MPA & TL3 feeding issue *UPDATE 3/19/19*

[Cajuntransplant]

Wanted to post this here and get it out of the build forums. Will update as I hear back from MPA and BigHorn and try different things etc.. That way I can pass along what I learn to anyone else.

Just got my first build done with everything coming from Altus in Florida. Guts are the Bighorn TL3, AW cut action with proof stainless barrel resting in the MPA Comp chassis folder (new one without the castle mag cut). Barreled action is in the chassis torqued to 65in-lbs and the MPA lug lock is in and torqued to 30in-lbs. No mag no problems... action is smooth and slides easily in and out with no binding or catching.. Try to seat a magazine and problems start.

I got a box of ammo down the barrel and break in is done. Having mag problems though. Rifle came with a 5rd Accurate Metal mag and trying to get that mag to seat with rounds in it is difficult and to use that mag and have it feed feels like I'm trying to close an action full of sand and gravel and the brass has some nice scrapes from feeding out of that mag. Have to use a lot of force on the bolt knob/handle to get it to strip the round and chamber and it binds up and catches. If i press my thumb on the back of the bolt assembly where the firing pin cocked pin protrudes I can actually get the bolt to close easier without any binding.

Switched over to my magpul 10rd and 5rd AICS mags and those don't want to seat at all with any rounds loaded in them and when I could get em to lock in place the bolt feeds a couple of rounds fine but then I get the bolt riding over the top of the rounds and the mag follower is stuck and the rounds arent coming up high enough.

This is with a brand new magpul aics mag and ones that are older and work fine in my other rifles. The magpul 5rd mag seems to work better as far as feeding goes but still does not seat properly.

Got home and tried the magpul "fine tuning" like MPA has a video of with shaving a little material here and while now they lock into place fine, they still have same feeding / bolt over the rounds issue. So I think the TL3 with AW cut I got isn't going to run with the magpul mags... which sucks... cause they've worked in every other rifle/chassis I had... So that leads me to metal mags and trying to decide on which ones to try now.

Emailed MPA and BigHorn to ask what could be causing the issues and also what suggestions they had for me. Seems to me like the magwell in the chassis is too tight for the magpul mags causing them to bind and follower not work properly. But the accurate mag maybe rounds are too high up and thats why there’s so much binding and requiring so much force to chamber a round.

**UPDATE 1 - botched a magpul mag up with trying a little at a time sanding in order to get it to seat properly. Was able to get is to easily seat and lock into place but still was getting bolt over rounds and could not make it through a 10rd mag without having problems.

**UPDATE 2 - sanded and adjusted the feed lips on the accurate 5rd mag some and can get “easier” feeding but still binds up my action and bolt throw trying to cycle through the rounds quickly and brass is getting scratched up still. But still working on this mag to fine tune it and see if I can get it working smooth.

**UPDATE 3 - MPA wrote me back saying that the short 5rd accurate mag (which shipped with the rifle) is too short to lock up and seat properly and that could be causing my feeding issues. BigHorn wanted and got some pics sent their way. Altus said they would reach out to me and call. Member here is sending me an AICS mag to try and I'm going to try to borrow a 12rd MDT mag as well to try.

**UPDATE 4 - more polishing and tuning the feed lips on the 5rd mag (actually closed the gap some so rounds weren't up as high) and it is seating solidly and a LOT easier to feed and cycle ammo and brass isn't getting chewed up. Going to polish a little more and run the bolt tonight on and over the mag while I watch some TV and wear it in more. Gave up on the magpul mags after losing one to the modification bin... but have a bud that wanted / needed some so that works ok. Hoping the AICS and MDT mags work out the get go and then I can just pick some up of my own. Still disappointed that it required that much work and tweaking to get a 5rd accurate mag to work but with all the reading I've done it seems like that is the case with metal mags and a lot of rifles members on here have.

**UPDATE 5 - talked with Altus, BigHorn and MPA. All three suggested same things as members on here and that some ‘tuning’ for metal mags might be needed. Never realized that would be the case until this rifle build but with their suggestions and everyones help on here I’m getting it sorted out. What i’ve learned so far.... Magpul mags simply don’t fit in my chassis without too much modifying. Too tight in magwell causes follow to bind and the front of mag feed lips hit inside at front of action so those mags are gone. My only metal mag (5rd accurate - came with rifle) is super short in the magwell (MPA said it might not actually be able to seat and lock properly) is seating fine and mag lips were adjusted from 0.445-0.450 (maybe more) down to 0.410-0.420 and the bolt is not binding and dragging / chewing up the next round and it seems to be feeding a lot smoother and better now. Never had to tune a mag before but also never had metal mags and a custom action. All a learning curve for me but I think things are smoothing out and getting sorted. Huge kudos and thanks to the companies ( @BigHorn / ZAI Team @MPA @Altus ) who all emailed back and forth with me and offfered their tips and suggestions. Big thank you also to the members on here who calmly dealt with me and all my questions and concern with my new rifle build and (calmly) offered their help and wisdom with me and my not being able to understand the quirks that can come with doing a custom build ( @Sheldon N @reubenski @padom , and everyone else ). After I get the borrowed mag(s) in hand and try them out I’ll do another update to this and then hopefully be able to start a new thread about how amazing the rifle build is working out for me. Thanks and Cheers!!

