Yep it’s a new set of nat match dies and I need to hone stem. 85-90 percent fill.
I can shake the cases and hear powder shaking. So not sure but I will do a water capacity test on one when I get home.Unless you have the most voluminous Lake City cases in history, I doubt that you're getting only an 85-90% fill with 23.5 grains of BenchMark. The 77 grain Tipped MatchKing is longer than the standard 77 grain MatchKing and it eats up more of the case volume.
Quick Load puts the fill at over 100% with 23.5 grains of BenchMark and you can hear the kernels being crunched together when the 77 grain TMK is being seated with that powder charge.
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30.6 grains of h2o water capacityUnless you have the most voluminous Lake City cases in history, I doubt that you're getting only an 85-90% fill with 23.5 grains of BenchMark. The 77 grain Tipped MatchKing is longer than the standard 77 grain MatchKing and it eats up more of the case volume.
Quick Load puts the fill at over 100% with 23.5 grains of BenchMark and you can hear the kernels being crunched together when the 77 grain TMK is being seated with that powder charge.
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I can guarantee you that was someone not paying attention to their rifle behavior or powder measure. I have 223 lapua brass that has over 20 firings all over max load.Brass can look "pretty good", right up until the shot that it doesn't.
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Any idea what powder was used in those?Black Hills MK262 is not "over pressure." Mk262 has always been clearly marked as a 5.56 load. Not only did Mr Hoffman sell the 5.56 cosmetic seconds of MK262 with the 77 grain MatchKing, he also sold some of us 5.56 Mk 0 loads with the 77 grain Nosler bullet.
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Non-cannister grade powder…Ive duplicated mk262 mod 1 using 25g AA2520, Remington 7-1/2 primers and 1x fired Lake City brass. Shoot the exact same load in all my carbines and mk12 mod 1. Prints, moves and flies identical to the black hills stuff. I would imagine it would perform similar with a 77g TMK.
You’re welcome and sorry to hear of the back issue…4895 has a similar burn rate as TAC so you should be able to get it to work though you may not achieve the same MV before over-pressure as you would with 2520 or perhaps Lever.
Outstanding. I have heard that much of the terminal effectiveness of the mk262 is due (at least in part) to the jacket coming apart at the cannelure. I have recovered jackets and fragments of 75gr hornady bullets from dirt mounds that seem to support this. Makes sense the thinner jacket of the Nosler would be ideal.This one.
The muzzle velocities of the Black Hills lot with the 77 grain Noslers were screaming.
20” Colt A2 barrel: 2867 FPS
16” Colt 6520 barrel: 2770 FPS
14.5” Colt M4 barrel: 2630 FPS
The terminal ballistic properties of the 77 grain Nosler are superior to that of the 77 grain MatchKing, but the Noslers have never shot as accurately in my AR-15 barrels as the MatchKings. The 10-shot group of hand-loads topped with the 77 grain MatchKing pictured below was fired prone off a bipod from my Lothar Walther barreled AR-15. The group has an extreme spread of 0.54 MOA.
The above load is charged with VihtaVuori powder and a 10-shot string over the chronograph with this load fired from a 20” Colt A2 barrel has produced standard deviations of 4 FPS.
Since the 77 grain Nosler has better terminal ballistic properties than the 77 grain MatchKing, I do use the Noslers for a defensive load. The accuracy of the Noslers is more than adequate for that intended purpose, as demonstrated below.
Nosler 77 grain Custom Competition
Nosler introduced their 77 grain Custom Competition BTHP bullet as an obvious competitor to the 77 grain Sierra MatchKing. The shape and ballistic coefficient of the Nosler bullet is very similar to that of the Sierra MatchKing. The Nosler bullet does have one major difference from the Sierra MatchKing; it is constructed using the thinner J4 copper jacket.
I recall an early Nosler advertisement for their Custom Competition bullet that included a phrase saying the bullet was “ideal for military and law enforcement,” hinting at the possibilities of improved fragmentation due to the thinner J4 jacket.
Thanks to the works of Dr. G.K. Roberts we know that the 77 grain Nosler bullet loaded to mil-spec velocities has superior terminal ballistic properties to that of the 77 grain Sierra MatchKing loaded in MK262. The terminal ballistic properties of the 77 grain Nosler bullet rival that of the Hornady 75 grain 5.56 TAP load. Unfortunately, there are no ammunition manufacturers that I’m aware of currently loading the 77 grain Nosler to mil-spec velocities. Nosler does produce a SAAMI spec load using this bullet.
The Nosler 77 grain Custom Competion bullet is typically sold without a cannelure, however Nosler occasionally releases the bullet with a shallow cannelure similar to the one found on the 77 grain SMK loaded in MK262. The cannelured version of the 77 grain Nosler will be the focus of this report.
