Issue with throat depth

[Missalot]

I had a .308 built with a Bighorn action/Bartlein barrel. I have had issues with factory 168g SMK GMM sticking in the lands as well as my 175g SMK seated to 2.800 (which is what Sierra recommends). On the other hand, Win Silvertip hunting ammo loads with no issues whatsoever.

I sent the barreled action back to the builder to check the throat and he ran the go/no go gauges through it and said there are no problems, it is in spec, and he is going to ship it back. When I asked about the throat depth, he suggested seating the bullet deeper than 2.8. Or for $75, he would ream the throat deeper if I provide him with 3 dummy loads.

When I load these rounds that stick, the bolt closes snuggly without much effort. It requires a good lick with my hand to open the bolt. I'm tired of getting a handful of powder when the bullet sticks and I having to tap the bullet out.

My questions are when the smith reams the chamber, how do they decide how deep to cut the throat and go/no gauge doesn't measure the throat depth, does it?

I'm not very happy not being able to load my 175g smk, my go to bullet, to 2.800, so I guess I'll send him my dummy loads and $75.

 

[Supersubes]

99% of the time the freebore(what youre calling throat depth) is ground into the reamer, so its a fixed dimension. It takes a separate throating reamer to run it deeper.


Headspace/chamber depth is a totally separate thing, and has nothing to do with freebore.

Is the 168 GMM ammo a priority, or the handload? If handload, you need to accurately measure where the lands are, and determine from there if merely seating deeper solves anything. If seating at 2.750 gives you .025 of jump for example, great, run it. You lose nothing. If it must shoot the 168 gmm, send it back to have him run the throat out.

 

[BuildingConceptsllc]

I had a .308 built with a Bighorn action/Bartlein barrel. I have had issues with factory 168g SMK GMM sticking in the lands as well as my 175g SMK seated to 2.800 (which is what Sierra recommends). On the other hand, Win Silvertip hunting ammo loads with no issues whatsoever.

I sent the barreled action back to the builder to check the throat and he ran the go/no go gauges through it and said there are no problems, it is in spec, and he is going to ship it back. When I asked about the throat depth, he suggested seating the bullet deeper than 2.8. Or for $75, he would ream the throat deeper if I provide him with 3 dummy loads.

When I load these rounds that stick, the bolt closes snuggly without much effort. It requires a good lick with my hand to open the bolt. I'm tired of getting a handful of powder when the bullet sticks and I having to tap the bullet out.

My questions are when the smith reams the chamber, how do they decide how deep to cut the throat and go/no gauge doesn't measure the throat depth, does it?

I'm not very happy not being able to load my 175g smk, my go to bullet, to 2.800, so I guess I'll send him my dummy loads and $75.

There's a thread where I asked, got answers, then did the operation and posted about it on ghe free bore of my 308. I will try to find it but it's in my post history a few weeks ago. It will help you, as this is what you need done to do what you want to do.

 

[BuildingConceptsllc]

Advice on chamber for 308

So, I bought this barrel from a nice guy on here, and its a sweet one too. I was going to start the load work up process and I noticed the chamber seems to have been cut different than my last 308 barrel that BMP did for me. Distance to lands (175smk)-BTO- 2.20 (it actually seems to be under...

www.snipershide.com

There ya go

 

[Missalot]

Advice on chamber for 308

So, I bought this barrel from a nice guy on here, and its a sweet one too. I was going to start the load work up process and I noticed the chamber seems to have been cut different than my last 308 barrel that BMP did for me. Distance to lands (175smk)-BTO- 2.20 (it actually seems to be under...

www.snipershide.com

There ya go

Thank you. I guess I'll just pay another $75 and turn my gun from a custom to a super custom.

 

[BuildingConceptsllc]

Thank you. I guess I'll just pay another $75 and turn my gun from a custom to a super custom.

If you have someone who's competent and will do it for that it's not a bad way to go. Renting the reamer will cost you $50 by itself. Just figure out exactly where you want to touch the lands at for what you want to shoot

 

[fdkay]

If it won't chamber factory FGMM 168's, then it is an issue the smith should fix for free.
He probably needs a new reamer.

 

[b6graham]

seems odd to me he would have used a reamer with such a short freebore that a standard 2.800" with 168/175gr bullet (factory ammo) is jammed

he should fix his own fuck up. not charge you more

 

[Feniks Technologies]

Commenting without knowing the entire story. But…..

FGMM is the standard .308 ammo. I’d expect a smith to either let a customer know he’s using a reamer that doesn’t fit that or somehow annotate it in the website or order form. (Obviously if they did, then it’s on you)

 

[Terry Cross]

@Missalot , Do you know exactly what .308 Win chamber was supposed to be cut in your new Bartlein?

Ask your builder to email you the dim print for the reamer he used.
Check the throat datum on the print against the touch point of the ogive on your 168MK ammo to see if </= to the print.

Either your builder used a match variant reamer with super short lead or his reamer is worn in the lead/throat area.

