Troubleshooting II or Help, why is brass changing its shape?

slimjim

I’m having so much fun learning how to load with a single-stage press I can only laugh. Here is my latest situation. New factory rounds feed from the magazine with no issues in my new 6.8 build. The reloaded rounds that have been FL resized will not consistently feed from the magazines without jamming. It takes prying with a screw driver to get the bolt back open. Because they are not feeding reliably, I started chambering the reloaded rounds single-shot by pushing them into the chamber as far as I can and drop the bolt on them to get them the rest of the way in (if they were not all the way in to begin with). At least I was getting some data for my OCW ladder. Yes this is the rifle that had indentations in the brass after firing.

www.huntingnut.com/ind...pic&t=9537

I started checking everything searching for knowledge as to why this would happen. I mic’d my brass. The shoulder was getting pushed back 0.003 to 0.004 but the base resizing wasn’t what I expected. New brass was 0.416, fired brass was 0.420, and resized was 0.418-0.419. Turns out max SAMI dimensions for 6.8 is 0.421. Thinking I had a tight chamber, I slugged the chamber opening with one of my .45-70 lead slugs and mic'd it at 0.4231 which is in the middle of the spec. This doesn't look at the entire chamber but at least gives me more data to proceed forward. Looks like I’m getting 0.004 clearance on the base which should be good. Redding also suggested I check and see if resized, unloaded cases drop straight in. I found everyone did and they fall right back out. I have to press fired case in and they need to be "helped" back out. Next, I loaded up 4 of the resized cases with bullets only for a quick check. 1 of the 4 wouldn’t just “drop” in all the way any more and had to be “bumped” out. So I put them in a magazine. They all cycled but the tight one needed to get bumped out.

That’s about all I can manage in one night. I’m left with the question, what could be changing in the brass during the reloading process such that the loaded cases don't just drop into the chamber anymore?

Thanks for any help and suggestions.

Ominivision1

Take a few cases and load them to max loads and fire form them a couple times to get a true idea of your chamber dimensions. Then set your sizing die to push the shoulder back back between .001-.002".

.003-.004" might be a tad to much.

SingleShotLover

Mic your sized cases against factory loads. I'm betting that the sized cases are slightly larger than the factory ones. Remember that brass is springy and will "spring" back slightly after sizing and the resizing die probably isn't bringing it completely back to factory spec anyway. Factory ammo is designed to fit into any properly chambered rifle, whether the chamber is slightly over-sized or undersized. Many times a really good, minimum spec chambering job can make chambering a handload tricky without trying various sizing methods or even sizing dies.

slimjim

Simply stated, somehow the brass is changing shape after its properly resized when powder is added and the bullets are seated which effects chambering.

0.003 to 0.004 shoulder setback is proper for an auto-loader.

Looks like I'll have to work up some loads and mic the entire length of the case like SSL suggested to figure out where the change is occurring. That isn't going to happen until this weekend.

slimjim

just mic'd the four rounds I used to test loading. The 3 that feed without issue were 0.418 or less at the base. The one that was sticky was 0.4193. I ran it back through the FL resizing die using 3 strokes and it did not change its dimension. I guess some individual brass pieces just don't like to conform. Before I go out for the next range session, I'll mic all the brass and separate them by base dimension. I hope this is all I have to do to fix this problem. Keep the ideas coming. Heading out to the left coast. Will report more this weekend.

PaulS

If your fired cases fall in to the chamber and back out again then you may be crimping the bullet before it is seated. That causes the shoulder and possibly the body of the cartridge to expand. That will cause the brass to have to be forced into the chamber if it fits at all. If the brass is sticking after being fired then your load is too hot for your rifle.
Brass will spring back after being fired and filling the chamber. If the chamber expands then the brass over expands and sticks to the walls of the chamber as the chamber shrinks back down, this means the pressures are too high for your gun. Just because the load is less than or at the maximum spec does not mean that it is below the maximum pressure that your gun should have.
Even a round that has to be "forced" into a chamber should pretty much "fall out" of the chamber after firing.

gelandangan

slimjim wrote:

just mic'd the four rounds I used to test loading. The 3 that feed without issue were 0.418 or less at the base. The one that was sticky was 0.4193. I ran it back through the FL resizing die using 3 strokes and it did not change its dimension. .

Are you saying that your case HEAD is expanding? Shocked

That could be caused by excessive pressure!!

slimjim

PaulS wrote:

you may be crimping the bullet before it is seated.

This may be a possibility. I can check this out over the weekend. Thanks for the suggestion

PaulS wrote:

If the brass is sticking after being fired then your load is too hot for your rifle .... Even a round that has to be "forced" into a chamber should pretty much "fall out" of the chamber after firing.

Paul, I believe this is all true for a bolt action. However, is this still the case in an AR when the brass is extracted from the chamber with under pressure?

slimjim

gelandangan wrote:

Are you saying that your case HEAD is expanding?

I'm measuring the case where the base of the FL die sizes the case (at the bottom of the picture for the right case below). The die does size the brass in this location. I see this dimension change even on my .270.

That doesn't mean my loads aren't on the hot side. Another aspect to look into more. My primers aren't indicating high pressure like my .270 bolt action does. The 68 primers still have roundness on the edges.

Elvis

the primers may look ok but whats with the shiney patches?????
what sort of / how much clearance from the lands have you?? if the projectile is engaging??? maybe interfering during chambering???

slimjim

I'm learning about the marks. As the AR bolt opens, marks from the plunger and extractor can be left on the brass. I've read if pressures get extreme, brass will go into the creavaces of the bolt and then be lopped off when the bolt rotates. They are called "swipes". The ones at the 3 o'clock position looked like indentations.

SingleShotLover

Maybe you have thought of this, but have you considered a "small base" sizing die? I'm not really well versed on auto cartridges in rifles, but I do know that some designs work much better and chamber cleaner using them. Of course, the down-side is that they work the brass even more than standard dies in an area that is prone to stretching and subsequent failure anyway.

Vince

This may seem like a silly question Slim, but is the base of the shoulder "buckling" and forming a ridge when you seat the bullet and crimp? Because the seating/crimp die was not set up correctly it would force/push the neck down into the case and put a small ridge on the bottom edge of the shoulder. Chambering was between difficult and "wouldn't chamber".

I had this problem with my 30.30 some years ago and the symptoms were very similar to what you are suffering mate.

Cheers, Vince

slimjim

SingleShotLover wrote:

have you considered a "small base" sizing die?

SSL, I'm trying to find out which companies make one. RCBS does. I may just go into Cabela's and ask them if I can take several dies home and try them.

slimjim

Vince wrote:

is the base of the shoulder "buckling" and forming a ridge when you seat the bullet and crimp?

Not silly at all, mate. PaulS suggested checking for issues caused by crimp. This is the first time I've used a crimp so I could be doing it incorrectly.

I won't be surprised if I have several contributors working against me. Here is what I have to check.

- small base resizing die
- loads are too hot (read where small primers on a 6.8 don't show overpressure signs before the pressure is too high)
- may need heavier buffer/spring to delay/slow-down extraction and reduce pressure levels
- crimped incorrectly

Keep the thoughts coming. This is what I live for!