For the first phase of testing, I hand-loaded the cannelured version of the 77 grain Nosler BTHP to a typical SAAMI velocity (approximately 2600 fps from a 20” Colt barrel) to establish an accuracy baseline. No case mouth crimp was applied at this phase.
As per my usual protocol, accuracy testing was conducted from a concrete benchrest at a distance of 100 yards. For this phase of testing I used one of my 1:7.7” twist Krieger barreled AR-15s . This barrel has produced sub ½ MOA 10-shot groups with my hand-load topped with the Sierra 55 grain BlitzKing. The fore-end of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rode in a Protektor bunny-ear rear bag. A Leupold Competition Scope was used for testing. Wind conditions were monitored using a Wind Probe.
Three 10-shot groups were obtained which had extreme spreads of
0.797”
0.827”
0.812”
for a 10-shot group average of 0.812”. The three groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The composite group had a mean radius of 0.26”. This test shows that the Nosler bullet itself is capable of consistent sub-MOA accuracy at 100 yards when fired from a semi-automatic AR-15.
For the second phase of testing, I safely worked up a load for the 77 grain Nosler BTHP to a nominal muzzle velocity of 2800 fps from a 20” barrel using a non-canister grade military powder which has a velocity-to-powder-charge ratio that is very close to that of the powder used in MK262. No case mouth crimp was used in this phase of testing either.
Since my Krieger barreled AR-15 has a 5.56mm Match chamber that is “a little too tight” for mil-spec pressure loads, I used my AR-15 with a 20” Noveske DCM barrel with a 1:7” twist for this phase of testing. This Noveske barrel has the “Noveske Match Mod 0 chamber which is designed to offer 100% reliability while retaining maximum possible accuracy. The chamber body is slightly larger than the 5.56mm NATO minimum, but within the 5.56 NATO tolerance. The throat is redesigned for proper bullet alignment with the axis of the bore. This chamber was developed to fire MK262 Mod 1 on AUTO in hot environments." This barrel has produced sub ¾ MOA 10-shot groups with my 55 grain BlitzKing hand-load.
Accuracy testing using the Noveske barreled AR-15 and the mil-spec velocity load of Nosler 77 grain was conducted in the same manner as described above in the first phase of testing. Three 10-shot groups were obtained from 100 yards. Those groups had extreme spreads of:
0.880”
0.857”
0.845”
for a 10-shot group average of 0.860”! These groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group which had a mean radius of 0.29”.
For the final phase of testing I added a taper crimp to the case mouth of the previously described load used in phase two. A 10-shot string of this load fired over the Oehler 35-P chronograph from my 20” Novekse barrel had a muzzle velocity of 2801 fps with a standard deviation of 12 fps.
Three 10-shot groups fired from 100 yards from the 20” Noveske DCM barrel had extreme spreads of:
1.033”
0.914”
1.241”
for a 10-shot group average of 1.063”. As before, the three groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the composite group was 0.31”.
For comparison, Black Hills MK262 Mod 1 fired from my Lothar Walther barrel AR-15 had a 10-shot group average extreme spread of 1.098”. The mean radius for the 30-shot composite group of MK262 Mod 1 was 0.33”.
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I switched from TAC to AA2520 for my mk262 mod 1 clone load in 2019. Above 24.5g, TAC was overpressure, and at 25g primers were falling out (only saw this in limited testing as i never loaded 25g in a TAC-based prod lot).
Because I am old and spent most of my time working with 308 F TR and 338 Lapua loads. Lol. I was told Tac was the powder to use back in the day and it worked well These days I shoot a bunch more 5.56 and basically relearning
I’ve shot 8208xbr the last 3 seasons, but have to switch this year due to availability.
Would be interested to hear how things go with Lever. TAC will likely max out at 24.0-24.6 before you hit pressure, assuming Starline has similar capacity to LC and many other 5.56 manufacturers.
Lever and CFE223 are almost the same. A good friend swears by CFE223 in his 77 grain loads and uses them interchangeably.
Ive tried cfe223 and wasnt getting near the same velocity and precision as i have w/2520. Of all the powders ive tried w/the 77smk, including XBR, cfe223, tac and varget, 2520 has been the best overall performer.
How well does 2520 perform with temperature changes? 8208XBR is so stable for me, and has a wide accuracy node.
Its going to be a little more sensitive than a single based powder like XBR but that said, I don’t see massive delta in mv and no poi shift from winter to summer…ill have to double check my dope but off the top of my head i think im .1-.2 flatter in 90 degree temps than i am in 59 degrees at 500m with the mk12 mod 1.
