[just_me_mongo]

At 25 yards, I would not bat an eye at the variation of +/- .007.

I would consider chamfering/deburring your cases prior to loading them. The jagged brass can "drag" or "pull" on the copper jackets of the bullets and cause variations in COAL. I have had it happen a number of times when I buy processed brass and start loading it without prepping it.

TC

 

[BoilerUp]

What barrel length and COAL?

8.5" barrel. I had some feeding issues if I loaded longer than 2.20 (for Berry's 220gr)

 

[Xman]

To eliminate 300 BO feeding issues with 5.56 PMAGs, I had to file down the left/right forward ribs in the magazine that protrude inward round the bullet. These ribs are designed for 0.224" bullets and contact the 0.308 bullets pushing the cartridge out of alignment.

 

[Jellysick]

For load development, I've been taking the approach of a ladder increasing in charge by .3gr as we've been discussing. To gain a better view into consistency, would it be advantageous to shoot say three rounds at one charge, then three rounds at the next incremental charge, then three rounds and the next incremental charge, etc? Each set of rounds could be it's own target as to separate the results per charge.

 

[Xman]

Yes, but .... you will burn up a lot of components and time. Some reloaders even shoot 5 rounds per charge weight. Their rational is it takes 5-rounds or more to know if that load will be consistent, e.g., a good load. The problem is I know on the second shot in a 3- or 5-shot group whether its a bad load. If the second shot isn't a kissing-cousin with the first shot, that charge weight doesn't have the potential to be a good load. So, what do you do with all those loaded rounds you don't need to shoot? Send them down range needlessly? Bring them home and do the extra work to pull them and reuse them?

You did a velocity vs powder weight ladder which did you an indication of where your consistency would be (optimum charge weight) plus you determined where your max performance boundary was (chamber pressure or powder efficiency). It was then suggested that you use 3-shot groups to confirm what the ladder information provided with a powder load of 15.3, 15.8, and 16.5 grains. Won't this answer your question with far fewer shots down-range?

Now that you have your shoulder set-back adjusted and have a ladder shot from a steady rifle, take the next step to shoot a couple 3-shot groups to verify performance and determine acceptability. You picked #6 which I would have also, so load 3 rounds at 15.3 grains. Then load TC's suggestion 15.8 (or 15.7 if you favor odd numbers like I do). If you plan to shoot this load suppressed, I'd do it with the can on. Or load 6 rounds per powder charge and shoot with and without the suppressor to understand the differences. Maybe do a group with 16.5 grains (#10) just for gins (1, 3, 10 are same hole).

Looking forward to seeing your results in group size and velocities.

Note: I go into the field to hunt with my 300 BO with a red dot, but I use a scope for load development because I desire precision results.

 

[Jellysick]

You did a velocity vs powder weight ladder which did you an indication of where your consistency would be (optimum charge weight) plus you determined where your max performance boundary was (chamber pressure or powder efficiency). It was then suggested that you use 3-shot groups to confirm what the ladder information provided with a powder load of 15.3, 15.8, and 16.5 grains. Won't this answer your question with far fewer shots down-range?

Yes, it seems like it certainly will. Just noodling over approaches that I see others using. The consumption of additional components was the first thing that came to mind.

 

[BoilerUp]

For load development, I've been taking the approach of a ladder increasing in charge by .3gr as we've been discussing. To gain a better view into consistency, would it be advantageous to shoot say three rounds at one charge, then three rounds at the next incremental charge, then three rounds and the next incremental charge, etc? Each set of rounds could be it's own target as to separate the results per charge.

You're increments should be generally based as a percentage of expected max. I start at ~0.7% increments, although I forgot why...probably copied from OCW method. That means larger increments for larger calibers, so I might start with .3 or even .5 gr increments for something like a .308 and as small as 0.1 gr for subsonic .300 BLK.

And the number of rounds you use to get a data sample depends on a few things, one of which is your confidence in the accuracy of your rifle. If you are very confident you have a good shooter (e.g., half MOA), you can feel better about making assumptions with fewer rounds. if you have a 2 MOA gun, even 3 rounds won't tell you much as far as accuracy of a load goes.

For a half moa gun, I like to run one ladder at one shot each to look for "flat spots" in velocity, e.g., the 3 consecutive charges that give the least difference in velocity, then I can start shooting 3-5 round groups in that area to confirm.

I geek out a little on custom targets and data collection, and make PowerPoint targets that are color coded to an Excel based load table and use corresponding sharpie colors to color the rounds so I can tell which is which. And example is below where I was experimenting with different techniques for sizing brass.

