Home Forums Hunting & Shooting Hunting Optics Super Sniper 3-9X42 on Kimber Montana

Hi Bob,

In general, I think the shooting community thinks in terms of "recoil" for these things... myself included, in general. This could be a sudden change in velocity of the rifle, the energy, overall acceleration, or even force depending on how it is investigated or what the perception of "recoil" is. More or less intuitive quantities in the time domain.

Or, we tend to think of "excessive" fastener torque when things break, or "insufficient" torque when they fly off. Of course, there could also be weak materials, manufacturing defects, etc. as well.

But, I wonder if there is more to it than that. I've mentioned in other threads that the ocular lock-ring on an FX-3 would not stay tight on that Kimber. The only other rifle that would loosen that lock ring was a 375 Ruger, and I tightened the hell out it. Other rifles, with much more recoil than the Kimber, would never loosen that lock-ring or jam-nut.

Were the ends of the scope whipping more, on the Kimber and 375?

That observation made me think that the internal ballistics of firing a cartridge, or vibrations in the system after the bullet leaves the muzzle, might excite the scope and mounts. This would be in the frequency domain... that many of us may not consider or find intuitive.

If this excitation is at the same frequency as the natural frequency, then there might be a problem! Think... Tacoma Narrows Bridge. That isn't the best example since it had a somewhat constant excitation (steady wind rather than limited duration powder propellant), but you get the idea.

Anyway, I'm sure someone more experienced and intelligent than myself has investigated this. But, I haven't seen any reports, papers, etc.

What I do know, is that the wimpy cartridge in that Kimber should NOT have cracked mounts and loosened jam-nuts.


Jason

Fred,

I know that Brad and others always bed Talleys on Kimbers, and it makes sense to me. If you look at the underside of the Talley mount, there is an area in the middle (of the cross-section) that doesn't make contact with receiver. With the clamp load of the fasteners, it would seem to put the mount in somewhat of a 3-pt bend, if over-torqued... spreading the ears of the mount. I suspect that Talley does this just to save weight, as other brands don't remove material here. But it's all speculation on my part and I could be completely wrong on all counts.

I haven't done the hand calcs, and am not a FE analyst, but suspect that the clamp load and friction between the receiver and mounts are sufficient for the theoretical shear during recoil (should be since "most" people don't have a problem ). But, this doesn't explain the anecdotal failures that we see and hear about. Again, material or manufacturing problems might be the problem instead.

However, I wonder if the loading might be more complex than we assume, and more than some mounts/fasteners can handle... over periods of time or cycles that exceed the expected use of the "average hunter". A recoil lug or pinning the base(s) seems to make a lot of sense. The lug slot on the M40 comes to mind. I'm guessing that the average M40 takes a lot more abuse than the average hunting rifle, but many assume that whatever abuse that can affect the mounts would destroy the scope. But this might not be the case.

Pic of the M40 slot that I scrubbed off the interwebs (rifleshooter.com):




And the M40 mount pic (also from rifleshooter.com):




I've communicated privately with other members on 24HrC about zero retention and mount integrity. Seems that the common thought is that steel mounts, or rugged alloy mounts, fair the best. And recoil lugs or pins don't hurt. But, these are just non-scientific drop tests and random impacts.

Jason

I feel obligated to post the link from the site where those pics were scrubbed. Personally, I think it was a really good series of articles.

rifleshooter link

I should also mention that I did a hardness test on those Talleys that cracked and they were in the correct "aerospace" range that Talley claims, but our material/metallurgy engineer told me that I need to have the chemistry checked to know for sure. To Talley's credit, they sent several pairs of replacements, so I can't complain. But I ended up going steel instead, without any issues.

Thanks for the response I will read the link as soon as I have a chance.

It's been 20+ years since I've messed with MM strain gages. We have an applied mechanics lab at work that I might be able to convince to gage a rifle, but I'm thinking more about accelerometers to measure whole-body rifle motion and barrel deflection for the internal ballistic portion. And a mic to record the transition to external. The modal test would be done with accelerometer(s) and an impact hammer.

Correlating the above with pressure data and accuracy/precision would be an interesting study though. I think some Olympic teams are working on this as just doing it willy-nilly seems to require a lot of time and luck.

Jason

Enjoyable, interesting info Jason. I agree there's lots of stuff likely going on that's hard to understand without more accurate ways to measure it.

