Inconsistent Pressure to Seat Bullets: Chamfer Problem?

[Phil3]

I noticed that when seating 53 grain flat based Sierra MatchKing 223 bullets with a Forster micrometer type seating die, that some bullets go in easily, and others are very resistant to seating. In those instances, I raise the press handle and try again once or twice, and generally, the bullet goes in more easily, but sometimes not. The Winchester brass has been deburred inside and out with a rocket-ship style tool. I am guessing the flat based bullets are hanging up on the edge of the case, or... Is the K&M tool (https://www.kmshooting.com/catalog/case-neck-chamfer-tools/controlled-depth-tapered-reamer_small_17-6mm.html) the best tool to provide a smooth entry for flat based bullets?

Phil

 

[Lapua40X]

Pistol cartridges use crimping dies so their cases can be belled to accept the flat base bullet. But our rifle cartridges don't have that luxury. Bullets that aren't at least slightly larger than the inside of the neck would have no neck tension. Boat tail bullets make things easy, but that's where it stops. The only suggestion I have is to chamfer the mouth of the neck enough to allow for even starting of the bullet and making very sure the bullet is straight before seating pressure is applied.
The K&M tool looks like it would do a good job but chamfering can be done with less expensive tools too.

 

[ronemus]

The problem is probably the rocket-ship tool (45 degree chamfer) - it tends to leave a bur. Any good VLD chamfer tool should do the job, and they usually don't leave a bur. I had problems with scratches in the moly coating on my bullets until I switched, even though I use poat tails.

 

[lpreddick]

i noticed factory brass(win-rem) neck thickness varies enough to give different resistence to bullet seating if the neck was bushing sized. unfired lapua 6 mm br brass necked at .267 seats bullets with more resistence than when i use the wilson neck expander mandrel after neck sizing...getting the same internal diameter. once fired the small amount of powder residue seems to allow smoother seating. i suspect varying resistence to seating is an indicator of varying neck tension(bullet grip) and significantly affects internal case pressure to start bullet release and of course group size.

 

[Tim Singleton]

You don't say how many times fired the brass in question has on it.
After several times fired the brass hardens and some of the brass hardens at a faster rate than the rest. Causing inconsistent neck tension or bullet grip. The softer pieces are taking the bullet being seated easier than the harder pieces.

Let us know how many firings are on this set of brass.
You can go down a bushing size if you are using bushing dies. So they are all tight. Or you can anneal the brass

 

[Shynloco]

You don't say how many times fired the brass in question has on it.
After several times fired the brass hardens and some of the brass hardens at a faster rate than the rest. Causing inconsistent neck tension or bullet grip. The softer pieces are taking the bullet being seated easier than the harder pieces.

Let us know how many firings are on this set of brass.
You can go down a bushing size if you are using bushing dies. So they are all tight. Or you can anneal the brass

Great advice! Sounds like time to anneal.

Alex

 

[wapiti25]

+ 1 on the anneal of the cases. I anneal every third load and use Imperial Dry Neck lube.

 

[BoydAllen]

Removing the burr is a good Idea, as well as making sure that the chamfer is large enough to contain the base of the bullet. Make sure that the bullet is centered on the case mouth when you start to raise the ram. The real purpose of the K&M tool is to remove any burr, so you set it so that it cuts very little at the bottom of the chamfer cut by a regular tool. VLD tools can leave a burr. The Whole issue is how hard you push, and how sharp the cutter is. Dull cutter+hard push = burr. Years back, I learned how to scrape out burrs by choking up on the blade of a pocket knife, so that I was just working with the very tip, and the edge that was inserted in the neck was almost parallel with the inside of the neck. It still works very well, but will probably not appeal to those who are loading a large volume. The new K&M tool has a guide wire that makes alignment with the case a lot easier to achieve. With the old one it was too easy to be at an angle to the case CL.

 

[jlow]

You would think polishing the inside of the case neck with 000 steel wool wrapped arond a bore brush chucked into a drill would take out and smooth over any burr?

 

[BoydAllen]

Yes, but I do not want to remove all of the fouling. This is particularly true if the ammo may be stored for a while. "Cold welding" is a consideration.

 

[jcampbellsmith]

One more suggestion. Pull the bullets on some of the problem rounds and inspect the bullets for scratches. If the bullets are scratch free then your de-burring regime is working.
Best regards
JCS

 

[Phil3]

You don't say how many times fired the brass in question has on it.
After several times fired the brass hardens and some of the brass hardens at a faster rate than the rest. Causing inconsistent neck tension or bullet grip. The softer pieces are taking the bullet being seated easier than the harder pieces.

Let us know how many firings are on this set of brass.
You can go down a bushing size if you are using bushing dies. So they are all tight. Or you can anneal the brass

The problem is happening with new unfired brass. Winchester brass in this case. Two things are happening.

1) Sometimes, the press comes to a hard stop when trying to seat the bullet. It is obvious there is a mechanical interference somewhere, most likely I think, the bullet base hanging up on the case neck edge. Sometimes raising the press handle reveals the bullet no longer in the case, but inside the seating die. I can lower the handle, after turning the case, and most of the time, the bullet will then seat with no apparent mechanical interference, and goes in normally.

2) Sometimes, a bullet will not present any mechanical interference, but will either go in quite easily or with noticeably more resistance than normal. I attribute this to varying internal neck diameters. Perhaps I should full length resize the brass or at least use a Lee Collet die to make internal neck diameters consistent.

At present, there is no way these bullets will sit on top of the case by themselves without great patience. I have to hold them at roughly straight up and down until the bullet goes into the die and I can no longer hold onto it.

Phil

 

[Tim Singleton]

Perhaps I should full length resize the brass or at least use a Lee Collet die to make internal neck diameters consistent.


Absolutely
With new brass they will vary wildly. This should cure the problem

 

[jo191145]

On cheapo brass I run the expander of a die through the neck without sizing. Takes out the dents, makes them more uniform than out of the bag and generally closer to the neck tension they,ll be on the second firing.

For polishing case mouths without removing carbon from the neck I use 0000 steel wool also. A cheap 5/8's shallow socket designed for a ratcheting screwdriver. Has the standard screw gun drive shaft mounted onto it. Shove a ball of steel wool in the socket and chuck it in the drill press. Super smooth, super fast and leaves my precious carbon deposits right where I want them.