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Reloading for Gas Guns?

 
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  #15  
Old 04-10-2013, 09:22 AM
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Re: Reloading for Gas Guns?

REDHEAD,

I'd have to give the Ballistic Tips, BlitzKings or any other poly-tipped bullets a very tentative okay in ARs. I say tentative because I've seen some of these bullets shed their tips when roughly handled. Seen others come loose simply because the machines weren't adjusted properly to ensure sufficient grip on the poly tips during bullet assembly. Regardless of the cause, that means there's always the potential for that little tip finding its way down into the trigger assembly (Murphy will put it there, trust me) and gumming up the works. I'd saw give them a try, but don't be too surprised if there's an occasional issue with this sort of thing.
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  #16  
Old 04-17-2013, 05:25 PM
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Re: Reloading for Gas Guns?

I've loaded and shot the 50gr Vmax out of the AR's for a long time, I heartily recommend them. Not so sure on any kind of sintered type bullet...worse case is it the gas system gets fouled up with copper alloy powder...
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  #17  
Old 04-26-2013, 11:29 PM
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Re: Reloading for Gas Guns?

Differences? For me, it is the following?

1) Full length resizing every time, with possible alternate of using a neck bushing. I found my fired brass measured .255, my Redding FL die pushed it down to .239 and the expander ball brought it back to around .248. That is a lot of brass working. Still, I would give some extra neck clearance vs a tight necked bolt gun. Also need to be sure of proper neck diameter if not crimping to assure bullet stays put under loading.

2) A bit more generous on shoulder datum line to case head dimension.

3) Very careful to fully seat primers.

4) Use harder cup primers. I use Remington 7-1/2s.

5) Selection of proper powder burn rate with consideration given to barrel length, to achieve reliable gas operation of bolt.

6) Selection of powder that also burns clean but does the job otherwise.

Just my $0.02 and maybe not worth that.

Phil
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  #18  
Old 04-27-2013, 06:43 AM
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Re: Reloading for Gas Guns?

I really like the AR platform. After firing several thousand reloads through four different rifles(Bushmaster/Remington, DPMS,Colt), for target competition and hunting, here are some of my experiences:
-I have never had a slam fire with standard CCI primers, including BR4's. CCI military primers can be too hard with some light spring after market triggers.
-I'm partial to the RCBS standard 223 FL X-Dye. I get 10+ reloads/case without trimming or annealing. I have tried several brands of brass, but settled on Lapua.
-For hunting where rounds may be kept in the magazine for extended firing of the rifle because one or two bullets may be added, recoil can push bullets deeper into the case if there is insufficient neck tension, or plastic tipped bullet can have the tip knocked out while in the mag due to being subjected to extended recoil. No problems when firing plastic tipped bullets directly.
-Most of my shooting is 500 yards max. For my 1:9 twist rifles I use Varget with 69grSMK's and 55gr SST's, BR4's, and Lapua brass. Very accurate, easy cleaning, and maintains accuracy and reliable function in all my rifles for 200+ rounds without cleaning.
-For precision shooting keep an eye on the play between the upper and lower. I have found that modified plastic wedges available from Broenells work best. Since they will eventually deform, I will drill a 1/8" hole in the base of the wedge and place a "cut to length" rebound spring from a Smith and Wesson revolver to apply additional tension. Any similiar sized 1/8" quality spring will work. They will work permanently when I make this mod.
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  #19  
Old 04-29-2013, 10:54 AM
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Re: Reloading for Gas Guns?

Regarding slamfires in M1 and M14 rifles, I've seen a couple dozen or so cases from them that slamfired. Every one had a full, normal, full depth dimple in them. No M1 nor M14 floating firing pin will do that to any primer made in the USA. All primers made in the USA need about .020" dimple depth to fire them according to an engineer whose worked at arsenals deep in such fields of ammunition issues. And firing pin tips need to protrude at least .060" from the bolt face to fire primers consistantly good. Therefore, I feel the hammer's sear engagement was too small to survive the mechanical shock of the bolt slamming into battery as it chambered a fresh round. Or, some foriegn body jammed the firing pin in the bolt and held it there as it closed on the chambered round.

Regarding accuracy with semiautos..... Few have had their bolt faces squared up with the barrel's chamber axis. This is the reason military teams shooting top scores with new ammo (arsenal and commercial match stuff) could never get reloaded cases from them to shoot accurate in their M1 and M14 platforms. Same thing for AR platforms. Those fired cases had their heads press way out of square and resizing them did not square them back up. So, unless your AR's bolt face gets squared up properly, new cases will probably produce best accuracy.
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  #20  
Old 04-29-2013, 03:23 PM
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Re: Reloading for Gas Guns?

