Throating a CZ barrel

[oddjob]

I would like to shoot longer rounds in my Shadow, but am restricted by the barrel. I use Bear Creek 130's and if loaded long it gets caught in the rifling. Has anyone here throated the barrel for longer rounds? Did it affect accuracy at all? Function ok?

thanks

[TeamGE]

I have done the same to a CZ75B. No problems. Call me for more details.

I had a custom reamer made to handle cartridge OAL out to 1.175".

Edited June 4, 2010 by TeamGE

[BMartens]

I have the same problem with my SP-01 and the BBI 130 bullets. In my gun 1.125 is just about all the chamber will handle.

I have also had problems with some other bullets, 147 gr LFP in particular, that will fit the chamber at max length [1.169] but will foul up in the magazines because of the radius. They will hang up on the radius farther down in the mag and cause feeding problems. If you just load 4-5 rounds for cycle testing the work fine. Don't hit the radius until they start double stacking farther down.

The magazines will handle the 130 BBI's at 1.169 but, the chamber is the limiting factor for them.

I have learned to load a full magazine and run them through to be sure the OAL will work in the magazine and the chamber.

I like to load longer too but, I have not had any issues with the BBI's at 1.125 OAL.

[SteelShooten]

Insufficient leade seems to be a common issue with CZ.

I was loading 124gr bullets at ~1.160 and while this fit comfortably in the magazine and would chamber, I ended up in a fight with the (loaded) gun when it came time to unload and show clear because the bullet had jammed in the rifling.

Rather than re-develop a load that works perfectly in a bunch of other guns, I had a machinist cut more leade in my CZ barrel. Nothing really aggressive. I loaded a cartridge out to 1.175 and gave it to him to use as a gauge. He cut a little at a time and measured often.

There were no functional issues that cropped up. The gun runs fine, UASC no longer requires a rawhide mallet.

No apparent difference in accuracy but this gun is used to shoot steel, and doesn't see much paper.

[sig2009]

My Shadow Target and 75B will shoot 115 and 124gn FMJ loaded out to 1.160 with no problem.

[pevadijk]

My Shadow Target and 75B will shoot 115 and 124gn FMJ loaded out to 1.160 with no problem.

But the bullet profile tends to differ between different brands, so you won't be able to load to the same length when you change your make of bullets.

My stainless 75B can take Fiocchi FMJ's to a COL of 1.555, but with most makes I can only achieve 1.14 and with Frontier bullets I can't get past 1.12.

I like to load long since my 9mm Edge likes long ammo and I like to be able to shoot my ammo in all my 9's.

[oddjob]

Just came back from the gun doctor with my CZ barrel. He said the chamber was cut short. I thought he said he had go in 90 thousandths? Either way my truncated cone bullets should be fine now. 90 thousandths sound right?

Edited June 11, 2010 by oddjob

[3gunner]

Ok, let me ask. Do you use a chamber finish reamer for this or is their a special reamer. A bud has 9,40 and 45 chamber reamers. I assume this is trial and error to cut the correct depth, Ny 75 is cut short. I would hate to have a long round lock the gun up.

[TeamGE]

If one has a "short chamber", then the length of the case is restricted from completely entering the chamber and not allowing the barrel to go into lockup. The terms "freebore, lead, throat" all describe the area where the exposed portion of the bullet (in a loaded cartridge), sits when loaded in the chamber. This area can cause problems with being too short (the bullet will make contact with the rifling before the cartridge is fully into battery, or the diameter of the freebore is too small, and the bullet will press fit into it. A properly made "chamber reamer" will cut the chamber and throat areas at the same time. The length of the freebore is a part of the reamer and is not adjustable after the reamer is made. If one needs to cut the freebore only, then a "throating reamer" is used, and depth of cut is controlled to meet the length of your loaded ammo. The diameter of the reamer is set at the time the reamer is made. When we load our ammo to "custom" specs, then it is possible to need custom chamber and freebore dimensions. You will need to know the dimensions of an "off the shelf" reamer to know if it will fix the problem discussed in this thread.

[SteelShooten]

My Shadow Target and 75B will shoot 115 and 124gn FMJ loaded out to 1.160 with no problem.

But the bullet profile tends to differ between different brands, so you won't be able to load to the same length when you change your make of bullets.

My stainless 75B can take Fiocchi FMJ's to a COL of 1.555, but with most makes I can only achieve 1.14 and with Frontier bullets I can't get past 1.12.

I like to load long since my 9mm Edge likes long ammo and I like to be able to shoot my ammo in all my 9's.

+1

I have a battery of things chambered in 9mm, including a 2011, and having one load that works any of them is...well, ideal.

We don't have a good way to describe the curve the nose of one FMJ has compared to another one. Normally it would go unnoticed but in the CZ chamber it can make a difference. Most people do understand bullet and weight and cartridge length though this doesn't quite capture the problem. You might be lucky, like SIG2009, or you may have to come up with a work-around like some others.

[SteelShooten]

Ok, let me ask. Do you use a chamber finish reamer for this or is their a special reamer. A bud has 9,40 and 45 chamber reamers. I assume this is trial and error to cut the correct depth, Ny 75 is cut short. I would hate to have a long round lock the gun up.

The chamber in this barrel was already properly sized. Going from the chamber to the point where the rifling was fully formed was a steep transition.

I bought a 0.355 straight reamer from MSC and had the machinist modify it.

The leading 1/4" of the reamer we ground down to Ø.201 and forced a brass sleeve over that portion to act as a pilot. The outside diameter of the pilot was determined by the largest gauge pin we could slide into the fully rifled portion of the barrel.

This gave us an unfinished reamer with a brass pilot that is the diameter from land to land but it had an abrupt step from the pilot diameter up to .355. He put the reamer back into the grinder and changed the step into a smooth transition from one diameter to the other.

From there the barrel went into the lathe. It was a matter of advancing the reamer in .010 increments and frequently checking with the over-length cartridge I provided as a gauge.

Given how little material had to be cut I might have over-complicated the procedure. The results were good though.

[oddjob]

Just wanted to add I shot the CZ at a match on Sunday. It ran like a champ, accurate and at the command unload and show clear the bullet didn't stick in the chamber. Glad I had it done.

Forgot to mention I was using rounds with an overall length of 1.150. Bear Creek 130 TC shaped bullets.

Edited June 21, 2010 by oddjob

[sperman]

I had a gunsmith check the chamber on my shadow custom. He said it was both short and slightly out of round. I'm good to go now, but you would think this would be covered in a "custom" gun that costs $1200.

[B_Seehawer]

Sent my G24 barrel to Grams, best thing I ever did for that gun!! It always fed but I got tired of that "struggle" at unload and show clear.

Brad

[oddjob]

I also had this done with my STI Trojan (.40 cal.) The gunsmith told me he has had several customers tell him the same complaint I had. Its the shape of the bullets according to him. Makes sense. Any ways if you have any thoughts about getting this done just do it. Its well worth it. I like the Bear Creek TC's because its so accurate....plus I bought a bus load of them and didn't want to change.

[Ken Mays]

A 9mm throating reamer is money well spent. I load my 9mm long, and never had a problem until I went to bullets with a smaller radius ogive... so the bullets get fat sooner than others.

The reamer is tapered so that you can go as far as you need to.