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[ARCHIVED THREAD] - 6.5 MPC (Page 1 of 2)
Posted: 6/22/2006 5:04:38 PM EDT
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Anyone see this new round from SSK? 6.5 MPC that uses 5.56 brass and uses unmodified M16 mags and bolts for Ar15s. 6.5 MPC... The 6.5 MPC (Multi Purpose Cartridge) is a SSK development urged by Brian Hormberg (USMC) based on the 5.56 cartridge shortened and opened to 6.5 MM and the same OAL as the 5.56. In the M-16-AR-15 rifles it utilizes the 5.56 bolt and magazines as well as all other parts except the barrel itself. Its design adapts it to a short Close Quarter Battle rifle with a 12” barrel moving a 107 6.5 SMK at 2400 FPS with superior full auto controllability and excellent accuracy. The 12” barrel model easily puts it into the realistic 300+ yard combat category and longer barrels stretch that realistic combat range considerably further. Factory ammunition is not yet available for the 6.5 MPC; however we are working on that. Ready to load brass and dies are in stock. The 120 grain BT is near maximum bullet weight for good performance. 85 grain is about the least weight for good performance. Some 140 grain bullets may be used but ballistically are counterproductive. 95 SSK Solid - - - - - - - 12" 2600 FPS 20" 2800 FPS 110 Sierra HP - - - - - - - - - - - 12" 2480 FPS 20" 2731 FPS 120 SMK - - - - - - - - - 12" 2220 FPS 20" 2400 FPS 
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We experimented with a very similar type of cartridge about 2 years ago. It was interesting, but because it didn't meet the capability of other readily available cartridges for the AR platform, we abandoned it. It is interesting, and there's an advantage in using the smaller bolt face, and existing magazines. We felt that end-users would be more likely to select an off-the-shelf cartridge like the Grendel or 6.8SPC over it. I wish them luck with their new offering. |
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At this point it's more of an academic interest, but I'd like to see an "optimized" cartridge based on the .223 bolt face. For me, and without any testing, that would be a 6mmx41 based on 80-, 90- and 100-grain high BC bullets. Although, perhaps 5.56 Mk262 with a 77gr truly is optimum, all things considered? John ============ 6.5 Grendel: World's Best Combat Cartridge |
Take a look at the 6x45mm I am loading the cartridge with Hornady 87 grain V-Max and a BC of .400. The Hornady 95 GR SST and 100 GR Boat Tail Spire Point look like a good match too. Joe |
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I'm just having a hard time believing some of these velocity numbers.. 110gr Sierra HP @ 2731fps out of a 20" barrel from a .223Rem/5.56 case while staying within current military specs for maximum average pressure? If I was forced to choose/guestimate, I'd put my money on this not being attainable in any kind of full scale production. It seems all new cartridges have wild velocity claims that they never live up to. They often still end up being great cartridges but at more moderate velocities. Not saying it's impossible, just that the introductory velocity claims are almost never correct so you can't blame me for being somewhat skeptical. "I'll believe it when I see it." |
I agree. Bring back some 77 fmj!!!! They made them in vietnam, why not now. I saw this 6.5 MPC used mentioned in an article and they said you didn't need to change followers in the mags at all. That is sort of a plus. |
The 77grn FMJ was developed for the Stoner 63 fitted with 1/8 barrels. A 68grn FMJ was also developed in hopes of extending the range of a 5.56 LMG. Terminal ballistics were poor by comparision to M193 and the bullet did not fragment, only yaw/tumble vastley reducing its effectiveness. It was more effective at defeating intermediate barriers and both were used sparingly in Vietnam with the Stoner 63 and literature also suggests both rounds were used with the Harrington and Richardson 33 rifle. These rounds would have provided the extended range which was so desperatly wanted and not realized until the adoption of the M16A2/M855. The biggest downfall for these rounds was the 1/12 barrel twist of the M16A1 which was incompatible with the very long 77grn FMJ. Infact, the DoD was so opposed to rebarreling M16A1's that it was opposed to adopting the SS109 and prefered there own semi/AP design, despite being inferior. SSK makes excellent and advanced ammunition, such as the .300 and .500 Whisper. Terminal effect is improved, especially when fired out of a carbine, but Mk262 offers a slight advantage in accuracy/terminal affect. The biggest advantage of the SSK round is its compatibility with existing