I've started load development for the 300BLK AR I've put together for 3 gun. It has an 18" barrel. I was chronoing some test rds today. I usually load 10 rds of each bullet wt/powder charge so that I can get an average. I had one bullet each of two test loads that made major PF. One was a 155gr lapua with 16.5 gr of LIL GUN powder, the other was a 175gr SMK with 14.5gr of LIL GUN powder. in both cases, only one out of the 10 I loaded made PF so I would need to increase the charge in order to be sure that I would be making major. The problem that I have encountered is that although I saw no signs of excessive pressure in the back of the cases, no blown primers, no problems with extraction or heavy extractor marks, I had several cases that split in the front where the LC brass was formed to fit the .30 cal bullets. I was hoping that someone might be able to give me some advice/guidance in this matter. Could anyone tell me if the split cases are likely caused by excessive pressure? could it be that the cases need to be annealed (new Lake City brass that I cut down and formed. I don't have a lot of experience in this and was thinking that if the problem was being caused by excessive pressure the two cases that had the highest MV should have split, but that was not the case. There doesn't seem to be any correlation between the ones that made the highest FPS and the ones that split. Any input or advice is much appreciated.
300BLK
- Thread starter Jgun
- Start date
Re: 300BLK
I forgot to mention, I have adjusted the COL on each of my test rds in order to have approx. .030" free bore before the bullet ogive picks up the lead. I was wondering if this could possibly have anything to do with the cases splitting
I forgot to mention, I have adjusted the COL on each of my test rds in order to have approx. .030" free bore before the bullet ogive picks up the lead. I was wondering if this could possibly have anything to do with the cases splitting
Re: 300BLK
Check out
http://www.silencertalk.com/forum/viewforum.php?f=128&sid=8536bfd3563a9ea61e52a9ee5e5a3ef5
Tons of info there.
Check out
http://www.silencertalk.com/forum/viewforum.php?f=128&sid=8536bfd3563a9ea61e52a9ee5e5a3ef5
Tons of info there.
Re: 300BLK
Anneal before, during and after forming. Expand in several steps if possible. That is a lot of working of the brass. After all, it was formed straight, necked to the .223, fired, then stretched out almost straight again. JMHO
Anneal before, during and after forming. Expand in several steps if possible. That is a lot of working of the brass. After all, it was formed straight, necked to the .223, fired, then stretched out almost straight again. JMHO
Re: 300BLK
I haven't done any case annealing before, so although it looks like I may have to do it in order use cut down 5.56 brass to load 300 to make major PF. I'm thinking that before I start to get set up and teach myself how to properly anneal brass, I'm going to see if I can get some new factory 300BLK cases, and see if the problem goes away. If so I'll know it's a brass problem instead of a pressure problem, and if so, THEN, I'll know that I have to do it to use the Lake City brass. I'm kind of suprised, because, when forming 300 from .223, you cut the case off behind the shoulder and only have to form it down from.355" to around .330" which doesn't seem all that drastic to me.
I haven't done any case annealing before, so although it looks like I may have to do it in order use cut down 5.56 brass to load 300 to make major PF. I'm thinking that before I start to get set up and teach myself how to properly anneal brass, I'm going to see if I can get some new factory 300BLK cases, and see if the problem goes away. If so I'll know it's a brass problem instead of a pressure problem, and if so, THEN, I'll know that I have to do it to use the Lake City brass. I'm kind of suprised, because, when forming 300 from .223, you cut the case off behind the shoulder and only have to form it down from.355" to around .330" which doesn't seem all that drastic to me.
Re: 300BLK
One of my friends, who also loads for 300BLK, made a good point, about the fact that, when using the cut down LC brass to make 300, I'm cutting the annealed neck off of the brass. He also suggested that I consider neck turning the cut down brass because the case wall is thicker in my newly formed neck than it was at the original .223 neck. Not sure how much the neck wall thickness contributes to the problem, but bottom line, I neeed to purchase some new factory 300BLK brass. Does anyone know where it's in stock right now?
One of my friends, who also loads for 300BLK, made a good point, about the fact that, when using the cut down LC brass to make 300, I'm cutting the annealed neck off of the brass. He also suggested that I consider neck turning the cut down brass because the case wall is thicker in my newly formed neck than it was at the original .223 neck. Not sure how much the neck wall thickness contributes to the problem, but bottom line, I neeed to purchase some new factory 300BLK brass. Does anyone know where it's in stock right now?
Re: 300BLK
I do not anneal and have not had any problems. Granted I only tried to make major a few times just to see if I could.
How are you forming the brass?
I am using a Dillon trimmer and CH4D die.
I have not seen any OEM brass for sale yet.
Lots on info at http://www.quarterbore.net/forums/forumdisplay.php?f=27
I do not anneal and have not had any problems. Granted I only tried to make major a few times just to see if I could.
How are you forming the brass?
I am using a Dillon trimmer and CH4D die.
I have not seen any OEM brass for sale yet.
