.300blk Bolt/Buffer/Spring Setups?

[jkrispies]

What are folks recommending for a bolt weight (ie, standard, lightened, etc.), buffer weight, and spring weight setup for .300blk?  I'm looking at a 9ish inch barrel and pistol gas, preferably non-adjustable gas block.  Also, any thoughts on rifle length buffer system vs. carbine length?  Thanks, J

[fastshooter03]

What ammo r u planning on using?  You may need different spring setups if you're going to switch between subs and full velocity.

 

[jkrispies]

FYI I’m chatting a bit with JP for suggestions and they recommended going with a lightweight carrier and H2 buffer, then backing off on the buffer weight and/or spring if it needs tweeking for reliable function.  

Edited June 2, 2018 by jkrispies

[jkrispies]

3 hours ago, fastshooter03 said:

What ammo r u planning on using?  You may need different spring setups if you're going to switch between subs and full velocity.

 

I’m not married to anything but thinking about 135gr SMK’s.  Looks like I can run those both sub and super, and the drop calculators look pretty good if I go 100yd zero with a 125 point blank at subsonic and 175yd zero with a 200yd point blank at supersonic.  That weight round shouldn’t move the gun too much either, I’d assume.  I’m planning to run dot and irons only, so these ranges are pretty acceptable to me so far.  

Edited June 2, 2018 by jkrispies

[fastshooter03]

Rifle length will give you more options for springs, buffers, spacers, etc but compactness usually rules that out.

With full power loads it will be hot and you'd want the most weight you can run.  Drops on subsonic 220s, 240s zeroed at 100yds is about 36" at 200 yds.

On my pistol 10" and carbine 16" I run a h3 buffer and cut down spring in Carbine tubes with 240 subs and burn rate around AA1680, 5744.  I only runs Subs with 300blk.

If I want supersonic I use 7.62x40WT to get most velocity.

 

 

[jkrispies]

2 hours ago, fastshooter03 said:

Rifle length will give you more options for springs, buffers, spacers, etc but compactness usually rules that out.

With full power loads it will be hot and you'd want the most weight you can run.  Drops on subsonic 220s, 240s zeroed at 100yds is about 36" at 200 yds.

On my pistol 10" and carbine 16" I run a h3 buffer and cut down spring in Carbine tubes with 240 subs and burn rate around AA1680, 5744.  I only runs Subs with 300blk.

If I want supersonic I use 7.62x40WT to get most velocity.

 

 

How hard do thise 200+ grain bullets pound the shoulder?  And when you run those at subsonic, what’s the actual velocity/power factor you’re going with in practice?  I’m thinking a 240gr at 750fps is basically going to feel like a .45acp at standard PF, but a 240gr at 1000-1100fps is still subsonic but I’d inagine a different beast altogether.  I hear talk of these really high grain 300blk loads but I wonder if in practice folks are really choosing them over lighter options?

 

And keeping in line with the topic, let’s say I choose a 240gr at 1100fps for my subsonic, and a 135gr at 2100fps for my supersonic (I’m just spouting theoretical numbers here) would those two power factors be close enough that the same set of springs and buffers could be used for both loads?

 

Thanks, 

J

[fastshooter03]

All you can do is try both and see.  You'll be able to run a faster powder with the 135's than with subs. 240 x 1050 = 252pf  135 x 2100 = 283.5 so they both have a bit of punch compared to 223@ 60 x 3000 = 180

The subs you need to keep around 1000fps so there's enough powder to run the action. At 40-50 cents/pc for 220-240 sierras you probably won't want to practice with them.  Find something cheaper like 220 RN  or lesser known brand.

Subs will give you a little push in the shoulder for sure.  I loaded up 50 that were too close to supersonic and burned them up rapidfire.  It was a bit much in a light rifle.

Like 223 you'll have to try em and see how it works with your system.