Questions on trimming case and bullet seating.

[v3glassworks]

I am reloading for a 30-06, 308, 300 win mag, 300wsm and 300 wby.  Can you tell I like 30 calibers.  When trimming the brass should I trim the brass to the same specs every time to a consistant length?  Does it matter that much?  Can it very .010 between cases and still be accurate.  Are we talking minute differences or 1/4" or above.  I hunt but like tight groups.  Have attained .401 with a 30-06 Tikka and .600 with the 300 wby vanguard and would like to keep that consistancy.  I would like to have every case the same length every time.  I have not found out what the case length should be for my specific rifle yet.  

Also I use a RCBS (OLD) with new dies.  Every time I seat a bullet it is not the same.  I get differences as much as .004.  Would that make a great differnce in grouping?

I have been reloading for a while but am getting more precise as I slowly replace old equipment.  I used to reload with not much concern on these things.

Thanks,
Victor

[Glanceblamm]

When trimming the brass should I trim the brass to the same specs every time to a consistant length?

I do this The First Time with new brass, or factory ammo. A good rule of thumb is to trim only when you go out of spec after this.
When a case needs to be trimmed the fifth time, it is a good idea to pitch it.

I would like to have every case the same length every time. I have not found out what the case length should be for my specific rifle yet.

Is easy info to find in the reloading manual. Perhaps you meant cartrige overall lenght?

[ricciardelli]

When I order new brass (generally 500 to 1000 of the same lot number) I run them all through a full-length sizer, then I trim them all to the length of the shortest.  They never see a case trimmer again.  (However, I only neck-size the brass after that, and only 1/2 to 2/3 of the neck, depending on my bullet selection.)

As for your bullet seating "problem"...make sure your seater plug is a perfect match for the bullet you are using, and it should seat on the ogive, not on the tip.

[Steve P]

I shoot new brass one time and when I have a box (50 or 100) that have been shot in my gun, I trim them to length of the shortest.  I then check them every 3 or 4 shots.  When more than a few thousandths difference, I trim again.

The OAL length of your cartridges my seem to be .004 different, but are they really?

A buddy and I make our own bullets for silhouette shooting.  We make sure the lead does not extrude out the top of the bullet jacket.  After the final point forming process, the bullets are usually within + or - .001.  

The big producers will often sell bullets with lead extruding out beyond the jacket.  After these bullets come out of the point forming die, they go into another die that uniforms the extruded lead.  When these bullets are then packaged and shipped, they knock around and the soft lead dimples and deforms.  

The die manufacturers put in a seating stem that will match the ogive of the typical bullet (whatever they feel that may be).  The ogive is the curve or taper of the bullet from point to bearing surface where the bullet contacts the rifling.  

So what does this all mean?  If you have bullets with lead extruding out the point, you may have what appear to be shorter loads due to deformed lead points.  If stem of your seating die is seating using the point, it could be deforming the lead and making a difference in length.  They could be dimpled from shipping. etc.  If your seating die stem is seating using the ogive of the bullet (not the very point of the bullet) they could be exactly the same length at that ogive bearing point, but appear different length due the the lead coming out the tip.  

This is one of the reasons they came out with the hard points that come in some bullets.  The early steel core or bronze points are good examples.  So are the new Nosler Ballistic Tips and Hornady A-Max and V-Max bullets.  

I have one seating die that I modified by using JB Weld.  I put a release agent in the die and put in JB Weld.  I then used a seated  bullet that my gun liked to form the JB Weld to exact bullet ogive.  After the JB Weld hardened, I used a dremel tool to remove some of the material in the tip point area.  The stem seated using the ogive of the bullet only.  

I know I type alot and I appologize for that.  I hope this does help you though.

Steve  

[Coyote Hunter]

v3 –
Here’s how I do it.  

1. First, new brass gets full-length sized, then trimmed to maximum less 0.010”.  Brass that is shorter than that will eventually stretch, I figure.
2. All my brass gets full-length sized after every firing.  
3. After that the brass gets checked every time and when a few cases get 0.004” over trim length I tend to trim again.
4. I do the brass in batches and set it aside until ready to use.
5. Trimming is done on a RCBS hand-crank trimmer modified to allow me to use an electric drill to turn it.  I can do 400 cases an hour with relative ease, so trimming is no longer the chore it once was.

As to the differences in COL, that’s not uncommon.  A better way to measure is to use a bullet comparator, like those from Stoney point and Sinclair.  

I would recommend investing in some relatively inexpensive tools if you don’t already have them:

1. Stoney Point ‘Chamber-All’ OAL Gauge with the appropriate modified cartridge cases.  This gauge will help you determine maximum cartridge length when the bullet is seated to the lands.  (And help you adjust your dies to seat 0.020” off the lands or whatever distance you choose.)  You will need one modified cartridge case for each cartridge type you want to use the gauge for.

2. Stoney Point ‘Chamber-All’ Bullet Comparator.  This tool attaches to your calipers and allows you to measure from the case head to a point on the bullet ogive with a specific diameter.  Readings will be much more consistent than COL, or should be.  The problem with measuring COL is the shape of the bullets varies slightly, especially on bullets with exposed lead tips.

3. A Sinclair Chamber Length Gauge.  This tool allows you to determine the maximum length of your chamber, from bolt face to the end of the chamber’s neck.  In other words, what the maximum length of your brass can be.  You can then use this measurement and trim your brass accordingly to 0.010” less or whatever number you feel is appropriate.

[VTDW]

Great Stuff!!  Copy and paste.

Dave

[JBMauser]

Ok, you question has to do with various neck length.  Here is what I know.  First - you only need one Cal in neck length to properly support the bullet.  that means a neck length of .308 in is all that is needed for any .30 cal.  Second.  the neck captures the bullet and holds it from moving until pressure rises to a point of release of capture.  That means that two cases sized the same but one being longer than the other will have two pressure curves and the resulting barrel vibration when the bullet overcomes capture.  The effect at the target will be subject to the barrels individual harmonics.  third - since our object is to gain consistancy, different neck lenghts could have the same effect as having different power loads as the pressure curve will change.  The last point I will make is that if the case is to long for the chamber it will jam the neck into the bullet and can cause the pressure to spike even high until the captured bullet reaches release pressure.  Hope this helps.  JB