Primers Blowing Out on Lake City Reloads for 300 BLK

I recently started reloading, starting with 300 BLK sub-sonic. To date I have had 100% success with sub-sonic. I am shooting through a 16” barrel with AAC Cyclone suppressor.

Today I loaded my first supersonic rounds; using Nosler 125 gr. Ballistic Tip bullets, 17.8 gr of H110, CCI #400 primers and 2.060” OACL. Nosler lists the max. powder charge as 18 gr, which was the most accurate load that they tested. Everything worked fine, with the exception of the Lake City cases. Nearly all the LC cases blew the primers, some of the bottoms bulged and some had cut marks on the very ends.

The Gorilla & PNW Arms cases all worked fine. In the photo below, the two PNW cases in the black tray were factory 147 gr loads. The two PNW cases in the black tray with gold primers tray were 220 gr. Subsonic reloads.




Based on the reloaded Gorilla & PNW cases and fired primers, I am assuming that my Nosler supersonic loads are fine; and I just need to avoid reloading the LC brass. I believe that the LC brass came from some Freedom Munitions reloads I bought, as well as one other source that uses once fired LC brass.

Any input is appreciated.

Walkalong said:

Case neck walls too thick? What does a loaded round measure at the middle of the neck?

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0.332" I forgot to mention that I am using the RCBS AR Series Small Base 2-Die Set with Taper Crimp. And I check each round with a Lyman case length headspace gauge.

I appreciate all of the replies. The Hornady link and discussion about pressure and suppressors is very helpful. I was not thinking about the published loads and how a suppressor affects things. I will certainly lower the charge, probably to 16 gr and see how it works from there.

I found this article regarding pressure someone linked to at the facebook group “RELOADING 101: Learning the Art”: http://www.primalrights.com/articles/understanding-pressure

This is an excellent article. All of my primers that did not blow out are cratered and I clearly have ejector ring printing on most of the Gorilla and PNW Arms cases. For the Lake City brass, it appears that the shoulder area expanding and deforming allowed the primers to more easily pop out.

The Gorilla brass are from their Troop line which they state are once fired, converted Lake City Military brass cases. Here are some average weights, sampling 8 - 10 of each:

Lake City – 83.7 gr
Gorilla Troop – 82.9 gr
PNW Arms – 84.5 gr
Hornady – 81.6 gr (from new 208 A-Max rounds)

Another thing I thought about is that I have no clue how many times the non-Gorilla LC brass has been reloaded. These were more than likely from the Freedom Munitions reloads. Perhaps some of these cases were already subjected to overpressure events. In hindsight, when hand priming, I recall some very easily installed primers. And my ignorance loading too high for a suppressed rifle pushed them well above their limit.

Hopefully I did not damage my rifle. I will thoroughly clean and inspect is today.

Again, I appreciate all the responses and input.

I cleaned and inspected my rifle, especially the bolt assembly, the carrier group and chamber. Everything looked fine. So I took much slower today, inspecting each spent case before moving on to the next round.

I think it went much better today. All rounds are still using H110 with CCI #400 small rifle primers.

The two Hornady and two Gorilla rounds each had 15.6 gr. And the two PNW Arms had 16.0 gr. Two primers flattened more than others. In the future, I will try using the Winchester WSR primers, which I already have in hand.



I think keeping it between 15.6 gr and 15.8 gr would work the best for this Nosler 125 gr bullet in my suppressed rifle.

Thanks again for all the help. This truly is one of the most knowledgeable and helpful sites I have found to date.