Girly man with the AIAT

[Iggy]

I've been alluded to be a girly man, Miata diving shooter who posts up cute 100 yard groups, so I thought I'd share what the AI did on her first round at 1K.

Today was shots 31-80 out of the gun, and it's first time outside 100 yards. With the exception of 3 pierced primers, that I couldn't figure out what caused them (maybe variations in cup thickness), the rifle did really well. I am really starting to like this gun.

These are the first 5 shots out of the gun at 1K. Caliber is 6.5x47 Lapua. So is she a keeper with this cute group?

[Pthfndr]

Where's the rest of the target? Where are shots 6-9?

Not too bad Iggy. Looks like you were keeping them about 1 moa at 1k.

For those that don't know, the 9 ring on that target is 8 inches wide.

[Iggy]

I can get a photo of the whole thing tomorrow. I just wanted to show the first 5, but I put down 13 at 1k.

I think 6 was a pierced primer so it lost a bit of velocity and dropped. The wind picked up and moved me a bit. Then I was able to dial it back in.

[NeverlosT]

I have gun envy. Looks like a good 1k group to me

[Iggy]

I resemble that remark. What are you trying to say

For a few years I drove a 91 miata ... In east Oakland... Blaring George Michael.

It was set up for spec racing but looked stock. Coil overs, turbo the works. I would eat mustang and vetts all day.

Sorry, had to brag.

Nice shooting

Haha! That was said when I posted a 100 yard group with a 20" rifle. I didn't mean to direct it to anyone!

Rob,

Here's the rest of the group. A few corrections, I guess I shot 14 on 1K and out of the rifle it was shots 41-80.

Shots 6, 8, 9, 12, and 14 are less than stellar. I noticed my rifle was canted a bit half way through and I don't know if that had something to do with the drop. I know for sure one of those was a blown primer.

[JMP]

With the exception of 3 pierced primers, that I couldn't figure out what caused them.

What type of primer were you using? I actually had this happen recently when I inadvertently started using Winchester primers on a batch of 6.5CD. I figured I'd just finish the batch, and I pierced some full thickness to the point they clogged the firing pin hole. But, a very nice feature of the AI bolt is that it just pops apart like a lego to remove the firing pin assembly by taking out the bolt with the safety engaged in the 2nd position, so an obstruction is very easily just popped out. It's really the most cleverly designed action, IMO, for tactical use with the three position safety on the bolt, rather than the trigger, so it allows for the mechanisms to be extremely simple and everything can be rapidly disassembled and reassemble in the field with minimal tools if anything were to go wrong.

I suspect that the AI firing pin will have a tendency to do this over some others as they hit hard. I haven't used the new "Miata driving, girly man" AT, but I expect they will be similar to the older manly man variants. I have never encountered any issues with CCI or Federal primers. But, if it were to be a recurring issue, I'd imagine you can have a gunsmith smooth it out a bit.

If I were to venture a guess, it might be that AI has never really made a rifle designed to use a cartridge that uses small primers like the 6.5 Lapua.

This is the standard AI short action firing pin vs. the standard size R700 short action firing pin. You will notice that the AI is a bit larger and less blunt. It's kind of hard to tell in the photo, but you may want to pull your pin and compare it to another rifle's to see how the dimensions compare. Like I said, I am not sure if anything has changed with the AT.

[Iggy]

JMP,

I am using CCI small bench rest primers, who's cups are as thick as the mil spec ones.

I know all about the bolt disassembly. I had to do it on 2 of the 3 blown primers as the pin was stuck with material that had ben blown in. Thank goodness for that feature! Other wise I would have missed out on a few firing lines.

I've pierced 4 primers so far. After the first one I adjusted the firing pin half a turn in to shorten the depth.

If you don't know how to do this, look for the 1.5mm set screw here:



There are two set screws, and after you remove them you can turn the depth of the firing pin in or out.

[JMP]

I've never had the issue except for the one time I mentioned using Winchester primers. In fact, I used two different bolts and they both did it. But, it really hasn't been of much concern to me since it's never happened to me with CCI primers. If you shortened the depth of the pin, and it still pierced, I'd wonder if it might have to do with the strike face circumference on a the small primer. I don't know as I don't have a small rifle primer chambering with an AI bolt. That's just one conjecture on my part.

It also has to do with the dynamics of the particular cartridge as I have shot Winchester primers pretty flat out of .308 Win and never had a problem. With the same bolt, I think I had four pierced primers out of just 50 rounds in 6.5CD with a Winchester primer.

