Primer Puncture

Phantom30 · July 20, 2019

Been using the recommended ToolCraft NiB BCG in my 22" 6.5 Creedmoor. Got about 120 S&B 140gr FMJ rounds, all same lot, thru it. Started punching the primers during firing, four times in last 8 rounds. What is happening? Measured the pin depth using recommended procedures and found the pin to protrude 0.050" the cited number in the archives for this BCG should be 0.040" so why is it screwing up now?

98Z5V · July 20, 2019

I've only seen that happen on 6.5mm loads when the loads are hot. I've been through it building my .260 Rem loads.

Run your cartridges through a chrono, and see where those hot-ass bastards are at.

What gas system are you running on that 22" barrel?

Edited July 20, 2019 by 98Z5V

Phantom30 · July 20, 2019

Oak Standard AR-10, rifle length. These things are usually fairly tight in the chrono. and you can see they are loaded right up there with those nice little volcano shape primer strikes. This happened at 1600' normally I am firing at 300'MSL think the pressure altitude was enough to juice them up. I might try some other ammo, but I hate using ELDs in this tip eater.

98Z5V · July 20, 2019

10 minutes ago, Phantom30 said:

Oak Standard AR-10, rifle length. These things are usually fairly tight in the chrono. and you can see they are loaded right up there with those nice little volcano shape primer strikes. This happened at 1600' normally I am firing at 300'MSL think the pressure altitude was enough to juice them up. I might try some other ammo, but I hate using ELDs in this tip eater.

Who is Oak Standard? Rifle gas in a 22" barrel is already more dwell time, so your pressures are already up.

Only projectiles I run in my .260 Rem are Hornady 147 ELD-Ms, and it doesn't eat tips.

98Z5V · July 20, 2019

12 minutes ago, Phantom30 said:

These things are usually fairly tight in the chrono.

What's their chrono velocity that you're seeing?

Phantom30 · July 20, 2019

Oak Armament. IL

Standard AR-10 gas tube

Rifle Length

No Chrono at this altitude

2657 near sea level

The ELD will deform slightly when hitting the counter bore or feed ramps, firing fast enough they don't have time enough to recover and it will add nearly a MOA to accuracy

Phantom30 · July 20, 2019

I fire these in my 24" same Gas system at sea level no problem

98Z5V · July 20, 2019

4 minutes ago, Phantom30 said:

Oak Armament. IL

The ELD will deform slightly when hitting the counter bore or feed ramps, firing fast enough they don't have time enough to recover and it will add nearly a MOA to accuracy

WHITE Oak Armament, you mean?...

That second statement, about the ELDs, is BS. Complete BS.

2657fps is the chrono data that you've shot from these 140gr S&B 6.5C loads, yourself? Same lot number through the chrono at 300' MSL, that you just shot at 1600' MSL? That's not even enough altitude difference to make a difference, honestly. That altitude difference will be very, very minor in muzzle velocity.

Phantom30 · July 21, 2019

Not IMHO, tested and verified, its NO BS, Facts jack. Granted the error margin is smaller for the ELD but if you shoot Hornady white tail the SP tips which obturate at 7KPSI. the accuracy is around 7 MOA instead of sub MOA. QED

Questions yes, yes. So if the muzzle velocity and resultant change in pressure is not that sensitive to that small of an altitude change then what is causing the primer punch. Probably fired maybe 700 to 800 of these in various rifles with no problems until now.

98Z5V · July 21, 2019

4 minutes ago, Phantom30 said:

Not IMHO, tested and verified, its NO BS, Facts jack.

Then post your tests and verification. Post your empirical evidence, Jack. Post your proof. Show me the money, post your data. I'm sure Hornady will want to talk to you about it, too.

98Z5V · July 21, 2019

6 minutes ago, Phantom30 said:

Questions yes, yes. So if the muzzle velocity and resultant change in pressure is not that sensitive to that small of an altitude change then what is causing the primer punch. Probably fired maybe 700 to 800 of these in various rifles with no problems until now.

If you would have answered my previous question, I'd probably have an answer for you already.

SAME LOT NUMBER ON ALL AMMO, OR NOT?...

Hopefully, you saw it that time...

DNP · July 21, 2019

Says all same lot in the initial post.

98Z5V · July 21, 2019

6 hours ago, Phantom30 said:

Got about 120 S&B 140gr FMJ rounds, all same lot, thru it.

