300 PRC load question

[MCC335]

Hi everyone!

I have been working up a load for a custom 300 PRC with a 24" barrel. This load shot 0.3 MOA at 100 yards several times, but intermittently opens up to about 1 MOA. ALL components I am currently using are from the same lots.

Lapua Brass
Federal 215
77.7gr H1000
Berger 215
COAL 3.747" (-0.020 from jam, +0.006 IL)
2844fps (ES 14-21 with multiple 3-shot groups)
RCBS FL bush die with 0.335 SAC bush
0.306 Mandrel


I have 2 questions that I need help with, both of which I think may be adding to my inconsistencies:

1. Is enough bearing surface of my bullet in the neck? At this COAL = 0.180" bearing in neck)

2. Enough neck tension? What bushing are you guys using in the 300 PRC Lapua brass? My loaded rounds are 0.3375 but my 0.306 mandrel is very loose after 0.335 SAC bushing.

Thank you,
Gino

 

[6.5saum/300rum]

I would try seating the bullet deeper that's not much surface in the neck. I think I'm running a .316 bushing for my 300 prc lapua brass.

The 300prc sammi reamer seems it's only ideal for the 225grain bullets and bigger. All the lighter bullets have to have a ton of jump.

Edit I am using a .334 neck bushing. Sorry I don't know what I was thinking!!!

 

[MCC335]

I would try seating the bullet deeper that's not much surface in the neck. I think I'm running a .316 bushing for my 300 prc lapua brass. I can't imagine your mandrel is even doing anything with a .335 bushing.

The 300prc sammi reamer seems it's only ideal for the 225grain bullets and bigger. All the lighter bullets have to have a ton of jump.

Thanks for the info! My loaded ammo neck OD is .3375, that's how I ended up selecting the .335 bushing.

I will try a few quick loads with them seated 0.070 shorter giving me .250" of bearing surface. I did try the Berger OAL test once.. 10, 50 and 90 OL.. they shot 0.39", 0.47" and 0.59"

 

[2buffalo]

Your issue could be many things so I won't speculate but for reference I have a load using all the same components. My rifle actually likes N570 more than H1000 so that's what I am using now.

78.3 H1000
.333 Neck bushing
.306 Mandrel
3.666 OAL (3.705 is touching lands = -.039 off the lands).
2956 fps MV

 

[Joefrazell]

Hi everyone!

I have been working up a load for a custom 300 PRC with a 24" barrel. This load shot 0.3 MOA at 100 yards several times, but intermittently opens up to about 1 MOA. ALL components I am currently using are from the same lots.

Lapua Brass
Federal 215
77.7gr H1000
Berger 215
COAL 3.747" (-0.020 from jam, +0.006 IL)
2844fps (ES 14-21 with multiple 3-shot groups)
RCBS FL bush die with 0.335 SAC bush
0.306 Mandrel


I have 2 questions that I need help with, both of which I think may be adding to my inconsistencies:

1. Is enough bearing surface of my bullet in the neck? At this COAL = 0.180" bearing in neck)

2. Enough neck tension? What bushing are you guys using in the 300 PRC Lapua brass? My loaded rounds are 0.3375 but my 0.306 mandrel is very loose after 0.335 SAC bushing.

Thank you,
Gino

So the load is a 1 moa load. Go shoot a 10 shot group and do it twice at the same target

 

[MCC335]

Your issue could be many things so I won't speculate but for reference I have a load using all the same components. My rifle actually likes N570 more than H1000 so that's what I am using now.

78.3 H1000
.333 Neck bushing
.306 Mandrel
3.666 OAL (3.705 is touching lands = -.039 off the lands).
2956 fps MV

Thank you for the load reference, much appreciated.