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Nice post op.
I have wanted one since I got a chance to shoot one in Afghanistan. Maybe it’s time to start part shopping. |
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Had mine built by Jason from Accurate Ordnance. Waiting for the can to shoot it. Form 4 was sent in August of last year so maybe soon....
Any word on the mk248 mod 0 with the long OAL on gunbroker? |
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''Hokey religions and ancient weapons are no match for a good blaster at your side, kid.''
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Very cool write up!
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Proud member of Team Ranstad
Member of the National Rifle Association, the Texas State Rifle Association and Gun Owners of America |
Originally Posted By KavonTN: Had mine built by Jason from Accurate Ordnance. Waiting for the can to shoot it. Form 4 was sent in August of last year so maybe soon.... Any word on the mk248 mod 0 with the long OAL on gunbroker? View Quote I bought a case, haven’t gotten a chance to try it yet though. The rounds are significantly longer than factory Federal GMM 190gr, but still fits in AI magazines without issue |
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Originally Posted By MickeyWHS: I bought a case, haven't gotten a chance to try it yet though. The rounds are significantly longer than factory Federal GMM 190gr, but still fits in AI magazines without issue View Quote The issue isn't with the mags, the issue is with the chamber. The Mk13 Mod 7 specifically has a chamber for the 220gr bullet (Mk248 Mod 1 ammo) and it's longer bullet that the 190gr (Mk248 Mod 0 ammo), which creates a longer OAL length. The new chamber reamer pushes the throat out more so that the 220gr bullet doesn't get jammed in the barrel's lands/grooves. I'm not buying any of that ammo because of this and if I did buy some, I'd run it through some properly set seating dies and seat the bullet to the proper depth for the Mk248 Mod 0 (if it is indeed seated long and that's what's causing the OAL issue). If the bullet is seated further out, they could have mistakenly run the 190gr Mod 0 ammo through loaders set up for the 220gr ammo, this is the only thing I can think of for why it's a longer OAL. And if they were running the 190gr Mod 0 ammo to the 220gr Mod 1 specs, there might also be an issue with more powder (IIRC the Mod 1 has more powder that the Mod 0 ammo, about 77gr vs about 74gr). Don't use this load estimation, go look up the actual load specs. If there is more powder than normal in these Mk248 Mod 0 rounds, you'll have to reduce the powder load before you reseat the bullet to the correct depth. Remember, it's always been recommended that you fire the Mk248 Mod 1 ammo in a rifle like the Mod 7 because it has the specific Mod 1 chamber. Mk248 Mod 1 ammo is loaded very hot and long (giggity), so if you put it in a regular Mk13 Mod 0/1/2/3/5 chamber, this might cause a serious issue with pressure spiking to dangerous levels. This longer OAL Mk248 Mod 0 ammo might not be loaded as hot as Mk248 Mod 1 ammo, but the longer seating depth could jam it in the barrels lands/grooves, which could also spike the pressure. Like I said before, there could also be an issue with the powder load, not just the OAL. The Mk248 Mod 0 chamber is only for Mod 0 ammo and it's a very specific OAL. It's not designed for Mk248 Mod 1 OAL lengths, if this is the case with this ammo. I have no idea if any of the above is what's going on with the newly released batches of long OAL Mk248 Mod 0 ammo, but use your best judgment. Unless you want to be nicknamed "lefty" for the rest of your life, you should put in a lot more research than "but still fits in AI magazines without issue." This goes for everyone who reads this, you've been warned. No matter what, always check your rifle and fires brass for signs of over pressure. If you see anything that points to it being over pressure, stop shooting the ammo immediately. TL/DR: Mk248 Mod 0 ammo could be loaded to Mk248 Mod 1 specs, just with a 190gr bullet instead of a 220gr bullet. This can lead to pressure issues in all .300 win mag rifles that don't have a specific Mk248 Mod 1 chamber. The silver lining is that this ammo might work just fine in Mk13 Mod 7 clones or other rifles that had the chamber cut with a specific Mk248 Mod 1 reamer. I hope this all makes sense, I'm just trying to think of what could be going on. I just did a Google search for Mk248 ammo and came across this post. There are plenty of other people who have run into similar issues. Make sure you know exactly what's going on before you pull the trigger! https://www.sniperforums.com/threads/military-mk248-mod1-psa-warning.35165/ |
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Thanks for the reply, it makes total sense. I figured I would pull some bullets, check powder / bullet weight, etc, and then if everything checks out with those rounds I could just seat all them to the proper OAL.
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''Hokey religions and ancient weapons are no match for a good blaster at your side, kid.''