components. The solution would be to further develop the 5.56x45 caliber as an interim solution and then adopt an entirely new caliber for the M16's inevitable replacement. Russia and China took advantage of our concept and further improved it, perhaps we can return the favor? Ironically, 77grn 5.56 bullets are all the rage, despite being a product of the 1960's. There is also an obsession with 6mm bullets for infantry rifles these days. In the early 1900's 6mm's reigned supreme and multiple countries used rifles chambered in this caliber, until it was deemed they were ineffective, and .30 caliber and larger calibers were utilized.....those who aren't familiar with the past are comdemed to repeat it. |
Actually, DocGKR tested some of the original 77gr NWM/IWK and 68gr IVI rounds in gel. As I remember it, the IVI only flattened, but the NWM/IWK fragmented like M193. Condemning certain bullet weights and entire calibers on previous performance of specific loads is foolish. Early yaw and fragmentation is really a matter of bullet design, construction, and manufacture. |
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I too am interested in seeing how the 6.5MPC plays out in testing. The benefit to 6.5MPC claimed is that to make the change to the new caliber requires nothing more than a barrel change. Current mags, pouches, bolts, etc are compatible 100%.... There is an article in the current "Gun Buyer's Annual" Special Weapons For Military and Police Magazine for those that might be interested.... |
Well, you sound like you know what you're talking about but I disagree with you on several accounts. The thickness of the jacket would change things. Why do you think the heavy BTHP's are superior in terminal ballistics. My suggestion is that from what I understand it's easier / cheaper to make a FMJ bullet than a BTHP. And you could make it a thickness that would be conducive to fragmenting. On top of that, like the other guy said I recall the doc saying that the 77 bullet did fragment. And if you are saying ALL .30 caliber bullets are more effective than ALL 6mm bullets, you are oversimplifying the matter. Again the construction of the bullet has everything to do with the performance. I'm actually just repaeting what dewatters just said, but so be it. 
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Reformatted the specs to make them more readable (this seems to be correct anyway). Copy/paste/post sometimes leaves unusual formatting... Very interesting cartridge. Yet another attempt at a short barrel optimised cartridge perhaps, like the MARS or KAC PDW cartridges? |
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I was just reading, in Barnes and Noble tonight, about this round in this month's Special Weapons - Military and Police. The author states that the only different thing needed is the barrel (good for 249 and can use the same links and feed system). Same mags as current M16, same bolt, same everything else. It also said the same number of rounds as 5.56 are held in the respective magazines. Whereas the 6.8SPC needed several changes made across the board (such as new mags) |
Cnatra, there's tons of detailed info on the 6.5 Grendel in the 6.5 Grendel FAQ section of the "AR Variants" forum. Enjoy! John |
Did they mention effective and max distances? |
They had various graphs but I forgot the numbers
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I've read all the 6.5 Grendel info. , wondering how the case volume & OAL of the 6.5 MPC compares |
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77 gr FMJ (head stamp: NWM 67) and 68 gr FMJ (head stamp: IVI 69) loadings were made for the Stoner 63A. Fired from an M16A2: 77 gr FMJ: vel = 2874 f/s, pen = 19.2”, neck = 5.1”, bullet fragmented like M193 68 gr FMJ: vel = 3014 f/s, pen = 14.6”, neck = 2.8”, bullet flattened but did not fx ========================= Loading a 6 to 6.5 mm bullet into .223 cases has been done for years--it just doesn't offer enough. I'd much rather use a 6.5 to 7 mm projectile in a case with a bit larger powder volume. |
This is the bottom line for me. I read the article and was instantly interested in the round. I can use the 50+ magazines I already have, and living in a blue state I can't buy new. I can modify my pet with only a barrel change. I will be giving up short range velocity for higher energy and a bigger hole. Is it the magic pill? No, but my M-4 is there for me professionally to handle 200m IN, not out. If I need to engage at that distance I can take cover and let the snipers play all day. Looks like it's an honest 400m cartridge, from an M-4 sized weapon what more do you want? I'll buy one if they become produced, period. waiting for the fisticuffs.
