I've had a grendel for over a year now and I have tried two different barrels numerous different powders and lead varieties. I cannot get anything to consistently group better then one inch at 100 yards. I have built ARs that are consistently 1/2 inch. I don't believe it is me but I am stumped. the one thing I have not tried is Alexander arms brass. I finally got some and we'll give it a try. Tell me what are your reloading secrets and what powders and bullets are you guys using to achieve what everyone else talks about with the grendel.
the 6.5 Grendel gets one last try
- Thread starter precision308
- Start date
What barrel are you shooting, and is your receiver face trued?
I dropped an 18" .223 Wylde JP Super Match barrel into an upper I had, expecting sub-MOA easily, especially with my 69gr SMK loads. It's over 1.2-1.5 MOA.
Pulled the barrel, and placed my lapping tool in the upper. All kinds of space on over 75% of the face, so it needs to be lapped. I'm actually getting great accuracy for how out of true the receiver face is.
My 16" Grendel with an economy AA/ER Shaw stainless barrel consistently has shot .79" to 1.2" at 100yds for me. At 200yds, it's 1.7" to 2.18". I haven't trued that receiver face either, but will do here shortly. It isn't a match-grade barrel by any means, but I paid $269 for the barrel/bolt combo from Midway back in 2009, and I'll take the accuracy I'm getting for that deal.
One of the most consistently accurate bullets for people has been the 100gr and 120gr Nosler Ballistic Tips, but you need to clean your bore after shooting them before shooting anything else. My best accuracy has come from 123gr Scenar and 123gr A-MAX.
Need way more details about your rig, assembly, bullets, powders, optics, mount, etc.
I dropped an 18" .223 Wylde JP Super Match barrel into an upper I had, expecting sub-MOA easily, especially with my 69gr SMK loads. It's over 1.2-1.5 MOA.
Pulled the barrel, and placed my lapping tool in the upper. All kinds of space on over 75% of the face, so it needs to be lapped. I'm actually getting great accuracy for how out of true the receiver face is.
My 16" Grendel with an economy AA/ER Shaw stainless barrel consistently has shot .79" to 1.2" at 100yds for me. At 200yds, it's 1.7" to 2.18". I haven't trued that receiver face either, but will do here shortly. It isn't a match-grade barrel by any means, but I paid $269 for the barrel/bolt combo from Midway back in 2009, and I'll take the accuracy I'm getting for that deal.
One of the most consistently accurate bullets for people has been the 100gr and 120gr Nosler Ballistic Tips, but you need to clean your bore after shooting them before shooting anything else. My best accuracy has come from 123gr Scenar and 123gr A-MAX.
Need way more details about your rig, assembly, bullets, powders, optics, mount, etc.
I have a Rainier Arms upper lower with a Yankee Hill quad rail free flow. JP single stage 3 pound trigger.I swapped several scopes everything from SWFA nightforce. the first barrel was a ERShaw 24" and the second was a 24 inch black hole weaponry barrel. both barrels show best results with 8208 XBR topped off with 1:07 grain Sierra MatchKing are 123 grain amax. both barrels had about equal accuracy. I even try adjustable gas blocks but no luck
Is the Rainier Arms upper a forged or billet? Pull the pipes and check the receiver face for being true.
One thing about mounting 24" or heavy barrels in a standard AR15 upper receiver:
About 50% of the rifles will benefit from having the barrel extension bedded into the upper, after the upper is trued. Do you have tools for doing precision work on an AR15?
Also, what shooting method are you using? Are you letting the rifle free-recoil, or are you applying steady rearward pressure with a rear bag?
One thing about mounting 24" or heavy barrels in a standard AR15 upper receiver:
About 50% of the rifles will benefit from having the barrel extension bedded into the upper, after the upper is trued. Do you have tools for doing precision work on an AR15?
Also, what shooting method are you using? Are you letting the rifle free-recoil, or are you applying steady rearward pressure with a rear bag?
It is a forged receiver not billet though. I've used different uppers for the two barrels. I don't have a way of checking or making the receiver true. I've always heard that before about billet uppers but have built heavy long barrels before in 204 and 223 with good accuracy.
