Question for AW cut Impact Action Owners

[achalmersman]

Question for you guys with AW cut Impact Actions. Was your feed ramp cut to accommodate the longer OAL available when using AW mags?

After receiving my action from Impact yesterday with no trigger hangers or hardware (after waiting since March) I decided to see if the AW fed properly. The cartridges are sliding forward in the mag, and catching on the feed ramp which hangs overtop of the AW mag. This is the first rifle I've built so yea I'm a newb. But I would have thought if the receiver was cut for AW then the feed ramp would be cut to be compatible with the AWs. Is this an unreasonable thought? I've ordered a MDT 12 rounder with binder plate to get me through till October and I'll load my ammo short enough to accommodate.

Yes I'll call Impact on Monday. But I've already called them and left a message and email about the trigger hangers and hardware last night. And besides even if they do say "send it in" I'm not doing that till October. I want to be able to at least shoot a single match this year after spending $1450.

 

[kthomas]

Any gunsmiths or machinists in your area with a mill? Just get the feed ramp notched.

I agree that would be really frustrating to not get the full package (trigger hangers and hardware), nor a functioning action with the mags it was cut for.

 

[mjh30]

What caliber in the aw mags

 

[achalmersman]

What caliber in the aw mags

6.5cm

 

[achalmersman]

Showing bullet nose under feed ramp

 

[Dthomas3523]

@morganlamprecht

 

[morganlamprecht]

I don’t think the feed ramps on them are cut longer for an AW, they have enough clearance as is...I’ve got an AICS cut Impact here in a KRG and it doesn’t overlap and a AW cut impact in a foundation and it doesn’t either...neither of my actions overlap (both AW cut) and they aren’t notched, but the bottom metals are also custom inletted to the depth and position I wanted them

It could be that the mag well of mpa is slightly different or the recoil lug cut is slightly further back...can’t say without having it in hand, but that’s where whoever put the gun together would need to fit it all up and make it right

Just dropping parts together doesn’t always work because of small variances between components, especially with AWs in a 2 lug action cause it all needs to be set up right

 

[achalmersman]

If you're saying you have an AW cut Impact receiver and the feed ramp does not overhang the magazine then your feed ramp must have been cut for it and mine isnt. We arent talking about little variations here. Its 0.080" difference between standard AICS (with binder plate) and AW OAL. Just like vendors are very clear about the need to notch the feed ramp if you purchase AICS mags with no binder plate I would assume the same is true for the AW mags.

What I'm saying is the feed ramp appears to need to be shorter for the AW. It's not even close to feeding correctly. The feed ramp overhangs the front of the AW mag quite a bit.

 

[morganlamprecht]

I’m aware of the mag differences...I’ve built and fitted multiple impacts with AICS and AW cuts

Ive got both an AICS cut impact and a AW cut impact here...neither overhang the AW mag in a krg chassis or my 2 foundations

Unless your action is cut differently than both of these AICS and AW cut actions...your chassis is different which wouldn’t be surprising being an MPA

both these pics are 25 creed rounds pushed all the way to the front of the AW mag


AICS cut action in a KRG

AW cut action in a foundation

 

[achalmersman]

Thanks for the pics. Yea yours obviously clear plenty. MPA is not exactly a rare chassis. I guess without placing the same action in multiple chassis (which I dont have) I have no way of knowing which is the actual problem. I guess when the AICS mag comes in I'll compare. Now that I've got copper traces to follow maybe I'll just get crazy and use a dremel and notch it myself. The chassis cant easily be changed. Tried to get a better pic with a flashlight. It's even worse on the close side but impossible to get a picture of.

 

[achalmersman]

@morganlamprecht also, I'm sorry I wasnt trying to suggest you didnt know the difference. I was trying to imply I find it surprising either Impact, or MPA would vary dimensions by 80 thousands. That's not a little deviation to me. I honestly thought the feed ramp would be machined shorter on an AW cut receiver and that was forgotten on mine.

 

[morganlamprecht]

Something to try...not sure how much forward room there is in the action screw holes...but you could try to layer some painters tape or scotch tape on the rear of the action recoil lug to push the action forward...if u can get it far enough forward to clear, then the action has space, it’s just not in the right spot in relation to the chassis

If u can move it forward enough to clear you could always bed it forward of the lug to keep it there permanently, kinda sucks to have to do, but it’s an option

The Mpa is a common chassis but they ain’t known for holding the best tolerances and QC...seem some doozies come thru the shop

 

[achalmersman]

Something to try...not sure how much forward room there is in the action screw holes...but you could try to layer some painters tape or scotch tape on the rear of the action recoil lug to push the action forward...if u can get it far enough forward to clear, then the action has space, it’s just not in the right spot in relation to the chassis

If u can move it forward enough to clear you could always bed it forward of the lug to keep it there permanently, kinda sucks to have to do, but it’s an option

The Mpa is a common chassis but they ain’t known for holding the best tolerances and QC...seem some doozies come thru the shop

Great suggestion. I'll give that a try tomorrow. I dont recall the action screw holes having much play but I'll give it a try.