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DocGKR: I can understand your statement if it is about military use, However many of us see the advantage of such cartridges. I have worked with the 6x45mm for a little while now and see no down side to my choice and I am sure many others feel the same way. The 6.5 MPC is just another option for those of us looking to try something other than the 5.56mm. Joe |
Dr. Roberts, Those velocity figures look fairly promisng though. The 110 gr. Sierra HP reaches 2,731 FPS from a 20" barrel:
In contrast, the 5.56 (not .223) pressure 75gr. Hornday TAP load reaches 2,821 FPS from a 20" barrel, with the .223 pressure reaching 2,638 FPS, as shown by AR15.com member Molon below:  www.ar15.com/forums/topic.html?b=3&f=16&t=283506 The 110 gr. Sierra HP weighs 35 gr. more yet the velocity difference between it and the 5.56 pressure 75 gr. Hornday TAP is approx. 90 FPS (and I wonder if the 110 gr. Sierra HP loaded to that pressure would close the velocity gap even further). Even the 95 gr SSK solid reaches 2,800 FPS from a 20" barrel. Is this a good indication to you Dr. Roberts? I mean, from the limited data I have seen, those velocities for the 110 gr. load look somewhat similar to 6.8 SPC loads, no? Justin |
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The numbers for the 6.5 MPC look real close to being what I would expect having experienced the same thing with the 6X45mm. With a case such as the .223 Rem an increase in bullet diameter to 6mm will generally give you an increase in velocity of around 100 fps with the same pressure and bullet weight. This is because there is more surface area at the base of the bullet for the gas pressure to push against. I have had no trouble pushing a 6mm 85 grain bullet to 2700 fps out of my 20" barrel, so I think that the 6.5 MPC 95 grain bullet at 2800 fps is a good number but a maximum load. Just like with any listed load you might not be able to reach this with all barrels before you start seeing signs of high pressure. We need to see some ballistic numbers from other sources to get a better picture of how well this cartridge can perform, and then start looking at what bullets give the best terminal effect. Lets not lynch this cartridge before it has had its day in court. Joe |
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Well, the necked-up design does allow more "push", due to the so-called "piston effect", which allows the pressure to act on a larger surface at the base of the bullet, which will give a boost. In addition, the 5.56-sized bolt face diameter allows more pressure in the cartridge, compared to cartridges with larger bolt faces, because of the bolt-lug strength limitations in the AR15. However, our testing of a similar cartridge showed that there were limitations to what we could get from a case like that, which did not meet our desired goals. Also, the case length of 45mm is too long to seat the heavier and longer types of 6.5mm bullets for maximum effect at longer ranges. We cut the case back a few millimeters, and changed the shoulder a bit, so that the cartridge could take the 123gr and even the 142 gr 6.5mm bullets, and still fit into the magazine to feed correctly. It is an interesting project, and does show some promise. But in the end, I think you're going to find out that these other cartridges like the 6.8 and 6.5G are going to exceed the abilities of the necked-up 5.56 in any configuration. Simply because you have more case volume with them, and that is the basic answer. That doesn't mean that the 6.5/223 doesn't have a good capability, or has no use. To the contrary, it could/probably will perform quite well for what it is. Just that I think that it won't be the top performer on the block. I look at it as a "case rim diameter vs case capacity" showdown. You can run higher pressures because of the smaller case rim on the 6.5/223. You can run more powder with the 6.8SPC or the 6.5Grendel, at lower pressures. The 6.5/223 will suffer from the longer case not being able to seat the longer bullets for its caliber, and still fit into the mag. The slightly shorter 6.8SPC will allow slightly longer seating, and still get the cartridges into the mag, and has more case capacity, at the expense of increased bolt-face diameter, and thus slightly weaker lug strength. The 6.5Grendel allows much more seating length to run nice long bullets that will fit into the mag, has more case capacity, but has to open the bolt-face up even further than the 6.8, so it must run at even lower pressures because of the bolt lug strength issues, and it is fatter yet, so it will stack fewer rounds in the mag. Take yer pick. |
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twl: Thanks for your perspective on this. I think cartridges like these do have potential, the big question will it have enough appeal to survive in the market. For now I am happy with my 6.8 SPC, 6x45mm and 5.56x45mm rifles, but who knows maybe a 6.5 MPC is on the horizon. Joe |
The voice of reason. |
| Something to keep in mind here is what the design goals for some of these newer cartridges actually are. IMHO, this round shares some design goals along with the new KAC PDW round, to wit, to improve terminal performance, reduce firing signature (blast & flash), and maintain usable ballistics out of subcarbine size weapons (12" and shorter), over existing 5.56mm. That's where I see the potential for this round, as an easy conversion for that usage. |
| Here's some load data for the 6.5mm TCU www.reloadbench.com/cartridges/w65mmtcu.html |
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Even if it performs slightly below the 6.8 or other wildcats, the fact that it uses regular AR mags and bolt is in and of itself a big advantage. It would still make a good 2 legged varmit stopper at distances out to 300 meters and it can be used for medium sized game as well. Now if someone said " hey, the Army is testing it", the band wagon would fill up quick. |
Exactly. All that needs to be changed is the barrel. And the magazine capacity remains at 30 rounds. I wonder what kind of numbers they could get with the improved St. Mark's powder? |
[ARCHIVED THREAD] - 6.5 MPC (Page 1 of 2)
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