The Grendel really pushes the capabilities of a standard forged upper when using a heavy barrel, as it has more bolt thrust than any of the .222 Remington-based cases, which it (the AR15) was designed for initially. It really should have been beefed up slightly for the 5.56 NATO, but the dimensions were so close, and time was ticking to get a new rifle into soldiers' hands with the aging fleet of Garands and M1 Carbines.
Anyway, for the 24" or heavier barrel profiles with the Grendel, you really want to true the upper and bed the extension with blue loc-tite. Brownell's sells an inexpensive tool that will true your receiver face using 180 grit lapping compound. You mount the stripped upper in an insulated vice, chuck the lapping tool in a drill, and carefully lap the receiver face.
Both of the barrels you listed aren't particularly high-end barrels, so you might just have luck of the litter too. Did you put them together yourself?
Anyway, for the 24" or heavier barrel profiles with the Grendel, you really want to true the upper and bed the extension with blue loc-tite. Brownell's sells an inexpensive tool that will true your receiver face using 180 grit lapping compound. You mount the stripped upper in an insulated vice, chuck the lapping tool in a drill, and carefully lap the receiver face.
Both of the barrels you listed aren't particularly high-end barrels, so you might just have luck of the litter too. Did you put them together yourself?
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My alexander arms barrel shoots bugholes with my handloads. Lapua brass made a huge difference over hornady and my hornady brass only lasted 3 reloads anyway. I had a blackhole barrel that fed fine but it wasnt a tight shooter. Best I could get was about 1.2moa. Id have 4 grouped perfectly but id always get a flyer.
Good luck,
Merritt
Good luck,
Merritt
I know that tree these barrels are both far from high quality I just always heard good about black hole weaponry. You bring up an interesting point with the lapping tool. So don't Brownells for $35 I may have to get one. what powder is everybody using
I had a similar issue with my two Grendel builds that I assembled myself.
Bitched and whined and tried everything I could think of but neither would shoot better than about 1.5" groups at 100 yards.
A friend, who is not a gunsmith but knows a lot about AR's and accurate bolt rifles offered to take a look and see if he could make it do better.
He messed with it and did his magic. He mentioned that there were several issues he took care of but did not go into specifics.
Now the 20" shoots just over 1/2 moa (holes real close but not usually cloverleafing at 100 yards) and still holds nice tight groups at 1000 yards and the 24" upper shoots under 1 moa reliably.
My load is Lapua brass and 123 A-Max bullets at 2625 fps from the 20" barrel but I don't remember the powder specifics.
My guess is that somebody who knows how to build a real accurate AR could make it shot quite a bit better.
Bitched and whined and tried everything I could think of but neither would shoot better than about 1.5" groups at 100 yards.
A friend, who is not a gunsmith but knows a lot about AR's and accurate bolt rifles offered to take a look and see if he could make it do better.
He messed with it and did his magic. He mentioned that there were several issues he took care of but did not go into specifics.
Now the 20" shoots just over 1/2 moa (holes real close but not usually cloverleafing at 100 yards) and still holds nice tight groups at 1000 yards and the 24" upper shoots under 1 moa reliably.
My load is Lapua brass and 123 A-Max bullets at 2625 fps from the 20" barrel but I don't remember the powder specifics.
My guess is that somebody who knows how to build a real accurate AR could make it shot quite a bit better.
Well I just ordered the receiver trueing tool from brownells. I'm planning on trueing the receiver and loctiting the barrel in. I've just loaded some AA brass that I've never used before. I must say it appears better quality than the hornandy. It closely resembles the lapua. Wonder who makes it for them. Ifbu could let me know what your friend changed to get yours dialed in.
Here's an upper I had a JP Super Match Stainless .223 Wylde barrel in. A buddy gave it to me, along with the radiators, adj gas block, Ben Cooley brake, and gas tube, otherwise he was going to throw it away. I just threw it in an upper and could only get 1.2-1.5 MOA with my 69gr SMK hand loads.
I pulled the barrel the other night, and checked it with the lapping tool, and there was all kinds of space in over 66% of the receiver face. The tool was only touching in a very small area. Here it is after getting about 50% of the face lapped:
I'm going to use it for one of my 6.5 Grendel Lilja barrels. The rest of the gun I already Cerakoted FDE, did color-fill on the lower, and dropped in a tuned RRA 2-stage that my buddy gave me as well. He was literally going to throw the stuff out. I will also lap the bolt to the extension, blend and polish the feed ramps, and radius the ejector face, along with several other little tricks.
