.308

[vtondeah]

Hi, I have reloaded some rounds and after firing 10 rounds I saw that all the shoulders had some dents.
The first 5 rounds were loaded with 40 grains and the second 5 was loaded with 41 grains of powder (Somchem S335).
Somchem specks are: 150gr PMP SP
Start 39.8 2 459 61.8
Max 44.2 2 795 63.2
The shell casings were Lepua and the head was Siera match king soft point-bow tail 150 grain.
The rifle is the Truvelo CMS 7,62x51mm Nato(the supplier does not want to talk about reloaded rounds but they say they only use .308 Hornady and Lepua bought rounds when target shooting-no risk guaranteed they say)
There is some discoloration/burn marks on the neck.
The shells are all within speck/length.
The total length is below max.
Around 65 rounds were fired just before and after the dented ones; these rounds are 150 gr solid point bow-tails, Danel/PMP shells and 41grain powder. No damage to the PMP shells were noticed.
I have been told by different loaders to: Increase my load, shorten the total length/seat the head slightly deeper, shorten/trim the shell even more, use the soft point heads in the PMP shell and see if it also happens.
Please what do you think of this?

 

[vtondeah]

How do I post the photo?

 

[vtondeah]

How do I post the photo?

 

[Gunner46]

I'm going take a SWAG at this and say it's the powder, or more accurately the powder's burn rate (BR). I checked the BR of S335 and it's comparable to H332. Nosler load data only lists H332 with the 110gr bullet. I'm thinking that if you're dead set on using Somchem you should take a step up to S355 which is more in line with Varget & RL15...... OR, just get some Varget or RL15 !

 

[Nimrod84]

Welcome vtondeah,

The dents and discoloration are consistent with gas escaping around the neck. This can happen if the cases are to hard to properly expand - work hardened from repeated firings and sizing. It can also happen if the powder charge is not fully pressurizing the case due to an inappropriate burn rate or weak charge weight for the hardness of the brass.

Lapua brass is going to be significantly harder than the PMP brass.

Since I am not familiar with how many times your Lapua brass has been used or the S335 powder, I will leave it to others to give specific recommendations. My gut says that Gunner 46's recommendations and thoughts are definitely worth exploring! A fast powder with un-fired Lapua brass (that is as hard as tank armor) would probably not allow for a good gas seal in the neck...
Additionally, I do not believe that Hodgdon lists any of their 308 loads with H322.

Once again welcome!

 

[jimbires]

the black sooty necks , and the dents , are caused by the brass case not sealing the chamber . low pressure is what causes this . I don't know enough about somchem powders to make a suggestion . the information I can come up with shows 40 gr at 40100 psi and 41 grains at 42665 PSI as very light loads , which your brass shows this .

 

[mjcmichigan]

I concur. Looked up Sonchem and the loads look light and the brass hard. Take it up or switch up powder.


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[vtondeah]

Thanx Guys for all the info, I have seated the heads deeper by 0.5mm and the denting of the cases on the shoulders has stopped completely. I was a bit afraid to up the load as the primers was pretty flat and showing cratering around the dimple. This is still weird as the load is at 40gr.

Thanx