Accuracy Loss After Change from HS Stock to Metal Chassis -- Help Needed

[bulldog284]

good evening

Im scratching my head a bit today this afternoon I took my 6.5x47 lapua built on a stiller action and a krieger varmint contour barrel that was in a hs precision stock that shot under a 1/2 moa consistently. Today I put it in a cadex strike nuke chassie with an aluminum bedding block and sighted it in and the accuracy is gone, now well over an moa goups.
Has anybody ever experienced this before ?

is it possible when I did load development it was in the hs stock and now going into the cadex chassie has changed the harmonics, I have never experienced this before. I’d appreciate anyone’s feedback.

 

[drop_point]

Check all your torque. Make sure you seat the lug properly.

 

[Sandstorm]

Yes, your harmonics have changed and you need to work up a new load,
It will come around just fine with a little tuning.
Make sure your action screws are tight and everything is up to snuff.

 

[J.d. Popkes]

HS is a chassis, aluminum bedding block…

Check the clearances, interfaces. Trigger etc. 700 footprints are not always identical plug and play. Does the action have a trigger hanger? Recoil lug contact? Tang supported?

 

[DLT]

good evening

Im scratching my head a bit today this afternoon I took my 6.5x47 lapua built on a stiller action and a krieger varmint contour barrel that was in a hs precision stock that shot under a 1/2 moa consistently. Today I put it in a cadex strike nuke chassie with an aluminum bedding block and sighted it in and the accuracy is gone, now well over an moa goups.
Has anybody ever experienced this before ?

is it possible when I did load development it was in the hs stock and now going into the cadex chassie has changed the harmonics, I have never experienced this before. I’d appreciate anyone’s feedback.

You might learn you can’t get used to a chassis. I tried and tried. Wasn’t for me

 

[bulldog284]

I have checked the torqu twice all good, the trigger is pinned into the action no hanger, the recoil lug is firm against the back of the action.
if i bedded the action to the chassie do you think that would smarten up the harmonics to get it back to were it was in the beginning?

 

[Nvcnvc]

I bet you will see improvement if you bed the action to the chassis, but it won't necessarily return it to the original condition when it was in the stock. You will still need to work up a load and play with seating depth.
I have a 300 PRC on a MDT chassis and while it is shooting at a decent accuracy level, I am not 100% happy with it. I am going to try one of those brake tuners to see if it makes a difference. Good luck

 

[bulldog284]

I wonder how much I will have to adjust my load

 

[NZ_Fclass]

HS is a chassis, aluminum bedding block…

Check the clearances, interfaces. Trigger etc. 700 footprints are not always identical plug and play. Does the action have a trigger hanger? Recoil lug contact? Tang supported?

Yes - I have seen "clones" of a high standard not completely fitting a Masterpiece Arms chassis. I don't know the Cadex, but a careful look at all the interface points is necessary. The tang is often a weak point. One could even use crush gauges between the action and chassis to ensure an even fit. I did have a Dolphin chassis back when that needed a skim bedding to correct the difference between aluminium and a Rem 700.

 

[bulldog284]

I know on the front the recoil lug only contacts the back and there is nothing in the front or sides

 

[BoydAllen]

Years ago an excellent benchrest gunsmith and world class competitor, Mike Bryant wrote a post about how he checks bedding with a dial indicator. I believe that it the only way that the bedding of the action body can properly be checked. Are any of you familiar with that method? As an aside, I would venture that no rifle that is built for actual benchrest competition is just bolted together.

 

[J.d. Popkes]

I know on the front the recoil lug only contacts the back and there is nothing in the front or sides

Okay, that’s normal, but only a small part of the contact surfaces.

 

[Bill Norris]

good evening

Im scratching my head a bit today this afternoon I took my 6.5x47 lapua built on a stiller action and a krieger varmint contour barrel that was in a hs precision stock that shot under a 1/2 moa consistently. Today I put it in a cadex strike nuke chassie with an aluminum bedding block and sighted it in and the accuracy is gone, now well over an moa goups.
Has anybody ever experienced this before ?

is it possible when I did load development it was in the hs stock and now going into the cadex chassie has changed the harmonics, I have never experienced this before. I’d appreciate anyone’s feedback.

Swapping stocks can be the easy button but it can also change the harmonics. You most likely will need to start a new load work-up to get back your accuracy.

 

[ShtrRdy]

I had the same thing happen to me when I went from a HS stock to an AG stock for a hunting rifle. That was several years ago so I don't recall what, exactly, I did to get it shooting again.

 

[J.d. Popkes]

Dykem

Modeling clay

A sharpi

Will show what is touching and what isn’t

 

[Keith Glasscock]

I've done a bit of experimenting with chassis recently. Swapping back and forth from stock to chassis had a near zero effect on tune.

The change in precision you are describing is too large to be a tune change. In my opinion, there has to be something truly wrong in the action to chassis fit up.

Check the bedding screw protrusion into the action. Too long of screws can screw your accuracy by either introducing firing pin drag (rear screw) or bolt displacement (front screw). Also check to ensure that the screws are actually torquing the action in and not shanking out.

Similarly, check the action flex (the result of a bedding deviation). If you flex an action enough, you can induce some serious problems. While in there, check for any indication of bedding block to action relative motion...

Much like previous posters, I think it would serve you well to ensure the rear face of the recoil lug is firmly in contact with the appropriate surface in the chassis before even starting to snug any of the bedding screws. I have found it really easy to induce a slight pretension that results in the recoil lug having a little gap because the screws are angled rearward and wanting to pull it forward.

After solving the immediate problem, I'd bed it. Just saying...

 

[C.E.Smith043]

I had a CZ 527 one time that shot very well. Took it apart and cleaned it. When I went out to check the zero, the groups were horrible.

Took me forever to figure out the problem, but while reassembling, I didn't get the magazine box placed correctly into the action and it was binding against the stock and not allowing the action to sit fully against the stock.

Everything was tight, but just not seated correctly. Once I figured it out and got the magazine box back in correctly, the gun shot like it used to.

 

[AlNyhus]

I've done a bit of experimenting with chassis recently. Swapping back and forth from stock to chassis had a near zero effect on tune.

The change in precision you are describing is too large to be a tune change. In my opinion, there has to be something truly wrong in the action to chassis fit up.

Check the bedding screw protrusion into the action. Too long of screws can screw your accuracy by either introducing firing pin drag (rear screw) or bolt displacement (front screw). Also check to ensure that the screws are actually torquing the action in and not shanking out.

Similarly, check the action flex (the result of a bedding deviation). If you flex an action enough, you can induce some serious problems. While in there, check for any indication of bedding block to action relative motion...

Much like previous posters, I think it would serve you well to ensure the rear face of the recoil lug is firmly in contact with the appropriate surface in the chassis before even starting to snug any of the bedding screws. I have found it really easy to induce a slight pretension that results in the recoil lug having a little gap because the screws are angled rearward and wanting to pull it forward.

After solving the immediate problem, I'd bed it. Just saying...

What Keith said ^^^^^^^^

 

[SKWERLZ]

Swapping stocks can be the easy button but it can also change the harmonics. You most likely will need to start a new load work-up to get back your accuracy.

This is often the case but it could be you just need to get it adjusted to you.

 

[jelenko]

I am not familiar with the MDT chassis, is it possible that the barrel is touching something in the barrel channel?