Remind me of how much crimp I need

[Tripplebeards]

I loaded up up cast in 9mm once and 10mm a couple months ago. Trying to remember the rule of thumb for crimp. If I remember with both calibers I just adjust my taper rump die down just enough to remove the flare and not really applying a crimp so my boolits do not get resized in the process? I removed the flare from my 10mm’s today. They measure around .423-.421 when I take measurements. Loaded them for my Glock 20. OAL is 1.250”. I took the OAL measurement from Lyman’s 50 th load data with 165 gr Jwords. I loaded 180 grain AMEC boolits a few months back at 1.375” and still had room to boot. Well I did the plunk test with the ones I just loaded up at 1.250”. They all drop right into my barrel but some of the rounds don’t drop freely out. Like they are stuck. They do drop out without any force and are seated in the chamber at the correct height. Guessing I need to apply a little more crimp or do you think they are good to go? I didn’t trim my brass. Could the variance in OAL could be causing it? None are longer than max. When I zoom up on my photos I can’t see any taper marks. But the flair seems to be gone. I did push a few against the table with extreme hand applied force and could not get the boolits to move so they seem to be crimped enough or there was enough neck pressure to begin with.







The last four I over flared the necks. I had to tap the press handle pretty firmly to get the brass into the crimp die. I ended up pulling one of them and tossing the brass. It didn’t pass the plunk test and would not nor seat flush. The neck edge was bent over from flaring to much and then bending over when crimping. The other three seem to look OK. The one I pulled didn’t have crimp damage on the boolit which surprised me. I’m a little paranoid since I shot some of my buddies AMEC loads yesterday and leaded my barrel because he crimped them to hard and resized the boolits. The ones I loaded I zero leading with.

[35remington]

Compare an identically treated case sans bullet to see if it falls out freely. This narrows the list of things to look at.

Examine bullets to see if they bear against rifling origin. Proper crimp is bullet diameter plus twice case mouth thickness minus a little bit.

[pworley1]

You only want to enough crimp to remove the flare. The case head spaces off the rim so you don't want much crimp. When you get enough crimp the loaded round should drop into the chamber. You can remove the barrel and test this easily.

[Tripplebeards]

That’s what I did. I removed the barrel and dropped each loaded round into the chamber. They all loosely fell in flush but some didn’t want to fall back out easy. Almost felt like the cartridges that didn’t want to release felt like they were a little sticky. They came out when I turned my barrel upside down and taped the opposite end lightly with my hand. All boolits were sized to .402 and crimped with my lee crimper without any adjustment to the crimper after the initial set up for crimping pressure. Don’t under stand why all would drop in easily but sone would act like they were sticking. The only conclusion is I didn’t trim the brass so some of the cases had a bigger flare on the bells. So some where probably crimped tighter than others?…if that makes any sense?

[35remington]

Some clearances may be less than ideal. Either it is the case or bullet and that can be isolated. Sounds like a function test is in order.

[Tripplebeards]

Thinking the same. I’ll have to getting around to order a 10mm trim die and shell plate for my RBCS trim set. Apparently 10mm is an oddball because it didn’t come with my set.

[JimB..]

You’re assuming that they are sticking because of the amount of crimp or case length, but I think it more likely some are slightly larger at the base than others. Dykem or marker up one of the cases that sticks, drop it in, spin it around, and tap it out to see where it is sticking before further adjusting your crimp, which looked fine in the first pic, or spending time trimming pistol brass.

[RJM52]

I use as much taper crimp as possible that doesn't effect headspacing to remove the possibility of bullet setback while the round is being stripped off the magazine, up the feedramp and into the chamber.

Put a round in the magazine and drop the slide on it 2-3 times measuring the LOA each time...if there is no setback you are good to go.

Bob

[Sig]

I'm with JimB. Do a marker or dykem test. I'm assuming your barrel & chamber have been thoroughly cleaned?

I had a similar problem that relates. I was getting setback on some of my 9mm J-word reloads. Turned out to be Federal & Blazer brass was the culprit. Their brass is thinner than all the other manufacturers I had on hand. I went to a Lee U die & setback went away.

What I'm getting at is maybe your sticking problem may be related to thick brass. See if it is the same head stamp that gives you grief.

[deltaenterprizes]

You only want to enough crimp to remove the flare. The case head spaces off the rim so you don't want much crimp. When you get enough crimp the loaded round should drop into the chamber. You can remove the barrel and test this easily.

9mm and 10mm cartridges headspace on the case mouth, that is why they use a taper crimp!

[Tripplebeards]

I’ll have to look…I might have mixed casings. I just grabbed a few brass casings I had laying around I already FLS and ran through my buldge buster. Maybe the heavy flair on the bell on pushed a few out of spec? I know when I loaded up nickel plated cases they all dropped in and out. I screwed up and adjusted the bell flair adjuster way to far down to the point a few of these cases were almost flat out. I would assume I buldged them a little may causing the sticking? I’ll try marking them and spinning to see what’s going on.

