doublegunshop.com - home Forums General Discussion German & Austrian Sporting Guns @ doublegunshop.com Scopes, claw mounts, "losing zero", etc.

Long thread with apologies: I'm running into some frustrations with a Mulcaz sxs back action hammer combo gun in 8x57JRS x 20 gauge and would love to get some collective wisdom. The scope is a Zeiss diavari 2.5 - 10 x 50 on beautiful looking claw bases. I have a separate thread on how this gun was a tack driver last year, grouped very tight at 200 yards and I confidently took an antelope at 300 last year.

I shoot in the field from a "V" gun rest mounted on a tripod from a sitting position. Point is to see how tight a group I can get in field conditions. This has worked well for years, but may be contributing.

I'm generally a decent shot with bolt rifles and recoil with the relatively heavy combo gun and 8x57JRS is a non issue.

The trigger pull could be classified as a bit robust. The set trigger is way too light for me, so I don't use it much if at all.

I wait several minutes between shots, walking to the target @ 100 or 200 yards between shots, and waiting quite a bit after returning.

Took a nasty fall several weeks ago which could be contributing. Boot got stuck under old barbed wire and down I went on a downward slope and cringed heavily when the gun hit the ground and a rock pretty hard. Thankfully the marks on the wood weren't too bad and no visible marks are on the scope.

To summarize what seems to be happening, and admittedly it could be all me:

I'll get a decent group, good group 3" high at 200 and clicked 'down' on the elevation turret the requisite number of clicks. Then subsequent shots are all over the place. This is after the fall.
I'll close to 100 or 80 yards, get an OK group and think everything's OK, then get fliers that are way, way off. Like 6" high or to the left, then maybe a decent group.

Do scopes really lose their zero? I did have a Nikon on a bolt rifle that had all the hallmarks of a scope that wouldn't hold zero and was sent a replacement that's been rock solid.
Could I have knocked something loose?
Not cleaning the barrel enough?
Check the hex bolts on the claw mounts?
Suck it up and use a bench to get a baseline?

Any insight, similar issues, recommendations before I try to send the scope off for a repair attempt? I'm far from the original owner, no warranty. If I need to buy a new Zeiss scope, REALLY hope the 50mm objective will fit in the very spendy existing claw bases!

Thank you for any insight, love this gun and it deserves to be used all year long!

Mt Al,
I took a fall right on my Merkel combo gun bearing the same type of scope some weeks ago. I checked with some shots on the rifle range, everything seems fine.
So thanks god I can only pass on hearsay:
yes, one can knock something loose:
- in the claw mounts, e.g the tiny "hooks" may be bent. Take the scope off, check those hooks, put the scope back on, try to find any wobble when pulling on the scope
- the crosshairs or the mechanism in the scope may be damaged. Fix the gun in sandbags, aim at a target, tap on the scope, look for any movement of the crosshairs. A collimator might help.
Good luck!

Mt Al,
The fact that it is a side x side may be contributing to the problem. When the rifle barrel heats and the shot barrel doesn't, the point of impact will change. I will also do this with an O/U or a drilling, but a SxS is the worst. Try this, set the target and fire one shot. Take the target home and do the same thing the next day (or week). Take the target home again and return the next day (or week) and shoot the third shot. If you are not satisfied with a three-shot group, repeat the exercise until you have the number of shots in the group you want. You can do it all in one day, but you have to wait longer between shots than you think would be necessary. The object is to have a "dead cold" barrel when you take a shot. Also, don't rest the barrels in the V, put your "off" hand in the V and hold the guns forearm, if a barrel is touching a solid object, it will shoot "away" from that object. It goes without saying that you should first do what fuhrmann suggested with the addition of holding the gun and scope up to a light source and see if you can see any light betwee the rings and bases, as well as ensuring the "slider" is fully seated. More than likely, if hook plate is moving in the dovetail, the whole group would move, not individual shots.
It seems that you have experience shooting groups or for score with different type rifles, but hunting is a different game; you don't win with the smallest group or highest score, you win when you put one bullet in the right place every time even when you are cold, sleepy, and need to pee.
Good luck,
Mike

Fuhrmann and Mike: Thank you both!
I hunted with a few drillings for several years 20+ years ago but kept things well under 100 yards, except for a long shot at a cow elk with a double rifle drilling - following what you wrote, Mike, on a 'dead cold' barrel that I had confidence in.
Back at it now, first ever combo gun and I can almost assure you that your advice on using my off hand to rest the barrels in the V has something to do with it. I have not been disciplined on consistency of how I'm lining up for the shot.
Also, I bet you're right on not waiting long enough. Pinky swear, it was at least 15 minutes between shots.
On the claw mounts: since I've had the gun there is the slightest perceptible movement up and down on the front base. It can barely be felt, but it's present. I did remove/replace the scope after the fall and it felt the same and, surprisingly, I took out the last target I had shot at and the post-fall-bullet-placement was within 2" at 200. This further supports your suggestion, Mike, as these shots were a few days apart.

As ever on this forum: thank you for your insights and I'll get back after it and report back. This long weekend may provide some opportunities to head out/back/out/back.

