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Old May 17, 2018, 07:54 AM   #1
homesick
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6.5 grendel

I finally got my 6.5 under 1" today in fact it is right at 1/2" its a 18" BCA barrel, bullets are seated at 2.270 with 28.7 gr of 8208 123 gr Hornady SST CCI 41 primers and Hornady brass. Every thing up to this load was 1 1/2" or larger. There does not appear to be any excess pressure as I have compared the fired rounds with factory cases and both measure the same as well as appear the same. I have a couple questions I see many of ya'll use CCI 450 primers where I use CCI 41s do you ever have doubles? I have a POF trigger in my AR and have experienced doubles with Remington 7 1/2s and Winchester SR primers. Since I switched to the 41s I have not had a double. I had the same problem in my AR 10 also till I went to the 34s by the way that's a hoot running 5, 308's out in a burst. Sure gets every ones attention on the line.
My next step will be to load 10 cases with this load to see if I have any stretching issues or primer pocket issues. I'm a little concerned as this load is a bit over the 28.5 most are using.
Any one else have thoughts on the Grendel what their using what seems to work and what doesn't.
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Old May 17, 2018, 10:41 AM   #2
Unclenick
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The extra 0.2 grains is well within what a lot of measures can throw. If you have no signs of high pressure or excessive cycling force, you should be fine.

In your case, the doubling and burstfire is a fired round followed by a slamfire(s), which we may surmise because your primer change stopped both. I have to say, slamfires in the .223/5.56 AR are unusual and you might want to double-check your firing pin protrusion is within spec on both guns. However, the most common cause is inadequately seated or high primers, and softer primers will be more prone to slamfire when seated less deeply than is optimal than others do. The CCI 450's and 250's will be more prone to slamfire than the #41's and #34. CCI changed the anvil foot tripod angle on those to reduce the sensitivity to military spec.

A properly seated primer will be about -0.003" deeper than the primer is when you just feel the anvil feet touch down on the floor of the primer pocket. If you can't feel where that happens on your equipment, a rule of thumb is about -0.004" to -0.005" below flush with the case head, on average. So, by whatever means you are seating the primers, you want to check that.

Many people believe a primer is best seated to just touch the floor of the primer pocket. This is wrong. Primers need to be slightly compressed to work optimally. This was confirmed 30 years ago by the Naval Ordnance Station at Indian Head (NOSIH) in this document, where you can see in the drawings at the end, their recommendation for reconsolidation (compression of anvil into priming mix during seating) as compared to Remington's wider (-0.002" to -0.006") recommendation. Going from just touching to proper reconsolidation typically cuts velocity extreme spread due to the more consistent ignition performance.

There are several primer seaters on the market that let you fix the depth of the seating action below flush. This is one, but the increments of 2.5 mils are a little coarse. I've seen a bench tool advertised that has 0.002" seating steps, but I'm not finding it right away. Perhaps another member will post a link. You can use shim sets with the Sinclair hand priming tool to set how far its primer ram sticks up into the primer pocket when its handle is pushed 100% of the way in, and those kits can give you 0.001" resolution. The primer seating system that is part of the Forster Co-ax press will give you fixed 0.004-0.005" below flush priming. (Note that the Forster Co-ax bench priming tool does not do this, though; only the press priming tool does.) The K&M Primer Gauge tool will let you individual measure cases and primers to get the primers exactly 0.003" reconsolidated beyond anvil contact with the floor of the primer pocket.

Or, you can try just seating hard.
"There is some debate about how deeply primers should be seated. I don’t pretend to have all the answers about this, but I have experimented with seating primers to different depths and seeing what happens on the chronograph and target paper, and so far I’ve obtained my best results seating them hard, pushing them in past the point where the anvil can be felt hitting the bottom of the pocket. Doing this, I can almost always get velocity standard deviations of less than 10 feet per second, even with magnum cartridges and long-bodied standards on the ’06 case, and I haven’t been able to accomplish that seating primers to lesser depths."

Dan Hackett
Precision Shooting Reloading Guide, Precision Shooting Inc., Pub. (R.I.P.), Manchester, CT, 1995, p. 271.
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Old May 17, 2018, 01:35 PM   #3
RC20
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Unclneick: The Link to NOSIH just brings up a link to Naval Entities in Google not the article .


I can testify about those "FEET"

Not an issue for me, but Unclenick has talked about them. I could not see them even under a magnify glass until I looked at the right angle.

Darned if there aren't 3 of this little buggers.

I always seating mine good but you really need that 3D perspective to see the protrusion and understand what he is talking about.

I do use a hand primer and they are seated below the rim by about .005.
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Last edited by RC20; May 17, 2018 at 01:41 PM.
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Old May 17, 2018, 04:41 PM   #4
mehavey
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Consider also the 123 Bergers, same powder....
https://thefiringline.com/forums/sho...28&postcount=8

and the Lapua Scenar, V-N540 powder
https://thefiringline.com/forums/sho...93&postcount=2


As to primer seating, I use an RCBS bench primer... seated until they just flat stop.
(Touchy-feely 'finesse' is over-rated.)
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Old May 17, 2018, 07:33 PM   #5
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"I see many of ya'll use CCI 450 primers where I use CCI 41s do you ever have doubles? I have a POF trigger in my AR and have experienced doubles with Remington 7 1/2s and Winchester SR primers. Since I switched to the 41s I have not had a double. I had the same problem in my AR 10 also till I went to the 34s by the way that's a hoot running 5, 308's out in a burst. Sure gets every ones attention on the line."
By "doubles" are you referring to slam fires or bump fires? The primer has nothing to do with "bumpfire".
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Old May 18, 2018, 10:04 PM   #6
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For the past couple of whitetail seasons, I've settled on using 120 gr Nosler Ballistic Tips in front of a 30.5 grain charge of BLC-2. COAL is 2.235" using Lapua brass and a CCI 400 primer. In my Alexander Arms 24" Overwatch upper, they deliver a sub-MOA group at 2546 FPS.
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Old May 19, 2018, 03:50 PM   #7
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I've consistently gotten .3", 5 shot groups. 30gr of CFE223, 123SST in Hornady cases, and WSR primers. No doubles, either.
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