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April 09, 2020, 07:45:56 PM

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Author Topic: Short Leade and/or short Throat  (Read 1833 times)

lklawson

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Short Leade and/or short Throat
« on: July 07, 2017, 01:34:37 AM »
OK reloaders, heads up here.  My tight chamber issue turns out to be, 100%, the issue of a short Leade and/or short Throat ("freebore").

This is true for the factory barrel which came with my 2nd Gen (replacement) and for the eBay barrel I bought.  Both appear to be within SAAMI specification.  Both chamber jacketed bullets safely.  This includes all Jacketed Hollow Points (JHP) and Full Metal Jacket (FMJ) ammunition I've tried.  It also includes 115 gr. FMJ dummy rounds and FMJ Profile "snap caps" I've tried.

The catch is when I try Hard Cast (HC) lead reloads.  With only one exception, all of the HC lead bullets I've tried, when seated to manufacturer recommended seating depth, all engage the rifling, leading to pressure spikes.  Seating the bullets deeper does solve this problem.  However, when seating deeper, you have to reduce the powder charge because deeper seating is the equivalent of intentional "bullet setback."

The one HC bullet which did not engage the rifling when seated to recommended depth was 115gr. coated HC from SNS Casting.  I believe this is due to the longer bullet profile which has a longer, more narrow ogive than the more domed shape of others I've tried.  However, the SNS Casting bullets, had other problems, including failure to enter the chamber and jamming point up.  Perhaps if I had seated the bullets further out they would feed better.

It also appears that the Out Of Battery disengage is more sensitive than some other guns.  I'll have to figure out a way to test this.  But it is an issue for me because I reload 9mm so that I can shoot cheaper.  To that end, I use a lot of mixed brass and range pickup.  That means that there is little consistency in case length.  I may have to buy and use a 9mm case trimmer.  Ick.  :(

Anyway, just a heads-up for reloaders.  R51 barrels still have a very short Leade/Throat.  Plunk plunk plunk!

Peace favor your sword,
Kirk

Ray R

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Re: Short Leade and/or short Throat
« Reply #1 on: July 07, 2017, 10:56:58 AM »
This is a re-post of a previous response I have made on this forum:

There is a problem that can occur with 9mm Luger reloads that I have experienced in several guns: a friends Kimber, my SA Range Officer and my R51. All these guns have fairly tight chambers.

If the reloaded round does not get fully chambered; and this is most common in a tightly chambered gun, the gun won't fire. This is often due to a bulge at the very back of the case that the sizing die doesn't get to. The gun may appear to be in battery, but a close examination of the back of the slide and the back of the rail will show the slide needs to move forward a little more. This mismatch may only be 1 mm and can easily go unobserved.

The reloaded 9mm case does not get sized down near the base because most sizing dies don't allow the base of the case deep enough entry into the die for sizing to occur in this location. Depending on the lack of tightness of the chamber in the gun that the round was originally fired from and the manufactured spec's of the brass, there can be a slight bulge at the case's base; just where the die doesn't get to. Many reloader's won't use range brass for this reason. It is too hard to identify which brass has bulged.

This type of problem is common enough that Lee just started making a special sizing die that sizes all the way down to the base of the case and actually undersizes the case itself a few mm's so it will always fit reliably in tightly chambered guns. You can see the details of this die in Lee's most recent literature. I just bought one and will use it to replace the standard sizing die in my 9mm tool head.

paul7177

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Re: Short Leade and/or short Throat
« Reply #2 on: July 07, 2017, 01:30:00 PM »
Thanks for the info on the Lee sizing die.  Do you have the catalog/part number?

Ray R

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Re: Short Leade and/or short Throat
« Reply #3 on: July 07, 2017, 11:39:46 PM »
Here is the information on Lee's Undersize Sizing Die 9mm: SKU: 90313.

They make this die for 6 or 7 different calibers. As you know all advise is 100 % correct until you try it and it doesn't work (Ha Ha). Let us know if this die solves your problem.

lklawson

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Re: Short Leade and/or short Throat
« Reply #4 on: July 10, 2017, 05:43:35 AM »
This type of problem is common enough that Lee just started making a special sizing die that sizes all the way down to the base of the case and actually undersizes the case itself a few mm's so it will always fit reliably in tightly chambered guns. You can see the details of this die in Lee's most recent literature. I just bought one and will use it to replace the standard sizing die in my 9mm tool head.
If you don't want to invest in another die, you can test the resized brass. 

Just resize the brass and then "plunk" the empty, unloaded, brass case in the chamber and maybe give it a little bit of a press with the thumb.  If it slides in and slides back out, then you know that piece of brass isn't ballooned at the rear of the case.

