MAX 10-15/11-15 Caliber Mod Thread

[techspy]

With my 10-15 on the way, I wanted to start a thread to see who has been successful with different caliber conversions. I plan on a 7.62/39 and 22 conversions. Please post what barrel and gas settings you found to work with your conversions and any other mods you had to add. Also, it would be good to know what optics people are using on a dual caliber setup.

 

[Gaujo]

Search is your friend

 

[strobro32]

I used a 8" 300 BO with a standard pistol length gas block. No problems with supper or subs. I use the same Holosun CARD for both. The Lage Extra power spring is needed for a 8" 300 BLK barrel and standard gas block for reliability. ROF increases but the extra power spring should be used.

I have not started on the 22 kit as I'm sure it will require relocating a fixed firing pin on the bottom of the bolt face. The plan is to solder a piece of .02 music wire there. Then I will need to add a sear catch to the bolt.

 

[techspy]

I used a 8" 300 BO with a standard pistol length gas block. No problems with supper or subs. I use the same Holosun CARD for both.

I have not started on the 22 kit as I'm sure it will require relocating a fixed firing pin on the bottom of the bolt face. The plan is to solder a piece of .02 music wire there. Then I will need to add a sear catch to the bolt.

Awesome info thanks. Did you use an adjustable gas block?

 

[strobro32]

Not for Blackout.

 

[techspy]

Here is my 7.62x39 setup. Bearcreek 18" barrel, adjustable gas block. Re-used the firing pin with the 7.62 bolt. Picked up a new handguard and low profile barrel nut so I can simply swap both uppers. Need to find a 50 or 100 rnd compatible drum mag. Test firing tomorrow.

 

[strobro32]

That looks like fun. I look forward to seeing a video of a concrete wall collapsing.

 

[techspy]

Well not having much luck with 7.62x39 in my Max 10-15. Now I will admit that I am not an ar bolt/fire control expert but am pretty sure I know how it operates and how the max 10-15 bolt operates.

I have had 2 out of battery discharges. Here is the sequence of events.

- Ran the stock setup with no issues. Using brass 5.56. It ran great with 30 rnd AR mags and even perfectly with a 100 rnd drum mag.
- Next range test was with the 7.62x39 barrel, bolt and cam pin. Used the original firing pin. Shot about 6 single shots with no issue while adjusting the gas block and ended up on almost full gas setting. (1 rnd at a time in the mag). Loaded about 5 rnds and did a couple full auto bursts with no issues. Loaded the same mag with 10 rnds and on the 2nd burst had an out of battery discharge. The bullet exited the barrel and mag got blown out. Bent the cam pin and bolt enough that I had a heck of a time getting them out. The upper got a bit gouged by the cam pin. Also, the firing pin got pushed back through the firing pin set screw.
- Ordered a new bolt/cam pin and firing pin. Modified the firing pin to match the original. Reinstalled everything and function checked cycling and dry firing many times. Looked good.
- Went to range today to test. Shot several single and full auto using the 5.56 upper. Ran perfect. Installed 7.62 barrel etc. Shot several single shots with brass 7.62 and adjusted gas. Ran fine. Loaded some wolf steel case (not lacquer coated). A couple single shot were fine but found I needed to adjust the gas. Ended up back at almost full gas setting. Shot approx 6 more single shots and then loaded 2 rnds an shot full auto about 3 times. Ran fine. Filled up the mag and about the 4th burst, another out of battery discharge. Another bent cam pin, bolt and broken firing pin. Blew out the mag. Upper more gouged from the cam pin.

Ended up brazing the gouges and it looks/operates fine again with the stock 5.56 setup (dry firing/cycling only so far)

So, seeing how the bolt operates, I cant see how the firing pin can strike the primer without it being in battery. I will be ordering another bolt/cam pin/firing pin and if I get the courage to try again, will record the ejection port in slow-mo in case it happens again.

Any idea what the heck is going on?

 

[m11stuff@hotmail.com]

Anytime you change the barrel for a new or different one, make sure you gage it with GO/NO GO gages for that caliber. I have encountered a couple of barrels from different manufacturers that are short chambered and will not close on a GO gage.

How the round is detonating out of battery is beyond me. The firing pin does not advance to hit the primer until after the bolt has rotated and locked. Any chance there was a squib round or barrel obstruction?

 

[m11stuff@hotmail.com]

Regarding having to open the gas block all of the way to get it to cycle, you probably need to open up the gas port hole in your barrel. Different barrels come with different gas port sizes. Go with the largest one you can get.

 

[techspy]

Thanks. I thought the same thing about the firing pin. Cant figure out how it could hit the primer without being locked. No squib round or stuck cartridge. I am wondering if there is a condition that would allow the bolt to rotate to the locked position before getting into battery? Like maybe coming into contact with the mag? But it shouldnt be allowed to rotate/push back until the cam pin clears. Both rounds seemed to discharge in the same position (the rim inline with the barrel locking pieces. I did a bunch of hand cycling etc before going to the range and all looked good. I will dig deeper.

