MDT ACC Howa 1500 SA inlet problem?

[crdixonaz]

First post here been lurking for a while. Just got an MDT ACC for my Howa 1500 SA that was in a KRG Bravo chassis. The inlet on the ACC has some center semi circular cuts behid the recoil lug and at the rear of the mag well where the action sits but the Howa has a flat bottom which is what I would have expected. There are flats on either side but it has much less surface area to contact. It seems odd and I have emailed MDT. Wanted to see if anyone has pics of theirs or any thoughts on this.

 

[Evintos]

Paging @MDT_Josh

 

[hereinaz]

Like a V block for flat bottom action?

Reduced surface area if something is not perfect?

I doubt it is a problem. They have cnc cut them.

 

[spife7980]

Honestly with a flat bottom my first thought on seeing it is “sweet, it’ll only contact in certain points and that makes it easy to bed as well.”

@MDT_OFFICIAL

 

[trdjohn]

following as I've got a howa and black Friday orders I'm waiting on from mdt

 

[crdixonaz]

@MDT_Josh emailed me back and said that is normal as was some flex I was seeing in the chassis and barreled action. I did shoot it yesterday and when I did my part groups were .2 -.3 moa.

 

[MDT_Josh]

Good question @crdixonaz ! The circular cut through the middle of that inletting is for tool clearance such that we can get the large cutters through the centre for better fit and barrel centredness. It will not affect the interface between the bottom of the action, chassis or recoil lug and we have done quite a lot of testing with this specific interface.

Josh

 

[Barelstroker]

Good question @crdixonaz ! The circular cut through the middle of that inletting is for tool clearance such that we can get the large cutters through the centre for better fit and barrel centredness. It will not affect the interface between the bottom of the action, chassis or recoil lug and we have done quite a lot of testing with this specific interface.

Josh

I purchased an ACC about 3 months ago. I've had some trouble getting my Howa action to sit properly at all in the Chassis.
The action recoil lug is deeper than the chassis bedding block so, the only parts of the action which contact the chassis are the bottom of the recoil lug, the face of the recoil lug & the bottom of the tang. No other surfaces contact the chassis.
I also have great difficulty in trying to centre the face of the recoil lug by feel. I simply cannot feel when the two faces are parallel.
The 1st time I mounted the barreled action into the chassis, the rifle would recoil & twist violently to the left. Since trying my best to realign the mating recoil surfaces, the rifle does recoil much better but, it's just been a guessing game.
When I inspect the action in the chassis, it appears very much that the action is more toward the right side of the chassis.
Does any of this sound normal or, do you think there is a problem somewhere?
Regards...............Barelstroker.

 

[MDT_Josh]

I purchased an ACC about 3 months ago. I've had some trouble getting my Howa action to sit properly at all in the Chassis.
The action recoil lug is deeper than the chassis bedding block so, the only parts of the action which contact the chassis are the bottom of the recoil lug, the face of the recoil lug & the bottom of the tang. No other surfaces contact the chassis.
I also have great difficulty in trying to centre the face of the recoil lug by feel. I simply cannot feel when the two faces are parallel.
The 1st time I mounted the barreled action into the chassis, the rifle would recoil & twist violently to the left. Since trying my best to realign the mating recoil surfaces, the rifle does recoil much better but, it's just been a guessing game.
When I inspect the action in the chassis, it appears very much that the action is more toward the right side of the chassis.
Does any of this sound normal or, do you think there is a problem somewhere?
Regards...............Barelstroker.

Interesting observations @Barelstroker ! IIRC the Howa 1500/Weatherby Vanguard inlet was giving us all sorts of issues for the longest time and we couldn't rely on the consistency of the main underside flat on those actions to reliably bed the action on (without additional bedding compound). That is when we decided to rather use the underside of the front recoil lug and underside of the rear tang as they were a lot more consistent. As you have seen though, the downside is that your action has the ability to translate within the chassis prior to you tightening it down, which we try to mitigate by keeping the side walls of the inletting at a tight tolerance. If your barrel is closer to one side than the other, that is fairly normal, however if it is very offset (> 0.040") then that could be another issue all together.

If you're concerned about accuracy or the quality of the product, be sure to contact @MDT_OFFICIAL directly at 1-604-393-0800 or go through the support portal on our website!

Josh

 

[crdixonaz]

Interesting observations @Barelstroker ! IIRC the Howa 1500/Weatherby Vanguard inlet was giving us all sorts of issues for the longest time and we couldn't rely on the consistency of the main underside flat on those actions to reliably bed the action on (without additional bedding compound). That is when we decided to rather use the underside of the front recoil lug and underside of the rear tang as they were a lot more consistent. As you have seen though, the downside is that your action has the ability to translate within the chassis prior to you tightening it down, which we try to mitigate by keeping the side walls of the inletting at a tight tolerance. If your barrel is closer to one side than the other, that is fairly normal, however if it is very offset (> 0.040") then that could be another issue all together.

