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Posted: 1/12/2016 9:34:24 PM EDT
[Last Edit: Molon][Edited]
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PMC 5.56mm 62 Grain X-TAC Ammunition Attached File PMC’s 62 grain X-TAC ammunition is loaded in brass cases that have the annealing iris still visible. The 62 grain projectile has a copper jacket construction with a lead core and a steel insert in the ogive. The tip of the bullet is painted green. The case mouth is taper crimped into the cannelure of the bullet and the case-mouth is sealed with asphalt sealant. Attached File Attached File The boxer primers are sealed and crimped and the load is charged with “ball” powder. Attached File (The individual squares in the red grid below are 1/10th of an inch.) Attached File After reading the above description of this PMC ammunition, some of you might be thinking, “I wonder how this ammunition compares to M855?” So, let’s compare! The US mil-spec for M855 (MIL-C-63989C [Amendment 4]) states that the average velocity of the cartridges “shall be 3,020 feet per second (fps) plus or minus 40 fps at 78 feet from the muzzle of the weapon. The standard deviation of the velocity shall not exceed 40 fps.” This specification is for a 20” barrel and depending upon variables equates to a muzzle velocity of approximately 3105 FPS (plus or minus 40 FPS.) As an aside, after reading the above specification, some of you may be wondering, “Why 78 feet from the muzzle?” The answer to that question is that this specification is simply an historical hold-over from the days when “circuit” chronographs (e.g. Le Boulenge Chronograph and the Aberdeen Chronograph) were used at Aberdeen Proving Ground, Frankford Arsenal and Springfield Armory. These types of chronographs required a significant distance between their first and second screens to produce accurate results. As an example, when using the Boulenge Chronograph, the first screen of the chronograph was placed 3 feet in front of the muzzle and the second screen was placed 150 feet beyond the first screen. For those of you who might not be aware of the following fact; chronographs determine the velocity of the bullet at a point that is midway between the first and the second screen (i.e. not at the location of the first screen). Therefore, with the above spacing, the velocity of the bullet is determined for a point that is 75 feet from the first screen. So, add the three feet (from the muzzle to the first screen) to the 75 feet (the midway point of the screens) to obtain the “78 feet from the muzzle” distance. Attached File Attached File I chronographed the PMC 62 grain X-TAC ammunition from a semi-automatic AR-15 with a chrome-lined, NATO chambered 20” Colt M16A2 barrel. Attached File Chronographing was conducted using an Oehler 35-P chronograph with “proof screen” technology. The Oehler 35P chronograph is actually two chronographs in one package that takes two separate chronograph readings for each shot and then has its onboard computer analyze the data to determine if there is any statistically significant difference between the two readings. If there is a difference, the chronograph “flags” the shot to let you know that the data is invalid. There was no invalid data flagged during this testing. The velocity stated below is the muzzle velocity as calculated from the instrumental velocity using Oehler’s Ballistic Explorer software program. The string of fire consisted of 10 rounds over the chronograph. Attached File Attached File Each round was single-loaded and cycled into the chamber from a magazine fitted with a single-load follower. The bolt locked-back after each shot allowing the chamber to cool in between each shot. This technique was used to mitigate the possible influence of “chamber-soak” on velocity data. Each new shot was fired in a consistent manner after hitting the bolt release. Atmospheric conditions were monitored and recorded using a Kestrel 4000 Pocket Weather Tracker. Attached File Atmospheric conditions Temperature: 78 degrees F Humidity: 54% Barometric pressure: 29.99 inches of Hg Elevation: 950 feet above sea level The muzzle velocity for the 10-shot string of the PMC 62 grain X-TAC ammunition fired from the 20” Colt barrel was 3073 FPS with a standard deviation of 14 FPS and a coefficient of variation of 0.46%. For comparison, IMI M855 chronographed from the same 20” Colt barrel had a muzzle velocity of 3110 FPS with a standard deviation of 21 FPS and a coefficient of variation of 0.68%. For those of you who might not be familiar with the coefficient of variation (CV), it is the standard deviation, divided by the mean (average) muzzle velocity and then multiplied by 100 and expressed as a percentage. It allows for the comparison of the uniformity of velocity between loads in different velocity spectrums; e.g. 77 grain loads running around 2,650 fps compared to 55 grain loads running around 3,250 fps. For comparison, the US mil-spec for M855 allows for a coefficient of variation of up to approximately 1.3%, while one of my best 77 grain OTM hand-loads, with a muzzle velocity of 2639 PFS and a standard deviation of 4 FPS, has a coefficient of variation of 0.15%. Attached File …. I conducted an accuracy (technically, precision) evaluation of the PMC 62 grain X-TAC ammunition following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any Group Reduction Techniques (e.g. fliers, target movement, Butterfly Shots). The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Also, a control group was fired from the test-rifle used in the evaluation using match-grade, hand-loaded ammunition; in order to demonstrate the capability of the barrel. Pictures of shot-groups are posted for documentation. All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrel used in the evaluation was free-floated. The free-float handguards of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was used. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below. Attached File The Wind Probe. Attached File The test vehicle for this evaluation was one of my semi-automatic precision AR-15s with a 20” stainless-steel Lothar Walther barrel. The barrel has a 223 Wylde chamber with a 1:8” twist. Prior to firing the 62 grain X-TAC ammunition, I fired a 10-shot control group using hand-loads topped with a 62 grain OTM bullet. That group had an extreme spread of 0.83”. Attached File Attached File Next, three 10-shot groups of the 62 grain X-TAC load were fired in a row with the resulting extreme spreads: 2.76” 2.24” 3.07” for a 10-shot group average extreme spread of 2.69”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the 30-shot composite group was 0.88”. The smallest 10-shot group . . . Attached File The 30-shot composite group . . . Attached File …. |
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Originally Posted By IE-EastTexas: You are an invaluable member of this site! Thank you! Indeed he is! Regarding the 300BLK question, would you entertain doing a review on it? I'd surly send you ammo...hell, I'd send you my rifle too if you wanted... ETA: I'd want the rifle back though...  |
I have nothing else CoC compliant to say...
