Gunsmithing Tight Bore Barrel

[l115a3]

Tight Bore Seat Depth



I just received 2 rifles from local gunsmith. Both were build on Stiller Tac 30.

• Bartlein Barrel 5R HV 1:10 tw (.300/.308 Bore)

• Bartlein Barrel 5R M24 1:11.25 tw (.299/.308 Bore)


Both barrel were chamber with the same reamer PTG F-TR .342"nk , .168 fb with 1-30

The suffer problem that I got from different in bore diameter was their Seat Depth to touch the land.


(.300/.308 Bore)
168 SMK
COAL = 2.900" , CBTO = 2.325"
175 SMK
COAL = 2.910" , CBTO = 2.325"
175 LRBT
COAL = 2.990" , CBTO = 2.329"


(.299/.308 Bore)
168 SMK
COAL = 2.770" , CBTO = 2.200"
175 SMK
COAL = 2.780" , CBTO = 2.210"
175 LRBT
COAL = 2.890" , CBTO = 2.226


Do you have an experienced of different in bore diameter?

The smaller of .001" bore will affect these huge number of Seat Depth around .100"?

 

[ShtrRdy]

I would think the difference in OAL is due to the cutting of the chamber and not the difference in minor diameter. I think that would imply that the headspace is different between the two. You would have to fire a few rounds through each and then measure the head space on the fired cases.

 

[Aeon1]

Tight Bore Seat Depth



I just received 2 rifles from local gunsmith. Both were build on Stiller Tac 30.

• Bartlein Barrel 5R HV 1:10 tw (.300/.308 Bore)

• Bartlein Barrel 5R M24 1:11.25 tw (.299/.308 Bore)


Both barrel were chamber with the same reamer PTG F-TR .342"nk , .168 fb with 1-30

The suffer problem that I got from different in bore diameter was their Seat Depth to touch the land.


(.300/.308 Bore)
168 SMK
COAL = 2.900" , CBTO = 2.325"
175 SMK
COAL = 2.910" , CBTO = 2.325"
175 LRBT
COAL = 2.990" , CBTO = 2.329"


(.299/.308 Bore)
168 SMK
COAL = 2.770" , CBTO = 2.200"
175 SMK
COAL = 2.780" , CBTO = 2.210"
175 LRBT
COAL = 2.890" , CBTO = 2.226


Do you have an experienced of different in bore diameter?

The smaller of .001" bore will affect these huge number of Seat Depth around .100"?

"Do you have an experienced of different in bore diameter?" No

"The smaller of .001" bore will affect these huge number of Seat Depth around .100"?" No

The OAL of the .299/.308 bore suggests a reamer with ~.050" freebore. The OAL is along the lines of what you might see with a 95 Palma reamer. Maybe the gunsmith got his reamers mixed up?

 

[ShtrRdy]

I thought of something else. Sometimes when I try to measure the length of a round by seating a bullet into the case with the bolt, I'll pull the bullet out slightly when I remove the round. So now I mark the sides of the bullet with a black permanent marker so that I can see where the case rubs against the bullet. Sometimes I have to use an eye loupe to see the scraping.

So, maybe the bullet is pulling out a little?

 

[Aeon1]

So, maybe the bullet is pulling out a little?

His OAL of ~2.9 with 168/175 SMK's in the .300/.308 barrel is consistent with a reamer in the neighborhood of .168" freebore so that's not likely.

 

[jsthntn247]

You need to bore scope the chamber. Something got jacked up on one of the chambers. .100 difference is a mile off when it comes to chambers. No way the same reamer was used or something went bad wrong on the short one.

 

[tsweetsam]

I also looking proper freebore for .299/.308 barrel


Can use the same spec as normal Chamber?

 

[Aeon1]

I also looking proper freebore for .299/.308 barrel


Can use the same spec as normal Chamber?

Yes

 

[tsweetsam]

just curious why my rifle which chamber with the same reamer got over pressure during shooting factory ammo.

Bartlein 5R 1:11.25"tw .299/.308 barrel

.342" nk, .114" fb with 1-30

Factory Federal Gold Medal 175 SMK

 

[Frank Green]

Tight Bore Seat Depth



I just received 2 rifles from local gunsmith. Both were build on Stiller Tac 30.

• Bartlein Barrel 5R HV 1:10 tw (.300/.308 Bore)

• Bartlein Barrel 5R M24 1:11.25 tw (.299/.308 Bore)


Both barrel were chamber with the same reamer PTG F-TR .342"nk , .168 fb with 1-30

The suffer problem that I got from different in bore diameter was their Seat Depth to touch the land.


(.300/.308 Bore)
168 SMK
COAL = 2.900" , CBTO = 2.325"
175 SMK
COAL = 2.910" , CBTO = 2.325"
175 LRBT
COAL = 2.990" , CBTO = 2.329"


(.299/.308 Bore)
168 SMK
COAL = 2.770" , CBTO = 2.200"
175 SMK
COAL = 2.780" , CBTO = 2.210"
175 LRBT
COAL = 2.890" , CBTO = 2.226


Do you have an experienced of different in bore diameter?

The smaller of .001" bore will affect these huge number of Seat Depth around .100"?

Something is going on but it's not the .001" difference in bore diameter. I just double checked two of my .30cal. rifles. Same chamber reamer used and one barrel is a .299 bore and the other a .300 bore. I got a difference of .010". Might be a difference of .001" or .002" in headspace between the two but that's not going to make a real impact on my .010".

What type of case gauge/oal gauge are you using or should I say how are you doing it to check the o.a.l.?

Later, Frank
Bartlein Barrels

 

[Frank Green]

just curious why my rifle which chamber with the same reamer got over pressure during shooting factory ammo.

Bartlein 5R 1:11.25"tw .299/.308 barrel

.342" nk, .114" fb with 1-30

Factory Federal Gold Medal 175 SMK

First round fired with the over pressure or did you fire several rounds?

Changing the bore size will not have a huge impact on pressures but changing the groove size will.

Also changing the freebore diameter, length of the chamber specs. can raise pressure higher as well.

Did you shoot a different lot of ammo or try a different brand?

Later, Frank
Bartlein Barrels

 

[Turd in the Pool]

Both barrel were chamber with the same reamer PTG F-TR .342"nk , .168 fb with 1-30

You're screwing up somewhere or your smith cut one too deep.;-(

If you've already fired them, I'd say it's you. If not, I'd check the headspaces before proceeding. ;-)

 

[Edds]

The smaller of .001" bore will affect these huge number of Seat Depth around .100"?

The most it can affect a 1.5° throat is .0191".

 

[jsthntn247]

The difference in those two numbers is just about the same difference in a f/tr reamer and a 95 palma reamer. I'd say the smith mixed up reamers. I have a 95 palma reamer and asked my smith to throat it out an additional .100. My distance to the lands is 2.324, which is exactly what your seeing.