I pulled the barrel the other night, and checked it with the lapping tool, and there was all kinds of space in over 66% of the receiver face. The tool was only touching in a very small area. Here it is after getting about 50% of the face lapped:
I'm going to use it for one of my 6.5 Grendel Lilja barrels. The rest of the gun I already Cerakoted FDE, did color-fill on the lower, and dropped in a tuned RRA 2-stage that my buddy gave me as well. He was literally going to throw the stuff out. I will also lap the bolt to the extension, blend and polish the feed ramps, and radius the ejector face, along with several other little tricks.
Nope, the M14 was adopted in 1957 and about the only M1 Carbines in combat use associated with the US were in the SE Asia Games and almost all in the hands of ARVN troops.
Other than giveaways to friendly troops and stolen/captured/otherwise acquired specimens in the hands of irregular troops on the other side of that little escapade, I never heard of M1 Garands being in use in combat zones when the AR was being finalized for USAF and Army use.
With that out of the way, may I ask what the groups LOOK like?
Unpredictable "two-holing" groups with 2+ shots in one bughole and 2+ shots in another one a half-inch or more away is a sign of uneven bolt lug/barrel extension engagement.
Round groups are a sign of just trouble. The benchresters taught us decades ago that sometimes, a barrel gets made that just won't shoot better than 1.5 or 1.0 MOA.
Bill Alexander at AA knows the Grendel inside and out. There is a REASON why they Loc-Tite the barrels in, especially on the 24-inch barrels. LRRPF52 has all the NON-US military history stuff spot-on in his post. The Grendel does push the platform.
Me, I believe that the AR receiver just isn't up to hosting 24-inch med-heavy or whatever they call it these days barrels.
If you're very lucky, the AA brass will improve things enough to satisfy you. But IMO, anything that's reliably and consistently never more than 1.1 inch performance at 100 yards is in the acceptable category, especially with a 24-inch bull barrel.
Unpredictable "two-holing" groups with 2+ shots in one bughole and 2+ shots in another one a half-inch or more away is a sign of uneven bolt lug/barrel extension engagement.
Round groups are a sign of just trouble. The benchresters taught us decades ago that sometimes, a barrel gets made that just won't shoot better than 1.5 or 1.0 MOA.
Bill Alexander at AA knows the Grendel inside and out. There is a REASON why they Loc-Tite the barrels in, especially on the 24-inch barrels. LRRPF52 has all the NON-US military history stuff spot-on in his post. The Grendel does push the platform.
Me, I believe that the AR receiver just isn't up to hosting 24-inch med-heavy or whatever they call it these days barrels.
If you're very lucky, the AA brass will improve things enough to satisfy you. But IMO, anything that's reliably and consistently never more than 1.1 inch performance at 100 yards is in the acceptable category, especially with a 24-inch bull barrel.
My 18" LW barreled Grendel would shoot a solid 1 MOA with anything I put in it (factory, reloads, ect). All reloads had been in the Hornady case. One day I decided to get nuts on a set of reloads (weigh everything & sort). I shot just a bit sub-moa with the 20 loads that I made, but it was such a pain that I have not made any more. Then I decided to try lapua brass - that was the fix I needed, the gun will group into a 3/4 minute and under now with minimal reloading effort. YMMV, good luck
M14 Initial Production Failures & the AR15
The M14 was adopted, but not magically mass-produced to fill the hands of US soldiers, Marines, and Airmen all over the world. Even cutting out Vietnam, which didn't see large deployments of conventional forces until 1965, the Pentagon had a real challenge of replacing WWII-era rifles and carbines for the military, and M14 initial production was not meeting the demand from the combat divisions in the US and Europe.
On top of that, the Air Force didn't want the M14, because it was too heavy for their local security needs. They wanted something like the M1/M2 carbine, which they had been using since the days of Army Air Corps, but the Army was still in charge of procurement for repair & replacement parts in the late 1950's through early 1960's, and they stopped requisitioning spares for the Carbines after Korea. It (M1/M2 Carbine)was basically a dead system in terms of logistics.