Lots on info at http://www.quarterbore.net/forums/forumdisplay.php?f=27
Re: 300BLK
I bought new unfired Lake City 5.56 brass from Midway, chucked it into a Hardenge (collet lathe) and cut them all off to finished case length, I then used the Forster dies to do the 1 step forming fl sizing. I satrted out with 145gr bt bullets loaded to 2.1" and those rds worked well and had no case splitting or pressure signs but didn't make major, the next time out along with the new heavier bullets I bumped the 145's up a grain and still have no case problems with them, the case problems are all with the heavier bullets that are seated deeper in the case. In theory that sounds good, but along with the case splitting I'm not getting any symptoms of excess pressure in the back of the case or the primer so I'm thinking to try the other brass to see what happens. Can you tell me what load/components you used to make major? And did you get an average oof several rds for major or just one or two rds?
I bought new unfired Lake City 5.56 brass from Midway, chucked it into a Hardenge (collet lathe) and cut them all off to finished case length, I then used the Forster dies to do the 1 step forming fl sizing. I satrted out with 145gr bt bullets loaded to 2.1" and those rds worked well and had no case splitting or pressure signs but didn't make major, the next time out along with the new heavier bullets I bumped the 145's up a grain and still have no case problems with them, the case problems are all with the heavier bullets that are seated deeper in the case. In theory that sounds good, but along with the case splitting I'm not getting any symptoms of excess pressure in the back of the case or the primer so I'm thinking to try the other brass to see what happens. Can you tell me what load/components you used to make major? And did you get an average oof several rds for major or just one or two rds?
Re: 300BLK
My experience loading the 300 Whisper is limited (aka still inside my first 100 laods) but I have a couple of thoughts. My LC 09 brass is discolored from the annealing process well to the rear of the shoulder formed for Whisper/BLK. I realize that the annealing will diminish as you go rearward, so maybe it is too hard for even the modest forming.
One possibility that would be very easy to rule out is oversize chamber dimensions, particularly in the neck area. Can you compare neck diameter from your fired casings to that of your loaded rounds? I'd think you would want 0.006" to maybe 0.008" neck clearance. If you're seeing dramatically more expansion, you could have a discussion with whomever cut the chamber.
Good luck and keep us posted on what you find.
Randy
My experience loading the 300 Whisper is limited (aka still inside my first 100 laods) but I have a couple of thoughts. My LC 09 brass is discolored from the annealing process well to the rear of the shoulder formed for Whisper/BLK. I realize that the annealing will diminish as you go rearward, so maybe it is too hard for even the modest forming.
One possibility that would be very easy to rule out is oversize chamber dimensions, particularly in the neck area. Can you compare neck diameter from your fired casings to that of your loaded rounds? I'd think you would want 0.006" to maybe 0.008" neck clearance. If you're seeing dramatically more expansion, you could have a discussion with whomever cut the chamber.
Good luck and keep us posted on what you find.
Randy
Re: 300BLK
Thanks for the idea RT, It hadn't occured to me to check the chamber. I haven't measured the actual chamber yet, but when I measure a few of the fired,split cases, I get an average measurement of .337" in the neck area with the largest one I measured being .338". All of the fired cases that didn't split, measure the same as the split cases. The loaded, unfired rds that I have, all measure .332" Would you gather from those measurements that my chamber is to spec, and not likely contributing to my problem?
Thanks for the idea RT, It hadn't occured to me to check the chamber. I haven't measured the actual chamber yet, but when I measure a few of the fired,split cases, I get an average measurement of .337" in the neck area with the largest one I measured being .338". All of the fired cases that didn't split, measure the same as the split cases. The loaded, unfired rds that I have, all measure .332" Would you gather from those measurements that my chamber is to spec, and not likely contributing to my problem?
Re: 300BLK
Here are a couple things to be aware of:
- 300 BLK chamber specs allow for the thicker brass in the neck area of modified 5.56 NATO brass.
(If your chamber is 221/300 Fireball or 300 Whisper, neck size can be a significant issue.)
- The 300 BLK chamber specs also allow for higher pressures than 221/300 Fireball or 300 Whisper.
IMHO
The splitting neck issue would indicate either brittle brass or excessive chamber size.
Neck splitting is not a common occurrence with the 300 BLK.
I have not ever seen split necks be an indication of excessive pressure in any cartridge for that matter...
The first thing that I would recommend is to check your chamber by measuring your once fired brass.
(You have already done this and your numbers don't seem to be out of the ordinary.)
Who made your barrel and what chamber does it have?
I would also try some different brass to rule that out.
It should be easy enough to pick up some free once fired 5.56 NATO brass and give it a try.
My gut says that it is the brass that you got from Midway USA...
Here are a couple things to be aware of:
- 300 BLK chamber specs allow for the thicker brass in the neck area of modified 5.56 NATO brass.
(If your chamber is 221/300 Fireball or 300 Whisper, neck size can be a significant issue.)
- The 300 BLK chamber specs also allow for higher pressures than 221/300 Fireball or 300 Whisper.
IMHO
The splitting neck issue would indicate either brittle brass or excessive chamber size.
Neck splitting is not a common occurrence with the 300 BLK.
I have not ever seen split necks be an indication of excessive pressure in any cartridge for that matter...
