Rifle OAL and brass MAX length Questions

[STORMINORMAN]

Two sorta' general questions...

1). If loading rifle rounds at the VERY low end (aka: START LOAD) of a range from, say from 101 to 108gr, how important is the OAL really? If, for example, the bullet is loaded 0.070" deeper, say 3.485 vs. 3.555" (and with the rim to the cannelure) because the load data length puts that bullet style into the lands? A "fatter" round-nosed bullet vs. a pointy FMJ.

So, 0.070" Shorter vs. Plus 7gr powder?

2). How important is case MAX length, as long as the rounds chamber? There is current load data, for example, for the 7x57 Mauser that has a MAX case length of 2.235" and a "trim to" length of 2.225". Other, earlier data and even diagrams show a MAX case length of 2.240" and even as much as 2.243".

If they fit the chamber, does an extra 0.005" case length REALLY make any difference?

Thanks in advance for your kind consideration and experience!

Cheers!

 

[Rogeronimo]

Just so long as a rolled case mouth doesn't extend into the freebore.

 

[tominboise]

The max case doesn't matter until it does. Unless you have measured your max case length in your rifle (typically can be done with a square base bullet seated backwards in a case, then chambered slowly), you don't really know if your case is is a jam situation. This is different that bullet seating depth to a jam condition.

I always check my case length's against a gage and trim if they are too long.

 

[rockquarry]

The max case doesn't matter until it does. Unless you have measured your max case length in your rifle (typically can be done with a square base bullet seated backwards in a case, then chambered slowly), you don't really know if your case is is a jam situation. This is different that bullet seating depth to a jam condition.

I always check my case length's against a gage and trim if they are too long.

Yes, check length after every resizing and trim back to recommended length if necessary. Very important. A case that's too long will often chamber easily, particularly in a bolt-action because it has a lot of camming power. The only way to tell for sure is by measuring the length of a sized case.

 

[Cdog]

I'm in agreement with the measure and trim brass regardless folks.

Different bullet types will of course have different overall length specs.

Working on the low end of recommended data will be more forgiving, but try to match the data to the bullet brand, shape, and makeup as possible. Barnes and other copper alloy bullets build pressure differently from most cup and core type projectiles.

 

[Drm50]

Best advice to beginner is follow the approved data. When you been at it awhile you will get the “ feel “ of things. There are to many variables to be giving off the wall advice with out knowing Anything.

 

[WR Moore]

Given the powder charge you mention (100+ grains) I expect your first question doesn't refer to the 7 x 57 mm. But, it originally was loaded with a round nose bullet heavy for caliber and had a long leade/throat. More modern loadings have led some manufacturers to change their leade/throat to something more suitable for the bullets in common use today. Generally, you don't want the bullet touching the lands as it jacks up pressure further when it's normally peaking. You might want to check a newer load manual for OAL. The 2012 Hornady manual lists an OAL of 3.065 in but specifies a length of 3.015 in for their 175 gr RN, 3.000 in for their spire point. I expect you could do 3.000 in for either with a minor fiddle on the powder charge.

I'd call the bullet maker or whoever provided your load data and ask them!

If you look at your load manual, you'll see there's a maximum cartridge case length and a "trim to" length. Both those lengths are for the sized case. The idea is you can let the case stretch to the maximum and then trim. The gun makers generally allow a little extra length in the case neck section of the chamber, but since you don't know what that might be, the occasional trim is a good idea.

I sympathize about the cost of a good case trimmer, but having used the cheap Lee trimmers, I finally realized they weren't consistent and splurged on a Lyman powered trimmer. But, if you only load the occasional box of hunting ammo, it's hard to justify the cost. The trim length mostly matters when you're crimping the bullet, but controlling the case length is a still a good idea.

 

[H Richard]

It isn't worth the potential result, I measure and rim my brass. Consistent OAL of brass aids in potential accuracy. Same as OAL with bullet. You need to know how "your" rifle's throat is, at what point the bullet touches the lead. The Hornady OAL gauge is very handy.