Yeah, it's one more step.  :(

Peace favor your sword,
Kirk

President Donald J. Trump

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Re: Short Leade and/or short Throat
« Reply #5 on: March 14, 2020, 03:35:51 PM »
     I just found this out myself and wanted to check and see if others have this problem.  I was reloading 124gn XTP and my max COL was 1.076 just touching the lands.  I was also loading TL-356-124-TC (124gn truncated cone) cast bullets and max COL 1.067 . Not a huge deal but takes some figuring and limits powder type/weight and possibly heavy for bore bullets.

Zenshot

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Re: Short Leade and/or short Throat
« Reply #6 on: March 15, 2020, 06:44:47 AM »
I think Kirk had the same issue with cast truncated cone bullets a while back.  Maybe he will post a solution if he ever found one.
In other forums, it seems truncated cone 9mm loads often have this issue though.
-David

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Re: Short Leade and/or short Throat
« Reply #7 on: March 15, 2020, 10:40:10 AM »
It isn't an issue with truncated cone bullets.  The barrel was machined with a short throat that seems to fit most commercial bullets( I will be "plunk" testing any ammo now out of curiosity). But many "do not exceed loads" require certain bullets be seated further out to allow for more uncompressed case capacity. Many of the loadings from Lee and powder/bullet manufacturers require COAL of 1.125 or greater for the extreme expansion bullets like the XTP and Gold Dot. The TXP touches the rifling in my R-51 at a COAL: 1.076. Most modern 9mms have a longer throat or free-bore to accommodate the heavy, max expansion hollow points.  I am going to work up a load with the 124xtp and Longshot with a COAL of 1.062.  I am going to start at 4.7gn and work up to 5.5gn. I will chronograph and check for pressure signs.  The R51 is rated for +P and should run fine on this. I have some accurate #7 and CFE Pistol to try if I don't have luck with the Longshot.  Rambling now...
« Last Edit: March 15, 2020, 10:45:09 AM by President Donald J. Trump »

lklawson

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Re: Short Leade and/or short Throat
« Reply #8 on: March 16, 2020, 02:18:58 AM »
I think Kirk had the same issue with cast truncated cone bullets a while back.  Maybe he will post a solution if he ever found one.
In other forums, it seems truncated cone 9mm loads often have this issue though.
The only solution I have found is to be careful about your loads.  Plunk everything, including commercial bullets.

Peace favor your sword,
Kirk

lklawson

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Re: Short Leade and/or short Throat
« Reply #9 on: March 16, 2020, 02:25:25 AM »
It isn't an issue with truncated cone bullets.  The barrel was machined with a short throat that seems to fit most commercial bullets( I will be "plunk" testing any ammo now out of curiosity).
I've had problems with 3 different truncated cone bullets.  Two were hard cast, coated, reloads that I had to set so deep that they were dangerous.  The third was with Winchester WinClean 124gr. Truncated Cone.  None of them would plunk.  I was surprised that the Winchester wouldn't plunk. 

I have two barrels and neither one of them likes most of the bullets I've bought for reloading.  However, I've recently purchased several hundred uncoated hard cast 115gr Cone Nose bullets from GT Bullets.  The profile looks promising depending on how deep I have to seat them.



Peace favor your sword,
Kirk

President Donald J. Trump

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Re: Short Leade and/or short Throat
« Reply #10 on: March 16, 2020, 02:36:45 AM »
     The only solution is to increase free-bore with a 9mm throat reamer.  I doubt I will do that unless i had an extra barrel to play around with.  Even then, I have better things to spend money on.  I will just have to work up loads specifically for the r-51.  More fun...

Throop

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Re: Short Leade and/or short Throat
« Reply #11 on: March 17, 2020, 10:13:44 AM »
Interesting posts.  I'm getting set up to reload.  Thanks for ther discussion.

funflyer

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Re: Short Leade and/or short Throat
« Reply #12 on: April 02, 2020, 12:46:47 PM »
Hi guys. It's been a while since I've visited the forum. I've worked up many good target loads that work well with the limitations of the R51 barrel. The picture shows the bullets I've tested. They all function reliably with the exception of the 105-SWC which has the occasional feed problem. The two best, and pretty much all I run through the R51 anymore, are the 120TC, and 115rn. I cast the 120TC from a Lee mold but I believe Bayou Bullets has them in hi-tek coated. The 115rn are from SNS. The cartridge lengths(oal) in the pic are .010" off the lands, and the bullet seating depth is shown below each oal for that specific bullet.

 

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