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Originally Posted By ControlledChaos999:
Regarding the 300BLK question, would you entertain doing a review on it? I'd surly send you ammo...hell, I'd send you my rifle too if you wanted... Thank you for your gracious offer, but I'm currently concentrating on 5.56mm/223 Remington loads. ... |
All that is necessary for Trolls to flourish, is for good men to do nothing.
In God We Trust. Everyone else must post data.
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Originally Posted By Molon:
Thank you for your gracious offer, but I'm currently concentrating on 5.56mm/223 Remington loads. ... Originally Posted By Molon:
Originally Posted By ControlledChaos999:
Regarding the 300BLK question, would you entertain doing a review on it? I'd surly send you ammo...hell, I'd send you my rifle too if you wanted... Thank you for your gracious offer, but I'm currently concentrating on 5.56mm/223 Remington loads. ... Any chance on reviewing the Federal 50gr Tipped Varmint or the Austrailian Outback 55 gr/69gr ammo? People seem to be getting good accuracy out of these and they run around $0.50/round. Either way, thanks again for the excellent work! |
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Originally Posted By Trey-W:
Any chance on reviewing the Federal 50gr Tipped Varmint or the Austrailian Outback 55 gr/69gr ammo? People seem to be getting good accuracy out of these and they run around $0.50/round. Either way, thanks again for the excellent work! Just some "SnapShots". Australian Outback Sierra 55 Grain BlitzKing 
When chronographed from a 20” Colt M16A2 barrel over an Oehler 35-P chronograph with “Proof Screen Technology”, the Australian Outback Sierra 55 grain BlitzKing load had a muzzle velocity of 2972 FPS with a standard deviation of 20 FPS. A 10-shot group fired off the bench at a distance of 100 yards from one of my AR-15s with a Krieger barrel that has a 223 Remington chamber and a 1:9" twist had an extreme spread of 0.98". 
I also fired another 10-shot group of the Australian Outback load from one of my AR-15s with a Krieger barrel that has a 5.56mm match chamber and a 1:7.7" twist. That group had an extreme spread of 0.92". 
..... American Eagle AE223GTV 
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Originally Posted By itssadbutdrew:
@molon you ought to be getting paid to do this. there should be a tab on this site (or any site) that catalogs your data. thank you! De rien. 
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All that is necessary for Trolls to flourish, is for good men to do nothing.
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Originally Posted By Another-Bill:
As always thanks again for you contributions. As always, you are quite welcome. P.S. Is that x-ray in your avatar of you? ... |
All that is necessary for Trolls to flourish, is for good men to do nothing.
In God We Trust. Everyone else must post data.
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Originally Posted By -Time-:
Have you ever thought of testing how much (if at all) the paint on the tips of military rounds effects accuracy? Ah, no.
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All that is necessary for Trolls to flourish, is for good men to do nothing.
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Originally Posted By itssadbutdrew: @molon you ought to be getting paid to do this. there should be a tab on this site (or any site) that catalogs your data. thank you! I'm working on putting together a "Molon Reference Links 2021" thread. Stay tuned to your local station.  ... |
All that is necessary for Trolls to flourish, is for good men to do nothing.
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Originally Posted By itssadbutdrew:
@molon you ought to be getting paid to do this. there should be a tab on this site (or any site) that catalogs your data. thank you! Up and running, more links to be added. Molon Reference Links 2016 ... |
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Originally Posted By samuse:
I burned through many cases of that ammo back in 2010-2012 in training classes. I didn't mention it in the original post, but I also had no malfunctions with this ammunition. ... |
All that is necessary for Trolls to flourish, is for good men to do nothing.
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LOL, I clicked to see if the OP had the same results I did, and found my original reply from 2016. im VERY GLAD you're back Molon |
Don't be so open-minded that your brains fall out.
General education should not be mere job training, but training of the mind to reason. https://welltrainedmind.com/a/classical-education/
General education should not be mere job training, but training of the mind to reason. https://welltrainedmind.com/a/classical-education/
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Originally Posted By ITCHY-FINGER: Last time I shot this load I was impressed with the accuracy, compared to the other M855 clones. For comparison . . .  ... |
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