StuBeef302 Posted November 6, 2020 Share Posted November 6, 2020 Anyone have any experience in opening up a 300BLK primer pocket to take a large rifle primer? I can't find any small rifle primers AT ALL. and I really want to throw some 300BLK downrange. I have plenty of large rifle primers. I have a lathe to make the primer pocket perfect size and depth, I also have access to CAD and can do an analysis of the strength of the altered brass, but in general, the chamber and bolt face take all the load. I'd start low on powder and work up looking for pressure sign, so I'm not trying to be stupid, but any thoughts would be appreciated. Link to comment Share on other sites More sharing options...
Chills1994 Posted November 8, 2020 Share Posted November 8, 2020 No experience... but I have to wonder.... 7.62X39 takes large primers right? getting a 7.62X39 bolt, barrel and mags might be easier than machining brass for primers.... that said, Hornady does make primer crimp removal tools (bits) that can be chucked in a drill. I don’t know if a large Hornady reamer would actually enlarge a small primer pocket. Link to comment Share on other sites More sharing options...
StuBeef302 Posted November 8, 2020 Author Share Posted November 8, 2020 Thanks Chills, I wasn’t planning to mod a ton, maybe 100 rounds. Good point about 7.62x39, I just am all setup for reloading the 300BLK and I use it for hunting and home defense so I just wanted the trigger time on that particular gun. And reloading is a fun past time. Just those darn small primers are unobtainable. (Except from gougers on GunBroker. Even though that makes $ and time sense over modded cases too ) I’ll give a batch of 10 a go and see how they turn out. Thx. Link to comment Share on other sites More sharing options...
Chills1994 Posted November 8, 2020 Share Posted November 8, 2020 Whoops! with respect to my comment up above... that’s ASSuming you could find any factory 7.62X39 ammo to start out with or once fired brass. which is probably just as UNobtanium as small rifle/small pistol primers now. Link to comment Share on other sites More sharing options...
bigedp51 Posted November 11, 2020 Share Posted November 11, 2020 (edited) If you are not loading "HOT" you could try using small pistol magnum primers. For the AR15 it is recommended to use primers with a cup thickness of .025 to help prevent slam fires. "BUT" many reloaders use the CCI 400 primers without ill effect. CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS http://www.sksboards.com/smf/index.php?topic=56422.0 CCI 400 -thin .020" cup, not recommended for AR15 use by CCI/Speer. Good for .22 Hornet, .30 Carbine. See Note 1 at the bottom of the page NOTE 1: According to Speer/CCI Technical Services - Both the CCI 550 Small Pistol Magnum and CCI 400 Small Rifle primers are identical in size. Both primers use the same cup metal and share the same cup thickness. Both primers use the same primer compound formula and same amount of primer compound. They can be used interchangeably. Edited November 11, 2020 by bigedp51 Link to comment Share on other sites More sharing options...
dannyd Posted November 11, 2020 Share Posted November 11, 2020 (edited) Here's what we know so far, it's easy to do with a Rcbs trim mate using Lyman large primer tool and a Rcbs large primer carbide tool. Going to do ten and just shoot the cartridge with primer and TB plugging the end. Next will be with wax bullets. Start with the Lyman first (one on the right) MY TEST will be done with a Bolt GUN not an AR. Edited November 12, 2020 by dannyd Link to comment Share on other sites More sharing options...
StuBeef302 Posted November 12, 2020 Author Share Posted November 12, 2020 Sweet, thanks Danny D, I was going to put them on a lathe using a forming die as a collet, but I’ve been distracted with some press mount changes. Putter with this... putter with that... Link to comment Share on other sites More sharing options...
StuBeef302 Posted November 12, 2020 Author Share Posted November 12, 2020 I did model a 5.56 case up in CAD to run a pressure simulation, but quickly realized that there is significant head thickness variation from manufacturer to manufacturer. So much that some thinner ones with small primer pockets yield more than thicker ones with large primer pockets. So as far as head strength, that shouldn’t be a significant issue when using thick brass. Link to comment Share on other sites More sharing options...
StuBeef302 Posted November 12, 2020 Author Share Posted November 12, 2020 One question dannyD, how’d you get the depth right with that RCBS rig? (Large pockets being deeper than small pockets) Link to comment Share on other sites More sharing options...
dannyd Posted November 12, 2020 Share Posted November 12, 2020 3 minutes ago, StuBeef302 said: One question dannyD, how’d you get the depth right with that RCBS rig? (Large pockets being deeper than small pockets) It comes from Rcbs ready to go at the right depth. Link to comment Share on other sites More sharing options...