Quote:
Originally Posted by Bart B View Post
Regarding accuracy with semiautos..... Few have had their bolt faces squared up with the barrel's chamber axis. This is the reason military teams shooting top scores with new ammo (arsenal and commercial match stuff) could never get reloaded cases from them to shoot accurate in their M1 and M14 platforms. Same thing for AR platforms. Those fired cases had their heads press way out of square and resizing them did not square them back up. So, unless your AR's bolt face gets squared up properly, new cases will probably produce best accuracy.
This got me thinking, so I did a test.

I placed a Sinclair case holder for 223 Remington into my lathe. I then inserted a series of cases into the case holder, so the case head faced away from the chuck. Then, using a test indicator, measured axial runout on the headstamp part of the case head. This is difficult due to the headstamp itself causing the indicator to jump around, but got some useful data I think.

In addition, I took of couple of the case and carefully faced the head, noting how much I had to take off before the bottom of the case was dead flat. This assumes of course that the Sinclair case holder is straight, and after some measurements, am confident it is. The test results.

Rifle - Home built AR-15.
- Krieger barrel chambered in 223 Remington minimum SAAMI spec.
- Young Manufacturing Match chrome bolt carrier group.
- Sun Devil upper.

Brass - "WCC 09" w/NATO stamp from box of Blackhills 223 Remington FMJ 55 grain ammunition (more on this later).

New unfired Blackhills with WCCbrass: .0025"
1x Fired Blackhills with WCC brass: .0025"
1x FiredBlackhills with WCC brass FL resized: .0016

Frankly, this in inconclusive since the dial indicator needle jumped around so much on the headstamp, I could never be sure of very high accuracy.

So, used the lathe to face off a couple of fired cases, until the head had been completely touched by the cutting tool showing shiny brass. I did this on two fired cases and both required a tad under .002" to square them up.

I did not do this on unfired cases, cause I didn't want to ruin a case by reducing its rim thickness, however small.

I may do more testing, but from where I sit, I am not seeing much difference between new cases, fired cases, and possibly even resized cases (even if they show a bit flatter). I need more confidence in the accuracy of the measurements.

There was one other thing I might test, but this is getting to be a lot of work!

As the case sits in the chamber, it is held tight against the right side wall. This is because the ejector plunger is pushing it that way, pivoting around the extractor claw. I wonder when the gun goes off, and the case is plastered against the walls, does the case straighten itself out, or does the left side blow further than the right? If it did, then the case centerline is not square with the bolt face. One way to find out is to mark where the extractor grabs it and then measure to see if measured case head runout is in any way consistent with where the extractor grabbed the case. A wild theory I know, but just wondering.

On the Blackhills ammo I said I would talk about. This ammo showed pressure signs. Yup, factory ammo. I wonder why 223 Remington ammo from Blackhills is using a 5.56 NATO case. The primers were slightly flattened and the brass had signs of ejector plunger smearing as well as the impression of the extractor seam on the bolt head. I am not shooting that stuff anymore.

Phil
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  #21  
Old 04-29-2013, 03:45 PM
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Re: Reloading for Gas Guns?

Quote:
Originally Posted by Phil3 View Post
I wonder when the gun goes off, and the case is plastered against the walls, does the case straighten itself out, or does the left side blow further than the right?
The case will expand as if it was all by itself and not in a chamber. The thinnest side of the case body will expand the most; just like a balloon being inflated as it lays on a table top. I've cut off case heads about half an inch above the extractor groove and measured thickness. The thin side could be anyplace relative to how the case was indexed in the chamber. I used the firing pin tip's imprint details to tell what side of the case was pushed sideways against the chamber wall by the extractor when it fired.

Best way for me to measure case head squareness is to first decap it, then stand it on a flat surface against a V block of some sort. Spin the case and watch the case mouth. If the case mouth spins about its center, the head's square. If it moves around in a circle, the size of the circle indicates how much out of square the case head is. Do the same thing with live ammo and watch the bullet tip. Standing the case/round under a fixed magnifying glass makes it easier to see the top make a circle when the case head's out of square.

Congratulations on being one of the few that knows the back end of a case gets pushed off center in chambers by and in the direction extractors' force. Do you know where the shoulder of the case is when it fires? Most folks think the case rests in the bottom of the chamber.

Quote:
I wonder why 223 Remington ammo from Blackhills is using a 5.56 NATO case.
I's available and cheap.
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