Nosler 77 grain BTHP
In 2003, 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 and B&T Ammo Labs, 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 loaded to mil-spec velocities rival that of the Hornady 75 grain 5.56 TAP load. Unfortunately, there are no ammunition manufacturers currently loading the 77 grain Nosler to mil-spec velocities.
Courtesy of Dr. G.K. Roberts
Courtesy of B&T Ammo Labs
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. The forend of my Krieger barreled AR-15 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 sighting. 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. (In previous testing, I found that the average muzzle velocity from seven different lots of Hornady 5.56 TAP was 2808 fps from a 20 barrel.) 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 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."
Accuracy testing using the Noveske barreled AR-15 and Nosler 77 grain BTHP at a muzzle velocity of 2800 fps 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.
Previous accuracy testing of the 75 grain Hornady 5.56 TAP load from my 16 Noveske barreled AR-15 produced a 10-shot group average of 1.22 at a distance of 100 yards with a 30-shot composite group mean radius of 0.37.
As previously mentioned the 77 grain Nosler BTHP has terminal ballistic properties on par with the TAP load. This testing shows that the 77grain Nosler BTHP bullet loaded to a muzzle velocity of 2800 fps, is capable of accuracy that is slightly better than that of the TAP load.
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Originally Posted by sinister
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