Obermeyer Chamber Opinion on AR10

P

Phil3

Sergeant
Full Member
Minuteman
Dec 13, 2008
402
17
San Ramon, CA
#1
I was talking to Krieger today and told them I wanted a 308 barrel for an AR10 used for 100 - 600 yards max with the purpose of maximum accuracy. They recommended 168 and 175 grain bullets, 1:12 twist, and the Obermeyer chamber (vs SAMI). Just what is the Obermeyer chamber? I see it mentioned, but not much on what makes it unique (or better). Anyone shed some light on it.

- Phil
 
#2
Re: Obermeyer Chamber Opinion on AR10

I'm guessing the Obermeyer chamber has a different leade or throat angle to the rifling than the SAAMI 308 WIN chamber.

If you're able to seat your bullets to a COAL of 2.820 (which works well for a standard 308 WIN chamber) then I would suspect the Obermeyer chamber would give you less jump to the lands, generally increasing accuracy given everything else is on point.

I just ordered a 20" M110 barrel Fluted under hand guards only 1/11 (they did recommend 1/12) and threaded 5/8x24 for a FH from Krieger and told Scott that I basically wanted to run the 175 SMK exclusively. ETA given was January next year, might come sooner.

I think they said the fluting is backed up 12-16 weeks.
 
#4
Re: Obermeyer Chamber Opinion on AR10

If I'm not mistaken the Obermeyer throat is 5* degrees included,or 2.30* per side, compared to factory or the normal 3* degree include or 1.30* per side!
 
#5
Re: Obermeyer Chamber Opinion on AR10

yes, it is actually an old M14 NM type chamber, and thats why Krieger recommends it, its an old holdover from the M14 Service Rifle days. its great for Mag length 168-190 grain Sierra bullets, thats about it. It does have the 2'30 leade, most now a days are 1'30. It has a very shallow throat, and doesn't give you much room to play with the huge variety of bullets available today. Also, the 1-12 twist isn't very ideal for what the AR10 can handle. Go 1-10 0r 1-11. The one Good thing about the Obermyer chamber is the slightly generous demensions, again M14 left overness, is a great fit to Lapua brass, as its base is just a hair larger in diameter than our brass. The AMU AR10's use a 1-10 Krieger, propietary chamber and they single load 185 Berger LRBT in Lapua brass over 45.0 Varget. Very effective combo, and with a deeper throat and 1-10 twist, its also a very adaptable combo. I had no options on My AR10 barrel for chamber, but its a 1-11 with Obermeyer, and after I discovered all the shortcommings, I ordered a throat reamer from Mr. Kiff at PTG and I can now keep the good part of the chamber, and recut the leade and depth to be more useful and adaptable. If you plan on shooting M852 or M118lr, its a fine chamber, but very limiting. Are you the same guy from National Match US that asked about this? if you are, then I guess you already heard all this from me there. Check the latest on that thread for another recomendation.
wink.gif
 
#6
Re: Obermeyer Chamber Opinion on AR10

First, I am not the guy National Match US. Just someone building an AR10 that is after best possibly accuracy using mag loaded rounds at 100 - 300 yards and maybe ocassionally 600 yards. When you say the Obermeyer chamber "doesn't give you much room to play with", do you mean there is little room to play with bullet seating depth and different bullets that might hit the lands, or...? Since I am using mag loaded only, I am not sure any restrictions in the chamber are of any concern. Why 1:10 or 1:11? Why would not 1:12 work well for the AR10. Muzzle velocity should be decent, since the barrel will be longish at 22".

Your comments indicate a rather loose chamber, which concerns me since I want a chamber that will deliver best accuracy. Krieger was told what I wanted and they recommended the Obermeyer. I expect to be shooting Sierra MKs in 168 or 175, and maybe some Bergers or other quality brands as well. I presume limiting is defined as being restricted on what bullets, but again, does that enter the picture with mag loaded rounds?

For what I want (mag loaded accuracy), what would you recommend?

- Phil
 
#7
Re: Obermeyer Chamber Opinion on AR10

Obermeyer Chamber on my Krieger M110 too. I put together some dummy rounds with 155 Laps, 168SMKs, 175SMks, and 190SMKs; all to mag-length (can't recall the measurement offhand). It wasn't liking the 155 Laps.
 