21 minutes ago, Phantom30 said:

Questions yes, yes. So if the muzzle velocity and resultant change in pressure is not that sensitive to that small of an altitude change then what is causing the primer punch. Probably fired maybe 700 to 800 of these in various rifles with no problems until now.

Also, says this, brother...

98Z5V · July 21, 2019

2 minutes ago, DNP said:

Says all same lot in the initial post.

Hit that one above... ^^^

This is the same guy that talks about the superfine 1/4 MOA adjustments that are superior when using a mil-dot reticle. :thumbup:

DNP · July 21, 2019

Saw it. Saw the super elaborate photo and spreadsheet too. My interpretation of what he has said is that he was shooting a batch of 120 from the same lot and that the last 8 rounds punched 4 primers. The statement about shooting many of the rounds through various rifles is referring to his general use of the round and it has been consistently good for him on other rifles in the past. I pick up a hint of distaste for the ToolCraft BCG that was recommended to him and sense that he is pretty sure it’s the main culprit. I could be wrong, this was just a recap of my perception of the posts.

98Z5V · July 21, 2019

He has a hot box of ammo from S&B, and he's chasing ghosts, trying to blame it on hardware. Not the first time there's been a bad batch of ammo from S&B, with the latest we've heard is the 300BLK jackets coming apart in @jtallen83's suppressor.

What I gained later was that he has a chrono number, but I asked him if he had chrono numbers on what he was shooting. The chrono number he posted was pretty low, for a 140gr 6.5C load - barely middle of the road on powder charge will yeild a velocity number like what he stated. And that chrono number he stated, if real, was 700 or 800 rounds ago, as the info came out from him later.

If he's smart, he'll save some of that ammo that's puncturing primers, and run it through a chrono. 300 feet, 1600 feet - not gonna make the difference he's talking about. We had guns and ammo from sea level (Boston, Mass) shooting at 4600 feet (SV, AZ) with zero issues and no punctured primers.... It's not the elevation, it's not the BCG or firing pin protrusion - the BCG and firing pin protrusion have been teh same this whole time. It's the bad box of hot ammo from S&B, but the OP doesn't wanna hear that.

Now, he'll argue his 1/4 MOA adjustments again, on his mil-reticle scope, tout how superior his "finer" adjustments are - while he sets his digital speedometer in his car to km/h, converts in his head as he drives, just to "stay sharp" on his conversions. He probably uses nothing but metric tools on all his standard hardware, and does the math in his head before he works, just to keep his edge...

My $0.02 on all this mess... He has a hot box of ammo, and doesn't wanna admit it. He wants to find a problem with the gun to explain it. It's the same ammo. It's not the same lot number over 700~800 rounds, unless he bought a few cases at the same time. Even if it's the same lot # - he's shooting a hot box of ammo... :thumbup:

jtallen83 · July 21, 2019

6 hours ago, 98Z5V said:

He has a hot box of ammo from S&B

That seems like an obvious place to start, eliminate the ammo, by the lot number, first, then start looking at the BCG.

7 hours ago, Phantom30 said:

Not IMHO, tested and verified, its NO BS, Facts jack

Please share that info! I have regularly recommended ammo with those "plastic" tips as accurate hunting bullets for AR's and will stop doing that if I see evidence of an issue like that.

Phantom30 · July 22, 2019

OK so you think I have a hot box of ammo. Fair enough. I have been buying them in 500 rounds batches. Now granted that doesn't guarantee they are all the same lot, so'll have to go through what boxes I have left to hard number confirm that.

As for the evidence, I can post it on the tips, it was a chambering drill for the ELDs, because you can't get the tips back to examine if you fire them. The other brand assessments were just based on target results.

OK, test the hot box concept, I Am still at 1600 feet and have some other boxes of S&B 140gr, defense systems 142gr, and Hornady ELDs147gr, in the bag, I can fire with Chrono on all and see what happens. Thanks for the hot box info, a useful starting point.

Patterns of Evidence: extracts from personal range reports:

next same day with HP

Phantom30 · July 22, 2019

same day example

Phantom30 · July 22, 2019

On a previous day this was the result with Hornady white tail, Was using it because it was cheap but was confused by wild results. it is what start the tip symmetry investigation.

Phantom30 · July 22, 2019

This is the Fed Fusion results, same day as white tail. Notice the burr on the tip in one of the four pictured, Not every round gets damage but flyers happen. Not good for consistency. Since the ELD stuff was not range data I'll have to collect it separately here.