Author Topic: Mounting a scope rail - how to (Read 1190 times)

Mamba_Driver · « **on:** April 29, 2005, 10:53:32 AM »

I need some advice on the best way to mount an ultra scope rail. I just got my .22 Hornet barrel back from a re-chamber job to a .22 K-Hornet. I had to remove the scope rail before I sent it to the gunsmith. I had NEF mount an ultra rail and remove the open sights when I had the barrel factory fitted to the frame. They just attached the rail to the barrel temporarily. In fact they didn't adjust the front screw and the locking set screws. They just mounted the rail with the 3 primary attaching screws.

My question is,.... do I just clean the rail and barrel well and attach the rail using Locktite or should I also use a small amount of epoxy under the rail to bed before attaching with the three mounting screws?

Also, If I should have to bed the rail,... what do I need to do to prep the mating surfaces,... anything special?

I know that someone out there will have an opinion

Thanks again for the help

quickdtoo · « **Reply #1 on:** April 29, 2005, 11:12:09 AM »

I've just been bedding the rail in blue loctite! After removing a couple, it was apparent that the loctite was filling in the gaps under it, so I've never felt the need for epoxy bedding. What you should do is make sure the mount holes are clean. They will appear to be but if the bottom of the holes aren't shiney, their full of loctite from the factory and can keep the screws from being fully tightened. I use a leather sewing awl to dig the thread locker out of the holes, it's pretty tough stuff so keep working at it until you see bright metal at the bottom.

To adjust the set screw to factory specs, it should be .0015" from the barrel, use an automotive feeler gauge or a piece of heavy duty aluminum foil for a thickness gauge.

Mac11700 · « **Reply #2 on:** April 29, 2005, 11:21:20 AM »

Quick:

Excellent...it's part of our FAQ's now...so it won't get lost

Mac

Mamba_Driver · « **Reply #3 on:** April 29, 2005, 01:26:40 PM »

Thanks quick,... never thought of using Locktite for bedding. Now I know what it was that was on the barrel under the rail from the factory. I knew it wasn't epoxy but I had quite a time removing the "substance" from the barrel. You're right,... once set up it is some tuff stuff.

quickdtoo · « **Reply #4 on:** April 29, 2005, 02:06:30 PM »

Thanks Mac, good idea.

Mamba Driver, you're very welcome, glad to pass along anything I learn.... :wink: It may bite me in the butt when it comes to the postal match.....but so be it!!! :grin:

Fred M · « **Reply #5 on:** April 30, 2005, 06:32:24 PM »

Quick.
Tell me if you are talking about the front screw, that is not threaded into the barrel if I understand it right what you are saying???

What possible good wouold it do to have .015" betweeen the screw and the barrel.

I do something totally different with that screw, if we are talking about the same screw.

Mamba_Driver · « **Reply #6 on:** April 30, 2005, 06:47:49 PM »

Hi Fred,

Yep, that's the screw quick was referring to. A gentleman at NEF seemed to be concerned about that screw adjustment/setting. He made it sound like sort of a warning. Told me to put a piece of paper under the screw as a spacer (I miced it at about .0015 to .002), screw in the locking set screws and NEVER touch it again. Why all the concern??? Could it be because of the recoil or something? What do you recommend? I actually was just sitting here and messing with the very thing. I noticed that there is some flex in the rail. I can move it enough to make contact between the screw and the barrel surface.

Thanks. :?

quickdtoo · « **Reply #7 on:** April 30, 2005, 06:57:16 PM »

It's only there to support a heavy scope if you happen to have it mounted on the extended part of the rail. If you think about it, when the barrel warms, if that screw is touching the barrel it will lift the front of the rail and in turn the scope, causing POI to change. I try to avoid having to mount a scope out the far if I can, preferring to mount the scope over the much more solid part of the rail above the chamber.

Mamba_Driver · « **Reply #8 on:** April 30, 2005, 07:13:49 PM »

Boy quick,... I wonder if that is also one of the reasons that some are having fliers toward the end of their shot groups. I just looked at two of my other barrels. This new Hornet barrel is the only one that I've ever messed with that screw. I had NEF remove the open sights on the barrel and give me a scope rail as a replacement. All my other barrels were factory setup as the rail came with the barrel installed. I've always removed the rails, cleaned and reattached with Loctite but never messed with that screw. The other two factory set barrels that I looked at have no clearance between the screw and the barrel surface. In fact, I could back off the screw 1/4 to 1/2 a turn before they came off the barrel.

It appears that whoever at NEF is installing the rails on the new barrels is not doing in practice what customer service is preaching :shock:

Huh.///

quickdtoo · « **Reply #9 on:** April 30, 2005, 07:28:00 PM »

I do believe it's possible, but it could also be caused by the barrel warming and changing the tension at the underlug and forend.....At least eliminating the scope rail movement reduces one of the variables!

Mac11700 · « **Reply #10 on:** April 30, 2005, 07:47:12 PM »

If the 2 side screws are not tight...the larger screw will work down pretty tight on the barrel too!!!!! Just thought I would pass that on...

