An odd AR10 build?

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gdcpony

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I was yesterday looking at a forlorn 98 action and adding up the price to turn it into the heavy barreled varmint rifle I dream of. Boy, did it add up! I figure I will have over $1200 in it by the time I am done.

So I look over at my current project- another Mauser- in my favorite caliber of .257Roberts. I plan to re-barrel it to the Ackley version upon wearing the current tube out. Beside it sat my trusty AR15 which as a Marine I love dearly. I love both actions (Mauser and AR) and calibers (.223 and .257)! I have both a bolt and semi .223, if only I could get the same in .257.

Then it struck me: Why spend so much to pretty much duplicate a rifle I already have? Why not look into an AR in .257? I swear there were angels singing! (ok not really, but you get it).

So I have begun researching the possibility of an AR10 build in .257Roberts. I have come up with these issues:

1. The .257 is a "mid length" cartridge. In my preferred 90-100gr bullets it is 2.780 which should be fine against the AR10's intended cartridge (the .308 I loathe so much) which is around a 2.8 OAL. So the mags should work. I just will have to keep away from the heavier 120gr bullets. Can anyone out there add anything to this? Will the longer case of the .257 eject cleanly?

2. Most people and even a few gun makers (particularly those I would have to deal with) don't even know what the .257Roberts is. So the barrel will be hard to source. This is especially true since I would want it to start out in the Ackley version. Any ideas there?

3. My wife will kill me once she finds out I plan to get rid of this derelict action and the Boyd's stock I have for it in favor of another black gun! How do you all convince your wives you NEED to build a gun just to be different?

It will probably be years before I can complete this rifle, but the lower will be gotten before it is illegal to do so (I fear a second term!). The workings of a standard AR10 would be fine given the rim of the .257 is a match and case size
 
I bet if you talk to shilen and they could build the 257 improved for your ar-10. 257 is only .007" different from the already available AR rifles in 6.5
 
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While I'm sure it could be done, chambering for .257 is going to be expensive because it's going to be an "oddball" job. You could save a lot of money by going to a standard chambering like .260 Remington, which would likely give nearly identical performance.
 
The AR-10 action is too short for any chambering based upon the x57 Mauser parent case. You might be able to short load light bullets to address the OAL issue but I indeed suspect that ejection will prove problematic.
 
The AR-10 action is too short for any chambering based upon the x57 Mauser parent case. You might be able to short load light bullets to address the OAL issue but I indeed suspect that ejection will prove problematic.
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Ejection is my big worry. Anyone know the ejection port size on an AR10? I am pretty sure the stroke would be long enough as the bolt has to come back far enough to rack a longer complete .308.
 
Why not run the .260 rem?
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Call it a personal preference. I have long held a soft spot for 3 calibers; the .223Rem, 7x57, and .257Roderts as well as Ackley versions of all three. The 7x57 just isn't useful to me anymore no matter how I justify it. I have plenty of .223's and only one .257.

The .257AI just sits as that perfect round for about every use I have for a rifle. Varminting, deer, and low recoil. I also like the idea of being different. Since the barrel and the ejection port seem to be the only obstacles to this it seems it would be a great one of a kind rifle to own without too much extra effort.

I am striking out in finding any .257 caliber barrels to be re-chambered so I guess the quarter bore has no following in the AR world. That is too bad as it is a better choice in my book than a .243 or 6.5. Better performance than one with no difference in felt recoil, and less recoil than the other with no real sacrifice in useability. Again just my opinion.

That all said I would like to build a SASS type weapon as I got to train on them on my last deployment. I hate the 7.62, but loved the weapon system. The only change I would make is a little extra barrel (22 or 24 inches) to make use of the additional powder stored in a .257AI case. And I doubt I will mount the same optic on mine either.
 
As far as cartridge length, there is or was a company named Carr who was making a AR style rifle in .30-06 which would be a long enough action to accomodate the .257 Roberts.

It would be an expensive proposition, but I think it could be done.
 
The AR-10 ejection port is big enough to eject a loaded .308 round, brass from the Bob shouldn't be an issue.

Getting a barrel is as easy as calling one of the myriad rifle smiths that make AR-10 barrels and tell them what you want. If they only do ARs they will probably charge you a rental fee for the reamer since they likely won't have one on hand. They will also have to order a .25cal barrel blank to make the barrel so the lead time might well be measured in double digit months.

D-Tech makes several .25cal AR-15s including .25WSSM and the .25DTI (based on the 6.8SPC case). Lead time for them is probably around 8 months for stuff they do regularly.