That is one of the main factors that drove the Air Force to start looking at the AR15, and this really pushed the Pentagon to start having to consider it as a viable service rifle, even though Army Ordnance had just declared it totally unsuitable as a military weapon within weeks prior to the USAF request to put the AR15 through service rifle trials. There is a very interesting history behind the adoption of the AR15, and you can read all about it in The Black Rifle, Volume I. It's better than a soap opera.
Hindsight isn't 20/20
The biggest tendency we often make when looking at the adoption of the M14 and AR15 is to associate that time period with Vietnam, when there were more significant factors in the need for a new service rifle, and Vietnam still didn't have many US forces there when all these decisions were being made. The fleet demand was driven by well over a dozen combat divisions, Marine Divisions, and Littoral & Maritime Navy units, many of whom would not have anything to do with SEA over the duration of the war. Think about all the Stateside Divisions, as well as European Mechanized, Airborne, and Infantry Divisions who were keeping the presence in Germany, for example.
The Infantry Board also saw the AR15 as a temporary stop-gap for the SPIW, so they reluctantly agreed to allow adoption of the AR15 along with the late-on-delivery M14 production line, with both systems planned to be replaced by 1968 with an uber over-under grenade launcher/saboted flechette rifle.
By the time conventional Army units started arriving in Vietnam, they were mostly equipped with Colt Model 601 and 602 AR15's (type classified as M16's), and the Marines transitioned over to the Black Rifle quickly. The AR15 had been going through several years of evaluation, modification, field-testing, and standardization by the time the first grunt Marines of the 9th Marine Expeditionary Brigade hit the beach in 1965. They did have M14's and M14A1's, but the M14's service was short-lived as a standard service rifle in that conflict.
Why this history is relevant to the discussion
This rush to get a viable service rifle into Soldiers, Marines, Airmen, and Sailors' hands also by-passed what probably should have been a re-engineering of the bolt, barrel extension, receivers, and magazine to accommodate the .222 Remington Special aka .223 Remington, with a bit longer COL, a slightly larger and stronger bolt, larger diameter barrel extension, and slightly larger upper receiver OD and ID for the extension. The reason why we have such limited COL with the .223 Remington and all these other cartridges we have tried to stuff into the mouse gun is because of the COL of the .222 Remington and the little tangent ogive varmint bullets it was specifically designed to shoot.
The AR15 really needed to be able to shoot long for caliber ogive pills to retain energy for the .30 cal nazis' attempts to make it fail the 500yd steel helmet perforation tests, which they thought surely no mouse gun could pass. There was a really insightful Army Ordnance civilian engineer who actually recommended they go with lower pressures, a 62gr to 68gr .224 bullet with a higher BC, in order to blast through the 500yd steel helmet, but McNamara's whiz kids dressed him down, not knowing anything about ballistics, but thinking they were geniuses because they could crank numbers with their computers in a statistical modeling reminiscent of McNamara's statistician background from Army Air Corps service, and then the Ford Motor Company, before he was selected as SecDef by Kennedy, Inc.
Fast-forward to the present: The 6.5 Grendel gets around the COL limitations by using a much shorter, fatter case based off the Russian 7.62x39/.220 Russian/6mm PPC. Because of the limited bolt geometry mass, the SAAMI MAOP is kept back down to where the .222 Remington's is, at ~50,000psi, and good metallurgy on the bolts accounts for bolt life. It also uses more shallow guide grooves and different angles on the feed lips, along with a Grendel-specific follower and M4 feed ramps.
There are plenty of guns that have been somehow doing well with this combo, but I tend to agree with you. The AR15 upper was always designed with lightweight being top priority, but the original barrels weren't as lightweight as we might think.
The fore ends of the original prototype .222 Remington Armalite AR15's took pencil to a whole new level, but the barrel underneath the Bakelite handguard was actually about .800" in diameter, with fluting to reduce weight.
If I was personally building a 24" gun, I would select an VLTOR MUR or thicker upper, but I am really enjoying the Grendel in the shorter lengths, which is why I ordered 16" and 18" barrels from Lilja for the next two guns.
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Something else that may help. When you are bedding the barrel extension into the receiver, the same principle applies to bedding the gas block to the area around the gas port using blue loc-tite. Clean the area well, don't get the loc-tite into either gas port, but do get the area around the gas tube bedded with blue loc-tite. This helps remove any play or rattle in the gas block.
