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Discussion Starter · #1 ·
I had mentioned this to Alex a while back since the 338 is based on the 308 cartridge. Has 7mm Mag power, just in a smaller package, and others are making AR type rifles in this cartridge already. Alex did say it was feasable. Just wondered if there's any interest in it other than myself. All you'd need is a different barrel, everything else is the same.
 

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Why stop at .338, lets shoot for .358 Win, .243, 7mm-08, .260?
 

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Discussion Starter · #3 ·
the 260 is already in development, with the trouble lying in getting acceptable accuracy. Alex said anything based on the 308 Win case is doable. I believe 243 is next in line after the 260 since its so popular. But I'm looking for more thump, and the 338 fed has the most your going to get in this particular envelop.
 

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So any chance of a bigger bore?
.338fed, .358win, .375raptor, .45raptor. Many great possibilities that would certainly sell some more XCR-M.
 

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I know I've harped on this before, but I'd rather go bigger bore with shorter casing and the ability to be quiet, inside 300 yards, with high energy terminal ballistics. The .338 Spectre is that cartridge. It's a necked down 10mm magnum casing with 160-300 gr projectiles. The 10mm magnum's rim is basically the same as 6.8SPC, so RA already has a bolt for it.

I like 308, but I would prefer to carry more business weight and less waste weight. That's basically what 300Blk gives you; .338 Spectre just tweaks the numbers a bit. And, Teppo-Jutsu has already done the ballistics work, so twist rates aren't a current mystery. SBR (Southern Ballistics Research) even has loaded ammo and casings available. Chamber reamers and dies are also available, so there are no road blocks. The only thing necessary to make an XCR-L in .338 Spectre is to work out the gas system for proper cycling, which the 300 blk would be a good starting point.

Now that I think about it, one could probably ream and rifle a 300Blk bore, re-ream the chamber and be pretty close to being done...hmmm.
 

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Resurrecting from the dead, because I really want a .338 federal conversion kit for the M. Is there really no interest in the round for this platform?
 

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Resurrecting from the dead, because I really want a .338 federal conversion kit for the M. Is there really no interest in the round for this platform?
I think what Mechanic suggested would be the best course of action:
Now that I think about it, one could probably ream and rifle a 300Blk bore, re-ream the chamber and be pretty close to being done...hmmm.
Just about any gunsmith with a lathe should be able to pull that off with a .300 BLK 20" barrel. As for RA itself, I would not bother with making/ordering barrels (which are harder to come by) for a cartridge that is so niche if I was them; I can't even find any .338 Federal on sale on AmmoSeek. Having all these ammo choices was great, like having a big old party, but the response to COVID and the gun and ammo buying craze that followed, like shitting yourself at the dance floor of said party, really showed us who our friends were after everyone else has left. From what I see that left us with 5.56 and .308/7.62 cradling your head and wiping your ass in the bathroom. When it comes to times of even mild distress, common calibers are better to put your money down on; you probably won't even have those special calibers around for practice. I mean, imagine if S really did HTF? You'd have your pick of what is actually being made, or rocks and handfuls of shit to throw at your enemies, really now?
 

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I'm doing pretty well on 308s and 556 is just a toy round in my opinion, and Im always over prepared, so if that means if I buy a gun with exotic ammo, I would buy enough to support the system, and once the initial investment is made reloading the round wouldn't be much money.. and if 338 fed was the chambering a person we're to choose as a primary fighting weapon, I think that would be pretty dumb for all the reasons you listed above. But as a big bore semiauto it has its place.
Are L and M barrels interchangeable? Like could that 300blackout barrel actually be mounted into an M upper? Idk because I've just treated my XCRs like an AR and just swap complete uppers. Also another thought on using a blackout barrel as a starter what about the gas port location, do any blackout barrels use a standard length gas port location, I thought they were all at least mini length..
 

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Also Mechanic was talking about the .338 spectre, which sounds really cool but I'm pretty sure would be something that would be better fit into an L...
 

