Recommended CB Loads for Subsonic 7.62X54R?

[36g]

Looking for recommendations for some subsonic heavy boolit CB loads for a suppressed Mosin Nagant.

Working up plans for an updated (internals) BraMit style suppressor and need a starting load...

Suggestions?

[Larry Gibson]

200 - 220 gr cast bullets; 7 gr +/- Bullseye

"Sub-sonic" (no "crack" out in front of the suppressor) velocity will be dependent on the nose shape of the bullet as it is the speed of the air traveling around the bullet that determines when it "snaps" or "cracks" not the speed of the bullet. Thats why a blunt RN will "crack" at a lower velocity than a spire pointed bullet.

Suggest the use of cases with the flash holes drilled out with a #28 drill. That will get the flash into the case better for more uniform ignition and less powder position sensitivity with the small charge in the larger case.

Also, unless the suppressor is self serviced by disassembly and cleaning I don't recommend the use of traditional lubed bullets. A copper coated like "Berry's" or PC'd bullets are better.

[36g]

Thanks for the info! In general, would loads for .45 ACP (200 - 230 grain bullets) seem to be a relatively good starting point? I hadn't though about the flash hole but that makes a lot of sense also.

The suppressor will be disassemblable for cleaning but I have considered a PC bullet as well. Once I slug the bore it will determine if purchased or self cast and sized will be the route to go.

Would magnum primers be a positive addition to the mix for consistent ignition as well?

[Larry Gibson]

36g

Thanks for the info! In general, would loads for .45 ACP (200 - 230 grain bullets) seem to be a relatively good starting point? I hadn't though about the flash hole but that makes a lot of sense also.

Haven't thought much about it that way or did any testing so I don't know. What i do know is that with Bullseye powder in the 7.62x54R out of my MNs it takes between 6 and 8 gr to run cast bullets of 150 -210 gr at 1050 - 1100 fps. How much BE for each cast bullet weight is dependent on the bore specs and condition along with the other usual variables. That's why you should work +/- from the suggested load to find what work in your suppressed rifle.

The suppressor will be disassemblable for cleaning but I have considered a PC bullet as well. Once I slug the bore it will determine if purchased or self cast and sized will be the route to go.

That's good. Be advised that i and others here have found PC'd bullets will also leave a bit of deposit on the baffles.

Would magnum primers be a positive addition to the mix for consistent ignition as well?

Yes, they can help as compared to some "standard" primers. Again, that's a variable only you can answer with your loads and your rifle. However, I generally have found CCI 200s and WLR primers to give very satisfactory ignition.

[36g]

While waiting for some heavy cast boolits, I loaded up a few Sierra 190 gr. Spitzers (.311 dia.) with 7.5 gr. of Bullseye (plus some standard velocity with IMR 4350). Standard velocity fired fine (no groups due to loose PE scope mount, now tightened).

Fired one anticipated subsonic load and it was VERY quiet. So quiet that I thought that I had a hang fire so waited and nothing happened. Ejected the fired brass and pulled the bolt. Yup, stuck bullet...

The bullet was stuck almost exactly halfway down the bore. So, headed home, BreakFree'd up the muzzle end of the barrel and retrieved a brass rod and punched out the bullet. It seemed to come out easier than I anticipated. Nicely engraved souvenir.

Pulled the bullets from the other rounds with the Bullseye charge and loaded up a couple of H4895 loads and will see how they work. Should have some cast bullets on Friday...

[Larry Gibson]

Might try 3031 under your Sierra 190s. I tried the 15 gr under a 225 gr PC'd cast in my 308W test rifle. Ran just subsonic but got no psi data as the minimal the rifle will measure is about 19,500 psi. Was accurate also. This data is for the 308W which is close enough in capacity with the 7.62x54R having just a tudge more.

[36g]

Might try 3031 under your Sierra 190s. I tried the 15 gr under a 225 gr PC'd cast in my 308W test rifle. Ran just subsonic but got no psi data as the minimal the rifle will measure is about 19,500 psi. Was accurate also. This data is for the 308W which is close enough in capacity with the 7.62x54R having just a tudge more.

Thanks again for your guidance! The .308 subsonic data was what I have been reviewing having come to the same reasoning as you in regards to case capacity and basic bore dimensions. I might even have some IMR3031 in a metal can left - will have to do some digging.