Insure that your muzzle device is concentric to the bore, and maybe even blue loc-tite the muzzle device to insure it doesn't move or "rattle".
Insure that your muzzle device is concentric to the bore, and maybe even blue loc-tite the muzzle device to insure it doesn't move or "rattle".
I lapped my receiver today and found that half of the receiver was nit making contact. Lapping didn't take long at all. This sounds good in theory lets hope that this helps.
Thanks everyone
Thanks everyone
Mage makes a badass stout upper as well
http://megaarms.com/ar-15/upper-receivers/billet-uppers/sbu-billet-upper-wo-ch-slot/
http://megaarms.com/ar-15/upper-receivers/billet-uppers/sbu-billet-upper-wo-ch-slot/
The lapping should help, it has on several I have built. Almost all of the standard mil-spec receivers I have dealt with needed it.
If you try that BHW barrel again and it still doesn't shoot, I'd give them a call as those pipes tend to shoot pretty good.
If you try that BHW barrel again and it still doesn't shoot, I'd give them a call as those pipes tend to shoot pretty good.
Mega is the only receivers I will use on my personal guns, most don't even need to be lapped. The fit, finish and consistency with their products is amazing.
Truing the receiver and bedding the barrel are nearly mythological modifications that do absolutely nothing to improve accuracy. There isn't a shred of vetted data that shows either of these woodshed modifications are effective. They only exist because there isn't much that can be done to an amalgamation of AR-15 parts assembled into a rifle that doesn't shoot well to begin with.
I had a couple of broken bolt lugs with my 6.5 Grendels. After the second one, I contacted a well known builder of Ar15 type precision rifles. He said that about 80% of the standard GI type uppers he works on need to be trued. The most likely reason my bolt lugs kept breaking was the uppers. When the barrel nut is tightened onto the barrel extension (in an untrued upper), the out of square upper puts uneven pressure on the barrel extension, thereby causing uneven pressure on the bolt lugs. This uneven pressure on lugs is what causes lugs to break.
I sent my uppers in to be trued, and I haven't had a bolt lug break since then. Maybe I'm lucky, or maybe it is true. I don't think that the small number of rifles I own is enough to come to an all inclusive finding, but in my case, it appears that the rifle builder was correct.
I sent my uppers in to be trued, and I haven't had a bolt lug break since then. Maybe I'm lucky, or maybe it is true. I don't think that the small number of rifles I own is enough to come to an all inclusive finding, but in my case, it appears that the rifle builder was correct.
I believe that a rifle will have more accuracy potential with a trued receiver. Itbis the same concept as truing a bolt gun receiver. I just hope this help mu accuracy enough to make me happy.
*scratches head* Do you have firsthand experience in this area? A buddy of mine who builds AR's has mentioned this and he is a pretty knowledgeable guy.
I do have a fair amount of experience in the "area". The legend behind these modifications is purely anecdotal. Correlation doesn't equal causation.
Will your buddy extend me a written, money back guarantee that my rifle will shoot better if I let him perform the truing and bedding mods on it?
If concentricity is truly at the heart of building accurate rifles and ammunition, then why would lapping an AR upper be voodoo?
One manufacturer has related to me that fleet-testing showed that heavy barrels do benefit from having the barrel extensions bedded, as well as the gas blocks.
When the fleet was not bedded, 50% of the guns shot fine, and 50% did not. After bedding the barrels and gas blocks of the poorer performers, they no longer performed poorly.
I think the concentricity and true receiver face speaks for itself, otherwise, why do accurate rifle builders blueprint an action? Is it voodoo, or physics?
In the AR15, just the balancing of the bolt lugs alone is worth truing the receiver face in my book. Any hi-power guys care to chime in? What does Zediker say about it?
I know two other local AR15 smiths who do their own barrel work. They are all about using top-end extensions, barrels, and they make sure they start with a true receiver face, that the extension threads are true, the barrel threads for the extension are true, they lap the bolt lugs, and other little tricks.
Both of them don't know each other. Both of them make AR15's and AR10's that shoot bug holes. I watched one at Lee Kay Range print sub-1/2 MOA groups with the first rounds through a newly-built Grendel after he explained all these tricks he was using.
