.223 primer comparison over chronograph (sr vs sp vs spm)

[kir_kenix]

Hi everybody. I just thought I'd share some interesting data I collected today shooting some cast boolits over the chronograph. A few of us shoot an informal small bore BR competition at 100 yards. We each bring different rifles every time we meet, so it's really just an excuse to BS, brag, and reason to work up new loads each month.

Anyway, I worked up some loads for a factory stock savage .223 with 22" barrel for next weekend. We discussed pushing the competition out to 150 or 200 yards so I wanted to shoot some over the chrony and try and get my velocity, ES, and SD dialed in so my load wouldn't fall apart at 200.

I had a bunch of the RCBS 22-55-SP's cast, checked, and lubed so I started with that. Nice bonus is that this boolit has a stated BC of .159. I've shot a bunch of these in several .22 caliber rifles...so I knew I would have to limit my velocity to about 2-2,100 fps to keep them happy in the 1:9 twist.

I worked up only 1 load that was showing much promise at 100 (8.0 gr Red Dot). 2400 (10.0gr is my go-to in 1:9 twist .223's was aweful), unique, h110, and 748 all failed me in this rifle. Fired 250 rounds and 8.0 gr red dot was approaching moa...so I came home to do some tweaking over the chronograph with red dot.

The most interesting finding is primer selection. I played with oal and doing several ladders with red dot again. 8.0 was the clear winner, and oal is hasn't shown me much.
Sorry about the word wall...my findings are below. After some tweaking I managed 3, 5 shot groups that averaged 1.05" at 100.

Rifle:
Savage model 10, .223 Remington (1:9)
Factory sporter barrel (22"), bedded in walnut stock
Weaver t36 scope
Nylon brush + 2 cotton patches every 25 rounds
Adjustable front rest and rear bag

Cartridge:
Fc headstamp (15+ firings, annealed every 5 or so)
Red dot: 8.0 gr, no filler
trimmed 1.750
Neck sized in Lee collet
Lfcd...very lightly
Oal: I messed with this a bunch...but it hasn't made a difference over the chrony or target at all. I'll try to iron this out next time out.
Primer: win srp, win spp, and win sp magnum


Boolit:
Rcbs 22-55-sp
Sized .225, carnauba red, hornady gc
Weight sorted into .1gr increments
Alloy: wdww with 2% tin
Average weight: 58.5 gr

Conditions:
17 July, 2019
82*, 74% humidity
29.77 pr
1,365 ft
5 mph crosswind, constant

Chrony at 21 ft

Win small rifle primer: 5, 5 shot groups
Avg velocity: 2039
Es: 178 (oh my God bad)
Sd: 64.8
Average group size: 1.97

Win small pistol: 5, 5 shot groups
Average velocity: 2027
Es: 97
Sd:43 (still really bad)
Average group size: 1.54

Win small pistol magnum primers: 3, 5 shot groups (chrony battery died)
Average velocity: 2042
Es: 53
Sd: 20
Average group size: 1.05" @ 100 yards! 1 group measured .78...really, really good for me with cast


Conclusion: switching primers, and primers alone, shrunk my group size in half. At least on this day, with this rifle. I've seen this before with .22 cast boolits, but maybe not this dramatically. Then again, I usually don't spend this much time in load development either.


So I still have a few things to tweak. I've never fired 5 consecutive 5 shot groups with .22 cast boolits averaging <1". Even heavy barrelled 1:12 and 1:14 twists. I don't think I'll get there with this rifle...but I'm going to give it a try. The 1:9 twist just has a tendency to throw a shot with this boolit for some reason.

Anyway, I thought somebody might find this interesting. Small pistol and small pistol magnum primers seem to really clean up groups in these diminutive cases with fast powders and cast boolits. I'll try to remember to update this post next time I get the rifle out and figure out an oal I'm happy with.

Jon

[JBinMN]

I "do" find it interesting, & Thanks! very Much!, for taking the time to share your results!

[dverna]

Good post

[kir_kenix]

I shot 5 more 5 shot groups this evening...all at 200 yards. These were all loaded with the win small pistol magnums with the same 8gr of red dot.

Unfortunately, I wasn't able to get the accuracy I was looking for. 3-5" groups. 2 boolits for sure showed definite signs instability/tipping. I think I need to bump the velocity some to keep them stable. I don't think going sub sonic is doing them any favors. But I haven't had much success with the rcbs 22-55-sp much faster in a 1:9 twist.

I'll be out of town for a few days for a funeral, but I'll get back on it next week. I have 200 FC cases annealed, match prepped, and primed ready to go.

[stubshaft]

Once you find the primer your load likes buy the same lot. Different lots may have different results.

[osteodoc08]

Thanks for the data points.

[kir_kenix]

Finally finished up testing this boolit, with this load, in this particular rifle. I fired 100 more shots on targets throughout the morning. 10, 5 shot groups 'for score' at 100 yards...and the same again at 200 yards. Temp ranged from 74*-89*...wind was <5mph while all shots were recorded.

Average 5 shot group size at 100 yards: 1.22"
Average 5 shot group size at 200 yards: 3.7"

Only good thing is all shots remained stable and showed no signs of tipping at 200 yards.

According to Bergers stability calculator...my load gets a SG of 1.4. This results in a 'marginally stable' projectile. I'm pretty certain this boolit is not happy about dropping below the speed of sound in flight.

So I don't think I'll be using this rifle for 200 yard target shooting. I have a bunch loaded up for short range coyote control around the house. Nice thing is with this rifle, when zeroed with this load at 100 yds, my generic 53gr vmax load shoots dead on at 300. So I guess all of this testing wasn't a complete failure.

Anyway, I hope this helps if anybody else tries this boolit in a 1:9 twist. Maybe they can get a bit more speed out of it than I have.