 

[mak91]

There is a slot milled in the inside of the charging handle half of the receiver, if that is milled in the correct spot there should be no way the cam pin should allow the bolt to rotate until the round has been chambered. Over charged or wrong powder used and the bolt unlocked under a huge amount of pressure? What length gas system is it ? Anything on the bolt face ?

 

[techspy]

No, nothing on the bolt face. Tried 2 different ones. It is a mid length gas system. I agree that it should not allow the firing pin to hit the primer until locked. However, I guess this depends on the firing pin length. The one that came with the max 10-15 was a small amount shorter than the stock ones I have. Although the initial out of battery occurred with the original firing pin so that isn't the issue. Am I right to assume that the firing pin should not protrude until the last little bit of rotation in the locked position? I mean that is a small amount of difference in rotation from partially locked to fully locked. Anyway, I just ordered a different 16" barrel, bolt, cam pin and firing pin. Oh, and a set of go/no-go blanks. I will do a lot of testing before the next range test. Thanks

 

[Galil#1]

Great to have trial blazing folks always pushing innovations, awesome Techspy! Wish you safe sucess Sir!
... Now makes me wonder what happened to all the other folks who wanted to bring other calibers/rifle calibers to the MAC world? Status check? (We are all very fortunate to have Richard and Sam of course!) Thank you All!

 

[mak91]

techspy you are correct, the firing pin should not protrude until the very last of the bolt/bolt carrier movement, in fact the bolt is most likely fully rotated during this last bit of bolt carrier movement where the firing pin protrudes. I was doing load development a few years ago for a 7.62x25 mini whisper custom barrel I had for a ar15. I grabbed accurate #5 when I meant to use accurate #9. The faster burning powder quickly exceeded normal pressures and when the bolt unlocked it pretty much did what you have stated. The mag base, follower and spring where blown out the bottom of the mag, the bolt carrier had jammed about an inch and a half back with a bent cam pin and what was left of the ruptured case looked just like the picture of yours. There was no question in my case that the bolt was fully closed and locked in the barrel extension in my case since this was a closed bolt ar15.

 

[techspy]

techspy you are correct, the firing pin should not protrude until the very last of the bolt/bolt carrier movement, in fact the bolt is most likely fully rotated during this last bit of bolt carrier movement where the firing pin protrudes. I was doing load development a few years ago for a 7.62x25 mini whisper custom barrel I had for a ar15. I grabbed accurate #5 when I meant to use accurate #9. The faster burning powder quickly exceeded normal pressures and when the bolt unlocked it pretty much did what you have stated. The mag base, follower and spring where blown out the bottom of the mag, the bolt carrier had jammed about an inch and a half back with a bent cam pin and what was left of the ruptured case looked just like the picture of yours. There was no question in my case that the bolt was fully closed and locked in the barrel extension in my case since this was a closed bolt ar15.

Wow, very interesting! Now I am really confused! Now I wonder if it is happening out of battery. Perhaps I have some out of spec wolf ammo? I suppose I can only tell if I get slow-mo video of it happening. Am I correct to assume in a "normal" full auto AR operation that the disconnector adds just a bit of delay to ensure the bolt is rotated and locked? I don't mine testing but the damage to the upper where the cam pin jams into it is concerning. I don't want to damage it beyond use. Unless Lage can sell me a new half upper and possibly bolt carrier just in case? I asked about a replacement spring some time ago but never got a response. I imagine they are slammed right now. If this was off the shelf AR stuff I could care less and would just buy more! I wonder if removing the firing pin and doing a lot of manual cycling with ammo will show something. I mean, if I never get a rotated bolt before meeting the barrel extension, that would eliminate and out of battery discharge..maybe.

Is the Lage provided firing pin standard? (other than the removal of the rear part). Would shortening the tip of the pin so it only protrudes at the last bit of bolt lock be a way forward? Any simple way to add a delay otherwise?

 

[rybread]

Great to have trial blazing folks always pushing innovations, awesome Techspy! Wish you safe sucess Sir!
... Now makes me wonder what happened to all the other folks who wanted to bring other calibers/rifle calibers to the MAC world? Status check? (We are all very fortunate to have Richard and Sam of course!) Thank you All!

For the Mac 11/9:
.22
.380
9mm
DMAC dual Mac upper (two receivers firing 9mm)
S&W 40
7.62x
556/223
(12 gauge upper build in progress)

This is what I have. Any missing?

 

[chili17]

The most likely thing that comes to mind is bad ammo or possibly the barrel extension is coming unscrewed. I would think that would be pretty obvious though.

 

[SecondAmend]

For the Mac 11/9:
.22
.380
9mm
DMAC dual Mac upper (two receivers firing 9mm)
S&W 40
7.62x
556/223
(12 gauge upper build in progress)

This is what I have. Any missing?

Why, .45 ACP is missing. Thanks for asking.

 

[Donut77donut]

Why, .45 ACP is missing. Thanks for asking.

Because he said m11-9