.416 isn't grouping well!

[njc110381]

This is my issue partly. I don't know how well it was shooting, well not really. I was shooting at gallon bottles of water with the iron sights at about 50m. The rounds were hitting pretty near centre of the bottle each time but with not many rounds down it and a fairly unsteady rest with no fixed aiming point as such I have no idea if this was luck? I need to get it on paper to be sure.

 

[Shootist43]

njc, I just got off the phone with Harlan Satrang the owner and principal gunsmith at Triple River Gunsmithing, (CZ's Custom Shop in the States.) According to him, the Action Screws are "supposed to be tight." He doesn't use a FAT wrench to any set inch pounds. With that info in mind, I'd go back to my original thoughts. Take the scope and bases off and go back to square one with Iron Sights and paper targets shot off a bench with sand bags. Determine how accurate the rifle is with the ammo you are using. You might try purchasing one box of good commercial ammo to compare against. For Bench work I use a PAST Magnum Recoil Shield. It spreads the "load" a bit and helps take the "me" out of the equation.

 

[postoak]

I agree with all that Shootist43 except the part about trying "one box of good commercial ammo". Anyone who has loaded for very long, much less decades, knows that his handloads are better than the best factory ammo.

 

[Shootist43]

Postoak, normally I'd agree with you. But right now njc is faced with a number of variables. A few shots with factory ammo could rule out one of them. If his 25 yd. groupings with handloaded ammo isn't up to his expectations, then I think he should try a few factory rounds. If the groups are still sub par, then without a doubt there are other issues that need to be rectified. You are correct about the reloading for decades part. For me it has been 39 years. I've loaded well over a 100,000 rounds for my competitive pistol shooting on a number of Dillon Progressive Presses and still cannot get groups as small as I get from ammo made by Atlanta Arms.

 

[postoak]

Fair enough Shootist43.

 

[Inline6]

This is my issue partly. I don't know how well it was shooting, well not really. I was shooting at gallon bottles of water with the iron sights at about 50m. The rounds were hitting pretty near centre of the bottle each time but with not many rounds down it and a fairly unsteady rest with no fixed aiming point as such I have no idea if this was luck? I need to get it on paper to be sure.

Listen a lot of information on here. 10" grouping is not your ammo 3"-4" yes. You said yourself the worst you have ever shot. That tell me you can shoot maybe not the smallest groups ever but you know how to shoot.

You know my thoughts on the scope rings then check the scope.

I took it for granted but I will ask this question. When you were on the sticks, you had it resting on the forearm correct? If the barrel was resting on the sticks that will cause big groups.

It had just dawned on me reading some of these post.

 

[One Day...]

Hello njc110381, it has been a pleasure walking the trail with you from your first post musing about a .458 Lott to do it all, to the actual ownership of this .416 Rigby.

This sense of camaraderie is emphasized, because I had exactly the same issue with exactly the same rifle

Here is mine:

CZ 550 .416 Rigby Rifle

• One Day...
• Nov 16, 2018
• 1

Allow me to proceed by elimination. For my rifle...

1) No, this was not the loads. All the folks, you included, who stated that 10" groups are not an ammo issue are correct.

2) No this was not a bedding issue. The stock on these rifles is made by Bell & Carlson and includes a full length aluminum bedding block and aluminum pillars. The barrel is free floated and you can take them apart as often as you wish, they will come back to zero. For information the torque specifications are 50 inch/lbs for both action screws. Tighten the front action screw first after assembling the rifle and slamming the stock vertically on its recoil pad on hard ground to sit the barreled action against the bedding block.

3) No this was not copper fouling. I had not, and you have not shot enough for that.

4) No the scope did not give up the ghost. Mine is a Schmidt & Bender scope 1 1/4-4x20 30 mm tube.

5) No the rings were not poorly mounted. I used Alaska Rings correctly degreased, and correctly torqued for the big cam screws at 30 inch/lbs, the lower lock screws at 40 inch/lbs, and the ring screws at 35 inch/lbs. And I do use a torque wrench so the numbers are reliable.

