Help me understand SAAMI Spec ranges

[broadhead]

I recently had a situation came up and was chatting with a few guys on another forum but I wanted to post a more specific question on here in the hopes of learning some more.

The situation is I went to measure the overall cartridge length and base to ogive on my 6.5 PRC with the intent of working up a few good hunting loads. I used the Hornady overall cartridge length gauge and to my surprise after multiple, multiple repeated measurements I found out the throat is shorter than the maximum SAAMI spec range. The SAAMI range for the cartridge is 2.755" - 2.955" and my rifle measures pretty much in the middle of that range at 2.865. I'm pretty new to reloading and up to this point have only loaded rounds that basically match the factory cartridge length but I was mistakenly believed most chambers were cut to close to but a little larger than the SAAMI max to accommodate the majority of factory ammo available. The bolt is a little stiff even on an empty chamber and I've only noticed a little bit of a heavy bolt lift from time to time which tended to happen in the heat of summer so I didn't think too much about it. I'm reconsidering now.

I'm pretty unsure of how to go forward from here. Tomorrow morning I'm going to chamber a factory cartridge with the ogive sharpied into the chamber to try to get a little better idea of exactly where it contacts a loaded round. Do I look at getting the throat lengthened? For a factory barrel is it pretty common to accept that some factory rounds will seat into the lands? Anyone that can share some insight here would be greatly appreciated. I have considered starting over with minimum charges and seating the bullets deeper to seat them off the lands but based on my throat that would be pretty deep and I'm concerned that might increase pressure already. Thanks everyone.

[AZAV8ER]

I would not expect a factory loaded round to engage the lands on a factory barrel.

[broadhead]

15 hours ago, AZAV8ER said:

I would not expect a factory loaded round to engage the lands on a factory barrel.

Neither would I. But here's what happened.

The pics show a factory round colored from just below the tip to just above the case and it's clear to see what happened to it once it went in. The pics are from different sides of the bullet. You can see in the first pic where the bullet was contacted significantly more along the length than the other sides were. The undeniable indicator that something is off is when I tried to lift the bolt and extract the round it was stuck. Like, STUCK. Actually worried me for a second until after enough force it lifted and ejected the round. This happened in a factory rifle that has about 350 rounds through it with no issues before. I took out the bolt, visually inspected the chamber and barrel, cleaned the lug recess and mopped the chamber. No obstructions from what I could see and no excess build up of any kind anywhere. Followed it up with a few patched down the barrel and a bore snake. The bolt closes on an empty chamber as usual.

Talked to the manufacturer and I'm sending it back but before I do that I want to make sure there's nothing else I can do on my end that would fix this. I need someone smarter than me about guns to see if they can diagnose what is going on. Thanks!

[L Cazador]

How many rounds down the bore? 350?  You could have carbon build up in the throat. What's your cleaning regimen and what products do you use? I'm in Tucson and I have a bore scope. I would be glad to inspect for you. PM me.

[johnrr65]

1 minute ago, L Cazador said:

How many rounds down the bore?  You could have carbon build up in the throat. What's your cleaning regimen and what products do you use? I'm in Tucson and I have a bore scope. I would be glad to inspect for you. PM me.

+1

[broadhead]

7 hours ago, L Cazador said:

How many rounds down the bore? 350?  You could have carbon build up in the throat. What's your cleaning regimen and what products do you use? I'm in Tucson and I have a bore scope. I would be glad to inspect for you. PM me.

Yeah so I think you guys are dead on. This was a new one to me but after doing some more research it seems like the culprit is a carbon ring. all the symptoms fit as does the explanation why it developed over time. I went ahead and ordered some JB bore past and Kroil with a FVG adaptar and some cleaning pellets off Brownel's which is supposed to do a good job with that problem. Thanks for the input and I'll update with the results once I get the items in. Hopefully it will help someone else too.

[L Cazador]

3 hours ago, broadhead said:

Yeah so I think you guys are dead on. This was a new one to me but after doing some more research it seems like the culprit is a carbon ring. all the symptoms fit as does the explanation why it developed over time. I went ahead and ordered some JB bore past and Kroil with a FVG adaptar and some cleaning pellets off Brownel's which is supposed to do a good job with that problem. Thanks for the input and I'll update with the results once I get the items in. Hopefully it will help someone else too.

I think you have more than a carbon ring. You also have a throat full of carbon. I think what you are seeing is not rifling marks on that sharpie marked bullet it's carbon in the throat. Note the irregularity. Use Bore Tech C4 on every cleaning to prevent any carbon build up. Also use a phosphor bronze brush with a bronze core to clean that carbon ring on every cleaning. Use a brush that;s larger than your bore to do an effective job on the carbon ring. So for your 6.5 you would use a .284 or 7mm brush and spin that brush till carbon ring is gone. Spin the brush on the cleaning rod with your fingers. Do not use a drill to spin it. JB bore paste will help but I doubt the Kroil will do anything. On the throat you would use a 6.5 phosphor bronze brush with JB bore paste. You have one heck of job ahead. I start every cleaning by patching with C4 till the black is gone. Then I spin an oversize brush and clean the carbon ring out.  I then dry patch the C4 out and then follow with two patches of Sweets, let Sweets stand for 10 minutes and then brush with Bore Shine 4 stokes for every shot fired.  I then run a patch of Hydrogen peroxide to neutralize and foam out copper and powder fouling. And then I dry patch till patches come out clean. Finally I run a patch with Kroil as a bore conditioner. This regimen is for factory barrels. For my custom barrels I use C4 and patch the bore till the carbon is gone. Then I spin an oversize brush with C4 to remove the carbon ring and then dry patch.  I then follow with a brush to remove any copper and then dry patch till clean. Sounds like a lot of work but it's all bore scope verified to be the best bore cleaning regimen ever! A clean bore will win matches and kill what you are aiming at. Two very important things when you clean never mix any chemicals and dry patch each chemical out before going to the next chemical with the exception of the Sweets and the Butch's Bore Shine which are both copper removers. Never clean without covering your scope lenses and never clean without a good bore guide. I use only Lucas bore guides but Possum Hollow bore guides are also good. Do not use one of those one size fits all bore guides. By the way I don't think the cleaning pellets are going to get into that throat or chamber neck. 

[broadhead]

15 hours ago, L Cazador said:

You have one heck of job ahead. 

There are worse problems to have. Definitely going to start implementing the C4 and some different cleaning procedures after this but the up side is I learned something new. The C4 will be here tomorrow and the rest of the stuff in a few days so I'll get to work on it little by little as time permits. Fortunately being home a lot for awhile affords me the opportunity to chip away at it.

[brademan76]

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[broadhead]

4 hours ago, brademan76 said:

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I concur.