SDlocal Posted April 26 Share Posted April 26 (edited) Hi, Long time loader but recently started 9mm and really looking at COAL. The conventional wisdom is that your round should plunk in and drop out freely. Makes perfect sense. Many also say that the round should twist freely as you headspace off the case mouth without engaging the rifling. It’s the spin test I question: Started to do this in a good after market P320 barrel with 124gR RMR JHP’s and ended up pretty short on the COAL not a big deal. Then I decided to look at factory 124gr Federal HST in a OEM p320 barrel. The spin test failed but clearly these rounds run fine in an OEM barrel. My thinking is the extractor holds the round back and it functionally headspace’s off the breech face thereby not engaging the rifling. with the spin test we are build in too much safety margin that results in a shorter COAL than is necessary. Am I off on this reasoning? Edited April 26 by SDlocal Link to comment Share on other sites More sharing options...
Sarge Posted April 26 Share Posted April 26 3 minutes ago, SDlocal said: Hi, Long time loader but recently started 9mm and really looking at COAL. The conventional wisdom is that your round should plunk in and drop out freely. Makes perfect sense. Many also say that the round should twist freely as you headspace off the case mouth without engaging the rifling. It’s the spin test I question: Started to do this in a good after market P320 barrel with 124gR RMR JHP’s and ended up pretty short on the COAL not a big deal. Then I decided to look at factory 124gr Federal HST in a OEM p320 barrel. The spin test failed but clearly these rounds run fine in an OEM barrel. My thinking is the extractor holds the round back and it functionally headspace’s off the breech face thereby not engaging the rifling. with the spin test we are build in too much safety margin that results in a shorter COAL than is necessary. Am I off on this reasoning? Why did the HST fail? Did you check to see if the round was hitting the rifling? Or are they just a little fat? There is a big difference. If they are not too long but just a little fat there will be enough friction to keep them from spinning. FWIW I only drop for the plunk test. I don't spin unless it seems there may be a length issue. Link to comment Share on other sites More sharing options...
ysrracer Posted April 26 Share Posted April 26 I always plunk and spin. Link to comment Share on other sites More sharing options...
OnePivot Posted April 27 Share Posted April 27 If it's plunking smoothly and easily it should also spin pretty easily. While yes it's technically headspacing off the extractor, that's not really how you want ammo fitting in a barrel, and passing the plunk test definitely doesn't add too much safety margin. If some brass has a thinner or thicker rim, you still want that ammo cleanly fitting the chamber. How short are you needing to load them? Link to comment Share on other sites More sharing options...
SDlocal Posted April 27 Author Share Posted April 27 (edited) 28 minutes ago, OnePivot said: If it's plunking smoothly and easily it should also spin pretty easily. While yes it's technically headspacing off the extractor, that's not really how you want ammo fitting in a barrel, and passing the plunk test definitely doesn't add too much safety margin. If some brass has a thinner or thicker rim, you still want that ammo cleanly fitting the chamber. How short are you needing to load them? 1.055 thinking about getting a throat reamer. Edited April 27 by SDlocal Link to comment Share on other sites More sharing options...
lgh Posted April 27 Share Posted April 27 I've never spun. Just plunk and dump. Larry Link to comment Share on other sites More sharing options...
Yeti Posted April 27 Share Posted April 27 I used to plunk and spin and I have caught some crimp or bullet oddities with short throated barrels. IMO, 9mm is a bit trickier than 45 and 40 due to taper and some manufacturers using a match chamber with old tooling. I think it is less of an issue now than it used to be. IE: CZ and SA (XD line) seemed to use minimal leade and freebore. Now, if it fits in the Hundo I dump it all into the ammo can. Link to comment Share on other sites More sharing options...
dmshozer1 Posted April 28 Share Posted April 28 How can you plunk and spin with a PCC? Link to comment Share on other sites More sharing options...