6) No it was not me, although for a while I doubted...

And then...............

All of a sudden, after 20 to 30 rounds, I do not remember exactly, the rifle started grouping 1.5" at 100 yd. I was dumbfounded...

What is was, I discovered by chance when cleaning the rifle, was that the scope had been progressively sliding forward in its rings imperceptibly with each shot, until the shoulder of the rear ocular came to rest on the rear face of the rear ring. From then on, problem solved!

Until...............

I took the detachable rings off and put them back on. "Deja vu" all over again. The next group was somewhat larger (~3") and had moved something, I do not exactly remember, like 6" sideways and 4" or 6" in elevation. What the heck !?!?!?

This one took a little more head scratching, but I found out the issue. The ring mounting grooves on the front bridge are not milled all the way. Since they are milled with a round cutter, they end up in a radius. Conversely, the edges of the rings are square. As the front edges of the front ring were biting forward under recoil into the radiuses of the grooves, they were digging into the grooves radiuses irregularly and never came back in the same place whenever I re-attached the scope. This was solved by moving the front ring back about 1/4 of an inch to provide ample clearance for the radiuses.

Since then I have encountered no more "inexplicable" accuracy issue with the CZ 550 .416 Rigby.

I am of course not saying that this will automatically be the issue with your rifle, but I do suggest you check these out. What I am pretty certain of is that: something mechanical is moving. Options are limited: barreled action within the stock; internal components within the scope; scope within the rings; rings on top of the action.

Good luck and let us know how it gets resolved. I would take a decent wagger that it will turn out to be pretty simple ... in retrospect

 

[njc110381]

Just came back here to reread some of the points made and realised I hadn't replied! Thanks for all that info, much appreciated. My mounts were set up right at the edge of the dovetail so I need to shift that for a start. I will also make a note of exactly where the rings are and fire a few more shots to see if anything is shifting, it could well be. I need to shoot it with irons again really, see where that gets me.

 

[Inline6]

Just came back here to reread some of the points made and realised I hadn't replied! Thanks for all that info, much appreciated. My mounts were set up right at the edge of the dovetail so I need to shift that for a start. I will also make a note of exactly where the rings are and fire a few more shots to see if anything is shifting, it could well be. I need to shoot it with irons again really, see where that gets me.

Something doesn't sound right. The recoil lug should be in the slot of the rear dovetail. If your rings don't have that built into them it will not hold. From you description it sounds like you may not have the correct rings.

 

[Graham Hunter]

Just go to your iron sights at 50yds off the bench and tell us what that does.

 

[One Day...]

Something doesn't sound right. The recoil lug should be in the slot of the rear dovetail. If your rings don't have that built into them it will not hold. From you description it sounds like you may not have the correct rings.

Not necessarily... I suspect njc110381 did his homework and has the proper rings...

As we all know, only the rear ring has a recoil lug. What happened in my case was that the rear ring with recoil lug was fulfilling its purpose, but the scope was sliding within the rear ring and moving the front ring forward, as apparently it is easier to slide the front ring forward than it is to slide the scope within the front ring, and the front ring digging into the radiuses at the end of the front bridge dovetails shifted the point of impact at every shot. In any case, i) resting the scope rear ocular shoulder on the rear ring (if the scope construction allows), ii) resting the rear ring recoil lug in the action recess, and iii) moving the front ring back 1/4" will eliminate any scope movement.

I am betting that iron sights will group an inch or so at 50 yd as there is likely nothing wrong with either rifle or ammo. Per previous post, my diagnosis - based on past similar experience - is that something mechanical in the scope assembly is moving, and there are not too many options

I am further betting that very soon this rifle & scope will group 1+" at 100 yd as it is possible that the scope is damaged, but it is more likely that something along the line I am reporting from my own experience is happening. We shall see...

Keep the faith njc110381, you will soon tell us what it was

 

[One Day...]