Mac

Mamba_Driver · « **Reply #11 on:** April 30, 2005, 07:57:44 PM »

Good point Mac. On both of the barrels that I checked out, the set screws were tight,... at least tight enough I believe,... and set with some type of thread locker. Regardless of that though,... they are new,... never been fired yet. :?

Mac11700 · « **Reply #12 on:** April 30, 2005, 08:27:48 PM »

I just got my 2 ultra rails from NEF that was supposed to be on the barrels I ordered...and installed them yesterday evening...both were not tightend...so it pays to check...I'll post my groups later tonite(Sunday)...from my range time today...The Public range changed their hours of operation on me...so it's off to shoot later...

Mac

stiff neck · « **Reply #13 on:** May 01, 2005, 05:14:01 AM »

I can't figure out what you guys are talking about. My 223 Ultra barrel came with 3 drill/taps in the barrel. There are 3 holes in the scope mount. I cleaned out the holes and threads and put all three screws all the way into the barrel with some lock tite. There is a slight amount of overhand near the front, but the most forward screw hole is not anywhere near it.

What's this about a set screw and leaving a space? I don't get it.

quickdtoo · « **Reply #14 on:** May 01, 2005, 05:18:49 AM »

SN, that means you got a standard rail on your Ultra barrel, H&R has done that in error before, both Mac's and my UltraComp barrel came with standard rails when they should come with Ultra rails which are an inch longer and have a vertical set screw in the muzzle end with a lock set screw on each side of it.

Standard rail

Ultra rail

Fred M · « **Reply #15 on:** May 01, 2005, 07:28:34 AM »

[

Quote

b]To adjust the set screw to factory specs, it should be .0015" from the barrel, [/b]

Wow, I have to figure that one out

Medium hard steel (gun barrel steel) has an expansion coefficient of 0.00067 for a change of
100 deg F per foot. So to put that in perspective we can divide that by 12 to get inches that is 0.0000558 x the thickness of the barrel at the base of 1.111" times the change in temp from say 80 -150F or 70deg F divided by 100. That comes to a whopping .000043".

That amount could change in machine gun fire perhaps double if you don't care for your barrel.

One thing that really gets me, the base is attached solid to the barrel and will expand at an even rate. The cantilevered portion will just follow that expansion.

Since the barrel is 13% thinner at the point of this screw, it follows that there is 13% less expansion at that point, and the 0.0015 space would increase by the difference in expansion.

I never did the calculation before but I mentioned in my Ultra tweaking write up what I did with that screw since I could not find any possible use for this screw. I employed it to stop oscillations/vibrations in the canteleverd part of the base.

I first bent the base down 5-10 thou at the point of overhang and then tightened the screw back to level or more if need to adjust elevation in the scope. This will put the hang-over in tension and stop free vibrations, this is very academic but it is better than doing no good at all.

Now lets take this one step further by saying the base would lift 0.000043 at the front of the base what would that do at 100 yards.
With the scope rings 3.96" ctr/ctr the result at the target would be 100x36:3.96x0.000043= 0.039"low. But since the base expands at an even rate it would only change 4/100000".

A feeler gage will do some good in many places but under that screw it will waste your time.

Mac11700 · « **Reply #16 on:** May 01, 2005, 07:42:25 AM »

Ya right...why don't you try it instead of just doing armchair mathmatics...it does change the point of impact if the screw is tight against the barrel. good grief ...even the factory tells ya that Fred.....enough of us have actually tried it both ways to know it really does change the POI at 100 yards...so...do all the calculations you want...the reality of it stays the same...it changes the POI...

Mac

quickdtoo · « **Reply #17 on:** May 01, 2005, 07:47:10 AM »

Quote from: Mamba_Driver

It appears that whoever at NEF is installing the rails on the new barrels is not doing in practice what customer service is preaching :shock:

Huh.///

Heh heh, it's probably the same guy that is stripping the butt pad screws!!!! :-D :-D :-D

Mamba_Driver · « **Reply #18 on:** May 01, 2005, 08:19:29 AM »

OK Fred,... I just realized after reading your post that I have nothing more of any remotely intelligent content to contribute :eek: :-D :-D How in the world do you know all this stuff?

Trying hard now to sound somewhat intelligent,... beads of sweat popping out on my forehead,.... rapid breathing,... face turning red,... E=MC... Oh crap,... I forget. OK,... I'm wasted now,... headache,... must get a beer to recover :-D :-D :-D

Fred M · « **Reply #19 on:** May 01, 2005, 08:24:08 AM »

Mac.
I have two Handis with the approach of a tight screw and nothing changes and both shoot fair enough. On the 257hr I have a base directly mounted on the barrel. No change a solid shooter. So you call me a lier, and who are all those people that found all these impact changes?

It seams to me you will always run down anything I have to say. You go to great length to prove yourself right. You might do some some armchair math yourself and proof me wrong.

Change impact, what you do, play with that screw every time you shoot?
If that screw was the only thing that changes the impact on a Handi I might go along with that.