Also, I enjoy shooting for load development so I don't mind loading up some extra rounds to get additional data points. Some folks fret over wasted components, but it's all entertainment for me anyway. Once exception even for me is on barrel burners, so I try to minimize my experimenting in my 6mm Creedmoor.

 

[tbase1]

The last load I'm working on is a subsonic load using Berrys 220gr and A1680 powder. Starting load guidance came from a combination of Hodgdon reloading data and https://accuratepowder.com/wp-content/uploads/2010/09/300_ACC_Blackout_Data.pdf

Hodgdon and the PDF above recommends a C.O.A.L of 2.089". Berrys Bullets recommends 2.15". Given I'm straying away from the Hodgdon and Accurate Powder recommendation by going longer, I considered this OK (versus shorter, the charge may have to be reduced to avoid higher pressures before working up). Also a concern was the Berrys COAL of 2.15, I was hesitant to go shorter as I didn't want to get into a situation of a compressed load without knowing more. Let me know if my approach is appropriate or not.

I shot an initial ladder a week ago with a focus on FPS, results below. The ladder approached downward to the starting load which looks to be the recommendation for subsonic load development. The 11.2 and 11.3 loads have no captured FPS as I had to adjust the sensitivity of the chrono before it began capturing velocity.
View attachment 78029

I was hoping to get a tad closer to 1000 FPS so I loaded up 5 more and shot them yesterday. Knowing 11.3gr was safe I started there and increased the charge, monitoring FPS and the resulting case after each shot. Results below:
View attachment 78030

View attachment 78032


So while there was an increase in FPS, it wasn't as linear as I expected, nor to the extend that I expected. Note #3 from 12/21/22 was 997 FPS but without shooting more of that load I'm unsure if that was an anomaly or not as the velocity of all the others were 940-950. The other component is if it would be valid to start over and actually reduce the C.O.A.L, which from what I understand should result in increased velocity at a lower charge. Need guidance on this though if this is a valid approach.

Berrys 220gr Spire Tip info: 300 Blackout 220 Grain | 300 Blackout Reloading Bullets
View attachment 78031

None of these were shot with a suppressor, and I realize I'll gain a few FPS with the suppressor on.

I find the 300 BLK easy to reload and lottsa fun to shoot! My COAL is 2.15, per Berry's recommendation, and a coupla my pet loads are 12.0 CFE BLK (1035 fps) and 11.7 AA1680 (1050 fps). These are in my 7.5" barrel (suppressed) but I actually see very little difference with my 9" barrel. I'm using a universal neck expander for ease of bullet seating and then a Lee factory crimp die to remove the ever-so-slight bell. And have you weighed your bullets? My last two Berry's orders actually weighed in at 215 gr.!
For jacketed bullets I've loaded the Sierra 220 HPBT with 11.5 AA1680 at 2.258" for 1000 fps.
I'm not overly concerned with precision for plinking loads but I do check CBTO with a Hornady comparator and verify a reasonable level of consistency. These loads work for me; as always, proceed with your own caution.

 

[Jellysick]

I find the 300 BLK easy to reload and lottsa fun to shoot! My COAL is 2.15, per Berry's recommendation, and a coupla my pet loads are 12.0 CFE BLK (1035 fps) and 11.7 AA1680 (1050 fps). These are in my 7.5" barrel (suppressed) but I actually see very little difference with my 9" barrel. I'm using a universal neck expander for ease of bullet seating and then a Lee factory crimp die to remove the ever-so-slight bell. And have you weighed your bullets? My last two Berry's orders actually weighed in at 215 gr.!
For jacketed bullets I've loaded the Sierra 220 HPBT with 11.5 AA1680 at 2.258" for 1000 fps.
I'm not overly concerned with precision for plinking loads but I do check CBTO with a Hornady comparator and verify a reasonable level of consistency. These loads work for me; as always, proceed with your own caution.

It's interesting that while seated at the same depth, the Berry's 220 at 11.7gr was around 950fps. I have a dozen or so loaded up to test at 11.5 which initially showed close to 1000fps. I'm not chasing velocity, just looking for a reliable plinking round while suppressed.

 

[Jellysick]

Range results are in, it'll take a bit to sort through and log the results. For starters this is the Berrys 220gr load at 11.5gr of AA1680. The 997 fps as noted from the previous trip didn't hold up. And I'm not that pleased with the accuracy. I'm not sure how high I can safely go with the charge as it seems like the case is pretty full. Also from the last trip, 11.6 and 11.7gr didn't provide any more velocity so as Xman stated, this might be the efficiency limit of the barrel length and charge/projectile combo?

