Does anyone know why the velocity in Remington .308 SPS chrome-moly barrels is typically around 100 fps less than average? I know the throats are extremely long, but are the bores larger or smaller than average?

Less than average when compared to what?

Other .308 barrels on average including mine, other's and load data tables.

Granted it is a small sample, and totally unscientific, but my Remington 30-06 is 60-90 fps slower than my Winchester 30-06. Both have 22" barrels. How much slower depends on the exact load, there seems to be a bigger difference the heavier the bullet. With 150's it is usually around 60 fps slower, with 165 or 180s closer to 90 fps.

I compared my Winchester to a buddies Remington 700 in 30-06 and his 165 gr handloads were 130 fps faster in my rifle than his.

And over the years I've ran across a handful of other posts similar to yours where others have observed slower than expected speeds from Remington barrels.

I almost never get the same speeds when comparing my loads in different rifles, 20-30 fps even from the same barrel length seems common and as much as 50 fps not uncommon. More than that is rare, but it does happen.

I don't know for sure, but suspect it has to do with tolerances of the chamber and barrels.

Yes, this is exactly what I'm talking about. I tested the Remington SPS against a non-Remington on the same day with exactly the same loads with 2 different powders and the Remington was down roughly 100 fps with the same barrel lengths. The other rifles's velocity was consistent with Hodgdon data. Other Remington .308 owners have reported similar. My real question is will setting the barrel back and rechambering with a reamer with a normal-length throat probably solve the problem (note also that this chamber gives a huge jump to the lands with a detrimental effect on accuracy), or is this issue more likely to be the bore? If it's the bore then I'm wasting money re-chambering and I really need a new barrel to improve the velocity and bullet jump issues.

No two barrels are the same. Some are faster than others. There are many, many things contributing to speed. Most barrels speed up after broken in, and factory barrels require a little longer to break in.

Variations include chamber/throat dimensions, bore diameter variation, bore/rifling uniformity, etc. Typically with a Remington, barrels may seem slower with factory ammunition because of an overly long throat and gradual throat taper.

For the record, I've found Remington barrels to be much FASTER than other brands, though I shoot exclusively handloads. My two Remington .308 barrels have been faster than others, not slower. Both around 100 fps faster than my Tikka and similar to my Ruger. My 6.5 Creedmoor was 150 fps faster than my Tikka! My ADL .270 is right on par with Nosler data, though mine is a shorter 22" vs the 24" in the publication. In fact, the only Remington barrel I've found to be slow is my .204 Ruger and a .30-06 I was loading for for a friend.

In my opinion, if you're going to the trouble of setting back and re-chambering a factory barrel, I would start with a new barrel from a quality manufacturer. It'll add $300-400 to the cost, but will most certainly be better than Remington barrel.

Simply Start At The Fhuqking Start...kiss,find pressure and rock on. Hint.

Extrapolate said COAL,while banking the velocity increase(it will run with anything/everything else,but simply takes more propellant to do so) and act in accordance. AICS binderless DBM's for me at 2.975". Hint..............

What Stick said is definitely the fastest path to success: just work up loads for that rifle.

If you're trying to pick the most likely culprit, it's probably the long throat. Larger chamber, same gas volume, less pressure, lower velocity.

For that same reason, if you're loading for the rifle, you will reach max pressure with more powder and at a higher velocity than if the rifle had a shorter throat. Some would consider this a benefit.

Long jumps don't necessarily mean less accuracy. But they can change barrel timing enough so that the load that shoots well in your buddy's gun won't shoot well in yours and vice versa.

The solution to this really is just to work up loads for that particular rifle. Most factory chambers aren't cut all that concentric so most gunsmiths won't want to rechamber them, plus Remingtons tend to have short barrel shanks anyway so there might not be much room to cut deeper.

If you're set on messing with the barrel (instead of just loading for the one you have) go to bugholes and buy a new barrel and pick the 308 reamer of your choice.

To touch the lands I have to seat way past the 2.85" internal mag length, in fact setting back 0.062" with one thread won't do it, I would have to set back 2 threads. I prefer a hinged floor plate rather than detachable mag. I also want to take .040" off the diameter and a stainless barrel is better with days of wet weather...think I'll just put a new barrel on. I can go to all that expense trying to modify the old barrel and it still might be slow and just shoot mediocre.