Thread: AR15 Issue?

Hi

Mate has just got a AR15, and had suppressor put on it

It seems to be inconstant with grouping even at 50m - good ammo too

Not tried without the suppressor though

This is what the cases look like - very dirty - had maybe 30-35 rounds fired

Overgassing??
Whats the signs of that

As soon as you put a suppressor on an AR you need to either increase the BCG weight or put an adjustable block on it, they will over gas straight away, the amount depends on the suppressor & its design.

That's normal, even without a suppressor after 30 rounds or.
Suppressor certainly increases back pressure, so best to have an adjustable gas block to bleed some gas off.
Good suppressors like ODL have a design which reduces back gas.

The dirty cases are typical of suppressed AR15s. It comes from back pressure from the suppressor. Not a lot you can do really.

Try it without the suppressor and you'll see the difference.

As to "It seems to be inconsistent", without giving specifics of the group size, type of rest and scope and how good the shooter is, there's not much to go on.

Inconsistent as in 1 inch to 10 inch groups? 6 inches to 9 inches? 2 inches to 4 inches?

Thanks

I'll ask what they actually did to the rifle

Groups - 4 inch plus at 50m - some really close then opens up

Dirty Brass is normal with a can.

Check:

Groups without suppressor
Barrel nut is tight (can you move the barrel back and forth with your hand whilst holding the handguard)
Scope tracks correctly (when you adjust 1" does it move 1")
Scope mounts are tight
Barrel twist is fast enough for projectile weight (1:12 up to 60 grains, 1:9 up to 69 grains, 1:8 up to 75 grains, 1:7 up to 90 grains)
Gas Key (the thing on top of the bolt) is staked and not moving
Gas tube / Gas block is all tight

Let us know after that...

Originally Posted by faregame

Thanks

I'll ask what they actually did to the rifle

Groups - 4 inch plus at 50m - some really close then opens up

4" at 50 metres...

Please give the shooter a rifle that groups well & get him to fire it.

If no improvement throw him in the nearest creek, if there is an improvement throw the offending AR in the nearest creek...

If inconclusive play it safe & throw both of them in the creek....

Disclaimer these are figurative terms only

adjustable gasblock ,make sure can is on tight if no change throw in creek far cheaper than playing around with these things as the are a fast track to financial ruin.

Even with an adjustable block your brass will get filthy it's just the way it is

Like all the good things in life brass from a suppressed AR is dirty filthy stuff. It's the next round in the mag that gets it the worse and if you don't fire that round it will be corroded by the next time you pull it out of the ammo safe.

So it's best to fire a mag until empty rather than topping it back up. I also brought a stainless steel pin tumbler to get those dirty dirty cases bling bling shiny again.

Originally Posted by faregame

Thanks

I'll ask what they actually did to the rifle

Groups - 4 inch plus at 50m - some really close then opens up

is that with no sights and off free hand ?

Sadly - nope - with scope (which is not in doubt)

Will see once tried without suppressor

If the scope is trusted, what about the mount?


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If you run out of ideas you're welcome to send it down to me and I'll take a look at it for you?

Dunno if you'll trust some random dude on the internet though....send me a PM?