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Post by lapriester on Mar 1, 2016 10:56:09 GMT -8
Given the number of posts stating that the go-to powder for this caliber seemed to be 8208 XBR, before completing my build I ran out and bought 4#of it. In 6.8 SPC I have always had exceptional luck with AA2200 so I figured I might try a few loads with that as well. My bullet choices were Sierra 85gr and 100gr Varminters because I was intending to building loads for a planned ground squirrel trip. I did not utilize a chrono for this testing since I was more concerned with best accuracy and pressure indications with the several loads I created.
Rifle: 22" BHW barrel 1-9 twist, target crown Palmetto slick side upper receiver AIM NiB carrier/AIM 6.8 bolt UTG Pro FDE 15" HG Midwest Low Pro long 3 setscrew gas block Palmetto lower, RRA Varmint 2 stage 3# trigger, Magpul fixed rifle FDE stock. Bushnell AR Optic 4.5X18 scope
Loads and results: SSA reformed 6.8 brass. Both the 85 and 100gr were seated to 2.21" OAL based on posts by others. CCI 450 primers
85gr Varminters:
29gr XBR - 3/4 - 1 MOA with some FTF cycles and failed full ejections. Bolt lock back inconsistent. 30gr XBR - 1/2 -3/4 MOA. Reliable function and bolt lock back. 31gr XBR - Consistent 1/2 MOA. Stronger ejection, reliable function, minor ejector swipes, no primer flattening.
With all XBR loads recoil seemed, for lack of a better term, "flat", mild. Brass necks were sooted pretty badly after extraction. Overall, not really impressed by this powder. I'm guessing it produced slower velocities than the AA2200 loads.
29gr AA2200 - Less than 1/4 MOA consistently. Full function, mild ejector swipes, no flattened primers. 29.6gr AA2200 - Almost single hole accuracy. Full function, moderate ejector swipes, mild primer flattening. 30gr AA2200 - Only fired 3 rounds due to heavy, cutting ejector swipes and flowed primers. I would consider this to be a > MAX load to be avoided.
Note; Loads with AA2200 had noticeable increased recoil and muzzle blast. Brass was cleaner after extraction.
100gr Varminters:
I didn`t have much luck with these bullets because, based on 85gr results I loaded them a bit hot. 30gr XBR - 3/4 MOA, moderate to heavy ejector swipes, primer flattening 31gr XBR - 1 MOA, heavy/cutting ejector swipes, primers fully flattened.
29.5gr AA2200 - XX. Only fired 2, pressure signs were unacceptable.
Next trip I'll start lower with the 100gr bullets. I suspect with both powders I'll find a sweet spot for them. For me, I personally like the performance of the AA2200 powder over the XBR. Perhaps XBR will perform better with heavier bullets. A work in progress, LOL.
BTW, I moved out to 200 yards with the 29gr and 29.6gr AA2200 loads behind the 85gr bullets and it still shot a sub 1" 5 shot groups with both with very little elevation change.
This an amazing caliber bound to be one of my favorites. I'm certain the squirrels will soon be facing a serious apocalypse out to 300 and greater yards.
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Post by GLSHOOTER on Mar 1, 2016 18:01:19 GMT -8
Look over the AA and Hodgdon data on the Grendel to get a good idea on load levels. You are right in the ball park. You can run slightly more pressure. You are probably a bit over gassed based on the swipes at those levels. That's why we recommend the adjustable gas blocks. It can make quite a difference in that area.
Great report on the accuracy. Always good to hear.
Greg
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Post by lapriester on Mar 2, 2016 1:49:48 GMT -8
Look over the AA and Hodgdon data on the Grendel to get a good idea on load levels. You are right in the ball park. You can run slightly more pressure. You are probably a bit over gassed based on the swipes at those levels. That's why we recommend the adjustable gas blocks. It can make quite a difference in that area. Great report on the accuracy. Always good to hear. Greg With the slick side I have observed my general ejection pattern was at 4 o'clock with virtually all loads. No matter what, they seem to always go there except the one load that was short stroking or failing to fully extract. I attributed the ejection pattern to no brass deflector. Do you think that ejection pattern is a product of being over gassed?