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Originally Posted By KavonTN: Thanks for the reply, it makes total sense. I figured I would pull some bullets, check powder / bullet weight, etc, and then if everything checks out with those rounds I could just seat all them to the proper OAL. View Quote That's the perfect thing to do. If you can, please post your findings with the OAL and powder weight in this thread. If they loaded the 190gr bullet to 220gr specs, maybe they also put the wrong amount of powder in the case. That would be a pretty bad situation, since the Mod 1 ammo is a compressed load that tries to replicate the low end performance of the .338 Lapua Magnum. If the long Mk248 Mod 0 ammo is indeed produced to the Mk248 Mod 1 specs, you'll have to drop about 3 grains of powder (about 77gr to 77gr) before reseating the bullet to the proper depth. My grain weight is just a guess, you'll have to look up the specifics on the load. These aren't things to be taken lightly and the information you post will be extremely useful to everyone here. You'll be doing a lot to keep things safe and your help is greatly appreciated. I hope everyone knows how to looks for over pressure signs if they decide to use this ammo as is. |
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Originally Posted By USMCSGT0331: The issue isn't with the mags, the issue is with the chamber. The Mk13 Mod 7 specifically has a chamber for the 220gr bullet (Mk248 Mod 1 ammo) and it's longer bullet that the 190gr (Mk248 Mod 0 ammo), which creates a longer OAL length. The new chamber reamer pushes the throat out more so that the 220gr bullet doesn't get jammed in the barrel's lands/grooves. I'm not buying any of that ammo because of this and if I did buy some, I'd run it through some properly set seating dies and seat the bullet to the proper depth for the Mk248 Mod 0 (if it is indeed seated long and that's what's causing the OAL issue). If the bullet is seated further out, they could have mistakenly run the 190gr Mod 0 ammo through loaders set up for the 220gr ammo, this is the only thing I can think of for why it's a longer OAL. And if they were running the 190gr Mod 0 ammo to the 220gr Mod 1 specs, there might also be an issue with more powder (IIRC the Mod 1 has more powder that the Mod 0 ammo, about 77gr vs about 74gr). Don't use this load estimation, go look up the actual load specs. If there is more powder than normal in these Mk248 Mod 0 rounds, you'll have to reduce the powder load before you reseat the bullet to the correct depth. Remember, it's always been recommended that you fire the Mk248 Mod 1 ammo in a rifle like the Mod 7 because it has the specific Mod 1 chamber. Mk248 Mod 1 ammo is loaded very hot and long (giggity), so if you put it in a regular Mk13 Mod 0/1/2/3/5 chamber, this might cause a serious issue with pressure spiking to dangerous levels. This longer OAL Mk248 Mod 0 ammo might not be loaded as hot as Mk248 Mod 1 ammo, but the longer seating depth could jam it in the barrels lands/grooves, which could also spike the pressure. Like I said before, there could also be an issue with the powder load, not just the OAL. The Mk248 Mod 0 chamber is only for Mod 0 ammo and it's a very specific OAL. It's not designed for Mk248 Mod 1 OAL lengths, if this is the case with this ammo. I have no idea if any of the above is what's going on with the newly released batches of long OAL Mk248 Mod 0 ammo, but use your best judgment. Unless you want to be nicknamed "lefty" for the rest of your life, you should put in a lot more research than "but still fits in AI magazines without issue." This goes for everyone who reads this, you've been warned. No matter what, always check your rifle and fires brass for signs of over pressure. If you see anything that points to it being over pressure, stop shooting the ammo immediately. TL/DR: Mk248 Mod 0 ammo could be loaded to Mk248 Mod 1 specs, just with a 190gr bullet instead of a 220gr bullet. This can lead to pressure issues in all .300 win mag rifles that don't have a specific Mk248 Mod 1 chamber. The silver lining is that this ammo might work just fine in Mk13 Mod 7 clones or other rifles that had the chamber cut with a specific Mk248 Mod 1 reamer. I hope this all makes sense, I'm just trying to think of what could be going on. I just did a Google search for Mk248 ammo and came across this post. There are plenty of other people who have run into similar issues. Make sure you know exactly what's going on before you pull the trigger! https://www.sniperforums.com/threads/military-mk248-mod1-psa-warning.35165/ View Quote Thanks for the info, I’ve been hesitant to shoot this new ammo for pretty much these exact reasons. However, I have conferred with Chris at Red Bull Armory and based on the OAL of the “seconds” he thinks it will be safe to shoot (at least in one of his rifles, which he states uses the same reamer/chambering on the Mod 5/7). I have also talked to other individuals who have used the same “seconds” ammo with the same “exceeds Sam spec” warning sticker and haven’t encountered one that has had issues thus far. I will try to chronograph this ammo in the next week or so and compare it to my factory Federal GMM 190gr (which chrono’s around 3050fps out of my MK13). Assuming the velocity isn’t crazy high I believe it will be alright to shoot through a properly built MK13. |
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''Hokey religions and ancient weapons are no match for a good blaster at your side, kid.''
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Originally Posted By KavonTN: Just keeping the thread alive... https://i.imgur.com/iweV6bn.jpeg https://i.imgur.com/15vdjMQ.jpeg Haven't been this excited for a stamp in a long time. Purchase date was 6/15/21. ETA quick mock up. My local gunsmith wanted the can when he finishes the barrel profiling so its not done yet. https://i.imgur.com/O4U9ZyW.jpeg View Quote Looks great! I have a feeling that all of the MK13 builds we’ve been seeing lately are gonna slow waaaaaaay down with the chassis and MK11 suppressors drying up once again. Sad, but it was bound to happen eventually |
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