Please help me understand chamber dimensions...

[JBMK262]

Not all of them...but in particular the neck and freebore.

The rifle I just picked up was chambered with a 223 Remington Match chamber reamer. I was told that the neck dimension is .253" and that is has 0 freebore.

Typically when loading for my Service Rifle I've always used LC brass, unturned necks, and a Redding S die with a .245 bushing. All of the barrels were White Oaks and chambered with a 223 Wylde reamer. Shot **** better than I could (darn standing slung at 200 with irons and aging eyes).

So in this new Remington Match chamber it's my understanding that the throat is right there at the end of the case mouth...and the lands right there too. So seating to touching the lands will have to be measure for each of my bullets vs. previous loads. From a neck tension standpoint would I benefit from turning my necks and finding a new bushing size to better suit this chamber?

I feel like I'm missing something here and looking for a little guidance on where to learn from.

Thanks!

Jake

 

[bigedp51]

 

[ShtrRdy]

I'm no expert but I think there has to be some amount of freebore.

Try determining where one of your bullets touches the lands. If you have a bullet which has a tangent ogive that might be better to figure this out.

 

[ar10ar15man]

no i have one that is very close to zero
but
without a print yes you are going to have to do some bullet by bullet measuring

 

[L.Sherm]

You could very well have a zero freebore reamer that was set up to run the 40-50gr bullets. You need to figure out how much neck clearance you have now, measure a fired case and then a loaded round that will be close to your clearance subtract .001 for spring back. If it's in the neighborhood of .004-.005 you could give some cases a little clean up and test to see if it shoots better. If there much more clearance than .005 I wouldn't worry about it.

 

[BallisticsGuy]

.253-.224=.029 .029/2=.014.5. Nominal brass neck thickness is from .010-.012. So you'll have ~.002 total clearance.

What it's telling you is that it's got a pretty tight neck but you won't have to neck turn. You will probably also find that your necks last a long time. The 0 freebore means it was basically meant for light bullets. You'd need a longer freebore to run the heavies but that has light bullets jumping across a canyon.

The last chamber I had set up like that had my fired brass coming out with the inside diameter exactly at bullet diameter so there was extremely little working of the brass during neck sizing and my brass lasted a very long time.

 

[243winxb]

I would worry about case trim length.. To long and the bullet gets pinched in the case on chambering. Pressures would be dangerous.

If chamber and trim length are both 1.760" not good.

No neck turning needed.

 

[J E Custom]

The recommendation to measure your chamber was a good one and the only way you will be able to use it safely.

Custom chambers are just that and sometimes the person that is designing the chamber Is ether very skilled in the art of reloading and understands what the effect of his changes are and how to deal with them, or he may be someone that has heard that certain changes in SAMMI chamber dimensions will make it more accurate and make him an expert if he can change the dimensions from what the experts recommend.

You must know what your chamber is and what bullets or range of bullets you intend to shoot and the only way is to measure or have a good smith chase the chamber with a known reamer. I always recommend the use of a SAMMI reamer or a Wylde to be able to shoot 223 or 556 ammo.

J E CUSTOM

 

[JBMK262]

Thanks @BallisticsGuy! Huge help.

Thanks @J E Custom.

I got the reamer print from GA Precision and finally got to talk to them. They are running 223 & 5.56 ammo up to 75/77 grain at mag length with incredible results. Heavier projectiles will need the throat cut.

Another guy has one and is running Hornady 80 grain ELD-M projectiles at mag length with good results.