A very reputable smith back in North Carolina I know was the first one I heard from about bedding barrel extensions into the upper, and the guns shot so well, his customers would frequently call him up from the range tickled & giggling. His clientele is such that he doesn't really advertise, and has been doing work for people on Bragg who have very high expectations for their personal guns. He was making flat-top uppers before most people had even seen such a thing back in the late 1980's and early 1990's.
So I can list one major AR15 manufacturer and 3 gunsmiths who specialize in AR15 accuracy work right off the top of my head who practice the true face and barrel bedding voodoo, to include large enough fleet samples to be of statistical significance. I also see that the higher-end billet receiver sets have true faces to them, so I'm going to continue to drink voodoo cool aid I guess.
When the fleet was not bedded, 50% of the guns shot fine, and 50% did not. After bedding the barrels and gas blocks of the poorer performers, they no longer performed poorly.
I think the concentricity and true receiver face speaks for itself, otherwise, why do accurate rifle builders blueprint an action? Is it voodoo, or physics?
In the AR15, just the balancing of the bolt lugs alone is worth truing the receiver face in my book. Any hi-power guys care to chime in? What does Zediker say about it?
I know two other local AR15 smiths who do their own barrel work. They are all about using top-end extensions, barrels, and they make sure they start with a true receiver face, that the extension threads are true, the barrel threads for the extension are true, they lap the bolt lugs, and other little tricks.
Both of them don't know each other. Both of them make AR15's and AR10's that shoot bug holes. I watched one at Lee Kay Range print sub-1/2 MOA groups with the first rounds through a newly-built Grendel after he explained all these tricks he was using.
A very reputable smith back in North Carolina I know was the first one I heard from about bedding barrel extensions into the upper, and the guns shot so well, his customers would frequently call him up from the range tickled & giggling. His clientele is such that he doesn't really advertise, and has been doing work for people on Bragg who have very high expectations for their personal guns. He was making flat-top uppers before most people had even seen such a thing back in the late 1980's and early 1990's.
So I can list one major AR15 manufacturer and 3 gunsmiths who specialize in AR15 accuracy work right off the top of my head who practice the true face and barrel bedding voodoo, to include large enough fleet samples to be of statistical significance. I also see that the higher-end billet receiver sets have true faces to them, so I'm going to continue to drink voodoo cool aid I guess.
This is a quote from Grump above-
"Unpredictable "two-holing" groups with 2+ shots in one bughole and 2+ shots in another one a half-inch or more away is a sign of uneven bolt lug/barrel extension engagement."
Ok so now think about what an AR barrel is doing if the receiver isn't square. Yep, pointing to the right and only the lugs on the left side touch. What would be the result if only half of the lugs touch? It's very easy to check. Coat the back of the lugs of the bolt with dykem, shoot the rifle 5 times and inspect the back of the lugs. I was rethreading the receivers concentric and lapping lugs on bolt guns in the early 80s for the same reason. When I started building ARs in the early 90s I didn't even consider not doing it. With the way a barrel is clamped in a AR receiver the chance of it not being square is greater than a bolt gun that is threaded in the receiver except when using Mega and Vltor receiver where the extension is a tight fit to the receiver.
What process do you all use to remove a locktite barrel. My guess would be to use a tourch to break up the locktite but it still seems like it would be difficult to remove the barrel
There is no reason for a torch, as a hot air gun will work fine for getting the blue loc-tite back to a liquid state.
A torch can heat-treat your parts into being brittle.
Now we have another AR15 upper manufacturer who says that truing the receiver face is important with the AR15. I know what I will continue to do on all my uppers.
There's no reason to think that having the bolt raceway, carrier, bolt, action face, barrel extension and bore in perfect alignment would possibly lead to better accuracy????? Sorry, I can't buy that bridge. If that were the case, why waste your money on seating dies for reloads? Just push those bullets in with a pair of pliers if concentricity doesn't matter. Those stupid benchrest guys waste so much money truing actions or purchasing precision actions like Surgeon and Stiller, when they'd be fine with an old Mossberg. I guess GAP has quite a racket going, because part of what people are paying for is an action that is square to the receiver face, the barrel and the bolt.