Al

Mt Al,
Do you still have the double rifle? If so, instead of waiting between rifle shots (at targets) you should shoot the second shot as soon as you can get back on target. Don't wait to see where the first bullet went if you are checking if the barrels are crossing or shooting "wide". You can check this without slowing down, by using two targets next to each other. Shoot the right target with the right barrel and before the sound goes away shoot the left target with the left barrel. Then let the barrels cool (the cold shot barrel will affect the warming rifle barrels otherwise). After you have shot three rounds from each barrel (cold) put one target on top of the other and mark the holes in one onto the other. What each barrel is doing will them be clear.
If the front base itself is moving, it may need to be re-soldered, but if the plate is moving in the dovetail, it can be tightened up a couple different ways. If the scope itself is moving, correction depends on the type of rings (soldered half ring, screwed full ring, or dovetail). BTY, I understand your discomfort with set triggers, but experience will remove that. Just set the trigger when you are ready to shoot. My German gunsmith friend cautioned that it is more dangerous to hunt with the safety on and the trigger set than with the safety off and the trigger not set. If you set the trigger and don't shoot, open the gun and unset the trigger. Some people unset it without opening the gun but a "slip", results in a shot. If it is open the firing pin can't reach the primer. I use set triggers on most of my guns, by just touching them when I am ready to shoot. If you are used to squeezing the trigger set triggers are entirely different but are helpful (but not for the second shot with a double rifle). You said you try to keep shots with a drilling under 100 yards. That is fine, but I find that drillings are surprisingly accurate (for one shot) because the rifle barrel being bound to the other barrels makes it very stiff, in spite of being very small in diameter and very light.
Good luck,
Mike

Mike, yes on the double rifle and getting great groups, "minute of heart/lung" at 60+ yards. I took your advice on targets side by side, right barrel on the right target, immediate left barrel on the left target, then superimposing for the composite group. Very pleased with where this is with 31.5 grains of IMR 4895, 7 grains dacron, cci large rifle primer and 345 grain buffalo arms .446 bullets.
got a universal decapper, universal bell-mouth-thing, took out the expander ball from the full-length die and just resize the neck/bell it out barely.
Just received some Hawk 350 grain .446 bullets that are next up for coming up with a formula. Plus a few more boxes of buffalo arms 345 grain to keep the love alive.
Wish Bertram would import some more 43 Mauser brass, but other vendors pop up now and again, plus I have 60 pieces of brass for now.
Will post pictures on that thread soon. Can't wait to take it to the field to fulfill its indented purpose!
Thank you for the advice on the double rifle as well. Getting there....

Mt Al,
If you take care of it, 60 cases will last you a long time. Your loading procedure sounds really good, but I couldn't understand about one thing. When you neck size, you didn't say how far down you size it. I use old CIL cases which are balloon head and are notorious for separating at the head. I discovered that the chambers of rimmed and belted cartridges in older rifles are usually longer than necessary. Setting the sizing dies by the usual instructions usually results in setting the shoulder back, which is blown back on the next firing. It doesn't take many cycles of this (depending on chamber depth and case type) before the case head is blown off. By setting the sizing die to "kiss" the shoulder you change from headspacing on the rim to headspacing on the shoulder and stops setting the shoulder back. If you worry about running out of cases for 43 Mauser, start saving 45-90 cases whenever you can find a good deal on them. I convert 45-70/90 rims to Mauser Base type, for looks; but as long as you size them to headspace on the shoulder, they will work fine without that. It is only necessary to reduce the rim diameter to fit the rim recess. The "book" says the rim should be .585" but .595" fits my rifles. Since the 45-70/90 head diameters are a little smaller than the Mauser Base they will expand on the first firing and making the rim fit the rim recess precisely ensures the expansion will be even. I size all my cases, rimmed, belted, or rimless this way. The only extra step necessary, when hunting, is to make sure each round chambers. (Ammo and loading die makers have to make sure their products fit in all rifles, we only have to make sure our ammo fits our rifles, and we don't need to build in tolerances.)
Mike

Mike,
Great points on quickly destroying brass! For the 43 Mauser: the virgin brass drops right in, is undersized from the chamber cast, so I do run the expander ball through the first time, prime, slightly bell the mouth, powder, dacron, seat the bullet. For seating I start out way long, then slowly turn until I get to max COAL which gets it right close to the rifling, but I don't go crazy on that.

For second and subsequent firings, I universal decap, then run the brass through the neck portion of the die the length of the part of the bullet that's inside the case, about 3/8"+, then bell the mouth, powder, dacron, seat the bullet. For this rifle, once-fired brass goes in even without having to kiss the shoulder in the die.

I've never annealed brass and might give it a whirl to undo the work hardening. Any idea how many firings until annealing becomes something to address?

I have brass from Bertram and Bluffalo Arms, made from 50x110 Starline brass. I'll look for 45-90 and that should give me an excuse to buy a harbor freight lathe finally!

Mt Al,
I likely have to anneal more often than you will. I rifle is an 1871 sporter and the barrel has .452" grooves, so I expand the neck of the fired case and seat a .452 bullet with the crimping and first lube groove seated outside the neck (all grooves filled with lube). Then I size the neck in a 444 Marlin sizing die, until it will chamber. My rifle will not shoot with .446" bullets but does well with the .452". I would like to size them .454" (.002" over groove diameter) but they won't clear the seating die. All that extra expanding and sizing means I have to anneal after 3 firings, but you may not need to do it that often. Whatever you choose, if you find a crack at the case mouth, anneal right away and reduce the number of firings. I use kapok instead of Dacron, but only because I found a kapok filled life preserver many years ago in a flea market.
Mike