Paulosantos our fearless Moderator is an LMT man and he reamed his chamber and also handloads for his LMT rifle that's a 10 twist.

You're right, a SPC II and 11 twist 4 groove is an ideal set up for lowering pressures and increasing velocities. However, you can make a major improvement in lowering pressures in your barrel by reaming the chamber to SPC II specs. I'll let Paulo go over what all he has done with his.

LMT barrels are nice, so I'd upgrade to SPC II and enjoy it.

 

If u get a 1:10 chamber reamed, you will be able to load the rounds to get an extra 100 FPS over the Saami chamber. You would be able to shoot all of the tactical loads that SSA sells. if you went to say a 11 or 12 twist barrel with the SPCII chamber or DMR chamber, you would prolly be able to get another 100 FPS over the 10 twist with SPCII. If you dont reload, I would just get the reamer and go to town.

 

The 1:11"/4-Groove/SPCII Chamber is ideal, but the 1:10"/6-Groove/SPCII is OK. It will lower your pressure by about 4K, which means you can add 1 GR more powder. Accuracy is still great in my LMT Barrel. Matter of fact, it is one of the most accurate SPC Barrels I've owned.

 

Thanks for the information! PauloSantos please add me to the reamer list. PM sent.

 

I know this is an old thread, but I was wondering if there are any reamers out there for rent?
I've got a black rain ordnance 1x11 3 groove polygonal rifled SPC barrel. I'm guessing I'd benefit from reaming it out to the SPCII specs.

 

You don't need to ream that barrel. The chamber and twist rate should be good for SPCII. Besides, all factory ammo is SPC pressure. Most 1-11 twist barrels are chambered right.

 

I agree with Moose Ears. Your barrel is probably fine. Many of the problems that were happening at the time this thread was started (2009) were later discovered to be from bad reamers and undersized barrels. The "1-in-10inch twist is too fast" theory is also wrong and was caused by the same bad reamers and undersized barrels. Believe it or not, there are 1:7" 6.8 SPC barrels sold these days to allow subsonic shooting along with normal supersonic shooting.

A lot of flawed reamers were made with a sharp angle at the place where the chamber stepped down from the case rim to the bullet freebore. This was especially a problem with the very soft copper-coated-lead-core Xtreme bullets that would expand (obturate) enough that a little of their jackets could actually be shaved off when fired. Those bullets are no longer being made. The SPCII freebore was lengthened to compensate for those problems. It is now widely believed that the SPCII freebore was made a little longer than needed.

I have not read of any problems with current-production 6.8 SPC barrels. I would be surprised if your barrel was not fine for all of the factory ammo out there. Contact the maker to be certain.

 

Thanks guys. I went through my records and saw that I purchased the barrel back in 2013. Using the "Internet Wayback Machine" I looked at the Black Rain website and saw that their barrels at that time were indeed SPCII.

 

Am very glad I caught this thread as it was resurrected from a 11 year slumber.

I am venturing out into 6.8 land for the first time, and have learned quite a bit from these forums. One question I am still researching pertains to this topic in discussion here:

Is my type 1 SAAMI spec 6.8 1/10 LMT MRP barrel needing to be reamed, or is it good to shoot all kinds of 6.8 factory ammo?

If there is a thread to reference here, I would appreciate that as well.

Here's my email that I sent to an LMT rep on Jan 29, 2021:

"I'd like to seek your help with a question regarding the barrel.

Chambering: Has LMT received any customer concerns about running SPC spec 2 ammo in the l7ya1b barrel? I am asking because I read conflicting data about whether the SAAMI chambering handles the higher loads or not. I'm also reading that on some barrels, this is an issue, but that on a LMT MRP barrel, due to the construction of the overall stronger MRP platform, that the l7ya1b barrel shoots both spec 1 and 2 ammunition just fine. I thought I'd get word straight from LMT. If you shed some light, or if there is an article/link you can reference to me, I would much appreciate it."



