• ODT Gun Show & Swap Meet - May 4, 2024! - Click here for info

300blk load help

I bought some 'ready to load brass' from midway, not one would fit in my new Anderson upper. Ordered a case gauge and could see the trouble, ran the brass through a Lee 300BLK die, no better. After reading all I could on line I ordered a set of RCBS small base dies. Problem fixed.

Larcus
 
I don’t know what caused it but the shoulder of the case was smushed out and made it wide so it jammed in the barrel. Problem I’m having now is the grouping. Factory 220gn cloverleafs at 50 yards out of my gun nice and tight. I loaded five with 8.5grns of lilgun and the group was about six inches and the bolt didn’t lock back and five with 9.5 grns were supersonic and had a four inch group but it did lock the bolt back..... any tips?
 
No 300BLK experience here, but:

Sounds like you need a powder that produces more gas. I would try CFE BLK, 1680 or 4198.

Or

Go with a lighter buffer spring/buffer setup to make LiL Gun work for you.
 
The group size may or may not shrink by changing powder. You just have to experiment when picking a powder. The crimp, and COAL should also be varied in the search for accuraccy.

The bolt is more likely to lock back after the last shot with more gas or a lighter spring/ buffer combo.

Another item to frustrate yourself with is the primer flash hole and uniformity. Some guys enlarge the hole for subsonic loads. One of my range friends told me that enlarging the flash hole helped him. Check out the flash holes in the factory subsonic.

I have found that on my guns, one one the biggest things that affects accuracy is consistant brass—same brand, same neck tension, same primer hole, same capacity.
 
The group size may or may not shrink by changing powder. You just have to experiment when picking a powder. The crimp, and COAL should also be varied in the search for accuraccy.

The bolt is more likely to lock back after the last shot with more gas or a lighter spring/ buffer combo.

Another item to frustrate yourself with is the primer flash hole and uniformity. Some guys enlarge the hole for subsonic loads. One of my range friends told me that enlarging the flash hole helped him. Check out the flash holes in the factory subsonic.

I have found that on my guns, one one the biggest things that affects accuracy is consistant brass—same brand, same neck tension, same primer hole, same capacity.
I changed the coal on this last batch of test rounds and it helped a little but still not quite like I like I think I’m going to get some 1680 and cfe blk and see if that makes a difference
 
8" barrel with carbine gas? You need a different barrel for those subs.

And small base dies to run all your brass before loading.


^^^^^THIS^^^^^.
I bet if he looks at his paper target, he will see that his bullets are key holing or starting to key hole. The other problem with the shoulder being pushed out was too much crimp in the die. For 220 subs, he needs a 1 in 6 or a 1 in 7 twist barrel. Powder will affect accuracy but not by several inches. He could also switch to a 125 grain bullet which should stabilize just fine and confirm the problem.

Also he said "Factory 220gn cloverleafs at 50 yards out of my gun nice and tight." Which means the factory bullets are stabilizing out to 50 yds but his reloads are not. It would be helpful to know what type of bullets are in the factory loads and what type of bullets he is loading. The ogive is likely very different on these two bullets and this is why one bullet is tumbling and the other is not. Cartridge overall length would not mean very much. What is more important is the distance from the ogive to the lands.
 
Back
Top Bottom