Well done and thanks!

Jason,

Good stuff. Appreciated the read and your thoughts. Understand it's quite theoretical, but certainly educated theory. Do I dare say, +P.

4 th that was a great read. Thanks again for the thoughts I believe your right on.

4th point

It is always a bit of a risk judging failures by photos, especially where you don't have any of the fracture surfaces, but those two look like brittle overload failures. This suggests that the material used had a comparatively low work of fracture - it snapped more or less like a stick of chalk. This is fairly typical of aluminium castings, much less typical of, say, your typical medium-carbon steel unless it has been incorrectly heat treated (and yes, I am leaving out large amounts of detail).

Looking at the Talley base, the first two things I'd be considering are first, excessive torque on a countersunk screw, acting like a wedge to apply stress laterally, popping the base open around the screwhole; second, clearance between base and receiver under the screw hole, allowing a bending stress as the screw is tightened - or a combination of these two - in conjunction with somewhat brittle material.

With the Leupold, I'd also consider the effect of turning in a tightly fitting ring to the base, as a possible factor, but it is impossible to say more really with just the one photo.

It'd be good to know the material composition and hardness, and have some good macros of the fracture surfaces.

To recap, the mounts broke because they're [bleep] up and [bleep] happens....

I will never use Talley's again myself. Only time I have ever had issues was with them and a torque wrench was used.

Pic of 3-9 on a Montana. All I had was Medium rings and will change them eventually, but the cheek weld is fine.



7-1/4 lbs empty.

How far can you drop the scope before the front bell taper meets the end of the extended rail?

The difference between .85" Lows and 1" mediums (nightforce LW rings) there is room. I was going to chop off that little extra but as is it worked.

The3-9 is a good scope as far as fit, function, etc. fit holds up, I see more in my future. I wish they had an illuminated version.

This thread has taken a great turn. Nice! Good stuff guys.

The NF scope I have mounted in Talley LW's on my Kimber is of comparable weight to a 3-9 SWFA, and further, it's a 7 WSM so likely has a bit more recoil than your typical "Kimber Montana"... I'll keep an eye on them but my own guess is that the breakage at the ring screws is as has already been hypothesized: the little screws are not flat on the bottom and are acting as a bit of a wedge. But I don't know. I don't gorilla-grip my ring screws (unlike some guys) and I'm willing to continue with the Talleys. I've got at least a half dozen pair. If/when I see a problem I'll address it then.

The NF Direct Mount for Remington actions has a recoil lug that prevents shearing of the 6-32 base screws. Running it on a SA Reminton; nice stuff. Similar to Talleys but a little beefier and, of course, the bottom part is unified.

You SWFA guys can laugh............ when I went to take off that SWFA "sticker" from my Kimber it took a bunch of camo paint with it! D'oh!

I mostly take Talley Lwt "failures" with a grain of salt. I've had in excess of 20 pairs of Talley Lwt's and have never, ever had an issue. But I do lap them and do use a Torque Wrench.

We do live in a material world and materials do fail...

Dan,

Thanks for the input.

I think I have the Talleys around somewhere and might be able to get our materials engineer to run the chemistry. But the Leupos were returned so I don't have access to them anymore.

At any rate, both were replaced with Warne steel bases that fit just as well and have held up fine with Maxima rings on top.

Jason

"when this baby hits 88 mph... you're gonna see some serious $h!t" re: wiseman universe receiver

You familiar with Bills test Receiver?

JeffZero,

Imitation is THE most Sincere form of Flattery. The ONLY thing you can do in the first hand,is to schlep Fhuqking STUPIDITY,to places it's never been before. "Luckily" for you,that has NOTHING to do with distance or grandeur. Congratulations?!?

I'll feign my "surprise",that you had to use Farmed Fish in your "compelling" picture,of your "hard charging" ways. Laughing!

Bless your heart.

Wow +P++!.................















'mike,

I've not shot/got any 270's in a twist rate slower than 8",nor of barrel length greater than 20",or of a contour more svelte than a streamlined Montucky OEM or greater than a short shanked MTU. Just sayin'.

I hear good thangs about the Hornie 105HPBT in same,whether it ADL,BDL or DBM and I've a "hunch",that I'm likely afforded the luxury of not being forced to fhuqking guess.

Funny how it actually works and I mean fhuqking FUNNY!

Hint.

Bless your heart.

Laughing!...............















