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Discussion Starter #1
I just finished a 2 day rifle class using the SCAR 17S and was very happy with the rifle. However, there were three problems.

First, a couple of loaded magazines go dropped from a low table onto grass covered ground and the base plates came loose. I have seen posts about this before so I will not worry about it now other than to mention it. One was able to be pushed back on and my friend took the other one off to look and got it stuck trying to put it back on. Not a problem as I had several spare mags.

The kydex belt attached mag pouch from DSG Arms had belt loops that would not fit the thickness of my belt from thebeltman.com. Luckily my Woolrich BDU pants had pockets that were the perfect size for the mags. Maybe I can heat up the kydex and bend the belt loops a little.

Now for the point of my post . . .

Shooting at 25 yards doing some multiple target engagements I noticed three or four bullets that did not impact the target straight on. At first I thought that this might have been do to shooting the targets at a angle while stacking the targets and moving to engage, but at least one was a dead on side of the bullet hitting the target that could not have been clearer had I cut it with an xacto knife.

I thought I had read here that with the 1/12 twist the SCAR 17 likes the lighter military type loads. My assumption has been that the max bullet weight for the 1/12 twist would be 168g.

The PPU is labeled "308 Winchester FMJ BT 145g, lot PPU 1202-04" and was recently bought from either Wideners or SGAmmo.

I am not sure, but I shot 80 rounds before the class and probably 200 at the class. There were four bullets that made non-circular holes.

When I was sighting the gun in at 50 yards before the class I was getting a two to three inch group. I am new to shooting rifles and do not have the greatest eyesight so this wide group is more likely my fault than the rifle's fault. From my limited experience it seems that the rifle is shooting OK. This was my first time shooting without a bench. I was not making great groups, but I was hitting the target all of the time.

Does anyone have thoughts or similar experience with the PPU ammo?
 

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PPU ammo is not terribly good. I've had pretty poor results with their 'match' ammo and I'm suspect their 308 match ammo was slightly out of spec (the case anyway. My rifles bolt did not close easily on it like Federal Gold Medal Match does).
 

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I have used 50 rds. of standard PPU . Definitley a last resort choice of ammo. NEVER GONN'A GET STELLAR ACCURACY OUT OF THE LOT . NOT SURPRISED THAT A WIDE VARIANCE OF VELOCITIES IS COMMONPLACE FOR THIS ....... '' stuff".
 

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Discussion Starter #4
Being a newbie, I apologize if my questions are obvious.

When you mention wide variance of velocity does that mean that if the bullet is traveling at a different (I suppose slower) velocity for a given rifling twist it will not stabilize as it should and therefore start to tumble?

One friend suggested that bullets need a certain distance to stabilize coming out of the barrel and that 25 yards might be two close for the stabilization to occur.

When we were simulation malfunctions to do clearing drills I found one ejected round that was nearly half an inch shorter than the new ones. I am assuming that this was the bullet getting seated when it was chambered, but I suppose it could have been a manufacturing defect that I failed to notice. In any case, I am extremely glad I did not fire the round in its shortened condition.

I grabbed a bunch of the PPU when it was recently available based on the cost and planning to use it for classes where I probably should be using an AR-15 but am taking my SCAR 17S instead. I suppose for this sort of stuff at 15 to 50 yards the PPU will be fine. I would hate to burn a lot of good ammo for classes like this.

From the comments so far I am taking away that the focus should be on ammo quality, not on any issues with the rifle. Is that a reasonable conclusion?

Thanks.

Joe
 

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Joe, PPUM80 shoots fine out of my 17, and I've never had a round keyhole at 25. Probably shot about 1000 rounds of it, though mostly at 100 yds.

It's possible your barrel is damaged, do you have any way to scope it? It's also possible you got a bad lot of that ammo.

Lack of stabilization does not mean a 90 degree hit, it would be a 2-3 degree offset. At 90 degrees (keyhole) the bullet is literally tumbling.

The "best choices for self defense ammunition" faq on ar15.com includes a stabilization graph of M855, where the peak deviation is up to 4 degrees as it leaves the barrel, but then approaches 1 degree max at 100yds.
 

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I'm wondering if the bullets are slightly undersized, or it could be your barrel is slightly over sized. I would first try some different ammo in the same weight and shoot it at the same distance and see if it does it. That would tell you if the gun is the issue.
 