StuBeef302 Posted November 12, 2020 Author Share Posted November 12, 2020 Oops, saw all the shavings on the right tool, didn’t notice the depth ring on the left tool. Nice. Link to comment Share on other sites More sharing options...
Chillywig Posted December 18, 2020 Share Posted December 18, 2020 Any updates on this LR primer mod? Link to comment Share on other sites More sharing options...
dannyd Posted December 18, 2020 Share Posted December 18, 2020 Haven't got to the range to test yet. Link to comment Share on other sites More sharing options...
TheHooter Posted January 31, 2021 Share Posted January 31, 2021 How about now????? Link to comment Share on other sites More sharing options...
Sigarmsp226 Posted February 7, 2021 Share Posted February 7, 2021 Thinking out loud on this idea...For wax bullets you may be fine but I would be a little concerned that your idea “could” reduce the thickness of the surrounding primer pocket brass thus possibly causing the rear primer area of the case to rupture if you intended to try this with real 1000 fsp loads.... Please know - I do not claim to know or understand the difference in the amount of material that surrounds the primer pocket but I would think removing this much brass could prove to “weaken” the structure of the brass case in this area... Interested to read your trial results with hopes that you and dis-prove my aforementioned concern.... Link to comment Share on other sites More sharing options...
StuBeef302 Posted February 7, 2021 Author Share Posted February 7, 2021 Hi p226, I did mention above that I analyzed that already On 11/11/2020 at 7:47 PM, StuBeef302 said: I did model a 5.56 case up in CAD to run a pressure simulation, but quickly realized that there is significant head thickness variation from manufacturer to manufacturer. So much that some thinner ones with small primer pockets yield more than thicker ones with large primer pockets. So as far as head strength, that shouldn’t be a significant issue when using thick brass. But! It’s been the pit of winter for a couple months where I live, but we should have a few above freezing days in a row, I’ll get out and post some pics. Link to comment Share on other sites More sharing options...
dannyd Posted February 7, 2021 Share Posted February 7, 2021 (edited) 5 hours ago, Sigarmsp226 said: Thinking out loud on this idea...For wax bullets you may be fine but I would be a little concerned that your idea “could” reduce the thickness of the surrounding primer pocket brass thus possibly causing the rear primer area of the case to rupture if you intended to try this with real 1000 fsp loads.... Please know - I do not claim to know or understand the difference in the amount of material that surrounds the primer pocket but I would think removing this much brass could prove to “weaken” the structure of the brass case in this area... Interested to read your trial results with hopes that you and dis-prove my aforementioned concern.... I does weaken the brass, so the number of times it can be reloaded may go way down. Haven't tried them yet also working on large rifle in 357 magnum cases. In 1935: 357 magnum used large primers, so I will be checking it out. Edited February 7, 2021 by dannyd Link to comment Share on other sites More sharing options...
Sigarmsp226 Posted February 7, 2021 Share Posted February 7, 2021 (edited) Thanks Danny for responding. Again do not claim to know what I am talking about. Was really asking more than stating I knew...Mark Stu - Thanks Sir for your response. The first time I read your post I was thinking “head” being the projectile end of the brass. After re-reading your post I realize your post addressed my post thoughts. Thanks for not slamming me for my mis-post.... Edited February 7, 2021 by Sigarmsp226 Link to comment Share on other sites More sharing options...
StuBeef302 Posted February 7, 2021 Author Share Posted February 7, 2021 My Bad, you are correct Danny, it definitely weakens the case head. My only point was that thicker head brass with a large primer pocket will not be as weak as thin headed brass with a small pocket. I’ll post some info. Link to comment Share on other sites More sharing options...
dannyd Posted February 21, 2021 Share Posted February 21, 2021 Got the 357 magnum test with large rifle primers out of the way and will start working on the 300 blackout again soon. Link to comment Share on other sites More sharing options...
StuBeef302 Posted February 22, 2021 Author Share Posted February 22, 2021 Here's where I'm at folks... First, setup in lathe with carbide tool: Link to comment Share on other sites More sharing options...
StuBeef302 Posted February 22, 2021 Author Share Posted February 22, 2021 Compare the batch of large pockets to the small pockets... Link to comment Share on other sites More sharing options...
StuBeef302 Posted February 22, 2021 Author Share Posted February 22, 2021 Finally primed... Link to comment Share on other sites More sharing options...
Steve RA Posted February 22, 2021 Share Posted February 22, 2021 I think it'll work fine. Link to comment Share on other sites More sharing options...
StuBeef302 Posted February 22, 2021 Author Share Posted February 22, 2021 I'm going to use Hodgdon CFEBLK because the pressures are significantly lower than anything else for this cartridge. 150gr FMJBT. I'll let y'all know... Link to comment Share on other sites More sharing options...
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