07-15-2023, 09:01 PM
I helped a buddy put together a Grendel. Ive done a number of Grendel and 5.56 builds and havent ever had an issue quite like this before. The bullets (spent or live) will jam in the chamber to the point that the charging handle alone cant remove them without excessive force.
We used a bcm stripped upper and an 18 Faxon fluted barrel. The tolerances on the bcm upper were such that we had to heat it with a torch (we did half a dozen rotations) to get the barrel on. (Ive thermally fit other barrels and never had an issue.). After build completion, the rifle wouldnt load a live round fully into the chamber. It would stop 1/2-1/4 from being fully seated in the chamber.
After completing the build and having this issue, we swapped to a different bolt to no effect. Next step, we removed the barrel and put a second identical barrel on the same bcm stripped upper. Put the Grendel back together and still had the same issue despite a new barrel. So we stripped it back apart and this time swapped out the bcm upper receiver with a different brand and this time no thermal fit was required.
Despite a new upper and new barrel the issue persists. The issue wasnt as pronounced as now the bullets will fully seat and it can be fired as essentially a single shot rifle but a live or spent round cannot be ejected even with the charging handle. Again, this issue persists even with a new barrel and a new stripped upper.
Thoughts?
We used a bcm stripped upper and an 18 Faxon fluted barrel. The tolerances on the bcm upper were such that we had to heat it with a torch (we did half a dozen rotations) to get the barrel on. (Ive thermally fit other barrels and never had an issue.). After build completion, the rifle wouldnt load a live round fully into the chamber. It would stop 1/2-1/4 from being fully seated in the chamber.
After completing the build and having this issue, we swapped to a different bolt to no effect. Next step, we removed the barrel and put a second identical barrel on the same bcm stripped upper. Put the Grendel back together and still had the same issue despite a new barrel. So we stripped it back apart and this time swapped out the bcm upper receiver with a different brand and this time no thermal fit was required.
Despite a new upper and new barrel the issue persists. The issue wasnt as pronounced as now the bullets will fully seat and it can be fired as essentially a single shot rifle but a live or spent round cannot be ejected even with the charging handle. Again, this issue persists even with a new barrel and a new stripped upper.
Thoughts?