357 GP100 7-shot ammo binding issue

[DaveKrueger]

NOTE: I posted this on the Ruger Pistols Forum. If there are rules against cross posting questions like this, my apologies and I understand if you choose to delete it. This is my first post here, so I'm a total noob. I'm also quite new to the handgun scene.

I just bought a 357 GP100 4" 7-shot revolver a week or so ago and have been to the range to shoot some 357 and 38 ammo through it a couple times and have noticed some binding issues that I only managed to figure out today.

When I load up factory Blazer Brass 38 spl FHP, the last round causes the rim to bind against the rims of the already loaded rounds. In other words, the rounds are so close together in the 7-shot cylinder, that the rims touch. It doesn't matter which chamber is loaded last and it doesn't matter which round is loaded last. It is not a round specific or chamber specific problem.

Unless I push the round in with some thumb pressure, it will stick out enough to bind against the frame of the gun when I close the cylinder interfering with the rotation of the cylinder and operation of the trigger.

If I push the round in with some thumb pressure, it will go in, the cylinder will close, and everything works fine. But, when I then try to eject the spent rounds, I have to really push on the ejector rod to get the casings to elect.

Using a caliper, I measured the 38 Blazer Brass FMJ rims and they come in at about 0.435" or so, which is less than the 0.440" specification for .38 and .357 mag. But, when I measure the 357 Blazer Brass mag rounds, the rims are definitely slightly smaller in diameter and I do NOT have this problem with their 357 ammo.

So, the question is whether anyone has heard of this issue with GP100 or any other 7 or 8 shot revolver where the cylinder chambers are so close together.

I plan to contact Ruger and Blazer to see what they say. I will report back here if/when they reply.

I did a google search to see if this issue has already been reported by someone else, but couldn't find anything. If someone has already posted about this please let me know. I may not have used effective search terms.

 

[Chuck 100 yd]

Interesting , I will be watching this thread.
I haven't fired a factory centerfire round ,except for shotgun , in many years.
If I encountered that problem,I would turn a batch of cases down to fit and dedicate them to that gun only.

 

[DaveKrueger]

Interesting , I will be watching this thread.
I haven't fired a factory centerfire round ,except for shotgun , in many years.
If I encountered that problem,I would turn a batch of cases down to fit and dedicate them to that gun only.

Thanks for the reply.

It seems unlikely that Ruger would cut the cylinder chamber separation so close that rounds that meet spec would bind, but it also seems unlikely that a commercial ammo supplier would crank out rounds that are out of spec on the large side. On the other hand, the 7-round GP100 is a fairly new gun. I think it only started shipping in December, so I suppose a design defect is possible.

If worse comes to worse, I will make a youtube video that shows the binding. I don't load my own ammo, so creating a batch of specially sized brass is not an option for me.

 

[rangerbob]

Before you fault the revolver, you need to try some different brands of ammo in it. If they all bind, then the gun is the problem. If other brands of ammo work fine, it might be the ammo. Bob!

 

[Jimbo357mag]

If the ammo is within SAAMI specs then woops, there is something wrong with the gun.

 

[DaveKrueger]

By measuring the individual rounds in the same box, I can easily identify some that have smaller rim diameters and they will fit in the cylinder with no problem. About half the rounds I measured are smaller and half are larger.

I also measured the chamber to chamber distance in the cylinder and it looks like there is essentially no tolerance. Without knowing the tolerances of the 38 special casing specs and having more precise measuring equipment than I have, it will be impossible for me to definitively point the finger at one or the other.

Unless it's just a bad batch of ammo, I think someone else is bound to have the same issue.

 

[Kevin]

I reload. But before I started reloading I bought ammo and just saved the brass. So now, especially with 357 I have a bunch of different brands of brass. And yes, between brands they are all slightly different sizes. I found the brands which fit best and recycled the others.

Without reloading, as mentioned you might just try several different brands. Wal Mart sells Winchester white boxed ammo and it's is pretty good.

 

[DaveKrueger]

I reload. But before I started reloading I bought ammo and just saved the brass. So now, especially with 357 I have a bunch of different brands of brass. And yes, between brands they are all slightly different sizes. I found the brands which fit best and recycled the others.

Without reloading, as mentioned you might just try several different brands. Wal Mart sells Winchester white boxed ammo and it's is pretty good.

One of the benefits of revolvers is supposed to be that they aren't picky about ammunition like auto-loaders are. Having to be careful what kind of ammo I use seems to be a pretty steep price for that 7th round. The six shooter has more space between chambers.

Nonetheless, I will definitely be trying other ammo as you suggest.

 

[hittman]

Welcome to the Forum.

 

[DaveKrueger]

Welcome to the Forum.

