Mandrel as last step?

[Dragoon300]

@

Just wondering if you are a QL user. Reason I'm asking is QL gives a start pressure of 3626 psi. When you use a COL that touches the lands QL says to increase the start pressure by 7200 psi for a total of 10826 psi. Some users agree with this # and other users do not. Just wondering if you ever tested this with your pressure testing equiptment. What would be your take on this. TKS

I use QL and use their suggested 10826 as my shot start initiation pressure when I am running my preferred . 010 off the lands loads. This is likely going to be a higher number than actual pressure because I am not touching the lands. I then compare predicted velocity to actual measured velocity, and pressure indicators on the brass to predicted pressure. I usually need to back the 10826 psi down to get velocities to correlate, but also pressure indicators on the brass to keep the number in the appropriate direction (high or low)
This has worked very well for me as I like being close to the lands and running towards the higher velocity.

 

[MagnumManiac]

@

Just wondering if you are a QL user. Reason I'm asking is QL gives a start pressure of 3626 psi. When you use a COL that touches the lands QL says to increase the start pressure by 7200 psi for a total of 10826 psi. Some users agree with this # and other users do not. Just wondering if you ever tested this with your pressure testing equiptment. What would be your take on this. TKS

I did use QL in the beginning with my Pressure Trace II, but they would never co-incident with each other unless A LOT of fiddling was done to QL.
I gave it away early in the peace.

Cheers.

 

[Mike Matteson]

Of course uneven neck thickness will expand very slightly differently, but we are talking ten thousands of an inch, not one thousands of an inch.
The time it takes is also a valuable number to know.
Light interference allows the bullet to engage the rifling earlier sealing the gap between the case mouth and chamber wall.
This changes start pressure and the node…so does using a dry bullet lube.
If the case is sloppy in the chamber, then erratic results occur between shots, as each case moves differently in the chamber.
Having pressure testing equipment has learnt me many things.
Tight neck chambers are actually detrimental to consistent bullet movement, .003" is ideal and trimming necks to a minimum of .014" is about perfect. Any thinner can cause erratic expansion.
Necks, and cases, are thinner on one side due to the drawing process, this doesn't change after you trim to get them the same, this continues through the life of the brass.
Anyway, this is the fundamental way to be consistent. Some fliers will for sure be caused because a case that you cannot measure will have expanded unequally.
Culling is the only answer.

Cheers.

I have seen neck out several thousand. Not top of the line brass but others. So you saying that even the necks cut to and even thickness, really doesn't help that much, because the entire case is out of balances or uneven in thickness.
Interesting, I am thinking that with the case neck would be the easiest to expand first into the neck area of the chamber. with the neck being trued hitting the chamber walls would keep everything in place for that split second. I do see or think that the powder burn starts at the primer pocket area and goes forward. Would have some bearing on the alinement of the case in the chamber. A 0001" would be that much, but a .001", I would think it would make some difference. Not much but some, and possible could never tell either. I feel that the more is lined up and thickness are even all the way around would be better.
I started cutting cases for thickness or better to be sure the thickness was all the away around over 20 years ago. I did note a better grouping right off. I did other thing too. Use neck sizing dies instead of FL dies. Two things happen then. 1. my 308NM rifle case stopped case separation at the base, and grouping improved. Part of the neck sizing was I was using a 300WM neck die for sizing. So it only size about 2/3 or less of the case neck. I anneal the old way with the case in the pan and heated with a torch. All those little things tighten my grouping. I did get into weighting my cases also, but not by volume. Now I set to do the volume weight system. Being I am using top end brass now, I may not even need to do that. I will see how the brass measures out. Just how close they are from case to case.
Now I have 220 swift that I never did anything special to the case. It would almost put a bug hole @ 100yds time after time. The one thing I did was use a Ohaus Dia-O-Matic powder scale all the time. It was $300.00 at the time if I remember correctly. I still use it today.
Now that I have better funding, I can purchase better equipment I believe. The culling is something I haven't tried yet. I have give it some though, and I am going to add that to my process of reloading shooting.
I'm alway learning, so I read and write.

 

[Texis]

Never used OD bushings but I've used the mandrels for several year with very good results. I removed the expander ball from the FL sizing die. My illogical logic thinks you should size the ID of the neck because that's where the bullet goes lol. Insertion pressure on each round is identical, SD are low and accuracy is good. I also order a .284 and .308 mandrel for jam test.. works perfectly. The brass will spring back about .001 and the bolt pushes the bullet to jam.
Mandrel sizing for me comes right after FL sizing, then they are off to the tumbler. Manually bevel the neck ID just before seating the bullet.
Lots of ways to do this, this way works for me