 

[STORMINORMAN]

OK, as far as the case MAX length question is concerned, there are two published sources of data: 7x57 listed in a Hornady manual as a MAX of 2.235" with the trim to as 2.225" & an older source (from the '70's) showing a diagram with the case length at 2.243" and a chart showing 2.240" for this caliber.

My cases are 2.240" and chamber in a single shot rifle with no problem: does the 0.005" really make any difference? The OAL for this example and question is not a problem as these narrow, spirepoint bullets are nowhere near the rifling.

The other question has to do with OAL, specifically as to how much of a varience (shortening) in rifle cartridge length compares to the difference in pressures anticipated by going from a START (101gr) to a MAX load (108gr). Case length is not a question here: the shape of the bullet (more squat, fatter) precludes loading to the suggested data for the same weight (250gr) spirepoint. I'm not positive that it is even protruding into the case as far as a similar spirepoint round that is 25gr heavier and has an even shorter listed OAL of 3.460"! Powder range for that heavier, shorter cartridge is 99.0 to 104gr.

This question is how much "wiggle room" exists vis-a-vis a shorter OAL (in this example 0.070" shorter) vs. the difference in a START load of 101gr with pressure listed at 47,000 cup and a MAX load of 108gr with pressure quoted at 51,100 cup?

I realize at near to MAX loadings OAL can be critical: when at START loads, just how important is it? Are the cannelures not on the rifle bullets for a reason?

I do appreciate your responses, and THANKS!

P.S. to tominboise: I'm going to try that reverse load flat based bullet suggestion: as I understand it if there is any bullet showing above the rim after fully chambering the round then case length is not crucial?

 

[rockquarry]

I've always used the 2.235" figure for maximum case length. I assume this is in compliance with SAAMI specs but I've never verified that.

As for bullet seating depth and pressure, it makes little difference with regard to most rifle cartridges of moderate to large capacity, like the .243, 7x57, .30-06, etc. with starting loads or even heavier loads. Best not to seat into the lands unless you're using cast bullets.

With something like the .22 Hornet or other very small cartridges, and most handgun cartridges, pressure differences could be very significant and potentially dangerous if you seat a bullet very deeply.

These comments are pretty general, but I think they cover the topic adequately enough to stay out of trouble. Good luck-

 

[STORMINORMAN]

The caliber on the OAL question is 338 Lapua Magnum: a very large case IMHO and in my limited experience.

Hard to find any powders (or primers!) available for this application currently...

Cheers!

 

[rockquarry]

The caliber on the OAL question is 338 Lapua Magnum: a very large case IMHO and in my limited experience.

Hard to find any powders (or primers!) available for this application currently...

Cheers!

Pardon me. Guess I fixated on the 7x57 mention. However, the advice still applies; with a case as large as the .338 Lapua Magnum, pressure differences in various seating depths would be minimal to none unless you really get carried away with extremes.

 

[STORMINORMAN]

No problem at all, rockquarry: I do appreciate your remarks! Most of my experience is with pistol calibers, where, as it has been previously noted, small increase in seating depth at near MAX loads can have serious implications pressure-wise.

The case MAX length question (vis-a-vis the 7x57) is certainly a physical one, but also raises the prospect of contradicting load data. I have a serious example, but that's for another day & thread.

Thanks, again.

 

[Rogeronimo]

The caliber on the OAL question is 338 Lapua Magnum: a very large case IMHO and in my limited experience.

Hard to find any powders (or primers!) available for this application currently...

Cheer

Midway currently has VV N170 available, 2 lb. limit.

 

[SMSgt]

Pistol loads and COLs and rifle loads and COLs are not comparable. I've reloaded various calibers in various rifles in various actions, and the only thing I've found "COL" useful for is determining if the round will fit the magazine. I almost wish data loads didn't even list it as it causes more concern and confusion that it resolves. For me, a published COL is no more than a generic starting point for any chamber. Seating a bullet "too" deep sets people off with a pistol round. Compressing a rifle load is often the norm.