If you're concerned about accuracy or the quality of the product, be sure to contact @MDT_OFFICIAL directly at 1-604-393-0800 or go through the support portal on our website!

Josh

My Howa is slightly off center as well, maybe 1/16 in or less. It messes with my OCD but it shoots great. I just get some side tilt in when I am snugging up the bolts trying not to force it. Works out just fine so far.

 

[308pirate]

I also have great difficulty in trying to centre the face of the recoil lug by feel. I simply cannot feel when the two faces are parallel.

I'm assuming that you mean the back face of the recoil lug and making sure that it's flat against the back face of the recoil lug pocket in the chassis.

If so, incline the chassis/barreled action muzzle upwards to let gravity help you keep those two flats in full contact with each other.

One other thing, because the front action screw threads into the bottom of the recoil lug, you need zero clearance between the bottom of the recoil lug and the bottom of the recoil lug inlet. Otherwise the action will be under tension perpendicular to its long axis which is no bueno.

 

[Barelstroker]

Interesting observations @Barelstroker ! IIRC the Howa 1500/Weatherby Vanguard inlet was giving us all sorts of issues for the longest time and we couldn't rely on the consistency of the main underside flat on those actions to reliably bed the action on (without additional bedding compound). That is when we decided to rather use the underside of the front recoil lug and underside of the rear tang as they were a lot more consistent. As you have seen though, the downside is that your action has the ability to translate within the chassis prior to you tightening it down, which we try to mitigate by keeping the side walls of the inletting at a tight tolerance. If your barrel is closer to one side than the other, that is fairly normal, however if it is very offset (> 0.040") then that could be another issue all together.

If you're concerned about accuracy or the quality of the product, be sure to contact @MDT_OFFICIAL directly at 1-604-393-0800 or go through the support portal on our website!

Josh

Thanks for the reply Josh.
The 1st time I mounted the action in the chassis, I had the chassis in the upright position as 308 pirate advised. That's when I realized that the action would not consistently or naturally centre.
With the chassis still upright, I centred the barrel in the barrel channel & tightened the action bolts, alternating between the two, front 1st a little then the rear & so on.
When I took the rifle out for the 1st shots off a sturdy bench, it would recoil harshly & jump 4 to 5 inches to the left on every shot.
When I inspected the action lug recoil face & corresponding chassis face, both showed significant markings on the left sides with very light markings on the right.
I do realize that it must be very difficult as you said, to try to keep tolerances workable in this situation. I immediately recognized why MDT had used the bottom of the action recoil lug & not the belly of the action.
I ended up very carefully filing some of the cerakote off the left side of the chassis face. I'm not sure whether the action is out or the chassis but, since doing this, the action now mates parallel with the chassis &, the rifle performs unbelievably better. There is still a slight jump to the left but, this may be rifling induced torque.
I've pulled it apart again & have added 0.008" of shim between the action & chassis faces to see if that helps with taking alignment. If the rifle settles down, I'll replace the shim with some bedding compound between the faces & call it good.
Otherwise, I'm very happy with the chassis. It's a definite significant step up from the old style stocks in every way.

Regards Barelstroker.

 

[Barelstroker]

I'm assuming that you mean the back face of the recoil lug and making sure that it's flat against the back face of the recoil lug pocket in the chassis.

If so, incline the chassis/barreled action muzzle upwards to let gravity help you keep those two flats in full contact with each other.

One other thing, because the front action screw threads into the bottom of the recoil lug, you need zero clearance between the bottom of the recoil lug and the bottom of the recoil lug inlet. Otherwise the action will be under tension perpendicular to its long axis which is no bueno.

Thanks for the reply 308pirate. I do appreciate anyone who chips in to help.
Never having used a chassis before, I originally thought that Aluminium must just feel very harsh because I took it for granted that the chassis was a straight bolt in & forget job which, they probably usually are. It doesn't surprise me that I got one that doesn't. I'm one of those guys that ends up with the stuff that has to be fixed or adjusted or something done. Seems to happen to me with most things I buy.
I realize that this could very well be the action that I have or, a combination but, I'll persevere with it &, no doubt, learn as I go.
Unless I can positively identify the problem as being the chassis, I don't want to send it back because that won't fix the problem so, I'll more than likely finish up using a dab of bedding compound betwixt the recoil faces &, hopefully that will do the trick.
Regards Barelstroker.