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I'm doing pretty well on 308s and 556 is just a toy round in my opinion, and Im always over prepared, so if that means if I buy a gun with exotic ammo, I would buy enough to support the system, and once the initial investment is made reloading the round wouldn't be much money.. and if 338 fed was the chambering a person we're to choose as a primary fighting weapon, I think that would be pretty dumb for all the reasons you listed above. But as a big bore semiauto it has its place.
Are L and M barrels interchangeable? Like could that 300blackout barrel actually be mounted into an M upper? Idk because I've just treated my XCRs like an AR and just swap complete uppers. Also another thought on using a blackout barrel as a starter what about the gas port location, do any blackout barrels use a standard length gas port location, I thought they were all at least mini length..
Pretty sure the bbl extensions for the M and L are different; at least when I ordered some I think I got different ones for each platform.
 

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I'm doing pretty well on 308s and 556 is just a toy round in my opinion, and Im always over prepared, so if that means if I buy a gun with exotic ammo, I would buy enough to support the system, and once the initial investment is made reloading the round wouldn't be much money.. and if 338 fed was the chambering a person we're to choose as a primary fighting weapon, I think that would be pretty dumb for all the reasons you listed above. But as a big bore semiauto it has its place.
Of course, I was being facetious when I said all of that. I just feel sorry for all those people looking for ammo types like this at a time like this. I thought I would be using my 6.5 Grendel barrel a lot more than this when I picked it up but now it's like ammo for it never existed. Anyway, I don't know why I didn't catch that the previous guy was talking about a different round. I honestly don't know the gas characteristics of the .338 Fed and I wonder if there is a chart somewhere that will help a gunsmith find the location to drill an appropriate gas port for the intended round on a barrel.

Has anyone reported making custom barrels for particular rounds for the XCR? Anyone with a lathe can turn a barrel blank but I imagine machining a barrel extension that matches with the bolt face of the XCR would be a challenge.

Pretty sure the bbl extensions for the M and L are different; at least when I ordered some I think I got different ones for each platform.
Well of course they are. I never really fucked around with the barrel extensions when handling my barrels; are the extensions screwed on or welded to the barrel?
 

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Hmmm. I maybe best suited to build it in an ar10 platform... I'm just not much of a fan of ARs... At least there are custom shop barrel options in that court. Hell I wonder if one could just start with a 308 barrel and re-chamber for 338... It's parent case is a 308 with a larger diameter bullet, so I would assume a 308 type 3 gas plug would be a good start... And if it were to need more or less gas some holes could be drilled larger or welded and redrilled smaller.. I would think cross referencing chamber pressures for all the calibers offered in the M with the 338 fed to see if a different calibers GB might be a better fit. Is there any other data y'all can think I should be looking at for trying to figure it out?

Also does anyone know if anybody has ever made a longer than 20" barrel for the xcr? I know Robinson doesn't offer any longer but curious if anyone has tried.
 

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Hmmm. I maybe best suited to build it in an ar10 platform... I'm just not much of a fan of ARs... At least there are custom shop barrel options in that court. Hell I wonder if one could just start with a 308 barrel and re-chamber for 338... It's parent case is a 308 with a larger diameter bullet, so I would assume a 308 type 3 gas plug would be a good start... And if it were to need more or less gas some holes could be drilled larger or welded and redrilled smaller.. I would think cross referencing chamber pressures for all the calibers offered in the M with the 338 fed to see if a different calibers GB might be a better fit. Is there any other data y'all can think I should be looking at for trying to figure it out?
Let's not surrender to the AR-10 just yet. I know less than you do about this but I would hit up a local gunsmith who specializes in barrels (and familiar with 338 Fed) and work with him to make a barrel for the XCR-M. I have been advised that removing the barrel extension from an existing barrel is destructive and stupid. I would ask if RA has any barrel extensions for the -M that they can sell separately first. That's key, it's a cinch to turn and thread a barrel blank to chamber a certain round and take an extension, but you'll need a CNC and the right dimensions if you want to make that extension. You'll need to work with him on figuring out where the gas port goes and your best bet might be trial and error. We might be over thinking this though. From what I can gather, .338 Fed has the same pressure as .308 Win and 6.5 Creedmoor (62K PSI) and RA feels no need to have different gas port locations for the other calibers for the -M like they do with the -L. You could probably get away with just copying the same port location as the .308 barrel and moving on. Remember that the XCR's 6 8 adjustable gas positions (EDIT: in type 3) can be used to level out any discrepancies in the gas if you are getting close to where you want it. Alternatively, you could just rechamber a .308 barrel but I don't think it's safe nor easy to remove the extension or bore the chamber through the extension.

