Barrel Tenon Threads Issue

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coleman1495

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I just ran into a new problem trying to assemble my Benchmark pre-fit/Savage.
I have a Benchmark barrel nut and a Benchmark pre-fit barrel. For whatever reason, I can’t get the barrel nut to thread onto the tenon. It feels like it goes on for ~1/2 turn then binds up.
The nut threads perfectly on my other Benchmark pre-fit perfectly, and both barrels thread into both of my receivers fine.

Also the Savage recoil lug won’t fit over the barrel threads either. The diameter of the recoil lug is slightly too small. Not sure if that’s related to the original problem.

Any ideas on what to do? I’m at a loss. Next step is probably bringing it to a gunsmith.
 
Do you have access to an accurate tool (preferably a micrometer) to measure the major diameter of the threads on the tenon? The fact the recoil lug won't fit over it suggests the tenon was cut too large.
 
Got a 1-2 inch micrometer and three identical small drill bits? Even a decent digital or dial caliper can work, in a pinch. Start with simply measuring the outside diameter of the threads on both the barrel the nut fits, and the barrel it does not.

Look up the PEE-Dee Three wire thread measuring charts, for the simple way, or sit down and do the trig for more or less random size drill bits. The formulas are online. Essentially, you place two wires in the thread, on one side, the third wire does directly opposite the two, so you can measure across in a straight line. The wires or drill bits, need to be sized so that they touch the flanks (sides) of the threads, and stick up above the top of the threads.

Use a magnifier to take a good look at the threads where you are trying to start the nut. Look for shiny spots and dents or damage.

It does sound like a cockup from Benchmark, I would suggest seeing what they have to say. The recoil lug not fitting over the thread really says that it is oversize by some amount.
 
Grizzlypeg said:
Do you have access to an accurate tool (preferably a micrometer) to measure the major diameter of the threads on the tenon? The fact the recoil lug won't fit over it suggests the tenon was cut too large.
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Unfortunately all I have is calipers. The problem barrel thread does measure ~3 thou larger. I suspect thats why the recoil lug doesn’t quite clear.
 
From Savage Tech:

The shank diameter on Savage's standard calibers is 1.055" The Savage rifles chambered in Remington Ultra Mag and Winchester Short Magnum have a larger shank diameter. These measure 1.120" The outside of the barrel nut is the same diameter on both the standard calibers and the Ultra Mag - WSM calibers. All barrels are threaded 20 threads per inch. Note: Some of the first Ultra Mag and WSM rifles were made with the smaller diameter shank. The larger diameter shank barrels will have a step in front of the barrel nut.
 
bdb.hunting said:
Someone will correct me if I'm wrong but don't savage have small and large shanks ? could the action be small shank and the barrel be large shank ?
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No personal experience with them, but my understanding was that the Large and Small shanks are far enough apart in size that there would be no thoughts of the wrong parts 'almost' fitting. Right? Wrong?

Interwebs says Small shank 1.055"x20p. Large shank 1.120"X20P. Dunno. Worth a check! Easy to see that difference with as basic a cheap digital caliper as can be got.
 
coleman1495 said:
Unfortunately all I have is calipers. The problem barrel thread does measure ~3 thou larger. I suspect thats why the recoil lug doesn’t quite clear.
Click to expand...

That says to me that you have a factory cockup on the thread size, and should talk to the Retailer, and then the makers to see what they can do for you, whether they swap you a barrel, or cover the cost of getting the thread cut correctly.

It's not 'that' big a deal to pick up a thread to take a bit off, but it is kinda fiddly work.

Being able to accurately measure the actual Pitch Diameter of the thread, will tell you if the thread is oversize, or if someone did not take a final pass off the outside. I'd guess the latter is unlikely, in a production environment, as they are like to be using full form threading tools on a CNC lathe.
 
coleman1495 said:
I just ran into a new problem trying to assemble my Benchmark pre-fit/Savage.
I have a Benchmark barrel nut and a Benchmark pre-fit barrel. For whatever reason, I can’t get the barrel nut to thread onto the tenon. It feels like it goes on for ~1/2 turn then binds up.
The nut threads perfectly on my other Benchmark pre-fit perfectly, and both barrels thread into both of my receivers fine.

Also the Savage recoil lug won’t fit over the barrel threads either. The diameter of the recoil lug is slightly too small. Not sure if that’s related to the original problem.

Any ideas on what to do? I’m at a loss. Next step is probably bringing it to a gunsmith.
Click to expand...

The barrels swap with the actions, the nut does not... buy a new nut or possibly the quickest fix is probably taking it all to a gunsmith.
 
