Interest in firing pin bushing service for AI rifles

[Known]

Price?

Sent from my Nexus 4 using Tapatalk

$80 - $110 he said

 

[Known]

I shot about 15 rounds yesterday with the reduced firing pin protrusion and 40.7gr of H4350 and I still got some cratering. The primer indents were noticeably shallower.

I went out shooting today. I have never had problems with cold bore shift but my first shot at 100 yards was a foot low. The only time I've been that far off is when I've used the wrong dope, but at 100 yards the shot goes way high. Thinking I was getting marginal ignition I went back to the factory setting. Interestingly enough, I had less cratering with the 40.7gr load when going back to the factory setting.

The 40.7gr load is very accurate but at 600 yards they cost me .7 mils from my preferred load. I'm getting 2670fps. I can get through the match this weekend and then the JC Steel match in a few weeks. After that Warner Tool will get my bolt. I need to stop experimenting and practice more.

 

[blurry6]

I just had my first, and only, pierced primer today at a match. It happened on my 3rd shot of the day, but didn't reappear at all after that. I was shooting an AIAE that I'd put a 243 Win barrel on. I'm shooting 105gr Berger Hybrids on 41.5gr of H4350 with CCI BR2 primers,... Again, it only happened the once and didn't happen at all the rest of the day (40-50 rounds).

Ry

 

[Known]

I just had my first, and only, pierced primer today at a match. It happened on my 3rd shot of the day, but didn't reappear at all after that. I was shooting an AIAE that I'd put a 243 Win barrel on. I'm shooting 105gr Berger Hybrids on 41.5gr of H4350 with CCI BR2 primers,... Again, it only happened the once and didn't happen at all the rest of the day (40-50 rounds).

Ry

Blurry6 and I were at the same match and the piercing looked exactly like mine. He's using a Benchmark barrel so the problem does not appear to be associated with a particular barrel maker. I have an AINA Bartlein barrel.

 

[matt2143]

Measured my firing pin protrusion. Came in at 0.083" and I backed it off to .065" or so. The next step down was about 0.018" less and put it in the 0.040's.

 

[Known]

Measured my firing pin protrusion. Came in at 0.083" and I backed it off to .065" or so. The next step down was about 0.018" less and put it in the 0.040's.

When you measured, was the bolt shroud facing down and hanging free? .083 is way out of spec.

 

[Known]

Measured my firing pin protrusion. Came in at 0.083" and I backed it off to .065" or so. The next step down was about 0.018" less and put it in the 0.040's.

When you measured, was the bolt shroud facing down and hanging free? .083 is way out of spec.

 

[matt2143]

Yes the shroud was hanging and the bolt head facing the ceiling as I used the depth mic.

All my primers look like they have been stretched and collapsed. Just only one pierced primer so far, I have not fired any since the adjustment. I will report my results this Sunday.

 

[Ring]

what do you need to do to measure it?

 

[matt2143]

Dial caliper using the depth side or a depth micrometer (more accurate).

 

[Ring]

no, i mean do i need to do anything specific to the bolt to make sure the pin is in the full fired position...

 

[matt2143]

Ohh. Nope, just turn the shroud to cause the firing pin to be released. Hold the bolt by the bolt head with the shroud facing the floor so gravity can ensure your firing pin is at the same depth it would protrude during operation.

 

[majohnson2]

Are small primers more prone to cratering and or piercing?

 

[Known]

Are small primers more prone to cratering and or piercing?

With an appropriately sized firing pin and aperture you should not have a problem. Many go down to .062 and run CCI 450 primers. I believe Zak Smith was able to run the 6.5x47 in his AI without piercing but he must be leading a very pure and virtuous life. Others that use the cartridge in the AI end up bushing the firing pin.

6.5x47 Lapua Tactical TackDriver

 

[matt2143]

I ran the different depth and fired 50 rounds. I had one failure to fire. I also had a little excess head space so that did not help. Overall the primers look normal now!

