021411 Posted October 9, 2018 Share Posted October 9, 2018 Didn’t know if I should have posted this in the Dillon section or here. This section seemed more appropriate because it’s 9mm related. I picked up an SDB and currently making tweaks to the bell and “crimp”. I’ve been using various coated 147gr bullets from respected companies and haven’t settled on one yet. The ones I have range from 0.355-0.356. Right now I’m using mixed range brass with varying thickness at the case mouth. A random grab of 10 averaged almost 0.13. The OD at the case mouth averaged 0.372. Using Dillon’s recommendation, I should be belling around 0.392. I’m belling right now at .400 and still getting some coating scraped off when I pull one to inspect. That’s one minor issue. Maybe I’m not dead vertical on setting the bullet before it seats. Any thoughts? Lastly on the “crimp”.. I’m currently at .380” after running it through the last station. Any issues in your opinion? Other than seating depth I want standardize my settings for all the coated bullets that I use. Link to comment Share on other sites More sharing options...
GrumpyOne Posted October 9, 2018 Share Posted October 9, 2018 Not all coated bullets are created equal. Some coatings are thinner than others, so I would suspect that on some, the coatings may get scraped. As for your "crimp", bullet diameter + case wall thickness x 2 = crimp. So, if your bullet is .355, and the case wall thickness is .013, .355 + .026 = .381....so you are right in the ballpark. Link to comment Share on other sites More sharing options...
021411 Posted October 9, 2018 Author Share Posted October 9, 2018 Yeah I figured on the coating. Not knocking Acme but I find the coating a bit thin. I don’t have any leading issues (yet). With that said, do you think I should set the crimp to .382 to cover everything or leave it at .381 for .355-0.356? Link to comment Share on other sites More sharing options...
IDescribe Posted October 9, 2018 Share Posted October 9, 2018 Case mouth spec for 9mm is .380. Your chamber should be reamed to accommodate that diameter right at the headspacing step. You should not go larger than that and should probably go one thousandth narrower to account for any crimp variation you get from cases of different length (because the taper crimp does taper, and different case lengths will be crimped to different degrees). I use .377 for .355 bullets, .378 for .356, and .379 for .357 when I care, but in truth, I typically use .377 for jacketed and .379 for coated and call it a day. Coating can be scraped on exit when using a kinetic bullet puller if you have crimped before pulling. The inside of the case mouth might not be perfectly smooth. If you are scraping coating on seating, the coating will build up around the bullet, on the lip of the case mouth, as the bullet is being pushed into the case. If you are not seeing coating build up on the upper lip, you have nothing to worry about. While all bullets can scrape if you don't bell enough, I have not seen any do it more than others when all else is equal, and I've loaded bunches of ACME. I'd recommend you drop back down and start over, belling a little more, a little more, until you don't see coating build up on the lip of the case mouth. Link to comment Share on other sites More sharing options...
021411 Posted October 9, 2018 Author Share Posted October 9, 2018 ^ Very informative. Thanks for the info! Link to comment Share on other sites More sharing options...
021411 Posted October 9, 2018 Author Share Posted October 9, 2018 (edited) I think I have it dialed in for now. The bell is right at 0.392-0.393" and the crimp is right at 0.3795-0.3800". I did not notice any seating issues or scraped coating in the process. The rounds dropped in my EGW chamber checker and plunked fine in all the barrels I had sitting around. I can't make any final adjustments until my X5 returns home with a Bar-Sto barrel. So far so good.. Edited October 9, 2018 by 021411 Link to comment Share on other sites More sharing options...
Hi-Power Jack Posted October 9, 2018 Share Posted October 9, 2018 Great advice from Idescribe, above As you mentioned, 021411, you won't really KNOW for sure until you test fire the rounds in your gun ... If the rounds will NOT feed, you probably have too little "crimp" or the OAL is too long. If the rounds are not accurate, you are probably "crimping" too much. Link to comment Share on other sites More sharing options...
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