H.S.S. reamers are especially prone to dulling and wear in the part that cuts the neck, lead and throat.
The issue here is not that the worn reamer cuts a shorter lead but rather that it cuts a smaller lead diameter.

Depending on the chamber reamer specs, a finished chamber that is true to the original specs can have as little as 0.0002 to 0.0004" clearance for the bullet to pass through the lead and engage the throat on some "Match" variants. Ex: Palma 95'

If the reamer is dull/worn, the finished chamber can result in a throat diameter that is actually touching the bullet's bearing surface.
If this issue exists, you may have issues right away or most certainly will once the chamber is fouled.
This issue will stay hidden on many barrels until the shooter needs to unload a live round, at which point you have the fun party with spilled powder and a stuck bullet.

If this is the issue and you are thinking about living with it, don't.

Ask for the dim print.
This will be quick, free and will lead you down the correct path to happiness.


./

 

[canezach]

Thought this thread was about my ex wife. Carry on

 

[Rubicon Precision]

Like Mr. Cross said, it’s likely a worn reamer resulting in a freebore diameter smaller than the bullet.

I find it hard to believe a builder would use a reamer spec’d with a freebore that won’t chamber factory FGMM unless specifically requested.

Either way, I’d expect the builder to resolve it without charge, unless you requested something shorter.

 

[Terry Cross]

. . . . and go/no gauge doesn't measure the throat depth, does it?

Correct. It does not.


./

 

[Baron23]

I'm def not one of the experts posting in this thread but my thoughts are:

1. If it won't chamber FGGM 168 then the chamber is fucked up as it is, as said, the gold standard and WTF....its top qual factory match ammo, right? If you didn't specify a custom chamber, would you not expect a SAAMI chamber which therefore should easily chamber really any decently made factory ammo?

2. I wouldn't pay him another nickel for fixing this error

3. You sure you want to go back to the same smith who, after you told him bullets where jammed into the lands, puts a go/no go gauge in the chamber and declares victory?

 

[Frank Green]

@Missalot , Do you know exactly what .308 Win chamber was supposed to be cut in your new Bartlein?

Ask your builder to email you the dim print for the reamer he used.
Check the throat datum on the print against the touch point of the ogive on your 168MK ammo to see if </= to the print.

Either your builder used a match variant reamer with super short lead or his reamer is worn in the lead/throat area.

H.S.S. reamers are especially prone to dulling and wear in the part that cuts the neck, lead and throat.
The issue here is not that the worn reamer cuts a shorter lead but rather that it cuts a smaller lead diameter.

Depending on the chamber reamer specs, a finished chamber that is true to the original specs can have as little as 0.0002 to 0.0004" clearance for the bullet to pass through the lead and engage the throat on some "Match" variants. Ex: Palma 95'

If the reamer is dull/worn, the finished chamber can result in a throat diameter that is actually touching the bullet's bearing surface.
If this issue exists, you may have issues right away or most certainly will once the chamber is fouled.
This issue will stay hidden on many barrels until the shooter needs to unload a live round, at which point you have the fun party with spilled powder and a stuck bullet.

If this is the issue and you are thinking about living with it, don't.

Ask for the dim print.
This will be quick, free and will lead you down the correct path to happiness.


./

Terry saved a few of us from writing a small book also! You said everything I was going to say!

Thanks Terry!

Any fitting we do and if the customer asks we supply a copy of the chamber reamer print. The reamer we used is referenced on the order typically unless it's a customer supplied tool.

As Terry pointed out about the throat on the reamer....this part of the reamer even if you use a roughing tool...the finish reamer the throat is always cutting and is typically the first thing that will start to cut undersize dimensionally. Also as it gets dull it will start to smear instead of cut and leave a burr over in the throat as well.

Later, Frank
Bartlein Barrels

 

[Missalot]

@Missalot , Do you know exactly what .308 Win chamber was supposed to be cut in your new Bartlein?

Ask your builder to email you the dim print for the reamer he used.
Check the throat datum on the print against the touch point of the ogive on your 168MK ammo to see if </= to the print.

Either your builder used a match variant reamer with super short lead or his reamer is worn in the lead/throat area.

H.S.S. reamers are especially prone to dulling and wear in the part that cuts the neck, lead and throat.
The issue here is not that the worn reamer cuts a shorter lead but rather that it cuts a smaller lead diameter.

Depending on the chamber reamer specs, a finished chamber that is true to the original specs can have as little as 0.0002 to 0.0004" clearance for the bullet to pass through the lead and engage the throat on some "Match" variants. Ex: Palma 95'

If the reamer is dull/worn, the finished chamber can result in a throat diameter that is actually touching the bullet's bearing surface.
If this issue exists, you may have issues right away or most certainly will once the chamber is fouled.
This issue will stay hidden on many barrels until the shooter needs to unload a live round, at which point you have the fun party with spilled powder and a stuck bullet.

If this is the issue and you are thinking about living with it, don't.

Ask for the dim print.
This will be quick, free and will lead you down the correct path to happiness.


./

No, I I requested .308 Win. chambering, nothing more or less. I will request a dim print.