Other than the COL limitation caused by magazine length, I use Cartridge Base To Ogive (CBTO) for all my loads. I base that on the maximum CBTO allowable to touch the lands for every particular bullet I load and then adjust for distance off the lands that I desire. I know I can have a max COL of 2.295 with my ASC .223 mags quite a bit longer COL than a Magpul will allow. So as long as my load CBTO length doesn't produce a COL exceeding 2.296, I'm good to go with my ASC mags.

 

[WR Moore]

OK, as far as the case MAX length question is concerned, there are two published sources of data: 7x57 listed in a Hornady manual as a MAX of 2.235" with the trim to as 2.225" & an older source (from the '70's) showing a diagram with the case length at 2.243" and a chart showing 2.240" for this caliber.

My cases are 2.240" and chamber in a single shot rifle with no problem: does the 0.005" really make any difference? The OAL for this example and question is not a problem as these narrow, spire point bullets are nowhere near the rifling.

Kinda depends upon when your single shot rifle was made. But, I'd go with current case length specs.

The other question has to do with OAL, specifically as to how much of a varience (shortening) in rifle cartridge length compares to the difference in pressures anticipated by going from a START (101gr) to a MAX load (108gr). Case length is not a question here: the shape of the bullet (more squat, fatter) precludes loading to the suggested data for the same weight (250gr) spirepoint. I'm not positive that it is even protruding into the case as far as a similar spirepoint round that is 25gr heavier and has an even shorter listed OAL of 3.460"! Powder range for that heavier, shorter cartridge is 99.0 to 104gr.

This question is how much "wiggle room" exists vis-a-vis a shorter OAL (in this example 0.070" shorter) vs. the difference in a START load of 101gr with pressure listed at 47,000 cup and a MAX load of 108gr with pressure quoted at 51,100 cup?

I realize at near to MAX loadings OAL can be critical: when at START loads, just how important is it? Are the cannelures not on the rifle bullets for a reason?

Given the volume of powder involved, I'd contact whoever provided the load data you're using and ask them. Or the whoever made the bullet. Shortening the seating depth can jack pressures up to catastrophic levels, at least at standard powder charge for cartridge/bullet combo.

As for cannelures, they're on there to provide a place to crimp the bullet. BUT the cartridge they were originally designed for may not be the cartridge you're loading. Or, the cannelure might be moved to meet the requirement of a newer, much more popular cartridge. I know I need to trim my own 7x57 brass, but I kinda doubt that's the main reason the cannelure on the bullet I generally use isn't at the case mouth. The OAL seems to have shortened over time by about 1/16 in.

 

[Mike0251]

Other than the COL limitation caused by magazine length, I use Cartridge Base To Ogive (CBTO) for all my loads. I base that on the maximum CBTO allowable to touch the lands for every particular bullet I load and then adjust for distance off the lands that I desire. I know I can have a max COL of 2.295 with my ASC .223 mags quite a bit longer COL than a Magpul will allow. So as long as my load CBTO length doesn't produce a COL exceeding 2.296, I'm good to go with my ASC mags.

Exactly! I'm .025" jump for my 6.5 CM. That is the proper way to do and know exactly what you have going on for cartridge development. Then comes powder type, charge weight, chrono data. And yes always measure and trim after resize for rifle.

 

[Nevada Ed]

With #1;
"Into the lands" is just a wee too much...........
For less pressures the bullet should not tuch the rifling..... but I have had loads that need to be fired, when I close my bolt, so I dont "Pull" the bullet in my light target load, and have powder all over the place.
It depends a lot on the rifle and the load.

Case length is good until the bolt handle needs "More pressure" to close it...........
or the shoulder or case has streached enough to cause a problem in feeding.

A case might need to be resized on the 1st or 2nd firing if you do full loads
but with a light target load, you might not need to full size until the 7th load.
The types of powder and bullet weights play a part in how the case will hold up, as well as the fit of your chamber, be it good or sloppy.

All my rifles are now bolt actions, so if you have a Semi, you will need another person to tune in, for help.

Have fun.

 

[SMSgt]

I've found a .002 shoulder bump works well in my bolt-action .223. My ARs need about .003-.004 bump for the bolt to lock without resistance. Distance off the lands is a nebulous number depending on rifle and load. I generally start about .015 and work back .005 until the rifle smiles and is happy.