#10
Re: Obermeyer Chamber Opinion on AR10

I have a bolt action SPR with a krieger 1-12 twist throated for the 175-190, it is a tack driver with 45 gr varget and 175 SMK's.
Unfortunately that load in my AR10 blows all the primers out, 43 gr varget is max.
 
#11
Re: Obermeyer Chamber Opinion on AR10

Phil,

Sorry this question came up over there recently. The obermeyer chamber is a little generous, but it won't hurt your accuracy. I'm talking about .001-2 more at the opening. Yes, I mean limited because of the shallow throat and steep leade angle. I mean it is MADE for 168, 175 old 180, and 190 sierra's. And they do well in it. But other bullets have issues. It just doesen't seem to like them. The 1-11 or 10 twist is a better option for 175 and up than a 1-12. 1-11.25 is ideal for the 175 sierra, The big Green money machine US Army tested and spent alot of time and money figuring this out. 1-11 is probably the most versatile, or a 1-10. the 1-12 is great for a 168, ok for a 175, iffy on a 190.

Not to be down on Krieger, but they are so used to M14 barrels and the old standard/accepted right thing to do answer they just spill it over to the AR10 barrels. Anyone that calls will get the obermeyer chamber 1-12 twist answer. Great set up for an M14 in NRA High power from 200-600 yds and 168 Sierra's. Lomg range no so much. I got to shoot the best NM M14's left in the world last year out to 1000, and the AR10's the AMU had destroyed the M14's reign as the LR service rifle. Before last year, the M14 was still king of the line, but the 1-10 Krieger non obermeyer chamber and 185 bergers ( not mag length btw, all single load) were ferocious competitors and were giving most bolt gunners a run. I scored a kid shooting one clean back to 1000, in the last 5 shots of the last 15 yd string, the wind got him and he dropped his first points, 3 9's. Thats a 447 on a 450 point palma course with an AR10 and Irons.

It will work, but its not the best choich for an AR10.
 
#12
Re: Obermeyer Chamber Opinion on AR10

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Phil3</div><div class="ubbcode-body">Yes sir, it is. I have built one AR15 prior to this AR10.

- Phil </div></div>

If accuracy with a particular bullet is your goal then you're on the right track. If you want a more portable rifle that can eat everything not so much.

What kind of accuracy are you hoping for? Are you using it for comps?
 
#14
Re: Obermeyer Chamber Opinion on AR10

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BCP</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2ndPanzer</div><div class="ubbcode-body">Thats a 447 on a 450 point palma course with an AR10 and Irons.
</div></div>

That's nuts. </div></div>

It's eye opening. The went on this year to set new records in mid and long range with them.
 
#15
Re: Obermeyer Chamber Opinion on AR10

It is apparent then that the best chamber is dependent on bullet needs, which are then driven by what is expected out of the rifle at what ranges. I don't know what bullet is best for my intended range. Due to severe shooting range limitations in the San Francisco bay area, I will realistically be shooting mostly at 100 yards, somewhat less often at 200 yards, quite rarely at 300 (range is a 4 hour round trip), and probably never at 600, even though at same shooting range as 300 yards (tight restrictions on use for 600+).

What bullet (and chamber) will work best for those ranges? If the Obermeyer is MADE for the 168s and 175s (mag loaded) and those bullets work well at the aforementioned ranges, then the Obermeyer does appear to be the best choice. But maybe a 155 is better for the these short to mid ranges, or something else other than 168 or 175s. ??? If using 168s and 175s, does the 1:12 twist rate make sense?

- Phil
 
#16
Re: Obermeyer Chamber Opinion on AR10

If thats all you will ever shoot, then yes it will work, 1-12 will be great for a 168 Sierra. I would recommend the Lapua case as it will fit that chamber the best. LC would fit good as well. A mag fed 168 sierra is basically the magic combo for the M14 in the exact same configuration your looking to run. The 168 Amax should be good to go in there as well. Expect FGMM and the new M1A match to shoot well in it too.

