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Posted: 12/13/2013 11:43:32 AM EDT
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I've got the craving for a 7mm-08 AR. I think I've read everything in the AR Variant section. I currently can't find a 7mm-08 upper listed by anyone, unless I'm overlooking it. RRA used to carry them, but don't now. I was going to find a 7mm-08 upper, then mate it to a AR10 lower from CMMG, DPMS, etc. I know the Remington R-25 is available in 7mm-08, but I don't really want the camo finish.
If I can't find an upper anywhere else, what's everyones opinion on the R-25? I like the S&W M&P 10, but it's .308 only. I hate to buy a M&P10, then have to rebarrel it to 7mm-08. I've got 7mm calibers in hunting rifles (280 Remington & 7RUM) and Thompson Contender's in 7-30 Waters, because I'm partial to the BC of 7mm bullets. I feel the 7mm-08 in an AR is as close as I can get to the 280 Remington, which is my all time favorite hunting round for whitetails (I've taken over a hundred of them), antelope (several) and muley's (dozens). I've got AR15's that I've either bought as complete or mated complete uppers to complete lowers, but I've never assembled an AR upper. Is that what I should do, or have done? Suggestions? Comments? Thanks in advance! |
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I'm interested in this as well.
One of my future builds may be a 7mm08 AR. I already have a Remington Model 7 in the caliber. It only has a 18.5" barrel though. So, if I do build one, I want the barrel to be over 20". Hopefully this thread won't turn into a .260 Rem vs 7mm08. |
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This is easy, don't over complicate things. If you go with a DPMS lower then get an DPMS upper receiver. Then add any 7mm barrel blank of your choice in the twist and length you want. Buy what ever forend you want that fits the DPMS upper, get your DPMS bolt carrier group, and make sure you get your DPMS LR-308 barrel extension.
Now, send your barrel and barrel extension to Thomas at Paladin Machine Shop Service, 803-475-4572, and IF he has a 7mm-08 reamer, in a few weeks you will get your barrel back and you can assemble it. You will need to decide what length gas you want to use and that will depend a lot on your barrel length. Have Thomas drill your gas port at about .065 inch. If you can find out from Remington (which is the same s the DPMS by the way) what size gas port they use then have Thomas drill it for that. Otherwise you get someone with Quick load to crunch some numbers so that you a maximum chamber pressure of about 55K psi and a muzzle pressure of about 5K psi. You need that range of muzzle pressure to make it work properly. Then using your Quick load info as a guide, work up a load and see how it functions. Then you start enlarging your gas port a few thousandths at a time until it functions. If you have enlarged your gas port .010 and there is no improvement in function, you may have to choose another powder and start over. The progression usually goes: not ejecting and rechambering the fired case and you have to mortar out the case or tap out the case with a brass rod. The it starts to eject but stovepipes. Then it ejects but does not pick up a fresh round. Then it picks up the fresh round but does not lock back. Then it functions normally. Do not exceed .125 inch on your gas port size. It if is not running by then it is not going to run with that powder since your gas tube is right about .125 ID so going bigger is not going to improve anything. If you guess wrong and used the wrong powder and it does not work, and you end up drilling your gas port way too big, no big deal. Throw on an adjustable gas block and switch powders and restrict gas flow if need be. I have done several wildcats this way in LRs and ARs and so far, knock wood, I have not had to resort to an adjustable gas block to tone things down. I usually end up around .075 to .095 inch gas port size. I have a 7mm-08 in my future but right now I have so many irons in the fire the 7mm-08 is on indefinite hold. I like longer barrels so I am going to do a 22 inch, rifle gas, gas port .065, and the bullet/powder I am going to start with is 140 gr. bullet and WW748 powder. I use this in my .358 HDH and it runs like a top, as does BL-C2. |
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