Freebore dimension question

[31moppie]

First post. Hi everyone and thank you for all of the info I have gotten from this website.

I recently purchased a Savage 12 LRP in .243 Win and am just starting to reload my own ammo. My first step was to determine distance to the lands in order to establish bullet seating depth. Well I didn't get very far before I ran into a problem. The ogive of the bullet is jamming into what I call the freebore area of the throat. In other words, the cylindrical part of the throat immediately forward of the chamfer leading from the neck area to the beginning of the chamfer of the rifling which I believe is call the leade area. It appears that this freebore area is the same diameter as the groove diameter approx .2425". The Hornady 105gn bullets I want to use are .243 in diameter and so won't go in far enough to contact the lands without considerable force. I reduced the diameter of one bullet to .242 and I am able to touch the lands easily. My question is this: is the freebore area supposed to be sized like this or should it be larger/tapered?

Just as a side note I have some 75gn V-Max bullets where my COAL measurement was actually 5 thou less than the factory round with the same bullet and sure enough, when I chambered a factory round and removed it without firing, it had visible ring around the bullet ogive.

 

[Catpop]

Looks like a cerrosafe issue

 

[Axis II]

Welcome to savage rifles! My savages all need seated short than book OAL and some factory rounds give me marks when i color the bullet and chamber them.

 

[RussellC]

I have different luck with different bullets. With my Savage 12FV rifle, this isn't such a problem with the heavier, longer skinnier bullets. I can seat the SMK 69 grain much longer, for instance than the 52 and 53 grain SMK...they seem more squat and don't fit s long as the 69 grainer. I never really thought about it stopping in the "freebore" but you are likely right. I suppose the one way to do it is use a new match barrel, and pay a gun smith to set it back and cut the chamber to your specifications? Or recut the chamber in the existing barrel?

Russellc

 

[243winxb]

larger/tapered

It tapers from .246" and is .177" long. By the SAAMI chamber drawing. The 243 win doesnt have a true free bore.

Does factory ammo chamber ok? If it does, use a shorter COL for your 105 gr bullet reloads.

 

[31moppie]

It tapers from .246" and is .177" long. By the SAAMI chamber drawing. The 243 win doesnt have a true free bore.

Does factory ammo chamber ok? If it does, use a shorter COL for your 105 gr bullet reloads.

Yes, it chambers factory ammo fine and I could shorten the COL for the 105 gr bullets but wanted to experiment with different jump distances.

Thanks for the link. I hadn't seen the drawing for the chamber which helps me greatly. I calculated from my measurements that I was hitting the freebore approx 50 thou from the lands and if it is .177" long then I'm not hitting the beginning of it like I thought I was. Does this mean that if I seat my bullets so that they touch the freebore that they are jammed or am I running a 50 thou jump? Is it a big deal for a gunsmith to open up the freebore slightly so that I can touch the lands if I want to?

 

[243winxb]

I was hitting the freebore approx 50 thou from the lands

Free bores are bullet diameter, to +.001" The 243 win doesn't have a free bore. Its tapered.

For a gunsmith to open it, i think the barrel has to be removed??

See how the 105 gr bullet shoots ,as is. Barrel twist rate needs to work with the length of the bullet.http://www.bergerbullets.com/twist-rate-calculator/

 

[Blue68f100]

Gunsmith should have what is called a throating reamer. All it does is cut the freebore & leads. I have one for 223R/5.56. Used it to adj a min spec chamber on a barrel I turned so it matched my other rifle .

 

[31moppie]

I will make some phone calls to see if there is a gunsmith close by that has the correct reamer.

 

[243winxb]

The 243 leade will increase with firing over time. About 600 rounds should do it. Its nothing like a 223.

SAAMI
LEADE (LEAD)
That section of the bore of a rifled gun barrel located immediately ahead of the chamber in which the rifling is conically removed to provide clearance for the seated bullet. Also called Throat or Ball Seat.

 

[Demi-human]

Sometimes a chamber will get a hard carbon ring in the throat area. After three hundred or so rounds my twelve F / TR, two-twenty three will begin to chamber very hard. Even with normal cleaning the condition was not resolved. I don't necessarily clean this one often, she doesn't like it.

Every three hundred rounds I take a mop soaked with Remington fourtyX bore cleaner and scrub the throat. Only the throat. And one or two patches to get the cleaner out, but not really to clean the bore, unless she needs it. After that cartridges will fall in and out and there will be no scratches around the bullet just ahead of the case mouth.

Sure would be nice to have a bore scope, huh? Wish I had one! Hope that helps anyway.

 

[Dudedog]

Welcome to THR.
Lots of great people here.

I will make some phone calls to see if there is a gunsmith close by that has the correct reamer.

I don't own a .243 but my first thought would be just seat them a little deeper and see if you can get them to clear. Who knows they might shoot really well with everything as is.
Some guns just have tighter chambers than others, yes the chamber can be changed, but just because it is tight (assuming it's in spec)does not mean you have a "problem" that need to be "fixed".

If the chamber is not within spec, that is a different story.

Looks like a cerrosafe issue

I believe what catpop is suggesting is to use cerosafe to make a chamber cast so you can determine whats going on with the chamber.

 

[quest4perfection]

Just spitballin' here-possibly cover the bullet with magic marker and repeat, taking note the "pattern" or lack thereof? Ran into same issue, as mentioned by others, after approximately 500 rounds. Clean symmetry?

Thoughts, anyone?