The first thing that I would recommend is to check your chamber by measuring your once fired brass.
(You have already done this and your numbers don't seem to be out of the ordinary.)
Who made your barrel and what chamber does it have?
I would also try some different brass to rule that out.
It should be easy enough to pick up some free once fired 5.56 NATO brass and give it a try.
My gut says that it is the brass that you got from Midway USA...
Re: 300BLK
Thanks for the input. I hope your right about it being brass related and not pressure related, because I still need to bump up my loads a little more to make major power factor for 3 gun. I had my barrel made as a 300 BLK and not a 300 whisper. It was made by Delta Arms. As previously stated, the brass I used was new mfg Lake City 5.56 brass that I ordered from Midway. I have some Remington 300 BLK brass, and some annealed 5.56 brass on their way to me in the mail from friends, that I plan to try out as soon as they get here. I will post the results as soon as I have tried out those cases.
Thanks for the input. I hope your right about it being brass related and not pressure related, because I still need to bump up my loads a little more to make major power factor for 3 gun. I had my barrel made as a 300 BLK and not a 300 whisper. It was made by Delta Arms. As previously stated, the brass I used was new mfg Lake City 5.56 brass that I ordered from Midway. I have some Remington 300 BLK brass, and some annealed 5.56 brass on their way to me in the mail from friends, that I plan to try out as soon as they get here. I will post the results as soon as I have tried out those cases.
Re: 300BLK
Aaron @ Delta Arms is GTG.
You will be happy with his products.
You will notice pressure indicators on the case heads first.
They are normally ejector marks & flat primers.
The bulk LC brass like you purchased from Midway is typically either production over runs or a LOT that did not meet MILSPEC criteria.
Brass / cartridges that do not meet MILSPEC are still within spec for commercial loadings and are sold as "XM" or "XM-PD" (PD indicates loose pack / bulk pack) , and are often marked "Not for Combat Use" or "Not for Duty Use".
Reference Link
It is possible in your case that the brass may be "Out of Spec" regarding annealing or thickness.
This is a pretty big assertion on my part, but with the information that you provided, it is the only likely source.
I'm about 85% sure that your issue is that LC brass.
Please let us know what you find out once you have a chance to try our some different brass.
Shoot me a PM if you can't get any other pieces in a reasonable amount of time and I'll send you 20 known good pieces of 300 BLK brass.
(Not 300 BLK head stamp, but converted 5.56 NATO brass that has been fire formed using subsonic loads.)
Aaron @ Delta Arms is GTG.
You will be happy with his products.
You will notice pressure indicators on the case heads first.
They are normally ejector marks & flat primers.
The bulk LC brass like you purchased from Midway is typically either production over runs or a LOT that did not meet MILSPEC criteria.
Brass / cartridges that do not meet MILSPEC are still within spec for commercial loadings and are sold as "XM" or "XM-PD" (PD indicates loose pack / bulk pack) , and are often marked "Not for Combat Use" or "Not for Duty Use".
Reference Link
It is possible in your case that the brass may be "Out of Spec" regarding annealing or thickness.
This is a pretty big assertion on my part, but with the information that you provided, it is the only likely source.
I'm about 85% sure that your issue is that LC brass.
Please let us know what you find out once you have a chance to try our some different brass.
Shoot me a PM if you can't get any other pieces in a reasonable amount of time and I'll send you 20 known good pieces of 300 BLK brass.
(Not 300 BLK head stamp, but converted 5.56 NATO brass that has been fire formed using subsonic loads.)
Re: 300BLK
I have finally gotten back to the range to test/chrono the 300BLK loads I made using the brass donated by friends and members, thanks all, repacement brass will be sent to you shortly. The case splitting I was getting with the LC brass I bought from Midway and formed, has disappered, even with my new hotter loads. I can only assume that as suggested by Dr Phil, I got a bad batch of brass from Midway. I have been able to make major power factor from my 18" barrel, using 145, 155, and 175 gr bullets, I got 2400 fps with the 145's, 2200 with the 155's and 2000 with the 175 SMK's all using LIL GUN powder, The only thing I saw was that the 175's might have been pushing the pressure, the extractor marks were more pronounced than with the other bullets, and they didn't cycle 100%. I plan to reduce the load a little and do further testing. Thanks to all that helped with advice and brass.
I have finally gotten back to the range to test/chrono the 300BLK loads I made using the brass donated by friends and members, thanks all, repacement brass will be sent to you shortly. The case splitting I was getting with the LC brass I bought from Midway and formed, has disappered, even with my new hotter loads. I can only assume that as suggested by Dr Phil, I got a bad batch of brass from Midway. I have been able to make major power factor from my 18" barrel, using 145, 155, and 175 gr bullets, I got 2400 fps with the 145's, 2200 with the 155's and 2000 with the 175 SMK's all using LIL GUN powder, The only thing I saw was that the 175's might have been pushing the pressure, the extractor marks were more pronounced than with the other bullets, and they didn't cycle 100%. I plan to reduce the load a little and do further testing. Thanks to all that helped with advice and brass.
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