I received one of MiHec's 227-75gr molds from the recent group buy that was start last spring and they were delivered right before Christmas. Unfortunately, with my alloy of Wheelweights (a blind mix of mostly COWW and some SOWW), I get a 68gr boolit that sizes as cast at .226". I size them to .225" when I gas-check them and lube them with BAC lube. The final checked and lubed boolit measures at .225 and weighs on an average of 69.1gr. Their final length is .745". The nose measures at .218" and the driving bands and gas-check are at .225".
A couple of weeks ago I did a quick function check with 23.2gr of IMR4831 and this bullet in my 1-7 White Oak Armament Barreled AR15 at 100 yards. It fired and was accurate but did not lock the bolt back on the last round in a magazine which indicates to me of a short-stroke situation. Coming home after the trip to the range I decided to do a ladder test with the same powder and boolit to gain 100% reliability as well as a more accurate load. I also intended to verify my projected speed with this load which was expected to be 2100fps.
Today was a day off from work so I piled everything into the van that I would need to do my experiments. I included another 20" AR-15 with a 1-9" barrel as well, to see if the loads would work in separate AR systems with equal accuracy. I also loaded a few test rounds of this boolit for a 22-250 rifle as well to see if the 1-14" barrel agreed with this heavier mold.
Today was a grey overcast, windy and cold day (25F) here in Central Indiana. Too overcast for my Chronograph to properly read the velocity of the boolits going over its screens. That will have to wait for a sunnier day.
All targets were shot at the 50-yard line over a sandbag to try to eliminate the blustery winds that were going over the berms as much as possible. All stages were shot in 5-shot strings
First firing test:
1-14" 22-250Rem
25gr of Russian Surplus 4895. - Not good. 4" group with a flyer pushing the overall group to over 6" at 50 yards.
11gr of Red Dot. - Also not good. A 5 inch group.
Both groups showed tipping of the boolits in flight. The 1-14" twist is not stabilizing the 69gr boolit enough at this expected velocity. No Keyholes at 50yds but the potential is there for further distances showing that issue. This mold will not be used in the 22-250 again. The slower twist barreled rifle will be used with the 55gr BATOR mold instead where it has shown consistent accuracy.
Second firing test
1-7" 223 Rem WOA 20" barrel AR15
69gr 223 Remington COAL - 2.224" with .472" of the boolit exposed. The boolit has .006" free-space in the AR15 magazine.
IMR4831 - Ladder Test
starting load 23.2gr and final load was 24.5gr
23.2gr - a 2" grouping in the black with 6/3rear sight setting. Scored at 46-1x for 5 shots. Bolt did not lock back on the last shot. Ejection was at 4 o'clock from me.
23.5gr - a 3.4" vertical stringing due to my breathing. a rushed group but still a 48-3x for 5 shots. Bolt didn't lock back on last shot. Ejection was at 4 o'clock.
24.0gr - a 4.2" grouping. This group was high in the 6-7ring and at 10 o'clock on the target. Bolt DID lock back on last shot. Primers are well-rounded and ejection was at 3 o'clock
24.5gr - a 4" group at 12 o'clock in the 6-7 ring. Bolt locks to rear after last shot. Primers starting to flatten and ejection was at 3 o'clock.
25.0gr - load was not fired due to appearance of the previous load's primer. They will be pulled later this month.
Russian I4895:
24.0gr - not good at all today. This data is counter to the previous experiment with this rifle a few weeks prior. Not sure if the two different stick powder residues conflicted in some way. The load will be shot one more time to determine actual velocity but it may not be a serviceable loading.
I will not load this bullet heavier that 24.0gr in IMR4831 due to the larger group size than the 23.5gr load. Additional ladder test from 23.5 to 23.9gr to determine the spot when the bolt does lock back is warranted on a warmer day. The Russian powder will be ladder tested with lesser amounts at a later date as well.
Third Test
1-9" Model1Sales 20" AR15
69gr 223 Remington COAL - 2.224" with .472" of the boolit exposed. The boolit has .006" free-space in the AR15 magazine.
IMR4831 - Ladder Test
starting load 23.2gr and final load was 24.5gr
23.2gr - a 1.5" grouping in the black with 6/3rear sight setting. Impact was different (lower) than previous rifle My son normally shoots th rifle so the front sight was set differently than my 1-7" WOA. - Scored at 41-0x (2-9s, 2-8s, 1-7)for 5 shots. Bolt DID lock back on the last shot. Ejection was at 5 o'clock from me. It could easily be moved up the 2" to the X-ring for a 100 yard rifle match
23.5gr - a 3.4" horizontal group due to rushing the shots because of excitement over first group. (1-9, 2-8s and 2-7s) a rushed group 31-0x for 5 shots. Bolt DID lock back on last shot. Ejection was at 5 o'clock. (This is the expected ejection pattern for Milsurp Brass in an AR15)
24.0gr - a 6" grouping. This group was low in the 5-6-7ring and from 8 to 4 o'clock on the target. Bolt did lock back on last shot. Primers are well-rounded and ejection was at 3 o'clock
24.5gr - a 12" group (Call it a pattern - not worth scoring) Bolt locks to rear after last shot. Primers starting to flatten and ejection was at 2 o'clock.
25.0gr - load was not fired due to appearance and performance of the previous load. As in the previous test, these will be pulled.
Russian I4895:
24.0gr - not good at all today in the 1-9" barrel. The load will be shot one more time to determine actual velocity but it will probably not be a serviceable loading either until I know if I'm shooting it too fast.
I will not load this bullet heavier that 24.0gr in IMR4831 due to the much-larger group size in the 24.5gr load. Additional ladder test from 23.0 to 23.5gr to determine the spot when the bolt does lock back is warranted on a warmer day.
Overall Findings.
The 22-250 barreled rifle will not properly stabilize the 69gr MiHec Boolit at its currently expected velocity of 2100fps. I will reshoot these same loads later for chrono data but not bother to repeat further 69gr experiments.
The 1-7 WOA has potential for a developing into a good 100 yard Highpower Rifle match round. Same with the 1-9" Model1 as well.
Finally, I have a custom .225 mold in 69gr. It is not the 75gr I was originally planning to receive but this weight boolit has a lot more potential than many may realize in a tight-twist AR. Since I tested in 1-7" and 1-9" AR Barrels, I would be confident to say that a 1-8" barrel would also be a viable twist rate for this boolit mold.
If I ever chamber a tight-twist 22-250 barreled rifle I would be very tempted to see what that rifle could do with this mold.
Bruce
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