Remington ModeL 7 barrels

[GooseGestapo]

What is the difference in M700 and M7 barrels? Are they interchangeable with M700 short action barrels?

I have a Rem M-7 in .260Rem. Though factory literature states a 1/9" rifling twist, by actual measurement, mine has a 1/10" twist.
The reason I measured it was because I found it won't shoot heavier tipped boat tail bullets with any degree of accuracy. Hornady 140gr SST bullets won't even reliably hit the berm at 100yds. 129's shoot 12" groups and leave key hole prints on the target.
It will shoot quite well with flat based bullets notably the Speer 120, 140, and even the discontinued 160gr Sierra. With these it shoots at or under 1" 5-shots at 100yds. I'd like to put factory contour replacement barrel with 1/8" twist bbl.
Curious about difference in M7 and M700bbls.

 

[dsink]

Model 7 and 700 barrels are the same size and thread.

 

[4v50 Gary]

The shank may need adjusting and headspacing should be checked after swapping out.

 

[Cemetery21]

Per this link, it looks like the threads are the same, but I would guess the profile is different. Hart (and I'm sure others) will profile a barrel from your takeoff.
http://www.practicalmachinist.com/vb/gunsmithing/remington-model-7-barrel-tenon-259736/

 

[Bart B.]

Have you slugged the barrel to measure its groove diameter? Commercial rifle barrels' groove diameters are often larger than bullet diameters. Did you weigh those Hornady 140's having only a few tenths grain spread to verify there are no voids in them that will severely unbalance them?

Boattail bullets typically don't shoot accurate in barrels with groove diameters larger than bullet diameter. Sierra observed this back in the 1950's testing their bullets in commercial rifle barrels. Flat based ones shot better in them. Boattails did better in barrels with smaller groove diameters.

I suspect there's other issues in your situation with "improved cylinder bore" shotgun patterns with rifle bullets. That huge disparity in groups proves there is; to me, anyway. The normal difference is about 1/2 MOA. A 1" difference in twist seldom causes more than a 1/10 MOA difference at a hundred yards. Keyholes at 100 are typical of bad bullets often showing up in "seconds" sold at discount. I'd send those Hornady's back to them asking they test them. If they're proved bad, you may get a couple boxes of new good ones.

 

[Jim Watson]

That being a hunting rifle, I would load the flatbase 140s and save the price of a barrel.