Greg, while I have you here, can you tell me the gas port size on your rifle gassed 260 Remington barrels. I have a 260 Remington rifle that's giving me fits (not one of your barrels unfortunately). I built it and can't get it to run reliably. Everything has been checked twice but the gas port, at .072", seems undersized. The rifle has all the feel of being under gassed even though I've loaded loads up to and above max. Mid loads barely move the BCG out of battery before slamming the spent brass back into the chamber. Max+ loads eject but no bolt lock back on anything. Recoil is very weak. Tried shortening the spring, lightening the buffer, swapped BCG's with my fully functional 308, checked for gas leakage and block alignment to no avail. I've drilled the gas port a bit and testing function tomorrow. But, knowing your gas port size may help me figure out how far I should go. I may have actually drilled it a bit oversized (my error) but an adjustable GB is always an option for that possible mistake.
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Post by GLSHOOTER on Mar 2, 2016 6:10:35 GMT -8
With the slick side I have observed my general ejection pattern was at 4 o'clock with virtually all loads. No matter what, they seem to always go there except the one load that was short stroking or failing to fully extract. I attributed the ejection pattern to no brass deflector. Do you think that ejection pattern is a product of being over gassed?
Greg, while I have you here, can you tell me the gas port size on your rifle gassed 260 Remington barrels. I have a 260 Remington rifle that's giving me fits (not one of your barrels unfortunately). I built it and can't get it to run reliably. Everything has been checked twice but the gas port, at .072", seems undersized. The rifle has all the feel of being under gassed even though I've loaded loads up to and above max. Mid loads barely move the BCG out of battery before slamming the spent brass back into the chamber. Max+ loads eject but no bolt lock back on anything. Recoil is very weak. Tried shortening the spring, lightening the buffer, swapped BCG's with my fully functional 308, checked for gas leakage and block alignment to no avail. I've drilled the gas port a bit and testing function tomorrow. But, knowing your gas port size may help me figure out how far I should go. I may have actually drilled it a bit oversized (my error) but an adjustable GB is always an option for that possible mistake.
I am not sure on how the slick side makes a difference in the pattern. Some of it really is going to be based on springs and ejector/extractor combinations. I know that slowing the opening down helps a great deal on swipes and also making sure your ejector is not ice pick sharp on the edges. I have no idea on the 260 port size. That would be a cal to t shop directly. Greg
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Post by lapriester on Apr 7, 2016 1:08:50 GMT -8
First Varmint trip with the 6.5X6.8 last weekend. I loaded my test load of 29gr 2200, CCI450 primers behind the 85gr Varminters. Deadly accurate out to 225 yards on those small 3X5" ground squirrels even with a 10-15 MPH gusting cross wind. Closer? They were insanely accurate. Anything under 200 yards was toast.
Problems though with function. For some odd reason the ejector swipes increased in severity as the day went by and intermittent function problems started showing up after about 200 rounds down the tube. Incomplete ejection, mag miss feeds, short stroking all started cropping up. The more it malfunctioned the worse the swipes became and the primers began to show flattening. Looking at the chamber, it is really dirty. I'm thinking, perhaps I'm over gassed and that's why the chamber and BCG are so contaminated. Or could it be that the AA2200 is a dirtier powder than I thought. Now that I think about it, my 6.8 began to have function problems shooting AA2200 behind 90 gr TNT's and mag primers after about 200 rounds. That chamber was also very dirty after 200 rounds.
You would think that actual malfunctions would be consistent but, I could shoot 50 rounds without a single problem then it would hang a case sideways with a round partially loaded or fail to lock back the bolt. Then 25 to 50 rounds would function fine followed again by multiple malfunctions. The type of mags didn't seen to matter either. ASC and C Products both were used.
All in all a good outing with the rifle but the malfunctions are troubling.
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Post by GLSHOOTER on Apr 7, 2016 6:06:13 GMT -8
Good report. The accuracy is certainly there.
The 2200 is a dirty one and does require a bit of cleaning depending on several factors. I try to at least swap every 150 rounds or so or hit it with some brake cleaner down the barrel and tube. (The tube thing is habit and not needed really)
You may also see some pressure changes due to heat. Did you work up your loads in the cool weather or similar to what you shot in? You do have the over-gassed thing spotted and just turning down the block will help it tremendously. I rarely use a standard block as an adjustable gives so much more flexibility for issues like this and in powder choices.
