Author Topic: Federal 75 TMJ won't chamber  (Read 287 times)

Offline TX0303

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Federal 75 TMJ won't chamber
« on: January 18, 2019, 01:54:24 PM »
Just completed a build using one of Constructor's SAAMI spec barrels. I bought some Hornady 88ELD-M and Federal 75TMJ for testing. The Hornadys chamber and cycle just fine. The Federals will not allow the bolt to close properly. I measured the CBTO and it averages 1.746. Is that the normal measurement for the Federals or did I get an early out of spec lot?

Offline Hammerhead

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Re: Federal 75 TMJ won't chamber
« Reply #1 on: January 19, 2019, 10:44:39 AM »
Hmm. Is it very hard to get the bolt back open? Also can you tell if the bullet is being pushed back into the case at all?

Offline TX0303

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Re: Federal 75 TMJ won't chamber
« Reply #2 on: January 19, 2019, 02:27:16 PM »
The first one I tried to load I just let the bolt fly closed. It was hard to get the bolt back open and I had to bump the stock on the ground. That round measures a little longer than the rest because I assume the bullet was stuck in the lands and pulled out some upon extraction. I tried a few others with the upper separated and pushing on the BCG with my thumb. All no go.

Offline Hammerhead

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Re: Federal 75 TMJ won't chamber
« Reply #3 on: January 19, 2019, 04:29:09 PM »
You're right I think that they are jamming very hard into the lands. I don't have any experience with the factory ammo.
The only 75gr that I use are Berger VLD's and they measure 1.826 in my chamber that I know is way wrong. Perhaps some
of the guys with experience with the federals will chime in or you could pm constructor, he can tell you for sure.


Edit:
In my data I came across CBTO for Barnes 78gr TSX's. They measure 1.788 to the lands, pretty close to what you're
getting. They are a tangent style ogive bullet that are much closer to the lands in my very out of spec chamber vs. the
secant style of the VLD's. Not knowing what style bullet the federal ammo is I bet it is old out of spec.
« Last Edit: January 19, 2019, 04:46:10 PM by Hammerhead »

Offline TX0303

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Re: Federal 75 TMJ won't chamber
« Reply #4 on: January 26, 2019, 06:47:53 PM »
I bought a .224 pin gauge and modified case to measure freebore, which came out to be 1.704.

Offline Hammerhead

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Re: Federal 75 TMJ won't chamber
« Reply #5 on: January 27, 2019, 08:01:10 AM »
If you are measuring the ammo at 1.746 and your chamber at  1.704 you have the answer, the ammo is long and you are
for sure jamming them into the lands.