Try these combos if you reload as they are the old Gold standards for that combo. LC cases, Sierra 168's

42.0 H4895, 43.0 Varget, 4064, RE15. somewhere in there, tweak to suit your rifle.

Also, loading for an AR10 is not the same as for a Garand or M1a/M14. No real port pressure issues or limits. Work up like you would a bolt gun, just look for the signs. I have found that MY AR10 NM with the Kreiger barrel will take some pretty stout loads, and I am lucky as it will shoot the exact same loads as my bolt gun very well. Its definately easy to load for compared to the others.
 
#17
Re: Obermeyer Chamber Opinion on AR10

It sounds to me like you're a plinker more than anything else.

My suggestion is:

Stainless, medium weight (2.75 or less pounds so probably a 16-18" which is enough length for what you want to do)
1:10 or 1:11 twist
Mid or rifle gas (rifle preferably)
A chamber that isn't super picky

A cheapie like a rainier select would be a drop in solution that fits all those categories and with a 90 day satisfaction guarantee I'd take a chance on it. If it's your first 308 AR any non-defective barrel will be more accurate then you are.

If you really want the krieger (pacnor, lilja, hart, rock, douglas, brux, broughton lots of good barrel makers out there too you know) I would say finished with obermeyer reamer.
 
#18
Re: Obermeyer Chamber Opinion on AR10

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">If thats all you will ever shoot,</div></div>

Yes, unfortunately, just short range of 100 - 200 yards is all I have unless I make the 4 hour round trip. Infrequent!

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">then yes it will work, 1-12 will be great for a 168 Sierra. I would recommend the Lapua case as it will fit that chamber the best. LC would fit good as well. A mag fed 168 sierra is basically the magic combo for the M14 in the exact same configuration your looking to run. The 168 Amax should be good to go in there as well. Expect FGMM and the new M1A match to shoot well in it too.

Try these combos if you reload as they are the old Gold standards for that combo. LC cases, Sierra 168's

42.0 H4895, 43.0 Varget, 4064, RE15. somewhere in there, tweak to suit your rifle. </div></div>

Have some Varget and RE15 sitting on the shelf right now!

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Also, loading for an AR10 is not the same as for a Garand or M1a/M14. No real port pressure issues or limits. Work up like you would a bolt gun, just look for the signs. I have found that MY AR10 NM with the Kreiger barrel will take some pretty stout loads, and I am lucky as it will shoot the exact same loads as my bolt gun very well. Its definately easy to load for compared to the others.</div></div>

New to reloading, but will start low.

- Phil
 
#19
Re: Obermeyer Chamber Opinion on AR10

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">It sounds to me like you're a plinker more than anything else.</div></div>

Well, yes, if shooting at paper targets at short range, developing loads, and building the rifle to maximum accuracy potential is a plinker.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">My suggestion is:

Stainless, medium weight (2.75 or less pounds so probably a 16-18" which is enough length for what you want to do)
1:10 or 1:11 twist
Mid or rifle gas (rifle preferably)
A chamber that isn't super picky

A cheapie like a rainier select would be a drop in solution that fits all those categories and with a 90 day satisfaction guarantee I'd take a chance on it. If it's your first 308 AR any non-defective barrel will be more accurate then you are.

If you really want the krieger (pacnor, lilja, hart, rock, douglas, brux, broughton lots of good barrel makers out there too you know) I would say finished with obermeyer reamer. </div></div>

I know a short barrel is enough for the distances I am shooting, but am opting for a 22". No other reason other than appearance. It is heavy, but for intended use, weight is of no consequence. Will use the rifle length gas system, but will use 1:11 or 1:12 as recommended here for shooting 168s.

I am building this AR and already have the bolt, upper receiver, charging handle, etc. I have never been able to find any AR10 upper (or AR15)that is what I want. So I build my own. The other barrel makers are certainly good and will explore this again, since Krieger is 16 - 18 weeks out for a barrel. As I recall, some will not sell ready to run AR10 barrels, forcing me to send somewhere else for finishing. Rather avoid that, unless someone can steer me to someone who can quickly finish the barrel (extension, timed, threaded for brake, etc.). Still, will explore the makers you listed, as I would like to have a barrel sooner than later.

- Phil
 
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