I would start on asking someone to make a 20+" .308 barrel like you were asking just to get used to the idea of making a custom XCR barrel, then move on to a .388 Fed. The worse that can happen is that you get a bolt-action rifle out of that barrel. YOLO it.
 

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Let's not surrender to the AR-10 just yet. I know less than you do about this but I would hit up a local gunsmith who specializes in barrels (and familiar with 338 Fed) and work with him to make a barrel for the XCR-M. I have been advised that removing the barrel extension from an existing barrel is destructive and stupid. I would ask if RA has any barrel extensions for the -M that they can sell separately first. That's key, it's a cinch to turn and thread a barrel blank to chamber a certain round and take an extension, but you'll need a CNC and the right dimensions if you want to make that extension. You'll need to work with him on figuring out where the gas port goes and your best bet might be trial and error. We might be over thinking this though. From what I can gather, .338 Fed has the same pressure as .308 Win and 6.5 Creedmoor (62K PSI) and RA feels no need to have different gas port locations for the other calibers for the -M like they do with the -L. You could probably get away with just copying the same port location as the .308 barrel and moving on. Remember that the XCR's 6 adjustable gas positions can be used to level out any discrepancies in the gas if you are getting close to where you want it. Alternatively, you could just rechamber a .308 barrel but I don't think it's safe nor easy to remove the extension or bore the chamber through the extension.

I would start on asking someone to make a 20+" .308 barrel like you were asking just to get used to the idea of making a custom XCR barrel, then move on to a .388 Fed. The worse that can happen is that you get a bolt-action rifle out of that barrel. YOLO it.
Yes, RA sells bbl extensions separately. No idea on current pricing... I bought 3 whenever 6mm ARC was released, JIC. IIRC...one M and 2 L extensions.

Uh...yes, there are different port locations on the M (stnd, mini, micro) as well...it's just not as drastic as 300 BLK. And Type 3 blocks have 8 positions....
 
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Yes, RA sells bbl extensions separately. No idea on current pricing... I bought 3 whenever 6mm ARC was released, JIC. IIRC...one M and 2 L extensions.
Jun 7, 2020 :
BTW, contacted RA today. Got an answer about bbl extensions cost:

Sean,

We can sell them for $60 for XCR-L and $70 for XCR-M. They are heat treated and the outside has to be turned down a bit after installation to maintain concentricity with barrel.

Sincerely,

RA Sales Dept.


Thinking of picking up a couple just to have on hand.
Sweet. We're in business then. Any price they charge is a bargain for a project like this. Do you happen to know if the thread of the barrel extension is the same to that of the AR-15 barrels? 'Cause then it would almost be too easy. How was the experience with turning a custom XCR barrel when you had it chambered for 6mm ARC? Did you do it yourself or did you have a gunsmith do it?

EDIT: For that matter, does RA sell the type 3 gas block by itself? That's also key to getting this to work.

Uh...yes, there are different port locations on the M (stnd, mini, micro) as well...it's just not as drastic as 300 BLK. And Type 3 blocks have 8 positions....
👏Listen to this guy and not me.

Right, I can infer that fact now. The different piston length parts for the -M aren't being showed on RA's website for some reason. Though, since I was assuming we were talking about 20+" barrel lengths, I believed that keeping it to the standard length gas was a given.

Note that if you are going above 20" with a .308 barrel, you're likely gonna need a longer gas port length and a longer piston to match. Since 20+" barrels exist for AR-10s already, I would bet you could just keep the gas port locations calculated for those barrels for the XCR and use the gas adjust to fine tune it. Just keep in mind you'll need to turn a longer piston for the Op-rod and a gas tube to go along with the longer port. Considering the number of new parts required and the fact that the XCR isn't really a precision rifle, I'd go with machining a 20" .338 Fed barrel instead and see how that goes.

Anyway, like I've always said, if the things you want don't exist yet, make it yourself! YOLO.
 

