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Head-scratcher of the week, freebore coming up very short.

LVLAaron

Gold $$ Contributor
I have a couple of guys with FTR barrels that share a reamer that they keep with me. Very boring team reamer .168 freebore etc.

One of the guys switched to a new brand of barrel (still one of the big 3). I send him home, he calls: "Hey, the freebore in this thing is like 70 thou shorter than before, what gives?"

Other than a barrel with a much tighter bore diameter than he's used to from the other manufacturer... What could cause this? The reamer did other barrels at the same time, never left the reamer holder, those barrels are fine.

I know bore size can change effective freebore... but 70 thou shorter seems like a lot.
 
Hi Aaron,

I just ran into the same thing. In measuring the reamer, I found that the freebore portion of the reamer had worn (diameter-wise) by about 0.0006". Enough to cause the bullet to not slide up into the leade.
I fixed it by running a throater into it.
You might measure your reamer.

Hope you find this useful.

Frank
 
Hi Aaron,

I just ran into the same thing. In measuring the reamer, I found that the freebore portion of the reamer had worn (diameter-wise) by about 0.0006". Enough to cause the bullet to not slide up into the leade.
I fixed it by running a throater into it.
You might measure your reamer.

Hope you find this useful.

Frank

Maybe... The same reamer did other barrels on the same day that came out correct.
 
I have a couple of guys with FTR barrels that share a reamer that they keep with me. Very boring team reamer .168 freebore etc.

One of the guys switched to a new brand of barrel (still one of the big 3). I send him home, he calls: "Hey, the freebore in this thing is like 70 thou shorter than before, what gives?"

Other than a barrel with a much tighter bore diameter than he's used to from the other manufacturer... What could cause this? The reamer did other barrels at the same time, never left the reamer holder, those barrels are fine.

I know bore size can change effective freebore... but 70 thou shorter seems like a lot.
At such a shallow angle bore diameter is very critical. Or possibly there is a burr that kicked up giving him a false reading of the actual freebore. How meticulous are his reloading skills? Maybe time to break out the bore scope. Just a few things to ponder. Keep us posted.
Paul
 
Same lot of bullets as before? I've seen this happen when the freebore diameter on the reamer wears out and causes the bullets to touch sooner, but if other barrels from the same day are okay that might not be it. Did you check bore diameter on the barrel when it was chambered? Could potentially be user error, maybe his calipers are whacky or not zeroed out. I often see the odd and random issues be human errors lol, not pointing fingers but we are all guilty to some degree.
 
How meticulous are his reloading skills?
He generally whoops everyones ass with a 600-40+ x count at mid range.

I'm confident the chamber is straight. I scope them, lands look even and "sharp". Reamer still sharp as a cats claw.

I still have the 1 inch I cut off the ends of the barrels... .300 pin fits perfectly, but we'd expect the end to be flared a little bit from lapping.


This is in two barrels, btw.


I'll have them in the shop this weekend.
 
Did the barrel in question seem to cut the same as the others Did you notice anything different when you cut the chamber
 
Is he using the Stoney Point/ Hornady tool or the stripped bolt method to check? Wouldn't hurt to mic the bullet he's using to check.
 
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If you hurt the reamer in a few barrels you need to seriously reconsider your methods. They do wear but it takes a lot of barrels for that to happen. It wont just do it from one barrel to the next. Reamers last at least 50 chambers in a worst case if your handling them right. Many go over 100 before needing replacement due to freebore diameter issues.
 

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