Inconsistent subs in my 300 blk

Beeron

Beeron

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Vancouver Island
Greetings
I am having some issues getting consistent velocities in my 300 blk sub loads.

So far i have tried 175 gr hornady sub X and 180gr SST’s.

I typically get the first round of a test load shooting a fair bit faster than subsequent rounds which gives me large ES and SD values.

I have read that this may be a case fill issue.

So if i use heavier pills, i can compress smaller loads more consistently.

I have some 190gr copper monos on order which will be long and may help but does anyone have any experience to offer here?

Im using;
Ruger Ranch Gen II in 300 blk
Starline brass (virgin but fl sized and expanded using a .306 mandrel)
CCI 400 srp
Hodgdon CFE BLK

Thanks.

The gun shoots supers well.
110gr Barnes Tac TX shoot sub moa at 1965fps.
 
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I had rough luck with CFE-BLK in loading 180gn 7.62x39 subs. Did way better with IMR 4198.
Also, try CCI 450 instead of 400. The greater brisance may compensate for the random lay of the loose powder and lower your ES.
Oh yeah, trim your flash hole too...
 
I shoot 210 and 245 grain cast bullets out of my 12.5 inch bolt action 300 Blackout using H110. Heavier bullets allow me to use a larger powder charge and seat bullet deeper to reduce the empty space in the casing. Cast bullets are are a lot cheaper.

I would suggest doing research on one of the many US forums as shooting subsonic 300 blackout is more common there than in Canada.
 
On a burn chart cfe blk is slower than 4227 and close to reloader 7. I load subsonic in a few cartridges but not the blk I would not use a powder that slow its dirty and inefficient although the hodgdon site says its perfect for subs I find that hard to believe
 
porpoise said:
On a burn chart cfe blk is slower than 4227 and close to reloader 7. I load subsonic in a few cartridges but not the blk I would not use a powder that slow its dirty and inefficient although the hodgdon site says its perfect for subs I find that hard to believe
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At


Its like shooting a musket.
The smoke cloud is hard to see through.
 
The vast majority of subsonic 300 BLK published loads use powders that produce a pressure curve needed to cycle semi auto rifles. There is no need to use such powders in a bolt gun. The typical 300 BLK powders will be much louder than a fast burning pistol powder.

A 300 BLK bolt gun will run on Trailboss and Unique, Red Dot and Bullseye. Stuff like Trailboss, Bullseye and Clays are much bulkier than 4198, 4227, W296 etc.

A 150gr subsonic running 6.0gr of Trailboss is something to behold when it comes to noise.
 
I Dont Care About You said:
The vast majority of subsonic 300 BLK published loads use powders that produce a pressure curve needed to cycle semi auto rifles. There is no need to use such powders in a bolt gun. The typical 300 BLK powders will be much louder than a fast burning pistol powder.

A 300 BLK bolt gun will run on Trailboss and Unique, Red Dot and Bullseye. Stuff like Trailboss, Bullseye and Clays are much bulkier than 4198, 4227, W296 etc.

A 150gr subsonic running 6.0gr of Trailboss is something to behold when it comes to noise.
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No doubt.
But trailboss is a unicorn at the moment.

I have a couple boxes of 190gr cutting edge that i would like to get to group at 1” at 100.
 
I Dont Care About You said:
So?

How do your loads group?

Are you interested in chasing a number or downrange results?
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I want decent groups.
1.5” at 50 is fine.
I wud like 1” at 100.

Also.
If my first round of each load is 70fps faster than the rest, its hard to get closer than 70fps to max velocity and still be sure of subsonic.

If i cud get SD’s down to 15 or so, i cud build a load for 30fps under and be confident im not gonna have a crack on that first round.
 
Beeron said:
I want decent groups.
1.5” at 50 is fine.
I wud like 1” at 100.
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Subsonics and accuracy are not generally spoken of in the same sentence. Accurate subsonics are very difficult to achieve.


Beeron said:
If my first round of each load is 70fps faster than the rest, it's hard to get closer than 70fps to max velocity and still be sure of subsonic.

If i cud get SD’s down to 15 or so, i cud build a load for 30fps under and be confident im not gonna have a crack on that first round.
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30 fps below whatever the speed of sound on the day you are testing is way too close. I typically shoot for anything in the 950-1000 fps range. Depending on where you live and the atmospheric conditions on the day, sonic crack can begin to be generated in the 1050- 1075 range. The sonic barrier is a range, not a hard limit. A little less velocity won't change anything downrange.

As has been discussed above, case fill can be an issue for some powders. Basically you want the bulkiest powder you can find.

There is another option for us as we do not have to worry about a sound suppressor. You can try stuffing a bit of cotton ball into the case to keep the powder in place at the back end. Then case fill doesn't matter.

You can also try lubing the bullets. That helps normalize the friction between the bullet jacket and the bore.
 
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