Headspace on New Tikka T3x 6.5CM: Go Gauge will not Fit

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FNG
Joined
Jan 18, 2023
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80
Location
Santa Fe, NM
I purchased a new Tikka T3x SuperVarmint chambered in 6.5CM in December and have noticed issues with closing the bolt and opening the bolt on factory and reloaded ammo. In fact, it appears to me that the shoulder in the chamber is cut almost .005" too short. I contacted Beretta USA yesterday, and now have an RMA to return it for service.

Here's the deal:
  • SAAMI spec calls for 1.551"/1.541" chamber headspace
  • Factory Hornady 140gr ELD-X ammo measures 1.534" from cartridge base to .400" dia shoulder datum
  • New Starline brass measures 1.535" from cartridge base to .400" dia shoulder datum
  • Once fired factory Hornady brass and hand loaded Starline brass shoulders are basically unchanged from new. 1.535"/1.536" to shoulder datum.
  • Bolt is tight to close on about 25% of Hornady factory ammo and also reloads.
  • Bolt lift is difficult on close to 75% of Hornady factory ammo and reloads.
  • Bolt is tight to close on once fired brass without bullet which has 1.535"/1.536 measurement to shoulder datum.
I took it to a local gunsmith and the bolt will not close on a GO gauge. That's when I contacted Beretta.

Considering that the minimum SAAMI chamber headspace is 1.541" and that my once-fired case shoulders are only blowing out to 1.536", this indicates to me that the chamber may be cut up too .005" too short (1.541-1.536=.005).

This is so disappointing to me, as I was really excited to begin load development and begin practicing for med-long distance shooting.

I haven't yet tried to full length size the brass to see if I can push the shoulders back any farther, but I'd like this rifle to accomodate factory ammo too.

Am I right to ship it back for repair, or is it better to have a tight chamber and only shoot reloads? This is not my preferance though.
 

pods8 (Rugged Stitching)

WKR
Rokslide Sponsor
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Are you using a Hornady comparator for those measurements? If so they aren't a precision instrument for measuring a chamber, they are a reference measurement for measuring form one thing to the next (IE shoulder bump back).

If the chamber is problematic with factory ammo then absolutely sent back if needed.

I don't understand how it could be tight on reloads though if you're bumping the shoulder back? IE run the once fired through the die and bump the shoulder, check in the chamber if it chambers freely, if not bump it back more. Now in this case don't ignore the short chamber that is problematic with factory ammo but in general be aware its on you to size your reloads properly in the future. :)

I got a 243win tikka that chambers a tad tight on midways dogtown ammo (I bought 450rds on sale for target ammo and a cheap source of brass that could be reloaded 2-3 times and burn out the barrel) but it does chamber and shoots great and once I run that brass through a die when I reload it then its good to go no issues.
 
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FNG
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Santa Fe, NM
Yes. I'm using a Hornady comparator for my measurements.

The reloads were with new Starline brass, and all I did was neck size prior to loading. Before I send the gun for repair, I'm going to see if I can bump the shoulder back on a couple pieces of the once fired brass to see if the die will move the shoulder back far enough to where they will chamber easily.

This exercise will be for my information only and testing of the full length die that I haven't used yet, because my inclination and the group consensus seems to be to ship the gun back for repair.

Everything is new. Gun, brass, ammo, and dies.
 

BrBa

Lil-Rokslider
Joined
Sep 20, 2023
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Sounds like you may have a short chamber. It would be interesting to see how your gunsmith's Go gauge measures on your comparator. Even then, I have been told that not all Go gauges have the same dimensions, brand to brand.
 
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FNG
Joined
Jan 18, 2023
Messages
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Santa Fe, NM
Sounds like you may have a short chamber. It would be interesting to see how your gunsmith's Go gauge measures on your comparator. Even then, I have been told that not all Go gauges have the same dimensions, brand to brand.
Good point. I should have thought of that just to have another point of reference.

Thanks.
 

blkqi

WKR
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Aug 21, 2017
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Not to be impertinent, but have you cleaned the chamber good?
 
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FNG
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Jan 18, 2023
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Santa Fe, NM
I cleaned the new un-fired rifle with a chamber brush and the barrel with patches upon receipt. I used a light coat of Hoppe's on the chamber and light amount of CLP on the bore. Everything indicated that they indeed test fired a few rounds, as patches came out with a small amount out fouling.
 
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