 

[308pirate]

Thanks for the reply 308pirate. I do appreciate anyone who chips in to help.
Never having used a chassis before, I originally thought that Aluminium must just feel very harsh because I took it for granted that the chassis was a straight bolt in & forget job which, they probably usually are. It doesn't surprise me that I got one that doesn't. I'm one of those guys that ends up with the stuff that has to be fixed or adjusted or something done. Seems to happen to me with most things I buy.
I realize that this could very well be the action that I have or, a combination but, I'll persevere with it &, no doubt, learn as I go.
Unless I can positively identify the problem as being the chassis, I don't want to send it back because that won't fix the problem so, I'll more than likely finish up using a dab of bedding compound betwixt the recoil faces &, hopefully that will do the trick.
Regards Barelstroker.

You're on the right path with bedding as the final way to fix this. It's actually the best way.

There's a misconception that a chassis that needs to be bedded is somehow defective. That's inevitable given the lack of understanding of manufacturing in much of the gun world, including here.

All dimensions on machined parts have tolerances. If chassis makers had access to an action's engineering drawings they could manager the tolerance budget on their chassis to minimize fit issues as much as possible.

However, OEMs like Howa, Sako, FN, etc don't share those drawings with the after market so occasionally you have two examples that don't work well together. Adding clearance to the inlet and applying bedding compound fixes it.

 

[Barelstroker]

You're on the right path with bedding as the final way to fix this. It's actually the best way.

There's a misconception that a chassis that needs to be bedded is somehow defective. That's inevitable given the lack of understanding of manufacturing in much of the gun world, including here.

All dimensions on machined parts have tolerances. If chassis makers had access to an action's engineering drawings they could manager the tolerance budget on their chassis to minimize fit issues as much as possible.

However, OEMs like Howa, Sako, FN, etc don't share those drawings with the after market so occasionally you have two examples that don't work well together. Adding clearance to the inlet and applying bedding compound fixes it.

As you say, the assumption that bedding is never necessary is not always realistic but, the chassis manufacturers do have some part in that general assumption however, as with all marketing, it is not usually wise to be brutally honest with the general public because this is more often than not, misunderstood. Very often, companies have no choice but to align themselves & their products with the most intuitive information &, leave things at that.
I'm well aware of the predicament that MDT & many other "aftermarket" companies find themselves in when supplying parts & accessories but, there's little they can do to limit bad experiences.
I don't really mind because I'm not in a large city &, sending items for exchange can take weeks or even months so, I simply fix the problems myself wherever possible.
With regards to the chassis, I'm still considering epoxy bedding the action directly behind the recoil lug as well as the lug face. I might contact MDT & see what advice they have or, MDT josh might chime in again.
Regards Barelstroker

 

[308pirate]

As you say, the assumption that bedding is never necessary is not always realistic but, the chassis manufacturers do have some part in that general assumption however, as with all marketing, it is not usually wise to be brutally honest with the general public because this is more often than not, misunderstood. Very often, companies have no choice but to align themselves & their products with the most intuitive information &, leave things at that.
I'm well aware of the predicament that MDT & many other "aftermarket" companies find themselves in when supplying parts & accessories but, there's little they can do to limit bad experiences.
I don't really mind because I'm not in a large city &, sending items for exchange can take weeks or even months so, I simply fix the problems myself wherever possible.
With regards to the chassis, I'm still considering epoxy bedding the action directly behind the recoil lug as well as the lug face. I might contact MDT & see what advice they have or, MDT josh might chime in again.
Regards Barelstroker

Make sure you bed the bottom of the lug too. Unlike almost all other rifles out there, you do not want clearance under the lug because the front action screw pulls directly on the recoil lug.

 

[Barelstroker]

Make sure you bed the bottom of the lug too. Unlike almost all other rifles out there, you do not want clearance under the lug because the front action screw pulls directly on the recoil lug.

Yes, if I go ahead with bedding under the belly of the action, I think it will have to be done in two stages with the bottom of the lug shimmed for the 1st stage to allow for shrinkage & then bed the lug section after the belly. I'll have to consult MDT about it.
If I don't allow for shrinkage of the belly & do it all in one go, it'll just be there for looks really.
The bottom of the lug may have to be shimmed up & 0.002" or 0.004" of pull-up on the chassis to ensure definite bedding pressure when the front is torqued down.

 

[308pirate]

I think you're making this way more complicated than it needs to be.

WTF is the deal with shims? Use Devcon 10110 to bed it. .0006 inches/inch of shrinkage, you won't even notice it.

Happy trails.....

 

[BAMAboy18]

My Howa is slightly off center as well, maybe 1/16 in or less. It messes with my OCD but it shoots great. I just get some side tilt in when I am snugging up the bolts trying not to force it. Works out just fine so far.

Devcon helps OCD...