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Discussion Starter · #1 ·
Is there any possibility of geting a 6.8 barrel for the XCR in a 1:11 twist? Is it possible to modify an AR barrel to fit the XCR?
 

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Discussion Starter · #3 ·
Yes, Art from Silver State Armory and Tim From Ko-Tonics, DokGR as well as many other high profile 6.8 proponants have done a great deal of testing and suggest that the best barrels for the 6.8 have a 4 groove, Spec II chamber with 1:11 twist. This barrel suposedly will stabilize all the normal/currently available bullet weights (90grn-130grn) at higher velocites with no pressure signs. You can read about their testing at 68forums and AR15.com in the variants section. My understanding is that the 1:10 is fine, but the 1:11 seems to handle combat loads the best.
I just wanted to see if it were possible to get a custom twist for the XCR somehow. I hope this does not rock any boats!!! :)
 

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I read a review in one of the rags. Ko-tonics and Silver State have done a lot of research into the 6.8 and they have a barrel/chamber combination that allows higher velocity ammo and better performance as a result. It was a good article.
 

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I read a review in one of the rags. Ko-tonics and Silver State have done a lot of research into the 6.8 and they have a barrel/chamber combination that allows higher velocity ammo and better performance as a result. It was a good article.
Stories? You mean all those words in between the ad's?

Art came up with the SPCII chamber idea after seeing this issues crop up with civilian users shooting his ammo. He saw that Remington screwed the pooch when submitting drawings to SAAMI.

If you run a SAAMI chamber, it is possible that a minimum dimensioned chamber is less than a maximum dimensioned loaded round.

Art gets around this by ensuring his ammo is at the lower end of the case dimensions. Not every manufacturer is doing this (namely Remington).

Essentially, Art lengthened the throat in his chamber design to alleviate any pressure spikes that might occur with maximum dimensioned factory ammunition.

Tim is touting the 1/11" twist because it is better balanced towards the 90-135 bullets that are used in the 6.8 SPC and he is trying (and succeeding!!) to carve out a niche for himself in the AR world.

Honestly, if you like AR's and want one in 6.8 SPC, Tim is one of the good guys, if a bit passionate.

The 1/10" twist is meant for the .270 Winchester to allow the use of long 150gr BT's and 160gr Noslers.

Honestly, if all you would ever do is shoot the 90gr to 115gr bullets a 1/13" would be ok.

The faster twists are not perfect, but it will not cause your XCR to blow up or become unsafe. Same thing in AR's.

No ballistician would sign off on some of the more 'exuberant' statements that are being said, vis-a-vie, the SPCII chamber and 1/11" twist.

If your handloads are so close to the edge that the 1% to 2% (at most!) pressure advantage gained by the 1/11" twist barrel is just not worth it. Stop being so ham handed on the powder scale.

If you use factory ammo*, you will not find any advantage to the 1/11" twist over the 1/10" twist.

The same thing cannot be said regarding the SPCII chamber vs. the SAAMI chamber.

The SPCII chamber, or one that is designed correctly (like Barrett's in their M468/REC7) IS the way to go.

Don't know about RA's chamber. Hopefully they'll chime in and inform us.

*Art's 'Combat' pressure ammo runs about 5% to 8% higher then their 'Standard' ammo and will get you a roughly an extra 80-100 fps in MV, as compared to his 'Standard' ammo.

If all you use is the 'Combat' pressure ammo in your AR-15, the 1/11" MAY be of some use.

I think that the use of either the MGI RRB buffer or the Enidine Hydraulic buffer in your AR would provide more benefit than the 1/11" twist, but then what fun is that to have an answer that simple?

I do not know what, if any, issue there is in the XCR in using SSA's 'Combat' ammo.

I'm leaning to the thought that it isn't an issue with the XCR because of it's design.
 
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