keeping 2.0 grains below listed max. The main reason for not approaching max, is that this rifle is a 1942 Husqvarna (type 96 Mauser), not as strong as the 98 Mausers.

Saturday, Lord willing, I'll be at the range when it opens and see how these loads shoot on paper and over the Chrony.

 

[arizona hunter]

Thanks guys for your feedback.
Bullet, your quote of Mr. Davis mentions pressure at both ends...I did recently read something similar in the new Hornady manual. For my loads, I'm using the starting charge to a middle of the road charge-keeping 2.0 grains below listed max. The main reason for not approaching max, is that this rifle is a 1942 Husqvarna (type 96 Mauser), not as strong as the 98 Mausers.

Saturday, Lord willing, I'll be at the range when it opens and see how these loads shoot on paper and over the Chrony.