For those suckers that have money to needlessly flush down the toilet, Rainier offers match upper (billet, if I remember right) that they guarantee true within .0003 or less. It's not a bolt gun, but if you want an AR that's a shooter, when everything is true, it'll surprise you.
For those suckers that have money to needlessly flush down the toilet, Rainier offers match upper (billet, if I remember right) that they guarantee true within .0003 or less. It's not a bolt gun, but if you want an AR that's a shooter, when everything is true, it'll surprise you.
You haven't "listed" anyone. I'll ask the question again, who can I send a rifle to to have the receiver faced and barrel bedded who will guarantee an improvement in accuracy?
0.0003, that's three ten thousandths of an inch, is aerospace accuracy and must include a temperature call out for the spec. The tooling and machining environment would be critical to achieving that tolerance. Rainiers claim of 0.0003 or better is dubious. If the claim included a qualification, there might be room for more discussion.
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Most manufacturers have gone to ISO-9000 series laser check quality control stations. Remember all those LAR M4 uppers that were on sale as blems? That was because a few thousandths was taken off the top of the spent brass deflector. Didn't matter, failed ISO so couldn't be sent to B2B customers. They were sold for $48 per, and were actually really nice uppers.
I know GAP has given me an accuracy guarantee with the two AR10's they built me, and both guns have exceeded that guarantee not only at 100yds, but at distance. My barrel extensions and gas blocks were bedded.
I've worked in TQM, and took courses on it in my business program, and will say that dimensional uniformity for production has changed leaps and bounds from the days when my grandpa was a machinist for Douglas Aerospace, working on Titanium tubing components on the A-4 Skyhawk. They didn't have laser inspection stations in climatically-controlled rooms with granite counters, and did a lot of measuring with calipers, feeler gauges, and micrometers.
Do you still stand by the statement that truing of AR15 receivers is inconsequential to accuracy, or are we spiraling off into a discussion about the dimensional control capacity of the industry? Either truing the receiver is valid as a foundation for an accurate rifle, or it is not.
I don't care who trues and beds and who doesn't, but I proved it to myself that it can help tremendously. On the advice of Mike at Dtech I tore down an upper (that I had built) that was underperforming and sent it in to him for truing. Upon reassembling the accuracy improvement was significant; the face of that upper had been off quite a bit. I've since had a receiver lapping tool made and use it on any builds I put together. I'm a believer.
I don't believe either modification has any effect on accuracy. Facing the extension on the upper receiver only squares it to the bore of the upper receiver and assumes that every other machining operation on the upper receiver and barrel assembly was done correctly.
1. Is the upper receiver bore parallel to the flat top?
2. Are the barrel breach threads parallel to bore?
3. Are the barrel extension threads and O.D. parallel to bore?
4. Is the front and back surface of the flange on the barrel extension perpendicular to bore?
Like I said in my OP, the facing operation and bedding process is the only mod that can be done to try and improve accuracy and bang someone for a few bucks in the process.
In a way you are correct it's all the builder can do. The rest is on the barrel maker and extension maker.
When making a barrel extension, everything except the lug cuts is done in one operation/setup from the front. The outside is turned and flange cut. The hole for the threads is drilled then the smaller hole through the extension lug area. The boring bar relieves the material behind the thread area and faces the lugs then the threads are cut single point. The piece is parted from the stock. So yes unless something is really screwed up all parts of the extension are concentric and square upon the part.
If the receiver is square and the extension is square with the receiver bore the lugs bare evenly.
As for the barrel it is setup and most is done in one op too. Barrel is indicated front and rear, threads cut and faced at the shoulder and chamber is reamed and chamfered.
It should be square and concentric with the bore.
There's a difference between those that build precision ARs and those that slap combat rifles together. That's why the mil spec says 3" is good enough.
Does anyone have the part number for the Brownell lapping tool?
I have two 6.5 Grendel uppers. One that I put together myself and one put together by GAP. They both shoot 1/2 moa at 100 yards. The one I put together was a barrel I bought from Midway. I have heard from other people that have bought barrels and then put them together and found that they would not shoot.
I have two 6.5 Grendel uppers. One that I put together myself and one put together by GAP. They both shoot 1/2 moa at 100 yards. The one I put together was a barrel I bought from Midway. I have heard from other people that have bought barrels and then put them together and found that they would not shoot.