As suggested, I shot 5 rounds to log velocity, this was done unsuppressed as I'm not setup to attach the Magnetospeed to the suppressor currently. Then two groups of three to check for accuracy, suppressed. I'm not impressed with the accuracy, or the velocity for that matter. Though I'm not sure how much my ability as a marksman is impacting the poor accuracy. I'm able to achieve better groups using other loads and rounds so I'm inclined to think this is not an accurate load.

I'm also assuming the 2136FPS noted on #3 was a sensor error on the chrono.

Others have noted a subsonic load using H110 and 220gr projectiles, maybe I'll give that a test unless you all have suggestions on the current situation using AA1680?

 

[Xman]

regarding the 2136FPS noted on #3 being a sensor error with the chrono, have you ever had a similar issue with other shots? When you pulled the trigger, did you notice any more kick than normal? That velocity looks like it could have been a double charge weight.

Regarding velocity, I don't know how much more you can get from an 8" barrel. I wasn't getting much more with my 16" barrel though I did have to back down the 1680 powder charge because velocity would creep up when the temperature got warmer and go supersonic on me.

Not seeing your set-up, its hard to tell if your accuracy is that bad for using a red-dot. 4 out of the 6 shots look pretty good.

 

[Jellysick]

regarding the 2136FPS noted on #3 being a sensor error with the chrono, have you ever had a similar issue with other shots? When you pulled the trigger, did you notice any more kick than normal? That velocity looks like it could have been a double charge weight.

Regarding velocity, I don't know how much more you can get from an 8" barrel. I wasn't getting much more with my 16" barrel though I did have to back down the 1680 powder charge because velocity would creep up when the temperature got warmer and go supersonic on me.

Not seeing your set-up, its hard to tell if your accuracy is that bad for using a red-dot. 4 out of the 6 shots look pretty good.

I don't recall it feeling any different in terms of recoil than the others. When I noticed the chrono reading I made sure to find the case to examine it. It didn't look any different than the rest as well. The cases are pretty full at 11.X gr, That's why I'm not sure how much I can even continue to work up before compressing the charge.

 

[Jellysick]

This is the brass from the 220gr loads. The 3rd from the left is the 3rd shot with the 2136FPS

 

[Xman]

Thanks for double checking. The brass looks pretty good.

 

[Jellysick]

Next up is the Hornady 150 FMJ BT. The approach based on recommendations in this thread (based off of the previous ladder) is 3 x 15.3gr, 3 x 15.7gr, and 3 x 15.8gr, using H110. For reference, data from the ladder is below:

These were all shot with the suppressor on, at 25yds. The groupings for each charge:

The brass from these loads:

To my novice eye all are pretty good. All 3 loads have two that are sharing the same hole. Do you go off of velocity at this point to make a determination?

Taking these results and comparing them to the Berrys 220gr load, you can see the groupings are much better here. Which, as I mentioned I'm not a marksman by any stretch, but these at least have some degree of accuracy.

 

[Xman]

Nice groupings. Of those 3, 15.3 looks to be the most promising group for accuracy. 15.7 and 15.8 are especially the same load. I was hoping to see 16.5 grains. Can you squeeze that one in for me?

 

[Jellysick]

Nice groupings. Of those 3, 15.3 looks to be the most promising group for accuracy. 15.7 and 15.8 are especially the same load. I was hoping to see 16.5 grains. Can you squeeze that one in for me?

I'll work it into my next range trip

 

[BoilerUp]

I'm not impressed with the accuracy, or the velocity for that matter.

What do you mean you aren't impressed with the velocity? The whole point of 220gr projectiles for the 300 BLK is to shoot subsonic so "chasing velocity" for subs means finding the max charge that keeps you subsonic.

Also, I don't think those bullet are really worth chasing accuracy. They are a cheap range round for subsonic plinking. To maximize fun, get some steel silhouette targets.

 

[Jellysick]

What do you mean you aren't impressed with the velocity? The whole point of 220gr projectiles for the 300 BLK is to shoot subsonic so "chasing velocity" for subs means finding the max charge that keeps you subsonic.

Also, I don't think those bullet are really worth chasing accuracy. They are a cheap range round for subsonic plinking. To maximize fun, get some steel silhouette targets.

I see most folks working up subs in the range of 1000-1050fps. Will 950 do? Sure. Without knowing more about the cartridge, powder, etc., it seems these are still on the slow side of what a sub load should be. Vague requirements, I understand. Simply making observations.

 

[just_me_mongo]

Jelly - you could try to go with a lighter load {10.6, 10.9, or 11.2}. That might get you better groups. If you are just looking for a snugger at 25 yards, that should be easy to do.

TC