Short Throat - Good Thing or Bad Thing

[Scalce]

Well I finally got all the pieces to my 300 Whisper build and then the site goes down for a few weeks.



I'm glad it's back up so I can ask all sorts of questions.

I received a barrel that seems to have a very short throat.

I was banging my head against the wall trying to figure out why my rounds would not chamber and I kept looking to the cases.

It turns out that most of the bullets seated to the recommended length would jam into the lands.

I know this is typically beneficial for bolt guns or single loading semi's but is it still good for loading a semi through mags?

Here are some estimated OALs (I need to get a good ogive comparitor):
150 gr FMJ BT - 2.115"
168 gr milsurp BTHP - 2.127"
175 gr milsurp BTHP - 2.1"
208 gr A-Max - 2.2"
220 gr SMK - 2.227"

What kind of pressure curve/gas issues will I run into since I will have less internal space and therfore may have lower charge weights?

[sha-ul]

to me, it seems a bit dangerous being that much non-standard. can you have a local gunsmith, or the manufacturer touch up the throat?

[Scalce]

Originally Posted by sha-ul

to me, it seems a bit dangerous being that much non-standard. can you have a local gunsmith, or the manufacturer touch up the throat?

Not sure something can be non-standard when there are no standards.

It is definately not the norm, at least by what I have read but someone did post on another board that they do have a few custom barrels with short throats.

[pomofo]

My M1S upper was short-throated also. I bit the bullet and bought Quickload.

[Scalce]

Originally Posted by pomofo

My M1S upper was short-throated also. I bit the bullet and bought Quickload.

I have Quickload so that's not an issue.

Did you have any issues with pressure or cycling?

I know your upper is a carbine gas length so it is different then mine but still curious.

What do some of your OALs look like?

[Scalce]

Well I figured out part of my issue.

One - I'm a dope and the chamber gauge is a just a case gauge. There actually seems to be some unfinished drilling which is what I thought was the throat.

Two - Even though LC brass resizes and fits in the gauge, the shoulder still gets jammed in the rifle's chamber and the firing pin will not ignite the primer. Actually most of the time the case will stay stuck in the rifle and the extractor will slip right off.


Well I guess I will just have to stick with commercial brass but at least I can load to 2.25" now.

[sha-ul]

Originally Posted by Scalce

Not sure something can be non-standard when there are no standards.

It is definately not the norm, at least by what I have read but someone did post on another board that they do have a few custom barrels with short throats.

That's what i was getting at, that it was outside of the normal practice, even though there may not be an official standard

[Scalce]

Originally Posted by sha-ul

That's what i was getting at, that it was outside of the normal practice, even though there may not be an official standard

See, and you were correct.

Now I need to go prep a bunch of commercial brass.

[pomofo]

Originally Posted by Scalce

I have Quickload so that's not an issue.

Did you have any issues with pressure or cycling?

I know your upper is a carbine gas length so it is different then mine but still curious.

What do some of your OALs look like?

Some of the OALs I settled on are:

220 & 240 SMK - 2.145"
200 Hornady RN - 2.000"
175 Berger VLD - 2.245"
168 Prvi HPBT - 2.260"
155 Nosler CC - 2.165"
150 Hornady FMJ - 2.135"
145 Wideners M80-style - 2.200"

I use Accurate 1680 for everything from 100 to 240 grains, H110 was too hot for the carbine system. The only problem is that the heavy SMKs won't lock the bolt back no matter how hot I load them. I've loaded them to what Quickload estimates as 55000psi and they'll eject more or less regularly but never activate the BHO. The (what I estimate to be) subsonic loads won't even eject the brass. But seeing how much longer you're able to load them, I'll have to check mine again to see if I can't load them longer. When I encountered the first ones jamming the lands I just seated them .020" to .030" deeper and kept checking until they wouldn't jam, then took another .015" off to account for any anomalies.