Greg
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Post by lapriester on Apr 7, 2016 8:27:15 GMT -8
The weather was about the same 50's to low 60's. I'll just plan on running a chamber brush every 150 rounds or so and work on getting an adjustable block. I'm using a rifle buffer system and fixed Magpul stock. I may try one of my carbine buffered lowers or change out the buffer spring to the Tubbs flat coil one I have. It might be right on the edge and maybe a different buffer combo will minimize or even stop the short stroking. You should see the squirrels fly when they are hit with those Varminters out of this gun. I had some fly 10-15ft in the air and drift downwind 15ft before hitting the ground again.
I'm also going to go back to the drawing board on powder and do further testing with 8208. I may also try some H335 and 10X just to see the results.
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Post by lapriester on Mar 19, 2017 19:45:53 GMT -8
Ok, next week, if the rain ever stops again, I'll be out to the range with the old girl to play. She had a very lonely late Summer Fall and Winter.
I decided to try some H335 this time and some different loads of AA2200 and XBR.
With XBR I bumped up the load to 31.5 with the 85 Sierra to see if that .5 will improve on the original .2 MOA (LOL). Last time the XBR loads seemed mild but function was good and no sign of pressure. The 31.5gr filled those Fed cases pretty full so I don't think there's much more room to play without having to compress the powder. Last time 30gr of XBR behind the 100gr Sierra was producing too much pressure so this time I loaded 28.5 and 29gr behind the same bullet. We'll see how that goes.
With AA2200 I loaded too hot with the 100gr Sierra last time so this time I loaded 26.5, 27 and 27.5gr behind them. Last time I found a killer accurate load with the 85gr at 29.6gr though it was a bit dirty when I went varmint hunting, trashed the gun and started short stroking after about 200 rounds until it got cleaned. Just this week I may have discovered why it ran so dirty. My neck tension may have been too loose the way I originally formed the cases. I corrected that this time but, that's still a work in progress. Neck tension seems great now after resizing the necks with the .287 bushing rather that the .289 I used last time.
With the H335, behind the 85's I loaded 30, 30.5 and 31gr and behind the 100's 29, 29.5 and 30.0gr
Everything I loaded has an OAL of 2.21", formed Federal brass and CCI 450 primers.
I doubt I'll be able to set up my chrono so accuracy and function will be the focus of the report. I'm also going to drag out the 22 Nosler if I get it together by next week but that's still up in the air. I can load and shoot with the finger I had surgery on two weeks ago but trying to build an upper the way it is may be a non-starter. The stitches come out next Wed so we'll see. Either way, a fun day at the range. It's been about 7 months since I've popped a cap.
Larry
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204ar
Full Member
Posts: 70
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Post by 204ar on Mar 20, 2017 14:52:51 GMT -8
Wow 7 months of no shooting? I rarely can go more than a couple of days lol. You are one patient dude!
Good luck at the range, I hope you can get your other upper together in time. Sounds like you have a great shooter there.
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Post by lapriester on Mar 20, 2017 20:39:39 GMT -8
Almost 6 months ago I had surgery to repair the tendon on my right middle finger which I jammed while cutting some huge Pine rounds. Apparently my system never liked the stitching he used to reattach the tendon and it never would stop swelling and burning for 5 months. He, of course said to give it more time. Bad idea. 3 weeks ago it got much worse, became an open sore and got infected. Last week he had to go back in (I didn't give him much choice in the matter), clean everything out and remove the stitches my body was apparently rejecting all along. The stitches from surgery come out Wed. It has been a very long 6 months of being right handed with a pretty much useless right hand that swelled up anytime I used it. No waterfowl season, no pheasant season, no deer season and no shooting anything. Now I may end up with the end of my finger crooked but will at least have a useful hand again and be able to shoot. Might get the end joint fused later but not for some time. Planning on busting squirrels at the end on the month, and some range time before then, sore finger or not. At least I got about 2K rounds loaded before the injury. Bullets need shooting and squirrels need killing.
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