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Didn't do it; just bought the parts to be able to do it, should RA go under. With the Canadian ban and that being a very large part of RA's business, one would be wise to buy what you think you might need now....this is a boutique gun manufacturer. A US ban could well mean they go under in short order. I pray that's not the case (for our sake and the country's), but let's face it....it's a real possibility.
 

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Didn't do it; just bought the parts to be able to do it, should RA go under. With the Canadian ban and that being a very large part of RA's business, one would be wise to buy what you think you might need now....this is a boutique gun manufacturer. A US ban could well mean they go under in short order. I pray that's not the case (for our sake and the country's), but let's face it....it's a real possibility.
I see. Were you able to order a spare type 3 gas block while you were at it? I have local gunsmiths who make one-off parts all the time but I would rather not risk it with something as small as the gas block. I haven't seen any breakdowns of the barrel gas block and I don't feel like tearing one of mine down just yet, but it looks like you can just remove and reuse one from an existing barrel without causing permanent damage (hammer out the dial valve, then unscrew the nut on the bottom of the port cover to slide it out and then pull out the port itself). I imagine we should be able to buy the gas blocks if we can get the barrel extensions, but we might be able to reuse one if we can't.
 

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I see. Were you able to order a spare type 3 gas block while you were at it? I have local gunsmiths who make one-off parts all the time but I would rather not risk it with something as small as the gas block. I haven't seen any breakdowns of the barrel gas block and I don't feel like tearing one of mine down just yet, but it looks like you can just remove and reuse one from an existing barrel without causing permanent damage (hammer out the dial valve, then unscrew the nut on the bottom of the port cover to slide it out and then pull out the port itself). I imagine we should be able to buy the gas blocks if we can get the barrel extensions, but we might be able to reuse one if we can't.
I have like 6 or 7 spare gas blocks...some are type 1s I've converted to Type 3. I also have several spare 16" bbls in various calibers in case I want/need to cut one down. The gas blocks aren't super expensive, yes...they are available for purchase.....no reason not to have a few on hand. Contact Holly for pricing/availability and she'll get you squared away. Man...I need to send that girl a gift card to a nice restaurant....she consistently takes great care of me.

Gas blocks can easily be swapped on the XCR (though my 6.5G one was on there tight AF....very tight, almost press fit clearance on that one for whatever reason). No hammer necessary.
 
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I had time and asked RA Tech department what they thought about my previous idea to rebore a .308 barrel for .338 (spoiler: not one of my best ideas):

RA Tech Dept said:
First of all, you cannot make a .338 Federal barrel from a .308 barrel because the bore of the .338 is larger. It's not just a matter of chambering it larger.

If you buy a .338 barrel blank thats at least .5" longer than your finished barrel length, and buy the chambering tools , and provide some test ammo; we can do the .338 for you. There's no guarantee it will work.

I'd go with the 6.5 Creedmoor.
I meant to say I wanted to rebore a .308 barrel, but now I realize that would be even more work and more risky, as I would have to worry about concentricity of the bore if I made it like that. I was mainly concerned about finding the 12 o' clock position for the gas block relative to the position of the barrel extension, because otherwise, a gunsmith would have to design a fixture or use the upper assembly of the rifle as a fixture to find and drill that gas port.

Later he added:

RA Tech Dept said:
The best way to do this is to buy a blank or two with the twist you want and in .338. The OD of the blank has to be at least 1 inch and preferably 1.125” minimum OD. It can be stainless or chrome moly or chrome moly vanadium. The chamber tool and gages will run another $300 to 400..
So this is an interesting bargain for anyone interested in building a custom barrel for the XCR, niche caliber or otherwise. This takes a lot of the risk and guess work out of making a custom barrel with a local gunsmith, but attaches additional production cost, the length of time that RA takes to produce parts, and comes with the caveat of no guarantee that it would "work" (though to be fair I think .338 Fed is similar enough to .308 Win that it should work as long as it chambers, and as long as it doesn't blow up, what harm could there be?). I'm sure RA would come to regret this offer if they get flooded with lots of requests for custom barrels like this, but right now it's untreaded territory. Have fun!
 
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