AR-Stoner 6.5 Grendel barrel short chambered.

[BjornF16]

From Shivesy's thread:

I have 2 Grendel barrels made by McGowen Barrels and I am having issues with them both. Actually I purchased 3 of them but 1 of the 3 seems to be okay. The issue I am having with 1 particular barrel is that I am pulling the bullet away from the unspent cartride when I use the charging handle to unload my rifle. The other barrel can be tough when removing the round but not to the point of pulling bullets from the case. Now this is a little tricky and I will try to explain myself better. I can hand cycle a 10 round mag for both barrels for example and all goes well and everything is fine. Now when I hunt and shoot lets say 5 of the 10 rounds and put the rifle on safe, then drop my magazine with 4 rounds left, here's where the problem starts. I have one more round left in the chamber. This round can be difficult to extract. I have actually pulled the bullet from the case a few times. Sometimes is worse than others. I am using factory grade Hornady A-max or SST 123 gr. ammo. No reloads at all.
I have sent the 2 barrels back to McGowen along with a 10 round mag, 10 SST rounds and a bolt approx. 2 weeks ago and today finally taked with their gunsmith who manufactured these barrels. He says that he used a 6.5 Grendel PTG reamer and the barrels are within specs and he could not duplicate my problem. He seems to be lost at what to do and so do I. He suggested that I have a ammo issue. I disagreed but anyway McGowen suggested that I send more ammo so they can do further test. Any suggestions??

Unless the tooling is measured and inspected against the correct drawing with tolerances included you can only say that you think you have a correct chamber. The alternative is to employ Replicast compound to examine the chamber directly. Cerrosafe while widely used is not the best choice as it does move slightly. Measurement needs to be with an optical tooling comparator. Calipers or even a micrometer will not let you resolve angles or determine any barreling that might be present.

Bingo!!!! Just hung up the phone with Dave at PTG. (Pacific Tool and Gauge) They made the reamer for the Grendel that McGowen used on our barrels. Dave stated that the Grendel reamers are made to SAMMI specs but the specs drawings are wrong in his opinion. To tight of tolerance. Dave also stated that he has heard of many many case of bullets being torn from the case when this reamer is used. When the barrel throat gets just the slightest of carbon fouling in it the bullet sticks. As soon as I said Grendel reamer Dave new exactly what I was talking about. The Grendel is a double throated reamer and he said to use a .264 LBC reamer and that reamer works just fine and much better with the Hornady Grendel ammo because this reamer uses a parallel throat. *Dave also stated that one could use a uni throat reamer and that reamer would open the throat a bit and probably solve the problem I am having.

The SAAMI spec reamer has plenty of clearance, it was designed to be extremely tolerant of bullet design, to the extent that many accuse it of being a machine gun chamber. The tolerance for the reamer is not specified within SAAMI only the minimum chamber size. The tolerance is the toolmakers descision.

The chamber is set to allow the guns to run excessively dirty and the carbon fouling deposits have clearance.

Hornady ammunition and the 123 Amax was designed for the Grendel chamber. Hornady is the SAAMI sponsor for the Grendel.

You have just found that you do not have a (correct) Grendel SAAMI chamber.

Shocker!...it wasn't AA factory ammo. Things that make you go "Hmmmm"

BTW, didn't Steve Satern say he was using a PTG reamer?