[Tripplebeards]

I used a black marker around the neck and base areas of the cases I was having issues with sticking. There were high spots around the case neck.IMO I was right on the border of needing a hair more crimp. I still shot them. I also had a little bit of leading in my barrel with the 7.8 Bah alloy so I am trying a couple of harder COWW alloys currently. Casted and PCd, just waiting a couple days for the alloy hardness to settle down.

[35remington]

If the rubbed spots were over the bullet bearing surface in the case that isn’t about crimp. Not sure if that is what you actually saw or not.

[Tripplebeards]

Nope, I over flared the case mouths and then never crimped them down enough. The edges of the case mouth had high spots that I could see it clear as day with the rub spots after the black marker I applied wore off.

I didn’t take a photo of it but here is zoom of some the ones that were sticking. I didn’t apply enough crimp. The high spots in the case necks edge I circled were rubbing when I rotated the case. I crimped one just a hair more and it stopped sticking and fell rough out.



Problem solved…accept that I used to soft of alloy and got leading. 40/1 is way to soft for 10mm velocities.

[35remington]

From that visual evidence I would have concluded the same thing.

[Tripplebeards]

Yes, was definitely the issue of not applying enough crimp. I loaded up more to test today. I adjusted my die where I had the crimp before and they were "sticky" again. I slowly lowered the crimp die till my dummy round easily fell in and out of my barrel chamber. I then pulled it and measured make sure I didn't sizey boolit down. Go to go!

Crimp looks alot better than the ones above. It measures .423 to .424 in spots and easily falls out of my chamber.



Checked size after I pulled it.



Stayed the same size as I originally sized it ....to .402.

[Bmi48219]

I’ve found variations in brass thickness and case length can result in variations in crimp tension. I have no control over brass thickness except by reloading only one HS of brass and hoping the manufacturer is consistent. I can control case length by trimming but for mass loading of common cartridges that isn’t happening. Again I rely on single source brass to be consistent with regard to length.
I prime off-press so I do eye-ball case length by standing a batch of cases up and looking for shorts. I also check every tenth reload as it comes off the press for OAL and crimp tension. It’s a QC compromise but best I can do.
Brass of calibers that are known for growth do get gauged for length after being sized. I really dread case trimming but for some cartridges there’s no way around it.

[Rodfac]

If I remember with both calibers I just adjust my taper rump die down just enough to remove the flare and not really applying a crimp so my boolits do not get resized in the process?

Yep that's my procedure...I may taper crimp just a hair more if I get case mouth vs feed ramp etc. interference. Best regards, Rod

[DougGuy]

Trpplebeards, you are right on it with the miking, of all the 40/10mm barrels I have throated I've never seen not one that had any .402" freebore from the factory. Just sayin. Sounds like the boolits are bumping the leade ins just enough to lodge and require a tiny bit more effort than gravity to extract, or the largest part of the boolit just in front of the case mouth is lodging just enough in the throat to not fall free without a tap on the barrel.

[Tripplebeards]

I loaded up a dozen of 16:1, 11 BH and some 12.5BH in 50/50 COWW alloy today. I had a little leading with both alloys sized at .402”. I powder coated both boolits again and didn’t size. They measured .404”. When I do the plunk test without any crimp applied some dropped right in and some stopped about 3/4’s of the way into the chamber. I did not apply any crimp what so ever but ran them up completely into my lee crimp die with the crimp adjustment plug screwed all the way up to the top. Just from running them into my crimp die without crimping was enough to push the case neck flare in and just enough that my loaded ammo drop in and out easily. I measured a couple of the necks after running them through the crimp die without crimping. They measured .423”. The boolits seemed to hold in place without any crimp applied so I will test this time without any crimp applied. I also still need to pull a boolit and make sure it didn’t size down from .404”. I also loaded them long at 1.272” along with a slower power and lighter charge. I tried 7 grain of unique last time. This time around 5.8 grain of green dot. I didn’t have any leading with .401 ACME boolits but did with my own cast HP’s sized ar .402 for some reason. I did try a hotter powder and higher charge which could have been the issue. The other issue I was worried about was maybe having a ruff bore. I swabbed the barrel today with some mothers chrome polish a good 50 to 60 times. Never got the black colored oxidation I get when polishing metal. So I tried again for about a minute and a half. The polish never turned black but was more of a darker brown. Hopefully if there were any burrs or ruff jagged cuts in my rifling they smoothed out. I’ll test the week after this coming to see if I get any leading. I’m gonna guess that some of them dropped in easily and some of them didn’t because I did not trim my cases? I’m also going to guess that the longer cases probably flared out a hair more causing them not to fit on my chamber… or maybe some of the Boolits just didn’t seat perfectly even when starting and buldged out some of the case necks? Anyways after running them through the crimp die without crimping took care of it. It seems like without cramping there’s enough pressure to keep them in place. I pushed the bullets against something hard and I couldn’t get them to move. So I would assume they’re just pushing the flare back even probably was enough pressure or the case next had enough pressure to hold the boolits in place without any type of crimp on these. I would assume it’s OK not to put any crimp on them since they are held in place tight enough? Guessing the extra .002” boolit diameter provides better neck tension.