[nplace]

I was able to shoot my ARP mk 68 recon for the first time recently. I sighted in my BUIS and scope plus did a barrel break in cleaning procedure. I fired 45 rounds, all without any functional problems. One thing I did notice from the first shot to the last shot was the brass being ejected at the 1:30 to 2:00 position. The brass looked ok from what I could tell. From what I have learned this could be a problem of being over gassed.
My first thought would be to try a SSS buffer spring and see if that may help. If that won't help maybe a heavier buffer. Any other suggestions? The lower I have is a Spikes Tactical build with what I was told a standard buffer and buffer spring.

 

[paulosantos]

A heavier buffer and/or the SS Springs will help.

 

[joshuades]

I'd say start with the SSS spring.

 

[Lastrites]

What ammo where you shooting, factory or handloads?

 

[Test_User]

What was the load? If hand lolad what was the recipe and was it crimped?

What was the temperature out when you were shooting? It has been in the 90s and up in many parts of the US. With air temps int hat range ammo and guns can easily get much hotter than that. It is why ARs work in a range.

Also how old is the buffer spring? Even without use normal buffer springs lose tension over time. I was surprised when I took a lower with a carbine setup that I had not used since I put it together a year earlier. I pulled the buffer spring and it was a 1.5" shorter than a new one. i have a ruler marked out on my worktable with marker set for new carbine and rifle buffers and the SSS full length and custom cut ones. All of this allows me to quickly check spring wear. I have marks that when hit I know its time to repalce the spring.

Be careful that you do not tune to far down. If you set your gun so it would eject at say 4:00-4:30 in the middle of the summer its possible in the middle of the winter it may short stroke in the first couple of rounds. Usually what people think is 1:30 is actually 2:00 or 2:30. When you have 1:30 it looks almost like the cases are being thrown straight down range. I had actually had my estimates on angles skewed as well until I was able to stand next to a person and have them shoot the gun. I found out I was off by 1 hour if it was either forward of 90 degrees (3 oclock) or rearward. FOr whatr ever reason it was very easy for me to see 3:00 or within that general angle but once it got a bit outside that what I thought was off. Exmaple was I thought I had cases ejecting at clsoe to 5:00 . the only issue was when I realized that woudl require my case to actually travel right thru the case deflector on the side of the reciever. That was when I went to get someone to shoot so I could watch.

If the loads you are using right now are the loads you plan to be your main rounds I woudl start first with only the SSS spring. See where those are ejecting. It woudl help to have some with you and lay out on the ground where the angles are so you can see for sure the ejection angle. I am fairly certain that will put you are 3:00 which for summer is ideal and will give you enough room for cold winter temps. If not add the H2 buffer. I eprsonally think the SSS spring should be one of the first buys for all with ARs. You can always cut a coil or two off if need but still get all the other benefits like not having to ever change out the spring for the life of the gun. If you plan to use lighter bullets and the ones youa re shoooting right now are 110-115 then you should set your gun up for those as more importnat than forward ejection is having a gun that SSS and doesn't cycle. Always set your gun up for your lightest load you will normally use.

 

[nplace]

What ammo where you shooting, factory or handloads?

I was shooting SSA 110gr Pro Hunters. Air temp. was close to 90 degrees. This is the first time the rifle was shot so the buffer spring is new.
I don't plan on shooting bullets much lighter than 100 gr out of this rifle.

 

[Test_User]

Given that I suggest you go to the SSS spring and see where that puts you. If it gets you to 3 oclock in the summer heat that will be perfect for the loads you plan to shoot year round.

 

[HTR]

If those loads are really ejecting at 1:30, the gun is over gassed. There is a very simple fix. The buffer spring and carrier weights are band-aids on a major laceration, so to speak, and will not likely move the timing enough to throw empties back to 3:30-4.

Get an adjustable gas block. If there is too large a gas port, you can't put material back, but it is ridiculously simply to tune a gas block to perfectly time the gun for whatever internals you happen to like whether they be high mass or low mass.

I especially like the ones made here. they may not be listed, as they just started full-time production, but Chino 556 is a staffer there and posts on this site now. You might shoot him an IM:

http://www.jetsuppressors.com/suppressors.html

***Also, keep in mind that Tim W and Constructor are among the most knowledgeable AR guys I have ever come across, so take their advice with equal or greater weight than mine. They are well known to try to perfectly gas every upper they build.

 

[paulosantos]

Get an adjustable gas block. If there is too large a gas port, you can't put material back, but it is ridiculously simply to tune a gas block to perfectly time the gun for whatever internals you happen to like whether they be high mass or low mass.

Actually, you can. ADCO has done that with my LMT. :a01::a01: They plugged it up and re-drilled it for me and it is very smooth.

 

[HTR]

Actually, you can. ADCO has done that with my LMT. :a01::a01: They plugged it up and re-drilled it for me and it is very smooth.

OK, now that's cool! I think I remember you telling us that story now....

I stand corrected :a21:

 

[Test_User]

If you actually set your angles with bore being 12 Oclock 1:30 from the shooting position would have the cases going almost straight down range. Its best to check ejection anglel by where the cases pile by setting down something that will not allow them to role or bounce or have someone mark the spot. As shooters it seems that anything other than 3 oclock is very hard to accurately guesstimate. IT sure was for me. I have had people mark where cases I swore were ejecting at 1:30 while I was shooting and came to find out they were more like 2:00-2:15. Something esle I have found is differences in reciever BCG lube etc all will effect the angle as well even when using the same barrel. I used the same barrel and switched it between 3 differnet uppers and had angle vary as much as what amounts to 45 mins. I see it especially when test firing uppers to go out to customers one may go 3:00 and others 2:30 and some 3:30 etc.. Now these are new so slight differnce that will "wear in" are effecting some of this but the point being there are tolerances for all these parts and how they match up can and do have an effect. Also with CL barrels it seems as they break in more and more and the rounds go faster and faster because of this the angle actually retards some even accuracy gets better. Jason Peterson has been giving me reports which I have been tracking as he has been putting a good amount of rounds thru his Xtremes; a few thousand so far.

 

[jasonpeterson]

I'm running SSS springs and carbine buffers in mine. I've been shooting max loads with the 110 pro hunters. I've been shooting groups prone out of the back of my truck. With bipod and rear sand bags. (shooting out of the truck keeps the ticks and chiggers away from me):a21:
I switched over to a heavy buffer a couple days ago. I put a hard gun case opened up running parallel with the truck bed so that it extends to the end of the tailgate. It works perfect for catching my brass. My loads were barely missing the corner of the case and some were ending up on the ground. So I switched to the heavy buffer and it is now ejecting perfectly. Lately I've been shooting Rem 100 grain psp bullets with 28.5 grains of 10x and they are still ejecting perfectly. Even with the lighter load. I will make a post with some pictures.