 

[Ring]

update on mine, switched to CCI mag's, to get the same accuracy, i needed to drop the load by .4gr

AIAE 260
140gr Hornady BTHP
42gr H4350
CCI MAG primer

2720FPS
COL 2.8

 

[Splat]

Tagged

 

[was21]

Thx for the info KNOWN.
Trying to get answers from AI is like pulling teeth.....something about having to know the handshake
and secret kiss before any unrepeatable knowledge is dispensed! HA

 

[dieselten]

I have an AIAE in 6.5x47L. Handloads work fine, I just tried some factory Lapua ammo with the 139 Scenar, it would pierce about 3 or 4 out of 10 primers. I checked pin protrusion, it was .051", I screwed the pin in a half turn, pin is now .037". I fired 21 rounds today and they all worked fine, no primer piercing and the rounds were very accurate. I will leave this alone for now.

 

[Ring]

2nd round test, same load, but HBN coated bullets..



i did test all the way up to 43.6 with the mag primers and they held ok, but never got over 2800fps, and the accuracy sucked..

my 123 load has less drop at 1k, the 140 has just a tad less wind, not much, a few inches..

 

[A SHOOTERS DAD]

All,

I figured out how to adjust the firing pin protrusion between information that I received from Lowlight via PM and another source. I searched around and couldn't find directions, so I'll supply them here. The setup that AI has is really quite elegant. I'm told this procedure is outlined in the armorers manual which I would like to get my hands on. We'll see if this addresses my issue. Along with any unauthorized adjustment to the rifle, you perform this at your own risk.

There are two set screws (one of top of the other) in the cocking piece. They take the same size wrench. The longer pointed one goes in first.

The firing pin is threaded through the cocking piece and you can turn it to adjust the protrusion. You can turn it by placing your fingers as shown. Half a turn will adjust protrusion by approx .010 - 0.012. You can remove the firing pin entirely by simply screwing it out. By removing the firing pin you will understand how the set screws work and why you have to adjust it half a turn at a time. In addition, you can't turn the firing pin more than one full turn past the factory setting or else the set screws will not work properly. You'll understand what I mean when you take it apart and examine it.

I took two pieces of virgin Lapua brass, primed them with CCI BR2 primers, and then fired them. There was NO powder or bullet. The cartridge on the bottom represents the factory setting. The one of the top represents one half turn of the firing pin inward. It's hard to see in the photo, but the factory setting really stretches the primer cup almost cutting into it where the tip radius meets the shaft. The adjusted setting looks more than adequate. If I turn the firing pin another half turn inward the primer will not fire.

I wanted to make sure that the reduced protrusion would not cause ignition problems. I took primers and seated them hard to the point they were flattened out and were .010 - .012 below flush. I used virgin brass which is set to minimum headspace. It fired using a CCI BR2 and a CCI #34 which is considered a less sensitive military grade primer.

I do not know which setting meets factory specs and AI will not share this information. That's their right. To their credit, they said they would examine the bolt and adjust protrusion. Personally, it's nice to have the flexibility of making these adjustments in the future.

Update: I found out from a well informed source who shall remain anonymous that the firing pin protrusion spec is .042 - .058. When you take the measurement make sure the bolt shroud is hanging in the air and not pressed up against a table.

THANKS!!!!!! You helped us solve a BIG problem!

 

[Jdun91764]

I know this is late in the game (by like 6 years) but I am shooting an AI AX with this problem especially with 300 Norma Mag, 338 Norma Mag and 33XC (David Tubbs Cartridge).

I had LRI (Long Riffles Inc.) Bush my AI bolt- I am assuming he will also adjust the protrusion. If not- then I will (thanks for the Info - that was outstanding). Ill post how things work out- I should have it back in 1 more week.

I was pushing 300 Grain bullet to about 2870 Fps with 33XC when primers were pierced (not blown- pierced). Also piercing primers can damage the firing pin and bolt face with the hot plasma jet that is created. I have had it happen to the pin- believe me. Tubbs said he gets upwards of 3200 FPS so obviously it is short - if I get to around 3050-3100 that will be enough for me- I want to hit the 2 mile mark. I am hitting pretty consistently in the high desert here in the Democractic Republic of California- with the 300 Norma. I wanted something to go to 2k, then 2,500, 3K and then the magic 3,500 Meter mark.

Thanks for reading-

JD