'shooter,

JeffZero can only guess,plagiarize and "live" vicariously...as a "best" case scenario.

Her heart is in it too and nobody "does" it better.

Laughing!.........................















FO',

Personally,I getta kick outta The Do NOTHING Gang's Vulcan Mind Fhuqk and copious elipsiseses.(grin)

Folks can only do the best they can and it is only fair,though funnier than fhuqk...to grant slack on that rope.

Never been tough to cypher who do and who don't.................















'45,

DD's are warm/fuzzy. Though I prolly have just about everything else there is too.

Hint...............















'heider,

I've zero doubt that LW's would do most folks proud. Obscene round counts(shooting out barrels) and weather that ain't always sunny,do tend to skew results and reliably expose potential.

LW surface area,in regards to their scope griptitude is reassuring,but trouble is that,is often where they puke. I've failed 'em both up top and below,as have others that gun in a similar fashion.

I'd slate LW's as being prolly 95% retired,as per folks I personally know,who flog on Riggin' as a mainstay. It wouldn't piss me off,to see 'em made in S/S with PosiLign-esque eccentrics.................















Jordan,

The 1913/'Horn melding is a PEACH. It capably melds griptitude,spacetitude and toughtitude...which is the ONLY way happiness can be realized.

Their sole bane being height,but for most applications(combs),they are Skookum +P+.................















FO',

Glen's stuff always rocks,but it's tough to leave inclination setting on the shelf...as the 'Horn's will happily cough up 40MOA via the rings alone.

If/when talking 2pc 1913,then you can of course eek more,by shimming the aft upwards. Conjoin same and 70MOA is easily granted with a mechanically centered windage,which do the scope even more favors.

It is impossible to have "too much" erector travel,despite The Do NOTHING Gang's valiant efforts,to "convince" themselves otherwise.

FUNNY schit!..................















hunting',

DNZ sucks ass,due ring spacing constraints. That is a HUGE concession to scope integrity and they are well shy of being viable,due that schit "design".

Been around lotsa them and all suck. I'd dangle pics,but am two-blocked.

Hint...................















'Boomer,

All wares are "equal" when setting idle.

'Tis only when they are truly flogged upon,that weaknesses reliably surface. I'm privvy to better than a dozen LW failures,though in fairness...none of them wares was Safe Queens.(grin)

We all gave 'em a fair shake and everybody has puked 'em....................















4th,

Purty mean of you to be danglin' pics of even more stuff that Fredrica has never seen,let alone "used" or heard of.

I have it on Good Authority,that the Marty double-lugged inclined 1913 rail aboard the LFB has prolly seen some trigger time and is holding like a rock. Have always liked the premise and the realization even more so,as it is a Skookum design +P...so I've a few.(grin)

Marty do alotta thangs right,though I'd love to see a 50MOA 1913 double-lugged rail wearing integral Max50's,with nice ring spacing and 8-40's everywhere................















math',

I'd dangle 30mm Fixed Fhuqker Lowtitude pics,but Imageshack is currently bein' peenched ala filter.

Tough to beat Maxima Low's on a Montucky 1913 rail.

Hint.....................















Brad,

That is "compelling" LW "Testimony". Congratulations?!?

Were you to take that amassed "round count" and weather exposure,it'd not rate 10% of my least used LW adorned rifle's USE. Hint.

Cheer up...I've suffered quite a bunch more than 20 sets.

Hint.

Bless your heart.

Laughing!................















RDW,

Have had lotsa LW's in winds/weather greater than 88mph,but that prolly weren't the culprit.................(grin)















Fredrica,

Didja' swipe more pics for "your" album,so you can now say you've "seen" the wares you are TRYING to "talk" about? Congratulations?!?

Here's to the perpetual hilarity of your Incredible Fhuqking STUPIDITY and it's oblivious delivery.

Bless your heart.

Laughing!................

The rings certainly seem to connect all the dots. In addition to longing for a bit lower option, I also wish the 1913 lug on the bottom was centered on the ring, rather than being offset. Because of the offset lug, I've got a slightly mismatched melding between the filed Warne base and the ring, which is still better than the regular Sig Zee's that sat there before, or the LW's before that, and should have enough clamping power to keep the scope from going places it ain't supposed to go, but it'd sure match up nicely if that friggin' lug was centered. Can't think of an instance where I'd want the lug offset like that, but maybe I'm missing something...