MK18 Vs. Geissele Super Duty 10.5

**okie** · 10-24-21, 10:57

Originally Posted by bear13

The A5h0 is what I went to. I have not yet tried a a5H3. That is on its way.

Also I have ran multiple types of ammo. The main problem it has now is that it does not lock back. With Norma tac 55grn it will eject a round and smash the round feeding in the ramp. It’s undergassed, I realize this. But I was hoping to try the right combination of buffer/spring. It did oddly run perfect with wwb 55grn.

It has had a low power spring and regular spring with all H buffers in a standard tube. I went to the a5 upon recommendation and that’s what I run in my full length rifles anyways.

Believe me. I have done due diligence with ammo and all the standard buffer spring/buffer combos. But at the end of the day I want it to work with all ammos. I know with a can this would be ideal, but I have no suppressor yet.

I pulled that barrel and threw in a rosco 10.5. I have another setup for a new upper to use the 10.3 with.

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Sounds like the easiest fix for this problem is just go ahead and build a Form 1 can. I've got a recipe for one that's a very proven performer, that's completely turnkey. With approval times at about three weeks, you could have it done in about six for a total of about 600 dollars, including SOT fees and tax stamp.

**bear13** · 10-24-21, 11:22

Originally Posted by okie

Sounds like the easiest fix for this problem is just go ahead and build a Form 1 can. I've got a recipe for one that's a very proven performer, that's completely turnkey. With approval times at about three weeks, you could have it done in about six for a total of about 600 dollars, including SOT fees and tax stamp.

Funny you mention that. I have been looking at jk armament setups for this exact reason. Also why I setup a upper to run all ammo.

The centurion barrel was ridiculously accurate and I have been hesitant to enlarge the gas port on her.

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**Wake27** · 10-24-21, 11:54

Originally Posted by okie

Sounds like the easiest fix for this problem is just go ahead and build a Form 1 can. I've got a recipe for one that's a very proven performer, that's completely turnkey. With approval times at about three weeks, you could have it done in about six for a total of about 600 dollars, including SOT fees and tax stamp.

And yet you're complaining about gas blowback from a .070 gas port while mine is great with a KAC CQB? Think maybe that's more of a suppressor problem than gas port problem?

Originally Posted by bear13

Funny you mention that. I have been looking at jk armament setups for this exact reason. Also why I setup a upper to run all ammo.

The centurion barrel was ridiculously accurate and I have been hesitant to enlarge the gas port on her.

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Have you emailed them? Their CS is reportedly outstanding and unless it was billed as a suppressed use barrel, I bet they'd want to know and may be able to help. If my MK18 is actually .070 and I'm running an LMT EBCG with no issues unsuppressed, it surprises me that the .01 difference in gas port is the issue.

**17K** · 10-24-21, 12:03

Originally Posted by bear13

The A5h0 is what I went to. I have not yet tried a a5H3. That is on its way.

Also I have ran multiple types of ammo. The main problem it has now is that it does not lock back. With Norma tac 55grn it will eject a round and smash the round feeding in the ramp. It’s undergassed, I realize this. But I was hoping to try the right combination of buffer/spring. It did oddly run perfect with wwb 55grn.

It has had a low power spring and regular spring with all H buffers in a standard tube. I went to the a5 upon recommendation and that’s what I run in my full length rifles anyways.

Believe me. I have done due diligence with ammo and all the standard buffer spring/buffer combos. But at the end of the day I want it to work with all ammos. I know with a can this would be ideal, but I have no suppressor yet.

I pulled that barrel and threw in a rosco 10.5. I have another setup for a new upper to use the 10.3 with.

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The A5 is not going to fix your issue. Failure to lock back is something you will see with the A5 more than a normal buffer.

I think you have a problem in your lower.

IMO, the A5 may be something that you can use to get a certain recoil feel, but if you’re looking for reliability I’d stay with the standard carbine setup.

**okie** · 10-24-21, 12:48

Originally Posted by bear13

Funny you mention that. I have been looking at jk armament setups for this exact reason. Also why I setup a upper to run all ammo.

The centurion barrel was ridiculously accurate and I have been hesitant to enlarge the gas port on her.

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I wouldn't recommend that style system for centerfire, especially centerfire rifle. It's ideal for rimfire, and maybe even okay for pistol calibers, but just not a good system for a centerfire SBR especially.

**bear13** · 10-24-21, 12:53

Originally Posted by 17K

The A5 is not going to fix your issue. Failure to lock back is something you will see with the A5 more than a normal buffer.

I think you have a problem in your lower.

IMO, the A5 may be something that you can use to get a certain recoil feel, but if you’re looking for reliability I’d stay with the standard carbine setup.

It is not the lower. Multiple lowers used. Same result. And yes I know now the a5 did not fix it. As I said I have tried multiple different things to make it work. I like the a5 and I like having a standard setup across the board. A friend has the a5 on his DD 10.3 and it works perfect. Also feels very smooth. He has a H3 in his though. And it works across the board suppressed/not.

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**bear13** · 10-24-21, 12:56

Originally Posted by Wake27

And yet you're complaining about gas blowback from a .070 gas port while mine is great with a KAC CQB? Think maybe that's more of a suppressor problem than gas port problem?

Have you emailed them? Their CS is reportedly outstanding and unless it was billed as a suppressed use barrel, I bet they'd want to know and may be able to help. If my MK18 is actually .070 and I'm running an LMT EBCG with no issues unsuppressed, it surprises me that the .01 difference in gas port is the issue.

No, I have not. I am going to before I do anything drastic. I have always had great luck with them. But I thought I would try some stuff out on my own first so I can give them as much info as possible. I am not out anything. Besides the a5h3 that I ordered I already had most this shit on hand.

I actually should just get ahold of them. I have exhausted basically everything I can think of short of trying to clip a buffer spring.

Thanks for all the suggestions. But believe me I have tried everything to make her run.

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**Diz** · 10-24-21, 14:40

Well yeah but I've stopped using steel-cased ammo, because it's so underpowered, among other things. So I don't worry about "tuning" (or de-tuning really) my rifles to work with it. Your previous comments about DD were spot-on concerning this issue. They, and many others, opened up gas ports so bubba could run steel cased crap in their lower-tiered rifles. I CAN run steel-cased ammo, but I choose not to. I stocked up on M193 right before covid hit.

I am running Ballistic Advantage "Crane Spec" bbls, which are 10.3" and .070" gas ports. I usually run suppressed, either AAC or SF. Also run SF OBC, which comes with it's own spring and buffer. Ammo is either M193, M855, or Mk 262. I've had zero issues with this set up. Supressed/unsuppressed, hot/cold, whatever. I think the SF bolt carrier system has a lot to do with this.