 

[morganlamprecht]

Hopefully you get it worked out, sucks getting everything in and it doesn’t drop in good to go, but it happens pretty often across all components

 

[achalmersman]

@morganlamprecht nailed it. There was just enough slop in the chassis holes I slid it forward and it just barely looks like its flush with the front of the mag. Ran about 25 rounds through it zero issues.

So now... can I just use a piece of shim steel between the recoil lug and chassis block? Anything special I need to be aware of? Thanks

 

[MikeRTacOps]

Yes I'll call Impact on Monday. But I've already called them and left a message and email about the trigger hangers and hardware last night. And besides even if they do say "send it in" I'm not doing that till October. I want to be able to at least shoot a single match this year after spending $1450.

I'd be Happy to fix it for you for FREE if you cant get fast service...

Mike R.

 

[achalmersman]

I'd be Happy to fix it for you for FREE if you cant get fast service...

Mike R.

That's an unbelievably generous offer and while I may contact you for help I don't expect anybody to work for free. As proof of concept I have put a 0.014" shim between the rear of the recoil lug and chassis, locked everything down using the MPA lug lock wedge thing, and everything seems to work now. Running lots of long cartridges through and it hasn't caught a single time. The common suggestion seems to be to bed it and I dont know why I have such a mental hangup about me trying to bed this myself but I feel like I'll mess up the action or chassis. Am I an idiot if I just use it with a shim for the next month or 2 and then look into bedding this winter?

 

[morganlamprecht]

One way to find out is zero it, bang the barrel on the bench and shoot it again...look for any movement and you’ll know how well it’s holding...it shouldn’t move if it is

 

[MikeRTacOps]

Just following up with you as I have been off comms for a day or so. You get this resolved yet ? I'd be happy to assist you like I stated...

Mike R.

 

[Terry Cross]

@morganlamprecht nailed it. There was just enough slop in the chassis holes I slid it forward and it just barely looks like its flush with the front of the mag.

My opinion...

If the rifle is built and assembled correctly, the action screw holes should absolutely have "slop" in them to insure that the stock bolts are passing through with 100% float. The inletting/pillars or chassis should be set up so that when the recoil lug is SEATED against the lug seat, those bolts float through. Sounds like you possibly did not mount your barreled action into your chassis properly if it had room to move to the rear. The bolt holes should absolutely not be used to align anything on that axis.

If you go shimming anything between your recoil lug and the lug seat to alter the position of the action, you could very possibly cause one or both stock bolts to bind in their perspective holes which is precisely one of the many things a builder should be avoiding.

Also when everybody is discussing the tips of their rounds catching under the ramp, there is a huge responsibility that lands squarely on the design of the DBM bottom metal or the chassis that the action sits above.

There is room on the long axis to locate the mag box too far forward or too far backward and still get a mag to seat under most actions. If your seated magazine resides too far forward in relation to the action, the issue might not lie with the action maker but possibly in the design specs of the stock or bottom metal.



./

 

[b6graham]

Just following up with you as I have been off comms for a day or so. You get this resolved yet ? I'd be happy to assist you like I stated...

Mike R.

you would be wise to take Mike up on his offer OP.

 

[b6graham]

My opinion...

If the rifle is built and assembled correctly, the action screw holes should absolutely have "slop" in them to insure that the stock bolts are passing through with 100% float. The inletting/pillars or chassis should be set up so that when the recoil lug is SEATED against the lug seat, those bolts float through. Sounds like you possibly did not mount your barreled action into your chassis properly if it had room to move to the rear. The bolt holes should absolutely not be used to align anything on that axis.

If you go shimming anything between your recoil lug and the lug seat to alter the position of the action, you could very possibly cause one or both stock bolts to bind in their perspective holes which is precisely one of the many things a builder should be avoiding.

Also when everybody is discussing the tips of their rounds catching under the ramp, there is a huge responsibility that lands squarely on the design of the DBM bottom metal or the chassis that the action sits above.

There is room on the long axis to locate the mag box too far forward or too far backward and still get a mag to seat under most actions. If your seated magazine resides too far forward in relation to the action, the issue might not lie with the action maker but possibly in the design specs of the stock or bottom metal.



./

its an mpa

 

[achalmersman]

Just following up with you as I have been off comms for a day or so. You get this resolved yet ? I'd be happy to assist you like I stated...

Mike R.

So I recieved the necessary hardware to finish the trigger etc and final assemble everything Wednesday night. There is enough slop in the action screws to accommodate the final shim I made. I settled with a 0.015" shim with more surface area than the MPA lug block face whatever it's called. I got it all assembled at 1am Thursday morning and put 50 rounds through it at 50 yards before heading out on vacation. I was just trying to verify function, and put rounds down the barrel to work toward getting past the speed up stage so I can eventually start doing load development. Everything fed 100% without issue. I pulled a random book load out just to use up some varget and 130g ELDs to start sighting in / get barrel speed stabilized. This is the first barrel I've watched since new. Found it interesting from round 1 to round 50 I gained 75fps. The last 20 were steady. Only had 50 yards where I was and it put the last 10 through a single enlarged hole with an SD of 5.8. I know it's only 50 yards but at least I didnt see some kind of unbelievable garbage telling me something was waaay off. I will be doing significantly more when I return from vacation.

I appreciate your offer, and if I have any further issues, I will be in touch. And I'm glad to pay for the work. Thanks again!