** UPDATE 6 - Final thoughts and mag results testing for me is done and posted below.

 

[Flatiron]

As far as the Magpul mag--I have both an AW cut and an AICS cut Tl3, and if I recall correctly, AICS mags runs great with AICS cut, but not well with the AW cut. You would think, since its wider, the AW cut would not have an issue, but someone who knows what they are talking about on here pointed out the issue to me once--I believe it is that the AW cut does not stop the mag in the proper place (vertically), which causes issues.

I can force a magpul AICS mag into my AW cut TL3, and it will go and feed okay, bit something does not feel right and there is tension on the mag release lever when it locks in. In the AICS cut Tl3, no problems. That may be your issue.

In the AW cut TL3, I have good luck with all other mags: AICS, ARC 10 rounders, and AW mags.

Hope that helps.

 

[Codiekfx400]

You need a Ruger 90563. https://www.brownells.com/magazines...e-polymer-magazines-30-caliber-prod97709.aspx
This is what I use in my aw cut TL3 mpa chassis and it works great for 6.5 creedmoor. If you are trying to feed a 6mm br or dasher it may not work. But for creedmoor and similar it works great and is reasonably priced.

 

[LawnMM]

Only issue I've had is with AW mags. Rest run fine, don't know that I've tried Magpul. My bet is the chassis mag catch is out of spec, sounds like on the short side, so it's harder to strip and a steeper angle up the ramp.

Try another chassis if you have one, or a buddy's and see what happens.

 

[Sheldon N]

Not sure that this will solve your problem, but here's a thread discussing troubleshooting mags in the TL3, plus explaining how I tuned my AW mags to run in MPA/TL3. AW's are my favorite mags by far, way easier to load, and rounds strip out of them with less effort.

Check out the discussion and tips/photos in this thread, starts at post #39

https://www.snipershide.com/shooting/threads/favorite-mags-for-bighorn-tl3.6894051/

 

[Cajuntransplant]

Not sure that this will solve your problem, but here's a thread discussing troubleshooting mags in the TL3, plus explaining how I tuned my AW mags to run in MPA/TL3. AW's are my favorite mags by far, way easier to load, and rounds strip out of them with less effort.

Check out the discussion and tips/photos in this thread, starts at post #39

https://www.snipershide.com/shooting/threads/favorite-mags-for-bighorn-tl3.6894051/

I read through all that this afternoon and I think tweaking the accurate mag I have has made it better. Magpul mags will not seat properly at all. Modified them to get it to latch and seat eventually but mag itself was binding somehow and causing follower to stick. Going to try an ARC 10rd mag. Only plan on ever using it for 6creed, 6.5creed, 308, 22creed, etc. not interested in the short dasher cases yet. So I think the ARC should be ok.

 

[Cajuntransplant]

Only issue I've had is with AW mags. Rest run fine, don't know that I've tried Magpul. My bet is the chassis mag catch is out of spec, sounds like on the short side, so it's harder to strip and a steeper angle up the ramp.

Try another chassis if you have one, or a buddy's and see what happens.

I think the mag well doesn’t like and is grabbing the magpul mags weird causing them to bind up. Tweaking the accurate 5rd mag has it working better now but not great. On the hunt for metal mags to try out now.

 

[Cajuntransplant]

As far as the Magpul mag--I have both an AW cut and an AICS cut Tl3, and if I recall correctly, AICS mags runs great with AICS cut, but not well with the AW cut. You would think, since its wider, the AW cut would not have an issue, but someone who knows what they are talking about on here pointed out the issue to me once--I believe it is that the AW cut does not stop the mag in the proper place (vertically), which causes issues.

I can force a magpul AICS mag into my AW cut TL3, and it will go and feed okay, bit something does not feel right and there is tension on the mag release lever when it locks in. In the AICS cut Tl3, no problems. That may be your issue.

In the AW cut TL3, I have good luck with all other mags: AICS, ARC 10 rounders, and AW mags.

Hope that helps.

It does help. And I did read something about the magpul mags and them jamming up that someone else posted up about. I’m on the hunt for metal mags to try out now.

 

[Sheldon N]

So I think the ARC should be ok.

