Bullet jam How to Question

Wow!

tjj said:
I'm new to this stuff but I am a machinist so I used what was at hand. I did this on my .308 and got results within a couple of thousandths of what the Hornady tool measured so I'm skipping buying the tool for my new 6BR.

Take the bolt out. Drop a light bullet into the chamber. The weight of the bullet into the rifling holds it in place while you put the rifle in a vise or rest. Use the depth measuring end of a set of dial calipers (i used my 8" digital Mitutoyo) to measure the distance from the rear of the bullet in the barrel to a flat surface at the rear of the receiver. Double check if you like. Record this length. Tap out the bullet from the muzzle end.
Now drop in a fire formed case and tamp it in firmly into the chamber. Take a depth measurement from the rear of the case head to the same reference location at the rear of the receiver. Record that reading.

Now most of you know what to do at this point. Measure the length of the case and bullet you used and you have all the info you need to determine the seating depth to contact point of the rifling. I make myself a little sketch of the case and bullet and just pencil in the dimensions. Now that I know how far in the bullet is seated when touching the rifling, I prepare a dummy round seated to the calculated over all length using the components used in taking the measurements and then just measure the ogive length of that round.
With the ogive to casehead length recorded, I can load up any bullet and seat the bullet where I want it when chambered.

It's easier to do than reading this post so give it a try.:D
Click to expand...

Unbelieveable.
 
Admittently,I dont have a lot of BR experience but I usually try for .002 neck tension,leave the bullets slightly long,jam and shoot.Does anyone else do this?
 
Ballistic64, yup EVERBODY does this a lot of the time..........but it's kinda' hard to tune from that ;)


This is kindofa' baseline, a quickie if you will. But for TUNING with seating depth, subtly altering the pressure curve for results of a tenth or three of vertical at 100yds, more must be done.


BTW guys, for all of you who're trying to set OAL by chambering a round and who're using virginal or resized brass with some endplay.......IF you have endplay, how many of ya's KNOW that the Rem extractor isn't seating the bullet off of the shoulder stop and leaving a gapper at the boltface??? And HOW MUCH gap if using virgin brass????


tjj,

All of the above ;)

Just picture for instance that I've got 10 or more barrels with .000 freebore......

And how do you consistently drop a bullet?

And why NOT just let the same riflings seat your same bullet in your same case the same way and just HAVE your dummy round all made up??? No tolerance stack?

And AS A MACHINIST......"double check if you like" and getting measurements "within a couple thou" is like....



wow




al
 
Different bullets like different seating depths, double radius near jam, single radius may shoot best with marks less than square. Some powders "need" more neck tension, others may not. If you have a powder that needs more neck tension and a bullet that likes quite a bit less than jam seating, you "soft seating" may be leaving something on the table, so to speak. On the other hand, if the powder likes less neck tension and the bullet shoots near jam, perhaps not. Just an opinion....
 
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