Thanks, hittman!

 

[DaveKrueger]

I have created a youtube video to illustrate the problem: https://youtu.be/ETlvR8zezgo

 

[recumbent]

Try some Federal 38 spl 158 grain.
I get mine at WalMart.

 

[DaveKrueger]

Try some Federal 38 spl 158 grain.
I get mine at WalMart.

The Walmarts in my area don't seem to stock much ammo (which seems strange considering I live in Alabama), but we have an Academy Sports store that has a lot of choices. I will pick up a few different brands and see how well they work. I don't really know which brands have the best reputation. I'll look for Federal and Winchester.

I took a set of the rounds that bind and gave them a few twists against some 320 grit sandpaper. It lessened the problem, but didn't eliminate the binding completely. I think a few more twists would have made the ammo useable.

I tried a 3rd box of Blazer Brass .38 SPL ammo that I bought before discovering the issue and it also has the problem. It's clear we are talking about differences in diameter of probably around 0.001". Tiny, but it's the difference between touching and overlapping.

 

[DaveKrueger]

I bought four different brands of ammo and compared them with the Blazer Brass. As a quick test, I measured 14 rounds from each of the four 50-round boxes and then loaded them into the cylinder. None exhibited any binding problems and the rims of all 14 from each brand measured noticeably smaller than the Blazer Brass rounds by 1 to 3 mils. None were as large as the Blazer Brass rounds.

Here are the four brands that worked:

Winchester 38 Special 130 gr. FMJ
Remington 38 Special UMC 130 gr. FMJ
American Eagle 38 Special 130 gr. FMJ
Aquila 38 Special 130 gr. FMJ

Even if my Craftsman caliper is off in absolute measurement terms, the above still applies because it would be near impossible for the caliper to be wrong in relative terms. The Blazer Brass rounds are larger and don't work well in the 7-shot 357 Ruger GP100. To me, this is a significant enough reliability issue to avoid using Blazer Brass ammo in any of my guns.

My plan is to check all 50 rounds in each box. If I find anything that contradicts the above, I will post about it.

 

[woodsy]

You can find the SAAMI specs in the Lyman Handgun Reloading Guide. The max diameter for the rim (both .38 Spl. and .357 Mag) is .440". If your (Blazer's) rims are larger than that, then they are out of spec. I HIGHLY doubt that Ruger would design/release a revolver which did not meet SAAMI specs. But first be sure that your calipers/micrometer is dead true.

 

[Tom-R2]

You did a great job on your video. It came out well and you made your point. I'm betting it's the ammo.

 

[DaveKrueger]

You can find the SAAMI specs in the Lyman Handgun Reloading Guide. The max diameter for the rim (both .38 Spl. and .357 Mag) is .440". If your (Blazer's) rims are larger than that, then they are out of spec. I HIGHLY doubt that Ruger would design/release a revolver which did not meet SAAMI specs. But first be sure that your calipers/micrometer is dead true.

Thanks. I found them here: http://www.saami.org/specifications_and_information/publications/download/205.pdf

I think I am happy with the outcome of the discussion since the other ammo brands seem to work fine. Before I retired, I had access to better measuring equipment where I worked, but I don't see much point in pursuing it further. It looks like there are plenty of ammo choices that will work fine, so I'll settle for that.

 

[DaveKrueger]

You did a great job on your video. It came out well and you made your point. I'm betting it's the ammo.

Thanks, Bearcat. I appreciate the feedback.

 

[DaveKrueger]

I received two form-letter style replies to my emails to Ruger describing the problem. One suggested I clean the gun and the other said that they would look at the gun if I called and requested an RMA number.

I received a more informed reply from Blazer asking whether I have any ammo left and, if so, to send them the date codes. If I send them the ammo, they will measure it to see if it is out of spec.

If they ask for it, I plan to send the ammo to Blazer, but will probably not send the gun to Ruger since there is no way they are likely to conclude their gun is defective or out of spec if it only has problems with ammo from one manufacturer. The form letters also didn't inspire much confidence that they would take the issue seriously enough to conduct more than a superficial analysis.

None of my testing allows me to definitively conclude that the ammo is out of spec or that the chamber spacing is too tight on the gun. All I can say is that the Blazer Brass .38 Special ammo has slightly larger diameter rims than the 4 other brands that I tested and will not work properly in my 7-shot GP100.

Finally, I made a followup video to demonstrate that the binding issue persists even after thoroughly cleaning the cylinder chambers: https://youtu.be/1lvjQCfRAKs

 

[woodsy]

All I can say is that the Blazer Brass .38 Special ammo has slightly larger diameter rims than the 4 other brands that I tested and will not work properly in my 7-shot GP100.

And that is the answer to your problem.