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Post by mefunkymxw on Sept 16, 2013 6:37:42 GMT -8
Hey All,
Prior .223 BHW AR owner, and just completed a 6.8 build with a BHW specII chamber. This is my first post on this forum. I am a prior 6.8 shooter on a Rob Arms XCR platform (more then likely a spec I chamber since i bought it over 3 years ago) and do handload (primarily 115 grain nosler HPBTs over 27.0 grain H322).
I just got my new barrel from blackhole and it is 18" with rifle length gas tube, and yesterday, after assembly I had difficulty extracting on every single one of the 40 rounds I put down range. normally on an AR I would attribute this to a canted gas block, but I validated the alignment twice. After assembly I did check the headspace with my go and no-go gauges.... the bolt went into battery with the go gauge and would not go into battery with the no-go gauge. I was using S&B 110 grain partitions (SRP brass) at the range. I did notice that bolt would come out of battery, but did not have enough energy to extract the round (the extractor stayed in place on the rim). When using the charging handle I did have to use some energy to extract the cases (more then I would have thought).
I did measure the shot cases which came in at 1.693" or so, which is above the max allowable of 1.686", so that could attribute to the FTEs but I am not sure. I wanted to get some of your all's input as to what it might be. my build is as follows:
Upper:
18" BHW 6.8 SPEC II with .75" profile past gas shoulder
midwest industries billet upper (non-mil spec)
BCM micro gas block (.75")
BCM rifle length gas tube
midwest industries rifle length FF handguard
LWRC NiB 6.8 bolt face
SMI NiB bolt carrier
barret 6.8 muzzle brake
Lower:
Noveske chainsaw lower
spikes tactical enhanced trigger group (NiB coated hammer, trigger and disconnector)
magpul UBR stock (carbine length)
spikes S2-T2 heavy buffer
bravo company carbine buffer spring
magpul MIAD grip
the major things i want to troubleshoot are:
1. the buffer, i might switch it out for a standard weight buffer for testing
2. ammo, i have hornady, remington and handloads that i know probably have better QA then S&B
3. recheck the gas block alignment, i do have a compressor so i can test air flow in the barrel
4. unrelated, but i did notice that i was having some trouble feeding some HP nosler rounds and i think this was due to the mismatched feed ramp widths between the BHW barrel and the MI billet upper, the barrel has thinner feed ramps and as such some of he hp rounds were getting stuck on the ledge created by the wider upper feed ramps (can anyone recommend a good mil spec upper in case i want to replace my MI billet)....
any ideas would be appreciated. |
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Post by GLSHOOTER on Sept 16, 2013 8:23:02 GMT -8
Were those handloads? This is usally a symptom of not bumping the shoulers back. They need about 0.003 to 0.004 clearance to run 100%.
Greg
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Post by mefunkymxw on Sept 16, 2013 8:31:51 GMT -8
Were those handloads? This is usally a symptom of not bumping the shoulers back. They need about 0.003 to 0.004 clearance to run 100%. Greg The only rounds i have actually shot were the Sellier and Bellot 110 grain varminter partitions, which are factory rounds (ableit a factory in serbia), not handloads. to answer your question i do use RCBS full length sizing dies for my 6.8 handloads and i do properly size and trim, i am going to test some hornady, remington and handloads as soon as i can get back to the range. |
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Post by GLSHOOTER on Sept 16, 2013 9:05:54 GMT -8
Were those handloads? This is usally a symptom of not bumping the shoulers back. They need about 0.003 to 0.004 clearance to run 100%. Greg The only rounds i have actually shot were the Sellier and Bellot 110 grain varminter partitions, which are factory rounds (ableit a factory in serbia), not handloads. to answer your question i do use RCBS full length sizing dies for my 6.8 handloads and i do properly size and trim, i am going to test some hornady, remington and handloads as soon as i can get back to the range. Did you use a case comparator to compare fired and unfired S&B? Did you load and extract an unfired round? Was it difficult? Nothing in my post was implying that you don't know how to size a case. I would try some other factory or your own brew. BHW chambers are cut to minimum. That is one reason they shoot well. Greg |
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Post by mefunkymxw on Sept 16, 2013 9:18:05 GMT -8
Only used a normal caliper to measure a fired case.... i did manually chamber and extract a few S&B rounds without firing and they all seemed pretty easy except one of them. all that could change after fire forming though.
i suspect i will get a better result with the hornady and handloads, but not sure if it will completely solve the issue.
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Post by GLSHOOTER on Sept 16, 2013 9:49:40 GMT -8
Only used a normal caliper to measure a fired case.... i did manually chamber and extract a few S&B rounds without firing and they all seemed pretty easy except one of them. all that could change after fire forming though. i suspect i will get a better result with the hornady and handloads, but not sure if it will completely solve the issue. Testing will tell you more. A caliper will not cut it for headspacing your cases. Case length has nothing to do with this issue. A comparator like Hornady makes is needed. Also a Sinclair tool is helpful for bullet seating depth when you go for the gusto. G |
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Post by mefunkymxw on Sept 16, 2013 10:22:31 GMT -8
one would think that factory ammo would have already taken that into account.... but maybe not.
like i said, i plan to do more testing with hornady, remington and handloads since the S&B proved to be unsucessful in the action cycling department.