And here's LMT's response:

"I have heard the same thing but as a rule I only suggest running the ammo your barrel is chambers in. Have a great day."


Courteous response. Still, I thought I'd ask the 68forums brain trust.



Thank you, all.

 

Well in answer to your question about factory ammo, yes. There is no factory ammo loaded to Spc II levels. There were some SSA loads labeled "combat" loads many years ago that were loaded hot, but no current commercial loads are loaded beyond the original SAMMI specs. Also, no published reload data is designed for SPC II. Anything beyond the published data is on the re-loader and at your own risk. So, buy any factory loads you can find and you will be fine in your rifle.

 

That's welcome news. Thanks, Chopperdrvr.

 

The one exception if I recall would be Druid Hill ammo, but they have it listed as SPC II. I don't know if they are listed as factory or special order. I would like to know if there are any reamers out there for rent. I am considering doing my Ruger Ranch Rifle 6.8 SPC.

 

I have a .277 Universal throating reamer you could use. It is new, never been used. The only diffrerence in the chambers is the length of freebore so all you would need is to cut the throat a little deeper.

 

Bison Armory and ARP are the two that I have seen posts about. First of all, the SAAMI chamber freebore length is 0.050" and SPC II is 0.100" In Feb 2018, Carnaby stated that Bison uses a freebore around 0.072" and last year Harrison from ARP stated that he uses a freebore of 0.085". It is important to understand the terminology they use though. For a chamber or reamer, the freebore is defined as the straight-walled cylinder slightly larger than the bullet's diameter which is immediately prior to the tapered throat. It does not include the 45 degree cone that slopes from the outside of the neck down to the freebore, which in these cases, adds another 0.015" to the total length.

Now comes the part that confuses a lot of people. If you try to measure the freebore with something like the back of a flat-based bullet, you will get a distance that is slightly longer. Why? Remember that part where the freebore is "slightly larger than the bullet's diameter" and the "tapered throat"? The throat tapers very gently (1.5 degrees per side), so it takes a little distance before it gets smaller than the 0.277" groove diameter where the rifling begins to show and a backwards bullet will hit the lands.

Because the taper is so gentle, tiny changes in the diameter of the freebore section (that are still within the SAAMI specified tolerance of 0.002") will move the beginning of the rifling foreword or back some. This can be noticeable to reloaders who measure the "distance to the lands" with bullets. It is possible to have several barrels, each with in-spec chambers and each having slightly different "distance-to-lands" measurements.

 

BOOM!! You just blew my mind. I will have to delay my plans until I do more research. This is why I like this forum so much, the vast amount of knowledge that is passed from one individual to another. I do recall H saying it was Bison.

 

Here are the threads I mentioned:

6.8 Chamber spec confusion

About 10 years ago I posted on 68 forums somewhere but it's too far back in history to find, I'll try this again. What I am talking about here is the DESIGN of the chambers, actual chambers will vary. 1)The SAAMI chamber "Remington 6.8x43 SPC" has a 45 degree cone in front of the case and...

www.68forums.com

6.8 SPC Forums

www.68forums.com

 

I hope that I did not overload you. My Dad would often say : "You ask that Boy what time it is and he will tell you how to build a watch."

 

I have to admit I am a little bit. The last thing I want to do is ruin my barrel, I highly doubt Ruger has any replacements. Plus I'm not really wanting to put an after market barrel on it (unless it looks like a Ruger barrel) and not a lot of barrel makers that carry them either.

 

The reason that I asked if your rifle has any pressure issues is that if the chamber happens to be near the large end of the tolerance range, you may not need to modify it. If you do decide to lengthen the lead, just be careful and don't overdo it.

Ten or so years ago I remember that a number of 6.8 SPC owners firelapped their barrels with Tubbs Final Finish kits to move the throat enough to shoot higher-powered loads. To be honest, I don't recall how successful they were, but you can do a search. I suspect that those with chrome lined barrels had less luck than others.