Gunsmith question. Short throat.

[robtattoo]

I managed to get to the range today with my Ruger American .223 shooting 77gn TMKs. I'd pre-loaded a bunch for my old Savage, plus a few test rounds. All were loaded to the same length of 2.414" COAL. Longer than SAAMI spec, but well within the mag length (2.55")
However at 2.414" I'm jammed into the lands. Not touching, but "damn this bolt is hard to close" jammed (I need to measure) Accuracy was absolutely spectacular at well under an inch for 5 separate 5 round groups, but I was seeing some pretty disconcerting pressure signs (cratered & flowing primers)

I'm giving serious consideration to having the throat lengthened. I know I could load to chamber length, but I'm giving up a ton of case room that I'd much rather utilize.

Could anyone recommend a Smith to do the work, and if anyone has had this done, a rough idea of what it would cost?

 

[Salmonchaser]

Boy, before I did something as dramatic as changing the throat I would simply try shortening the coal a few thousands first. Ran into the same thing with my 338 Jarrett. High pressure tight to the lands and great accuracy backed off just a little and pressure signs went away. Still had sub 1/2 accurac.

 

[robtattoo]

I just did a quick & dirty chamber measure (bullet jammed into the chamber & measured from the crown, then crown to bolt face)

I get a consistent measurement of 2.236" COAL with 77gn TMKs. That's terrible. My OAL is 2.416 so I'm into the lands by 0.178"! That's over a tenth of an inch (2.54mm in Catholic) I couldn't even load them to AR mag length at that measurement.

This throat gotta go.

 

[RMM]

Gotta hate a shallow throat

 

[MidGAHunter]

Gotta hate a shallow throat

There's a joke in there somewhere...

 

[RMM]

There's a joke in there somewhere...

Yeah it was meant to be a double entendre haha

 

[Salmonchaser]

Now I understand.

 

[Wrench]

Something doesn't sound right. At .17" you should be pushing the bullet into the case and or pulling it on extraction.

What was the process for determining length?

 

[eoperator]

Just put a new bartlein barrel throated for 77's on my 223 it gained about 50-75fps over the old barrel. A powder with less bulk may get enough to forget about throating your barrel. That's up to you if the juice is worth the squeeze.

 

[robtattoo]

Something doesn't sound right. At .17" you should be pushing the bullet into the case and or pulling it on extraction.

What was the process for determining length?

Bare bullet pushed into the throat until it hits the rifling & stops. Hold on place with small Allen wrench. Insert cleaning rod with flat face insert into the muzzle until it contacts bullet tip. Mark rod.
Remove bullet, insert bolt & leave cooked on empty chamber. Reinsert rod into MySpace until it stops & mark.
Measure distance between 2 marks.

I inserted & extracted 1 live round that was over crimped (setting up dies in my new press) & it shows long rifling marks on the shank.

 

[robtattoo]

Just put a new bartlein barrel throated for 77's on my 223 it gained about 50-75fps over the old barrel. A powder with less bulk may get enough to forget about throating your barrel. That's up to you if the juice is worth the squeeze.

24gn of Tac. It's ever so slightly compressed but I can't imagine there are many less bulky powders!

 

[Wrench]

Try this, take a fired case and new bullet. Place a small bit of locktite in the neck of the case. Insert the bullet into the case and close the bolt.

Let sit to cure.

There's a lot of variable in measuring with the oal tools and your method....but if you are that short throated.....it'll give you a solid number to work with.

 

[Wrench]

Obviously do not let the locktite ooze out of the case.

 

[sndmn11]

Bare bullet pushed into the throat until it hits the rifling & stops. Hold on place with small Allen wrench. Insert cleaning rod with flat face insert into the muzzle until it contacts bullet tip. Mark rod.
Remove bullet, insert bolt & leave cooked on empty chamber. Reinsert rod into MySpace until it stops & mark.
Measure distance between 2 marks.

I inserted & extracted 1 live round that was over crimped (setting up dies in my new press) & it shows long rifling marks on the shank.

Wouldn't you need to add in the distance from ogive to bullet tip?

 

[eoperator]

24gn of Tac. It's ever so slightly compressed but I can't imagine there are many less bulky powders!

24g of tac is over book max, if you need more velocity than that a 22-250 will do it safely.

 

[robtattoo]

Wouldn't you need to add in the distance from ogive to bullet tip?

Nope. COAL is COAL. Ogive measurement would give me a distance from bolt face to lands, if the bullet is jammed 0.178" into the lands, the difference between my ogive measurement & measurement to the lands would still show a difference of 0.178"

 

[robtattoo]

24g of tac is over book max, if you need more velocity than that a 22-250 will do it safely.

*sigh. Is it?

But do you know a gunsmith who could lengthen my throat?

 

[robtattoo]

Try this, take a fired case and new bullet. Place a small bit of locktite in the neck of the case. Insert the bullet into the case and close the bolt.

Let sit to cure.

There's a lot of variable in measuring with the oal tools and your method....but if you are that short throated.....it'll give you a solid number to work with.

I just sped that up with superglue.....2.238" 2 thou out the old fashioned way ain't too shabby!

 

[eoperator]

Could try a ptg uni throater. I did that to a 280 of mine with good results.

 

[Wapiti1]

You can do the work yourself with a uni-throater. Ryan Furman has a good video on the prcess: https://www.longrangeonly.com/how-t...t-length-with-a-chamber-uni-throating-reamer/

It's simple, but measure twice, cut once.

Jeremy