Need 300 Blackout HELP!

[wool1]

I am in serious need of help on a 300 blackout load. I have two molds.....a RCBS 2-Cavity Bullet Mold 7.62mm-130-SPL 7.62 mm GC, and a NOE 311 247Gr. FN GC. Still need loads for these two molds.

The problem is I am scared to try them.....as the first 3 loads with j-word bullets have blown primers (thats putting it mildly)

The load I was thinking would be a no brainer was Hodgdon load of a 130 gr bullet over 17.9 gr of 296/H110. Tried both powders. (this load actually blew the bottom of my mag out) Seated with an OAL of 2.165. Loaded in mag and chambered well. I have read many times not to reduce 296/H110 because of preasure issues. Don't know which way to go with this.

I also tried a load with LilGun again at starting load with the same results.

The brass is reformed and annealed LC brass I ordered from GRUMPA here on CB. Using Winchester small rifle primers. I'm at a loss, any help would be appreciated.

[Jupiter7]

Never blown a primer. And where did you get your data? No offense, but when beating a new path, it's best to tread slowly. Maybe reduce that load a bit down to 16grs h110 and see what your at. There's not much room in that case and very little variance from min to max loads. Also, no offense to grumpa, but did you resize this brass and/or check it against the saami drawing?

Also, assuming an AR15, how's the gun set up? Did you build it it? Did you check headspace?


Do you have a manual that your going by? Did you visit hogdon's sight?

Max load of 110 with vmax 110gr bullet is about 20grs.

[wool1]

None taken....I full length resized, and measured case for specs. Took the data off of Hogdon's site.....17.9 gr start load with 130 gr bullet. Ar-15 Upper came assembled from SOTA arms.

[Jupiter7]

Just re-read your post. What jacketed loads blew primers? I've tested the limits of the cartridge with different designs and weights using jackets data as a guide, only overpressure I've seen is flattened primers, pins swipes, cratering and ejector marks. I've used h110 and lots of lil gun. I also shoot the accurate 245gr 31-240e a bunch. And have downloaded h110 with no issues other than function as it lacks pressure at the gas port to cycle reliably.

[garym1a2]

Double check your scale, use Mag or military primers. I had a lot of gas leakage with very old CCI primers.
Make sure primers don't seat too easy.

[wool1]

Double check your scale, use Mag or military primers. I had a lot of gas leakage with very old CCI primers.
Make sure primers don't seat too easy.

The primers did seat easier than I would liked them to. In process of checking case volume.....thinking maybe internal volume is lower with LC brass, increasing preasures.

[Jupiter7]

Brass thickness is negligible of converted brass. I've chrono'd mixed converted brass, no noticeable difference. The thicker brass cases usually won't chamber w/o neck turning. I don't convert any foreign manufactured brass like S&B, lake city brass is about the best I've found along with RP headstamped brass.

Are you hand priming?

[Mike Hughes]

I have popped out a few primers with lil gun. Reloader 7 seems to be a excellent powder for cast in the 300 blk. 17 grains is pretty much a case full and has never shown any signs of pressure. I have been shooting the Lee 312-155. It has also been the most accurate load I have found

[wool1]

Yes....hand primed, digital scale (calibrated)

[Artful]

Wow that's more of a faster burning powder than I use of 680 for the little pills! Wonder how they came to that amount of 296/H110 (a powder I no longer use due it's issues with temp sensitivity).

https://travis-furry.squarespace.com/300-aac-blackout
showing 14-16 grains 296/H110 with Nosler 140 grain J-word

I usually use 5744 or 680/1680 powder
http://www.accuratepowder.com/wp-content/uploads/2010/09/300_ACC_Blackout_Data.pdf

[Jjed]

Have the same problem with h110/296 in a 16 inch carbine barrel, the loading data for the carbine in 300 bo is wrong imho blowing out primers and the case looks like a belted round after i get it out of the barrel!. loaded some 110 gr fmj and 130 gr sp with 4227 a slower powder and they worked fine as far as cycling the action go's I still have to see how they will shoot ( when i get time) I think h110/296 is too fast for the longer gas tube. hope to get this figured out soon so I can load some cast.

[nhrifle]

Sorry in advance if I missed any answers to my questions above.