The ARC's fed very smooth for me with only a minor modification to the stock follower. I filed of the "wings" so it wouldn't cause the nose of the follower to hang up.

Just be aware they don't like dusty conditions.

 

[Cajuntransplant]

Just be aware they don't like dusty conditions.

I’ll keep that in mind. Going to borrow mags from friends in area and see what works best for me. Hoping to try ARC, AW and MDT in next couple weeks.

 

[Timo Turl]

For the AW cut in an MPA comp chassis you need the MPA Long Action mag release catch. You’ve alomost certainly got the short action one installed. Call Josh at Altus. He’s familiar with this and will get you sorted.

 

[Cajuntransplant]

That sucks. Let me send you an AICS mag to try instead of you going out and trial and error buying/ trying different mags. I've used AW, ARC, and AICS without issue. The AICS mag I send you works perfectly in my MPA) TL3 AW cut

Just sent you a message back. Thank you!!!

 

[Cajuntransplant]

For the AW cut in an MPA comp chassis you need the MPA Long Action mag release catch. You’ve alomost certainly got the short action one installed. Call Josh at Altus. He’s familiar with this and will get you sorted.

I’ve never heard of this. I’ll shoot them an email and see what they say. I got the whole setup from them so I’ll check to se what they sent me. Thank you.

 

[Cajuntransplant]

The ARC's fed very smooth for me with only a minor modification to the stock follower. I filed of the "wings" so it wouldn't cause the nose of the follower to hang up.

Just be aware they don't like dusty conditions.

Referencing that other thread and seeing other posts you’ve made in regards to magazines, which ones do you prefer and why. I know I’m going to get metal mags and it seems like I can tweak feed lips or followers to get most anything to work if I have to. But if I’m going to use this rifle and have multiple barrels eventually (6.5prc, 22creed, 6creed, 308, 300wsm, etc) is there one style / type magazine that would work batter you think? AW, ARC, MDT, AICS. Just trying to learn as much as I can from those you have done a lot of the testing and trial and error before me.

 

[Sheldon N]

Referencing that other thread and seeing other posts you’ve made in regards to magazines, which ones do you prefer and why. I know I’m going to get metal mags and it seems like I can tweak feed lips or followers to get most anything to work if I have to. But if I’m going to use this rifle and have multiple barrels eventually (6.5prc, 22creed, 6creed, 308, 300wsm, etc) is there one style / type magazine that would work batter you think? AW, ARC, MDT, AICS. Just trying to learn as much as I can from those you have done a lot of the testing and trial and error before me.

Perhaps I'm just fortunate but most everything has worked pretty much straight out of the box for me. AICS should be plug and play and would be my first choice for "easy button". I'd take up @reubenski on his offer to try one out.

AW mags are my favorite and are what I run now, but they did take some dialing in. I use Accurate mags for when I shoot magnum caliber because that's the only real option.

IMO mags and feeding are just things the end user needs to be willing to troubleshoot when you are sourcing your own components and putting them together. Calling different manufacturers is likely to have them pointing at the other manufacturers as the cause of the problem.

 

[arm017]

The ARC's fed very smooth for me with only a minor modification to the stock follower. I filed of the "wings" so it wouldn't cause the nose of the follower to hang up.

Just be aware they don't like dusty conditions.

One of the things that made ARC mags reliable for me in a TL3 (or any other action) was the use of the LRI follower. I've done some torture test type stuff on purpose- and could not get them to do the infamous ARC mag lock up salute. I think the arc mags with the LRI follower are one of my favorites. AICS mags/ Accurate/ MDT mags are too tall for my preference, and have a habit of bottoming out on stuff and getting in the way. The AWs are awesome, but I could not keep tweak them into being reliable- maybe Sheldon will open up a side gig business tuning mags for us. I agree that AW is by far one of the smoothest feeding mags.

 

[Cajuntransplant]

@Sheldon N I understand what you mean. And I am taking him up on the offer for sure. Super generous of @reubenski and it is greatly appreciated.

And I’m not trying to blame any one vendor or anything I just am trying to understand what the hiccup is. MPA and BigHorn have both been in contact as well as Altus already this morning.

BigHorn wanted some pictures and MPA suggested a different mag catch but both have said (I think) the magpul mags might require modification to seat and function properly.

 

[Cajuntransplant]

One of the things that made ARC mags reliable for me in a TL3 (or any other action) was the use of the LRI follower. I've done some torture test type stuff on purpose- and could not get them to do the infamous ARC mag lock up salute. I think the arc mags with the LRI follower are one of my favorites. AICS mags/ Accurate/ MDT mags are too tall for my preference, and have a habit of bottoming out on stuff and getting in the way. The AWs are awesome, but I could not keep tweak them into being reliable- maybe Sheldon will open up a side gig business tuning mags for us. I agree that AW is by far one of the smoothest feeding mags.