Proper scope mounting on big bore CZ 550

1) The scope ocular shoulder rests on the rear side of the rear ring, and the front side of the rear ring recoil lug rests on the front side of the rear bridge recess. Here, a Schmidt & Bender 1 1/4-4 x 20 with 30 mm tube in Alaska Arms rings:

Note: this may not be possible with all scopes. In some scopes, there is no ocular shoulder, and resting the scope against the rear ring would block (and likely damage) the magnification ring...

2) The front edge of the front ring is well clear of front bridge dovetail radius:

The bottom line is that is the scope moves forward within the rear ring and drives the front ring to dig into the front dovetail radius, the front ring will move sideways and upward in unpredictable ways at every shot.

I know, it happened to me

If you look at this pic at maximum magnification, you can see the marks where the scope slid forward in the front ring that was resting on the dovetail radius, during the first 20 to 30 shots, until its forward move was blocked by its ocular shoulder coming to rest on the rear ring, and you can see where the front edge of the front ring dug into the dovetail and shifted position accordingly until it was re-installed back 1/4" or so...

And, trust me, it had nothing to do with improper rings, scopes, or installation (everything was degreased, rings were lapped, screws were torqued, etc. etc.)...

 

[BeeMaa]

I was sighting in my 375 H&H with a new Trijicon scope and it broke the parallax adjustment.
I sent it back to Trijicon, had it repaired and it was fine after that.

Listen to these guys and move slowly and methodically to determine the cause.

 

[Shootist43]

What happened to setting the scope for the proper eye relief? One Day, I don't believe your "experience" is applicable to every scope.

 

[fourfive8]

I'm having trouble following this. "it had nothing to do with improper rings, scopes, or installation (everything was degreased, rings were lapped, screws were torqued, etc. etc.)..." Seems like in that instance it had everything to do with installation or the rings/mounts weren't up to the task-- painfully obvious.

Back to the OP... the best approach would be to first re-check mounts and rings (mounting technique or installation or whatever you want to call it) and make sure you are using good quality and designed for heavy recoil. Next check scope for failure. Then rifle, ammo and shooting technique. One thing at a time starting at the mounts and scope then moving outward in a logical way, eliminating each possible cause until the ONE cause is identified and corrected.

 

[One Day...]

What happened to setting the scope for the proper eye relief? One Day, I don't believe your "experience" is applicable to every scope.

Nothing happened to that concept, Shootist43, yours is a very valid point, to which I would submit the following answer.
There is nothing inherently wrong with having a scope as forward as mechanically possible (within reason) on a DG gun with substantial recoil. At best you avoid a painful scope bite, and a worst, you have a slight black shadow at the edge of the sight picture, which has zero practical effect on your snap shooting and which you can avoid by moving your face 1/4" forward if you so wish in deliberate shooting.
On a CZ receiver with built-in ring bases, it would be mechanically difficult to locate the scope too far forward. This could happen on other rifles with offset bases, and my suggestion would indeed not apply, just as you state, but we are talking about a CZ here, which is why I share my "experience" defined not as "it happened to me."
Just trying to help, not pretending to have a universal solution, and the checks I suggest are cost-free and easy...

We shall see how this thing turns out, I place my wager on something mechanical and, in retrospect, simple...

 

[One Day...]

I'm having trouble following this. "it had nothing to do with improper rings, scopes, or installation (everything was degreased, rings were lapped, screws were torqued, etc. etc.)..." Seems like in that instance it had everything to do with installation or the rings/mounts weren't up to the task-- painfully obvious.

point well made fourfive8. What I meant to communicate was that it was not an issue of broken scope or incorrect rings type as suggested along.

To your point, I noted that when torqued in place the Alaska Arms rings halves do not show any gap as typical on other rings (see pics). And no, this is not due to over-lapping as the Alaska Arms rings are so well machined that verifying concentricity and alignment (i.e lapping) did not even remove the bluing... I wondered if the absence of gap was not resulting in less friction on the scope tube than other mounts would have, hence explaining that the scope slid... Then, I remembered that I had the same issue on my .340 Wby with the scope moving forward in Talley rings, which do show a gap despite being torqued at 30 in-lbs, which significantly exceeds Talley specs of 15-20in/lbs.