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Post by GLSHOOTER on Sept 16, 2013 10:39:37 GMT -8
one would think that factory ammo would have already taken that into account.... but maybe not. like i said, i plan to do more testing with hornady, remington and handloads since the S&B proved to be unsucessful in the action cycling department. Have you tried hand cycling some of the other brands? Greg |
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Post by mefunkymxw on Sept 16, 2013 10:44:22 GMT -8
yea, hornady seemed to work very easily, i was getting some nicks toward the tip of the bullet and just below the shoulder of the case more the likely due to the feedramps, but other than that they seemed to cycle fine.
my nosler handloads were getting hung up literally where the barrel feedramps met the feedramps machined into the upper, they are of slightly different widths and the create a type of flange that will shear off some copper on the tips of those projectiles.... i think a mil spec upper will resolve this. i havent tried my remington FMJs yet, but i will take a mix with me next time i hit the range.
only brought S&B yesterday cuz i just got back from out of town and wanted to get to the range before it closed.
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Post by mefunkymxw on Sept 16, 2013 11:06:09 GMT -8
i looked up the MI billet upper on brownells, they say it is cut for standard M4 feedramps, is there a reason this wouldnt mate up perfectly with a BHW barrel feed ramps?
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Post by GLSHOOTER on Sept 16, 2013 11:43:38 GMT -8
i looked up the MI billet upper on brownells, they say it is cut for standard M4 feedramps, is there a reason this wouldnt mate up perfectly with a BHW barrel feed ramps? Not a clue. The regular BHW feed ramps are cut by BAT the preeminent machinists in the US. They buy them by the gross and the ones I see are extremely consistent. On this one I will blame your upper supplier. The mismatch issue is common. Tolerance stking may be occuring. The only cure is swapping parts or careful use of a file and Dremel tool that I am aware of. On the nicks and hang ups sometimes the mags need to be tweaked to bring the bullet up. The 6.8Forums speaks to this frequently. Cartridge oal can also be a cause in tandem with the presentation angle. Greg |
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Post by mefunkymxw on Sept 16, 2013 12:02:37 GMT -8
looking at some pics of other MI billet uppers on AR15 and other sites, it looks like a few other have the same issue. i have a dremel, but i think that would be way too much gringing and polishing on the barrel feedramps. i dont want to get into the business of material removal.... thats why i was asking what brand/model uppers other folks were using with their BHW 6.8 barrels to see if there are others with a nicer fit.
I use c-products 6.8 mags which work great in the XCR, but might need some tweaking in the AR
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Post by GLSHOOTER on Sept 16, 2013 12:13:13 GMT -8
looking at some pics of other MI billet uppers on AR15 and other sites, it looks like a few other have the same issue. i have a dremel, but i think that would be way too much gringing and polishing on the barrel feedramps. i dont want to get into the business of material removal.... thats why i was asking what brand/model uppers other folks were using with their BHW 6.8 barrels to see if there are others with a nicer fit. I use c-products 6.8 mags which work great in the XCR, but might need some tweaking in the AR I am using Aero almost exclusively. I bought some from other places and the forgings were obviously identical. Greg |
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Post by Deleted on Sept 16, 2013 15:00:53 GMT -8
I have read through this thread several times. S & B ammo is not worth the box it came packaged in. It seems to be very inconsistent. Try shooting a group with it. I would be amazed if it even groups under 6". Also pull a couple of bullets and measure the case length. You will find the same lengths you mentioned in your previous posts. While you are measuring check to see how close your ammo is compared to your go gauge. It should be very close to the same measurement You said you checked the head space on this barrel. The only way the dimensions of a chamber can change is with pressure. Again look at what ammunition you are shooting. Try some of the Hornady ammunition, it should run fine.
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Post by mefunkymxw on Sept 16, 2013 16:23:39 GMT -8
ok, just got back from the range.... the news is better, but still not good tried 3 types of ammo | AMMO Brand | Result | | Hornady 110 gr V-Max | shot about 50 rounds, some ejected (50% ish), none with enough force to feed the next round | | Handloads (115 gr nosler, 27 gr H322, LRP) | all ejected, i hand fed each of the 10 rounds i shot as the noslers were getting stuck on feed ramps | | Remington 115 gr FMJ | shot 40 rounds, almost all ejected, none with enough force to feed the next round or lock the bolt open |
at this point i am beginning to think that it might be undergassed due to gas block misalignment, i am going to take off the the FF tube, gas block and remove the gas tube completely, reset the gas block and try to see exactly how the alignment is. i had to pin the gas tube first when assembling because the barrel nut i have is so deep so as to accommodate the FF tube. i will let you know the result. i did forget to bring my standard weight buffer, so i am going to put it in my range bag now so i dont forget for next time. |
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