I do not need to contribute to this forum and perhaps I should not.
I will not go further in this asinine discussion.

mt3030 · « **Reply #20 on:** May 01, 2005, 08:33:21 AM »

My best grouping Ultra (25-06) came from the factory with the front set screw is not even extended out of the bottom of the base. This rifle will clover leaf three, both factory and handloaded 117 Seirras, @ 100yds. I have never touched the set screw because I'm afraid it might change its habits. The rest of them have all come different. Some touching, some with a gap no where near .0015. I guess I had better remove scopes and adjust the set screw to the magic .0015 and compare range performance. (Except for the 25-06, I AM NOT screwing with her!!) I agree that a touching set screw would give POI changes, but wouldn't it be the same if you just put a fourth threaded mounting screw out there? I still can't see a reason for it, unless the base is so weak that the flex under recoil will cause it to fracture. How about a base made of steel? Remove this set screw variable completely!

quickdtoo · « **Reply #21 on:** May 01, 2005, 10:01:42 AM »

Like I said, I think it's to support a larger heavier scope. If the scope were bumped, it could bend the rail down at the end. With a slight gap there, it's just going to stop against the barrel and spring back up to the pregapped position, but it's not touching so barrel heat/expansion shouldn't affect POI.

quickdtoo · « **Reply #22 on:** May 01, 2005, 10:32:52 AM »

Well, the proof's in the pudding as the old saying goes! Here's a couple 5 shot groups Mac shot this am with his new 30-06 UltraComp with the ultra rail set as per factory spec...50°, wind gusting left to right....shooting the new Federal Fusion 150gr ammo at 100yds....The targets are GrampaMike's post cards for the postal match, center orange is ½", IIRC. He'd post this himself, but he had to go to work, he'll post more pics later of his .243 and 95gr CT Ballistic Silvertips targets.....

Mac11700 · « **Reply #23 on:** May 01, 2005, 07:36:03 PM »

Mamba_ Driver;

First off...let me apologize for this needless bickering...I certainly didn't want to see it come down to this...at all...and even though this thread is still on track...I see no purpose for it to continue further...but...I do have to say something to Fred...because he accused me of calling him a Liar...

Fred...I have never called you a liar...nor have I gone out of my way to "Run down things you say"...you do that easily enough to yourself...I have in the past couple of weeks pointed out a couple major blunders on your part...this being 1 of them...the other on your so-called computer program calling a perfectly validated load DANGEROUS and over MAX and you standing by it and arguing with everyone on it...then having to eat crow about it......but I have never called you a LIAR...if you wish to continue this off forum or even thru PM's ...I'd be more than happy to accommodate you...otherwise...this ends now...

Mac

stiff neck · « **Reply #24 on:** May 02, 2005, 04:38:04 AM »

Quote

SN, that means you got a standard rail on your Ultra barrel, H&R has done that in error before, both Mac's and my UltraComp barrel came with standard rails when they should come with Ultra rails which are an inch longer and have a vertical set screw in the muzzle end with a lock set screw on each side of it.

Now I'm really confused. Can somebody please post a close up picture of the two different rails?

I don't understand the benefit of having a longer rail with the set screw. Seems like it can hurt accuracy if it's not set up right, but how does it have any ability to help? Why is it desireable over a standard rail? Should I call NEF and have them replace the one they sent me? I ordered the Ultra barrel w/rail and hammer ext but apparently that's not what I got.

quickdtoo · « **Reply #25 on:** May 02, 2005, 04:50:05 AM »

The Ultra rail is 1" longer and has one more cross slot in it so you can mount a larger scope on it due to the longer spread between rings.

Mac11700 · « **Reply #26 on:** May 02, 2005, 05:08:32 AM »

Also...when you look down on the top...you'll see the 3 mounting screws and another larger set screw...this one should be in it from the factory......this other larger set screw is just beyond the 5th slot on top..but before the 6th slot on the ultra...this set srew...has 2 smaller set screws on each side of the rail to lock it in place..

Mac

stiff neck · « **Reply #27 on:** May 02, 2005, 02:30:47 PM »

So what is the benefit of the Ultra rail vs the standard rail? It's just longer? Seems like the set screw idea is just asking for trouble eventually, what's the point?

quickdtoo · « **Reply #28 on:** May 02, 2005, 03:01:22 PM »

Quote from: stiff neck

So what is the benefit of the Ultra rail vs the standard rail? It's just longer? Seems like the set screw idea is just asking for trouble eventually, what's the point?

Quote from: quickdtoo

The Ultra rail is 1" longer and has one more cross slot in it so you can mount a larger scope on it due to the longer spread between rings.

Mamba_Driver · « **Reply #29 on:** May 02, 2005, 03:40:42 PM »

Mac, no apology necessary. Given a hundred people, you will almost always get ninety differing opinions on any given topic,... but hey, that's what it's all about,.. right? :grin: I find this forum of infinite value and extremely helpful. Everyone has been so very helpful and kind to answer my seemingly endless questions :?

Even though I personally don't have much to contribute, there are many people here who unselfishly give their time, experience and expertise to help others,... and I, for one am extremely grateful!

So,... thank you all!!!!!