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I'm wondering if the bullets are slightly undersized, or it could be your barrel is slightly over sized. I would first try some different ammo in the same weight and shoot it at the same distance and see if it does it. That would tell you if the gun is the issue.
Change ammo?
Shouldn't that automatically be the first step? Yes. I'm sure I read that somewhere.
 

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I shoot lots of 150gr prvi and never had any issues.
 

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Not unusual and unless you're expecting it, it can be a bit of a surprise when you walk up on the target.

Here's an example where I broke in a barrel with SMK 220's. after the break-in, I fired some FGMM 168's and she performed as expected, dropping 10 rounds in .542" @ 100 yards...
100_2266.jpg
 

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Discussion Starter #10
Thanks for the info.

Sarge - I looked up the SMK 220 and see that it is subsonic and I am guessing 220g. It said that it requires 1 in 8 twist or faster. I can see that this should not get stabilized in the SCAR 1 in 12 twist barrel. But the PPU is 145g so I would expect it is light enough for the 1 in 12 twist. Are you saying that this happening with the PPU for me is normal as well?

When I got the SCAR I decided not to do the meticulous barrel break in process that I did with my FNAR.

I did one shot then clean with Bore Tech Eliminator about five times. Then I shot 20 and cleaned. I don't remember if I shot more in between, but last Friday I shot 60 then cleaned before the class.

At the class I shot 150 or 200 on Saturday and was too tired to clean it. I ran three patches through it with BreakFree CLP before class on Sunday. I shot another 100 or so rounds on Sunday which included the four sideways ones.

I will give it a really good cleaning later this week and shoot another 150 or so rounds on Sunday.

In the relatively cheap ammo department I have Winchester and Federal 7.62x51 147g and 150g if I recall the weights correctly and the PPU.

Should I continue to shoot the PPU on Sunday and see if it happens again after or good cleaning, or should I shoot the Winchester or Federal to see if it happens with different ammo?

Thanks.

Joe
 

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Your FNAR and SCAR don't need a barrel break-in as they're chrome lined.

As to what you should shoot Sunday, I would shoot the other ammo first.
 

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Sarge - I looked up the SMK 220 and see that it is subsonic and I am guessing 220g. It said that it requires 1 in 8 twist or faster. I can see that this should not get stabilized in the SCAR 1 in 12 twist barrel.
The Sierra 220gr. Matchkings I loaded were for breaking in the barrel on the Remington SPS bolt gun, as noted on the target. They ran supersonic but weren't stabilized and the results were wide dispersion also noted on the target. Point of aim remained the same throughout the break-in and no sighting corrections were made to the glass.

My LR bolt-gun has a 10 twist barrel, chambered in .30-338 WM and it stabilizes the 220gr SMK's fine at 2850fps.

-SS
 

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I used to shoot a lot of Prvi Match back when I had a M1A NM, no difference in group size between Prvi, Black Hills Match, and FGGM (all about 1".)
 

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Take two and call us in the morning :wink:
 

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Discussion Starter #15
OK. Sunday I will bring Federal, Winchester, PPU and maybe even some of my precious TAP 155g. It is only a 4 hour beginner class, expecting to shoot about 200 rounds. My only worry is that the zero might jump around as I change ammo. I suppose I could ignore the zero and just work on trying to get good groups and not worry if they are off a little. I am still at the point where I need to practice mounting the rifle properly, leaning forward into it and getting a good cheek weld.
 

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Discussion Starter #18
A lot number on this PPU ammo would be a help for others
I gave it in the initial post. Here it is again.

The PPU is labeled "308 Winchester FMJ BT 145g, lot PPU 1202-04" and was recently bought from either Wideners or SGAmmo.
 

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My .02. I can't imagine key holing unless something is seriously foxtrot. Make sure you aren't sending bullets down a barrel with oil in there, the "essentially incompressible" fluid can actually change the diameter of the barrel due to extremely high pressures as the bullet attempts to slide past the oil.

If I hadn't seen it with my own eyes I wouldn't believe it. There I was shooting 3-gun at the 50y pig with Wolf 12 ga slugs and they were peppering the target! The slugs at unpredictable intervals would disintegrate leaving the barrel. Maybe these bulk rounds you have are severely out of round, perhaps they too are not keeping shape or they are getting damaged passing over oil in the barrel.

Just my .02 but this does leave me with a Wtf....
 
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