It's just thought, I'd be curious to know the outcome. But, who knows? It might just go away on the next primer sleeve.

[mattt]

Did they pull the target after each shot? if not then your vertical went south.I wouldnt post it if it was a string of 13 shots even out of a 308 at 1K. But you might shoot tac so that is great for an open cal.

[Iggy]

Girly man with the AIAT

mattt, it was a tac practice so they pulled each shot and my guy was pulling for two. It was a little slow so things changed a bit from shot to shot.

[mattt]

Looks like you are holding x ring vertical with that load .I would stick with it.

[ar15barrels]

This is the standard AI short action firing pin vs. the standard size R700 short action firing pin.
You will notice that the AI is a bit larger and less blunt.

The larger diameter of the firing pin hole in the boltface is what makes that action poor at handling the higher pressures.
700's do it too, especially the ones with the chamfer on the firing pin hole.
The cup will blow out because it's not supported well enough for the pressures being used.
This is why many target rifles get built with 1/16" diameter firing pin holes and smaller firing pins to fit them.

[Iggy]

The larger diameter of the firing pin hole in the boltface is what makes that action poor at handling the higher pressures.
700's do it too, especially the ones with the chamfer on the firing pin hole.
The cup will blow out because it's not supported well enough for the pressures being used.
This is why many target rifles get built with 1/16" diameter firing pin holes and smaller firing pins to fit them.

This is not necessarily true with my (possibly current models) AT (AW) action.



This is a shot of a the same batch of reloaded ammo originally designed for my Stiller Tac30. On right is are the rounds fired by the Stiller and on the left are the same rounds fired by the AIAT.

If you look closely the Stiller has some cratering caused by the difference in diameter between the firing pin and firing pin hole. You will also notice the AT does not have this issue. The fit between the firing pin and firing pin hole is very good with the AT. I think what causes the issue is the larger size of the firing pin and the protrusion depth.

[Kiba]

Some AIs do experience occasional primer issues with higher pressure calibers like .260, 6.5x47, and 6.5CM. 6.5x47 seems to be a little more problematic possibly because of the small primers. The AIs were built around 308 to be absolutely reliable in all field conditions with hard mil-spec 308 primers but certain calibers can have issues because of the large firing pin diameter. As Randall said, a smaller diameter firing pin is the ideal fix for higher pressure calibers. For problematic Remingtons one option is to reduce the firing pin diameter and bush the bolt face but it seems no gunsmith wants to even attempt bushing an AI bolt. I've heard the hardness reason but even if the bolts are case hardened I can't see a reason why so many gunsmiths turn the job down; with proper tooling it shouldn't be an issue. At least one gunsmith is willing to do the job as a few AI users over on Sniper's Hide have had bushing jobs done-- and as an odd coincidence all the guys that had their bolts bushed were running 6.5x47.

One suggestion would be to try primers with thicker/harder cups. Perhaps give the Wolf/Tula KVB-556M or KVB-223M primers a try? They're both pretty darn stout in terms of the cups and I've seen excellent ES/SD numbers and accuracy from both of them (although not in a 6.5x47.) The KVB-556M is supposed to be a little hotter than the KVB-223M.

Another suggestion and one that you can do in 5 minutes without buying anything or changing loads is to slightly reduce firing pin protrusion; that has helped some primer issues in AIs running non-308 calibers. My AI runs 6.5CM fine, a friend's AI in 6.5CM was a little harder on primers than mine. I slightly reduced firing pin protrusion and it really helped the primer condition.

Pics & info on how to easily adjust firing pin protrusion here... granted it shows an AW/AE style bolt but I believe the new AT and AXMC use the same arrangement for firing pin protrusion adjustment. http://forum.snipershide.info/showth...=1#post2930025

If you've already reduced firing pin protrusion to the low end of spec (.042" minimum) and are still getting the occasional pierced primer and don't want to bush the bolt there isn't much left to try except experiment with different primers or powder to try and find a load that plays nice with your rifle. I wish AI would start offering an .062" firing pin and bolt for non-308 calibers but AINA says they have no plans to do so in the near future.

[Iggy]

For the record, I'm not worried about the primer issue. I appreciate the input, but so far I've tried what I can do without voiding the warranty.

I think in my case it may be a primer cup issue, but it's not a problem with the firing pin hole being larger than the firing pin.