77gr SMK (blems) and Shooters World Precision rifle powder

[Wormydog1724]

Review of the Load process thus far:

Firearm:
- KAC 18” LPR Mod 2 upper with a Krieger barrel (1:7 twist)
- Equipped with an AAC M4-2000 suppressor and Ecco conversion, utilizing the Grffin taper mount system
- Rifle buffer system (Tubb spring on order)
- LaRue MBT2S trigger
- NF NX8 2.5-20x50 Tremor 3 scope
- Atlas bipod featuring an Area419 arca attachment and rail
- Utilizing a heavy fill rear bag for stability
- Feeding from a 20-round ASC magazine for long loading



Reload Details:
- Utilizing mixed range brass, which is full-length resized and trimmed using a Dillon RT1200 to a length of 1.7590"
- Cases are chamfered, deburred, and processed with a Dillon superswager tool
- Dry tumbling is performed for cleaning
- CCI450 primers are used
- Employing Sierra 77gr SMK bullets with cannalures, specifically MidwayUSA blems
- Shooters World Precision Rifle powder is chosen for the loads
- Cartridges are loaded to a COAL of approximately 2.290"

Loading Process:
- Dillon 550b is used for reloading
- Brass is run through a Redding full-length die, backed out to merely act as a neck die as its already been FL resized and trimmed
- The Redding die serves to clean media from the flash hole, while the button is left on to slightly open and round the case mouth
- The Dillon trim die may exhibit excessive neck tension and potential impact on the bullet jacket
- Dillon powder dropper is utilized without modifications, throws are consistent with SWP
- Seating is performed with a Redding die, and a light crimp is applied using a Lee die, barely touching the mouth

Load Testing Results:
- Commenced with a starting charge of 22.5gr and increased in increments of 0.5gr up to 25.0gr
- The following results were obtained for the combination of Shooters World Precision Rifle powder and 77gr Sierra MatchKing blems:

22.5gr
- High: 2444
- Low: 2419
- Average: 2428 (still locked back on the mag)
- Standard Deviation: 10.1
- Group size: 1.3moa (0.62moa without cold bore)



23.0gr
- High: 2495 (last shot)
- Low: 2426
- Average: 2468
- Standard Deviation: 29.2
- Group size: 0.53moa



23.5gr
- High: 2556
- Low: 2495
- Average: 2529
- Standard Deviation: 24.4
- Group size: 0.83moa



24.0gr
- High: 2631
- Low: 2532
- Average: 2574
- Standard Deviation: 36.5
- Group size: 0.72moa



24.5gr
- High: 2657
- Low: 2601
- Average: 2638
- Standard Deviation: 23.4
- Group size: 0.51moa (0.7moa second group, chrono off)




25.0gr
- High: 2740
- Low: 2677
- Average: 2717 (21, 25, 25)
- Standard Deviation: 23.8
- Group size: 0.88moa



25.0gr #2
- High: 2751
- Low: 2675
- Average: 2713
- Standard Deviation: 29
- Group size: 0.57moa



Overall Assessment:
- The groups obtained are satisfying, but the standard deviations could be improved, being they were 10-36 SD for the various groups
- At 25.0gr, the velocity was good for the shooter, with the primers showing slight signs of flattening but not at the edges
- No swipes or ejector marks were observed
- Longer loading may have contributed positively to controlling pressure
- Future testing with charges in .2 increments from 24.7gr - 25.5gr is planned, with potential seating depth adjustments, although unlikely
- Regarding the MidwayUSA blems, they have exhibited consistent weight and dimensions, with minor variations in the cannelure placement across different bags
- No significant differences have been noted during testing, although the obvious blems were excluded from the load development
- As a personal consideration, the use of HBN coating on bullets has previously shown lower velocity, lower pressure, and reduced standard deviations
- In upcoming sessions, the shooter plans to sort brass by head stamps, clean primer pockets and flash holes, and apply HBN coating to the bullets for potential benefits

[markm]

Great results. Is your COAL really 2.290"? Seems like that would be slightly longer than mag length.

[Wormydog1724]

Great results. Is your COAL really 2.290"? Seems like that would be slightly longer than mag length.

Yes, I am using ASC 20 round mags (blems from MidwayUSA also) and they allow about 2.230" or a little more. Just something I prefer to do.

[MarshallDodge]

Nice shooting! That LPR is impressive as well as your ability to shoot it.

The blems are kind of interesting to deal with. I've had four go into .25" and then one will go off to make a .5" group. This makes it interesting when you are trying to do load testing.

It's also good to see SWP working for you. I've had some initial success but have it as a backup to my stash of 8208XBR so I didn't spend a lot of time with it.

The CCI 450 is a good, hard primer. I'll give that a try the next time I try loading SWP. The Fiocchi SRM is another one that I am playing with. It is really hard, and sometimes gives me issues in my bolt guns, but an AR has no problem with them. They were $20/k before the pandemic...if only I had a magic ball.

I love the ASC mags!

[Wormydog1724]

Recently, I headed back to the range for another ladder test, this time spanning from 24.7gr to 25.3gr. As previously mentioned, I applied HBN coating to the bullets, hoping it would improve the SD/ES. I had planned to sort the brass cases by headstamp, but I didn't follow through as I shoot competitions with mixed brass.

Here are the results of the ladder test using 77gr SMK (blem) with SWP powder:

- 24.7gr:
Max 2622,
Min 2555,
Avg 2598,
SD 28.4,
1.02moa


- 24.9gr:
Max 2708 (last shot),
Min 2628,
Avg 2650,
Sd 33.1,
1.08moa


- 25.1gr:
Max 2691,
Min 2631,
Avg 2661,
Sd 23,
0.85moa


- 25.3gr:
Max 2749,
Min 2679,
Avg 2707,
Sd 39.5,
0.44moa


Following that, I loaded 10 more rounds with 25gr, but I didn't keep detailed notes. The average for 25.0gr was 2670, with a grouping of 0.65moa.


I feel comfortable in the 25.0-25.3gr range.

During the tests, I didn't observe any pressure signs, although the case was completely full and compressed at 25.3gr. The temperature was 92°, and that didn't cause any issues. I plan to try another 15 rounds at 25.0gr, and if it proves satisfactory, I'll stick with it.

Unfortunately, the HBN coating didn't reduce the SD/ES as expected, and it seems to have lowered my velocity, as it usually does. Additionally, the group trends weren't ideal, but they might be related to the shooter. More testing and careful consideration are needed to improve the results.

[markm]

Looks like you're getting more info than I've ever got when trying the ladder thing.

[turnburglar]

I got a good 0.7" group with these midway blems and 24.7gr of CFE223.

I have shot over 1k of these bullets and I continue to buy them 2k at a time until midway stops carrying them. I love these things for the price.