My simple (simplistic?) conclusion is that reaching the 45 to 55 ft/lbs recoil threshold does have consequences on scoped rifles... Heck! I saw a friend's .416 Taylor sheer off the base screws (which is why anything I have over .300 that has scope bases screwed on, has been re-drilled and taped for 8-40 screws

Anyway, not pretending to have the answer here, just trying to share a similar "inexplicable" accuracy issue with a newly scoped CZ .416 in the hope that it may (?) help our British friend

 

[Shootist43]

One Day ,we are all curious to see how this turns out. Not being there all we can do is speculate. Like most that have offered "tips" I too think that the "fix" is going to be something simple.

 

[One Day...]

One Day ,we are all curious to see how this turns out. Not being there all we can do is speculate. Like most that have offered "tips" I too think that the "fix" is going to be something simple.

Yep. Here is a very simple and cheap diagnosis tool. Borrow the wife's nail polish and apply one drop on the scope tube at the front and rear edges of the rear ring. Let dry. Shoot 3 times. If the nail polish drops cracked, you know that your scope is moving...

 

[Tokoloshe Safaris]

Hello njc110381, it has been a pleasure walking the trail with you from your first post musing about a .458 Lott to do it all, to the actual ownership of this .416 Rigby.

This sense of camaraderie is emphasized, because I had exactly the same issue with exactly the same rifle

Here is mine:

CZ 550 .416 Rigby Rifle

• One Day...
• Nov 16, 2018
• 1

Allow me to proceed by elimination. For my rifle...

1) No, this was not the loads. All the folks, you included, who stated that 10" groups are not an ammo issue are correct.

2) No this was not a bedding issue. The stock on these rifles is made by Bell & Carlson and includes a full length aluminum bedding block and aluminum pillars. The barrel is free floated and you can take them apart as often as you wish, they will come back to zero. For information the torque specifications are 50 inch/lbs for both action screws. Tighten the front action screw first after assembling the rifle and slamming the stock vertically on its recoil pad on hard ground to sit the barreled action against the bedding block.

3) No this was not copper fouling. I had not, and you have not shot enough for that.

4) No the scope did not give up the ghost. Mine is a Schmidt & Bender scope 1 1/4-4x20 30 mm tube.

5) No the rings were not poorly mounted. I used Alaska Rings correctly degreased, and correctly torqued for the big cam screws at 30 inch/lbs, the lower lock screws at 40 inch/lbs, and the ring screws at 35 inch/lbs. And I do use a torque wrench so the numbers are reliable.

6) No it was not me, although for a while I doubted...

And then...............

All of a sudden, after 20 to 30 rounds, I do not remember exactly, the rifle started grouping 1.5" at 100 yd. I was dumbfounded...

What is was, I discovered by chance when cleaning the rifle, was that the scope had been progressively sliding forward in its rings imperceptibly with each shot, until the shoulder of the rear ocular came to rest on the rear face of the rear ring. From then on, problem solved!

Until...............

I took the detachable rings off and put them back on. "Deja vu" all over again. The next group was somewhat larger (~3") and had moved something, I do not exactly remember, like 6" sideways and 4" or 6" in elevation. What the heck !?!?!?

This one took a little more head scratching, but I found out the issue. The ring mounting grooves on the front bridge are not milled all the way. Since they are milled with a round cutter, they end up in a radius. Conversely, the edges of the rings are square. As the front edges of the front ring were biting forward under recoil into the radiuses of the grooves, they were digging into the grooves radiuses irregularly and never came back in the same place whenever I re-attached the scope. This was solved by moving the front ring back about 1/4 of an inch to provide ample clearance for the radiuses.

Since then I have encountered no more "inexplicable" accuracy issue with the CZ 550 .416 Rigby.

I am of course not saying that this will automatically be the issue with your rifle, but I do suggest you check these out. What I am pretty certain of is that: something mechanical is moving. Options are limited: barreled action within the stock; internal components within the scope; scope within the rings; rings on top of the action.

Good luck and let us know how it gets resolved. I would take a decent wagger that it will turn out to be pretty simple ... in retrospect