Good to know! I’m learning a ton about mags over the last 24 hours from all the members on here. Too many decisions but hoping to try a couple mags out soon. The ARC and AW appeal to me cause of the overall size but I’m having a hard time justifying the costs of mags for this right now. The loaner trial and error will help me decide where to spend my money. Thank you for the info on the ARC mags though!!

 

[Cajuntransplant]

I really feel like you should be able to run AICS mags for every normal .484" based cartridge. They should be straight up plug and play. Maybe open up the front of the lips a little to relieve tension on chambering. They are reliable, durable, and should be the common mag template chassis manufacturers and action makers base their designs around.

I agree and I would think I should just be able to pop a mag in and have it work properly but something is off. I'm going to pull the action out of the chassis I think tonight when I'm home and see how mags are seating and catching the mag release. I know for sure the magpul mags are jammed too tight in the magwell and the front of the mag is making contact on the front of the receiver so that's why they are not seating and functioning. But I'm waiting to see how the metal AICS mag does.

 

[Sheldon N]

One of the things that made ARC mags reliable for me in a TL3 (or any other action) was the use of the LRI follower. I've done some torture test type stuff on purpose- and could not get them to do the infamous ARC mag lock up salute. I think the arc mags with the LRI follower are one of my favorites.

The mag locking up in dust doesn't have anything to do with the follower, so even the LRI follower would not fix the issue I had. It's an internal mag geometry thing. The mag is wide, double stack, so they can have that short length. Then the cartidges have to "shuffle" inside the mag to work back into a single stack formation for feeding. They are under a lot of spring pressure which creates a lot of outward pressure against the mag walls. That creates drag and can cause the mag to lock up in really dusty conditions. The mag does have some sort of "teflon" type coating, but as the mag ages and wears that gets less slick too.

My ARC mags ran great for about a year, seemed to do fine in some dust and I was really happy with them. But then I encountered some tougher Utah dust and they went full lockup... worthless in the middle of a 2 day match. I went from being in a top ten position to finishing 30th or something. Totally tanked my last 4 stages of the last day, I think I shot 56 points the first 6 stages of the last day, then something like 8 or 9 points total across the last 4 stages. Travel costs, match fees, time, all out the window.

So no, I don't have a soft spot in my heart for ARC mags.

 

[arm017]

The mag locking up in dust doesn't have anything to do with the follower, so even the LRI follower would not fix the issue I had. It's an internal mag geometry thing. The mag is wide, double stack, so they can have that short length. Then the cartidges have to "shuffle" inside the mag to work back into a single stack formation for feeding. They are under a lot of spring pressure which creates a lot of outward pressure against the mag walls. That creates drag and can cause the mag to lock up in really dusty conditions. The mag does have some sort of "teflon" type coating, but as the mag ages and wears that gets less slick too.

My ARC mags ran great for about a year, seemed to do fine in some dust and I was really happy with them. But then I encountered some tougher Utah dust and they went full lockup... worthless in the middle of a 2 day match. I went from being in a top ten position to finishing 30th or something. Totally tanked my last 4 stages of the last day, I think I shot 56 points the first 6 stages of the last day, then something like 8 or 9 points total across the last 4 stages. Travel costs, match fees, time, all out the window.

So no, I don't have a soft spot in my heart for ARC mags.

Interesting, that is good to know. I dropped them in fine dirt multiple times and fed them with the lri follower, and 5 mags fed fine, but i'll keep an eye on it. Mag issues are the most frustrating thing in PRS in my book. I had a similar issue with AW mags - where my tweaking was not sheldon grade and apparently opened the feed lips too wide where a bit of water got in the inside and the cases all spewed out mid stage. The PTSD is real.

 

[Cajuntransplant]

Update and final results.

Got a loaned AICS ten round mag in from @reubenski and feed lips are drastically different than the accurate mag I got in as far as spacing and how high rounds sit. The AICS ten round mag from him feeds flawless with no rounds doing grinding or catching or dragging as they get picked up and chambered.

So I took measurements and looked at how the rounds sat in that magazine and I tweaked my accurate mag a little more and it got even better.

I also ordered up (at recommendation from some friends) the MDT 12-rd magazine and it came in while I was out of town and I got to try it out and it feeds better than the accurate mag and almost as good as the AICS mag. I might just need to do a tiny bit of tweaking with it and get it broken in but I think it’s a winner too.

Magpul AICS mags (for me) are just a straight no-go as they won’t seat proper without heavy modification and I think get pinched in the magwell and cause feeding issues.

Learned a lot bout magazines and feeding and tweaks and tips with this being my first full custom build. Thanks and kudos to everyone offering their advice and tips and suggestions. It was all appreciated!! Thank you!!