Those loads may be a touch on the hot side, but it is not explaining to me why you are blowing so many primers, or why the bottom of your mag was ejected. How old was the brass you used, do you know how many times they were loaded? If they were military cases, how were the crimps removed and was it possible the primer pockets were swaged/reamed too much (will enlarge the pockets).

As to the rifle, is it carbine or pistol length gas system? Do you have an adjustable gas block? What is your gas port hole diameter? I would definitely suggest you check headspace as well as extractor function.

I have loaded some fairly stout loads through my 300 AAC and have yet to see anything besides some flattened primers and marking of the case head and rim. Something is just plain not right in your setup and I would start looking at mechanical reasons for these failures after you do a bit more tweaking with your loads. Don't take much of the current data at face value. Start several grains below their starting load and work up until you get reliable function, then load up slowly until you start seeing sharp edges on the corners of the primers and then back off a half grain.

[wool1]

The brass (to my knowledge) is once fired. I am wondering about the primer pockets being a tiny bit over sized. It is a 16" barrel with carbine length gas system. without adjustable block. It's acting like something is right on the limit of specs.

The loads from Hodgdon site..

130 GR. SPR HP Winchester 296 .308" 2.005" 17.9 2056 40,400 CUP 19.0 2155 48,400 CUP
130 GR. SPR HP Hodgdon H110 .308" 2.005" 17.9 2056 40,400 CUP 19.0 2155 48,400 CUP


This data is quite stout compaired to the Nosler data Artful linked above. I am going to attempt to load some down at the 14 gr level in the morning and run through the chrono to see how fast they are being thrown. H110/296 always makes me a bit on the nervous side....guess I screwed the pooch on this one. Thanks for helping me figure this out guys.

[nhrifle]

I just checked their site and yup, that's the data they list for that bullet. 19 gr. of H110 is about my max load for a 110 gr. bullet in my Blackout. Beyond that I start to get pressure signs. H110 loaded to 14 gr. should be safe, but might be a light load. I'd load a few cartridges in steps from 14 to 16 grains and see where that takes you. And if all of your brass isn't allowing the primers to be seated securely, I would scrap the batch and get some fresh stuff from one of the members here. Also, pay attention to the brand of brass. R-P brass, either factory 300 AAC or reformed 5.56 has had reports of loose primer pockets. All the cases I have reformed have been WCC, LC, or Winchester commercial and I have not had any primer failures.

[blikseme300]

I have popped out a few primers with lil gun. Reloader 7 seems to be a excellent powder for cast in the 300 blk. 17 grains is pretty much a case full and has never shown any signs of pressure. I have been shooting the Lee 312-155. It has also been the most accurate load I have found

This is the combination I use with great results in my 2 AR-15's.

[bikerbeans]

I have converted about a 1,000 pieces of 223/5.56 brass to 300 AAC. During this process I converted a bunch of mixed HS brass and kept it separated from my good brass. What I found is there is a lot of variation in the wall thickness. Some brass is so thick the 300 AAC neck will be too thick to chamber with a .309 boolit. I pitched the too thick brass and never checked the case volume but I would think it would have to be less than the thinner walled brass. I would verify the water case capacity of your 300 brass and the check with hodgdon to find what brass they used for the published data and see what the capacity of that brass is.

BB

[wool1]

Just returned from shooting..... Looks like 14.5-15 gr of H110 is throwing the speeds it should, Chrono'd in the 1700-1800 range. The rounds cycled as they should, but everyone of the primers blew out. So I am thinking I have a brass issue.

[GRUMPA]

I'll chime in on this even though I don't load for the 300BLK myself. I'm wondering if your chamber was cut to deep myself. If I haven't done a million of the 300BLK conversions I would be utterly surprised and this is the first time something like this has come up with anything I have done.

All the brass I use is 1x fired LC brass unless the customer specifically requests I use something else like W.C.C. or FC brass which doesn't happen very often.

With an issue like this I almost wish there was a way to get a hold of a few of your spent cases and compare to the .001 to the formed brass unused. Not trying to CYA here but I would also like to get a hold of a couple of the primers and check the O.D. to find out what those are as well.

I'm just looking at the possibilities here to come up with a direction to go in. Often the simplest of things are overlooked in some cases, me...... this is a challenge and would dissect the you know what out of it to come up with an absolute answer.

EDIT: Anyway at all to post a picture or 2 of what you've used in the head area?

[wool1]

I'll get back to the shop later today and get some measurements. I'm hoping it is something simple too.