CocoBolo Posted April 28 Share Posted April 28 It is a bit more complicated than that. You could look up OAL in the Reloading Manual, but pay attention to the details. You probably don't have a Norma bullet. Lets stick with 9 mm, the worst of the worst when it comes to jams. There are probably a few dozen different bullets out there all with a different OGIVE. I always use my CZ Shadow when loading 9 minor because it has the shortest throat. The round might drop check fine but the CZ won't eat it. To figure it out I just size a case and then put a bullet in it leaving it super long, and then put it in the CZ. When it comes out I measure it and then subtract .009 load another dummy that length and try another fit. When I think I have it, I load up 5 or 6 shove them into a mag and dry cyle them. Among 124/5gr RN bullets the OAL I use varies from 1.120 to 1.145 depending on which MFG it came from. JHP are usually longer. (note this applies to minor only and anything 1.10 or shorter should raise concern). (add in checking for contact scratches on bullet to the above). You could paint them with dykem as well. When it fits the CZ it will run in all my guns. That said my PCC will not eat JHP's reliably it likes RN. When plunking it has to drop all the way in and fall out freely. If it falls all the way in but the rim doesn't it is a fat girl do yourself a favor and put it in the reject bucket. I've never given them the spin test. All plunkers are not created equally, the Dillon is not as tight as Wilson plunker, but both work well. Link to comment Share on other sites More sharing options...
SDlocal Posted April 29 Author Share Posted April 29 The Norsso bull barrel I am working with appears to have almost no freebore. The difference in what spins in an OEM sig barrel and the Norsso barrel is 0.06. The COAL for the RMR 124gr HP is 1.05 in the Norsso. I can load a little longer at 1.08 and it runs but it won’t spin freely. Link to comment Share on other sites More sharing options...
shred Posted April 29 Share Posted April 29 The "spin" is to make sure you aren't plunking into the rifling leade and really are hitting the chamber mouth. It's not uncommon for CIP-cut chambers to need long-bearing-surface bullets like truncated cones and HAPs to be loaded down around 1.05" Link to comment Share on other sites More sharing options...
SDlocal Posted April 29 Author Share Posted April 29 (edited) 7 hours ago, shred said: The "spin" is to make sure you aren't plunking into the rifling leade and really are hitting the chamber mouth. It's not uncommon for CIP-cut chambers to need long-bearing-surface bullets like truncated cones and HAPs to be loaded down around 1.05" What is CIP cut? Never mind. Search is my friend Edited April 29 by SDlocal Link to comment Share on other sites More sharing options...
OnePivot Posted April 30 Share Posted April 30 On 4/28/2024 at 12:16 PM, dmshozer1 said: How can you plunk and spin with a PCC? I plunked my PCC barrel when I bought it and ended up reaming it before installing. I would have ran into weird problems, I'm glad I checked. Link to comment Share on other sites More sharing options...
dmshozer1 Posted April 30 Share Posted April 30 30 minutes ago, OnePivot said: I plunked my PCC barrel when I bought it and ended up reaming it before installing. I would have ran into weird problems, I'm glad I checked. I try different profile bullets and weights on a regular basis so that does not work for me.To avoid the problem I also reamed my barrels to the max. Link to comment Share on other sites More sharing options...
ysrracer Posted April 30 Share Posted April 30 On 4/28/2024 at 12:16 PM, dmshozer1 said: How can you plunk and spin with a PCC? Pencil, blue painters tape. Link to comment Share on other sites More sharing options...
Joe4d Posted April 30 Share Posted April 30 On 4/28/2024 at 3:16 PM, dmshozer1 said: How can you plunk and spin with a PCC? lock bolt to rear lower barrel, drop in round,, you will hear the sound of the brass hitting, chamber vs bullet hitting. . Tilt barrel up, bullet should fall out. I mean I usually figure out the max OAL for any given firearm and bullet combo and just load to that.. FOr a major match, Id pull the barrel from my gun and just drop all the rounds and mark them for match use. If I had a gun I couldnt easily pull barrel and do that,, Id probably just hand cycle them through magazines.. Link to comment Share on other sites More sharing options...
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