I was considering a bolt rifle in 25-06 but bullet selection soured me to that one very quickly. This would be a pretty cool project, but because you're limited in bullet weight, you'd honestly be better off with one of the 6mm or 6.5mm cartridges (.243 or 6.5 Creedmoor) where you have the full selection of bullets at your disposal. If you really want a .25 cal I would say either look at the 25WSSM in the AR-15 platform or have a .250 Sav AI built on an AR-10.
 
The AR-10 ejection port is big enough to eject a loaded .308 round, brass from the Bob shouldn't be an issue.

Getting a barrel is as easy as calling one of the myriad rifle smiths that make AR-10 barrels and tell them what you want. If they only do ARs they will probably charge you a rental fee for the reamer since they likely won't have one on hand. They will also have to order a .25cal barrel blank to make the barrel so the lead time might well be measured in double digit months.

D-Tech makes several .25cal AR-15s including .25WSSM and the .25DTI (based on the 6.8SPC case). Lead time for them is probably around 8 months for stuff they do regularly.

I was considering a bolt rifle in 25-06 but bullet selection soured me to that one very quickly. This would be a pretty cool project, but because you're limited in bullet weight, you'd honestly be better off with one of the 6mm or 6.5mm cartridges (.243 or 6.5 Creedmoor) where you have the full selection of bullets at your disposal. If you really want a .25 cal I would say either look at the 25WSSM in the AR-15 platform or have a .250 Sav AI built on an AR-10.
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Thanks for the insight. I have a few emails out to a few shops, one of which lists .257Roberts in their ar10 selection. I know there will be a fee for getting the .257AI, but it is my round of choice.

I should have thought of the ejection that way. Why after the number of times I have emptied a Condition 1 weapon, I didn't consider the loaded round ejection as a basis for size is beyond me. Definitely a "duh" moment.

I know that modern cartridges best my preference, but I am still getting more and more set on doing it this way. I just love the round and having both a bolt and semi in it would be the stuff of dreams to me.

Bullet choice is fine for me. As long as I can get my two (Sierra 90gr hpbt and 100gr spbt- both GameKings), I am good. Those will more than cover any shooting I would use it for. I only chase deer and varmints and do a little long range work for fun.

I am now to the point of picking between the two styles of lowers. It seems it is either a DPMS or an Armalite. I keep finding pros and cons to each, but it seems there is more out there as well as being more economical for the DPMS so I am leaning that way. I am generating a wish list of parts now.

Either way I figure on a lower and parts kit for a common caliber and then replace the barrel later with my chosen barrel. The first barrel might end up being in .243 as I like light kicking rounds.
 
Accuracy systems builds AR-10s in .257 Roberts. But I didn't see any in the 7x57 Mauser parent cartridge. they are NOT cheap. (I have a Remington 760 in .257. the problem I am having with it, is that I must load my own, because all I see for it on the shelves is +P, with I won't run through a pump rifle.)

If you despise the .308 (?!) ok, but wouldn't it be easier to do the job with a cartridge that is already established to the platform, like .260 Rem, or 7mm-08?
 
Im with you. Be different. Dont just go half a## on something just because they already make one in .xxx caliber. Your rifle upper build shouldnt be all that much more than a custom build in another caliber. Just remember to get the barrel in the right twist rate for the bullets you are wanting to use. Since you already need to order a .25 cal barrel, this shouldnt cost anymore. I wish I had my small buisness up and running already. (Long term project as well) Im wanting to make one off and custom ar uppers and this is right up where I wanna be. but Its prolly not In the mIx for the next couple years... Please keep me posted on your build.
 
Well, in light of recent tragic events, I went out and picked up a whole rifle. Carbine actually, a DPMS base model in 7.62. I know something is coming and wanted to make sure I had one before then.

I figure it will be used as is for a year or so (wife rule) then I can mod the living crap out of it. I have a list of parts already. Maybe a few will sneak in earlier.

I will put some rounds through it sometime this week hopefully and post the groups up. I hope it surprises me. Right now the trigger seems creepy but not heavy. The 16" barrel doesn't worry me, but it not being free floating does. None the less I should be able to wring some good groups out of it.

Handloading .308Win for a 16" barrel? Maybe light bullets and a powder on the fast side? Hmm... The horrible thought of loading for a new rifle. LOL
 
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Load it like any other barrel length. The only difference is that you want to avoid the slowest powders to keep the port pressure under control. That's not a barrel length thing but rather an AR-10 thing.
 
I already load with two powders for rifle that I can use (keep the shop simple and cheap)- H335 and H414. It seems the 335 is listed for lighter bullets and 414 for heavier. Makes sense considered their burn rates.
 
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