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guntech said:
The barrels swap with the actions, the nut does not... buy a new nut or possibly the quickest fix is probably taking it all to a gunsmith.
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Ordering a new barrel nut was my first thought until I realized the recoil lug wouldn’t fit either.

If a new barrel nut fixed the problem, would it be fine to sand a little off the inside of the recoil lug?
 
Small shank thread is supposed to be 1.055x20 but a lot of companies are making them 1.062x20 which takes some slop out. Your threads need to be really clean to fit one of these barrels on, and once you have it cleaned you need to clean it again and get any lint or fibers off the threads or it will bind a little. I fought one on and ended up heating up the action and nut just a bit with a torch just to squeeze it on. I used a bit of nickel anti seize on the threads but that stuff is messy so be careful. If it really is that tight, there is a bigger problem or you have the wrong diameter altogether.
 
DonnieM said:
Small shank thread is supposed to be 1.055x20 but a lot of companies are making them 1.062x20 which takes some slop out. Your threads need to be really clean to fit one of these barrels on, and once you have it cleaned you need to clean it again and get any lint or fibers off the threads or it will bind a little. I fought one on and ended up heating up the action and nut just a bit with a torch just to squeeze it on. I used a bit of nickel anti seize on the threads but that stuff is messy so be careful. If it really is that tight, there is a bigger problem or you have the wrong diameter altogether.
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That makes a lot of sense. The IBI nut is listed as 1.062”. I’ll try ordering an IBI nut and try that.
Benchmark probably changed from 1.055 to 1.062” sometime in the years between my first barrel and my second barrel.
 
DonnieM said:
Small shank thread is supposed to be 1.055x20 but a lot of companies are making them 1.062x20 which takes some slop out. Your threads need to be really clean to fit one of these barrels on, and once you have it cleaned you need to clean it again and get any lint or fibers off the threads or it will bind a little. I fought one on and ended up heating up the action and nut just a bit with a torch just to squeeze it on. I used a bit of nickel anti seize on the threads but that stuff is messy so be careful. If it really is that tight, there is a bigger problem or you have the wrong diameter altogether.
Click to expand...

Threads self centre as they tighten. There's no slop once torqued. Not sure I understand the benefit of making them larger diameter than spec.
 
if the new barrel threads into the action but the tenon OD is 3 thou larger than the recoil lug, I would spin that barrel in a lathe or even a micky mouse wood pilot set-up with a power drill and file .0015" of the OD so the recoil lug fit over then try the nut again...if it spins on ,your golden you will still have lots of thread engagement to do the job, but if the nut still doesnt spin on then your going as Trev suggested getting the threads lathe chased for a pass or two.
 
Some barrel tread are cut sharper and a few thousand bigger. For the barrel tenon, I had the situation and just sanded the ID with 220 sandpaper. Short of having dykem, trying it on as you go, and sand were it touch will make for a perfect fit.

For the barrel tenon and barrel nut, a good cleaning with a brass hand brush, and a very light sanding of upper Sharp edge of treads work great. It really does not take much to make it all fit.
 
Sound like the action is on the large side of spec... the new barrel is on the large side of spec... the barrel nut and recoil lug is on the small side of spec.

New barrel nut can help... if also made to the larger size.

Opening up the recoil lug will work for the new barrel but that can make it sloppy for the other barrel. Do you have access to a new recoil lug?

Ideally, you have a barrel nut and lug specific to each barrel tenon to reduce slop there.... or make the big barrel tenon fit current parts (as others have said)

YMMV

Jerry
 
I gotta fess up, that I am more than a little stumped as to why a "Pre-Fit" that "Doesn't Fit", should be your problem to fix.

Further, if it IS a matter of a spec change, get a new recoil lug while ordering the nut, and save it from becoming a loose fit on your other barrels.
 
I doupt the barrel nut was purchased with the barrel., if so, it will have been easy if it was not fitting to ask the dealer to replace it.

When you buy a prefit, with no barrel nut, you are on you own on this. I change barrel nut on each barrel I install. New barrel, new nut. It seem the new nuts - non Savage- are better made.

For the tenon, even from one brand to the other, there is some ´play’ in the ID, be on the tight or ´loose side’. All custom match tenon have different ID than Savage and must be fitted.

The barrel nuts system invented by Savage was to allow changing between Savage barrel. ( was probably cheaper to make also) They could have never took into account the large number of barrel made today, by so many different maker.

My guess is all prefit are made on the large side of the allowed tolerances. It will make to sense to go on the small side of it.
 
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