I just had a new rifle built on a 700 action and a pac nor bbl. .260 Remmy. It’s very accurate and shoots most everything I’ve Fed it so far into 1/2-3/4” groups. But it seems to have a tight chamber. Before I even fired it, it would not load factory new Hornady brass. Bolt wouldn’t quite close all the way. Once I ran the brass through my re sizing die it was fine.

Today while testing a load using H4350 and a Barnes 127 LRX at .080 off lands (mag length) I got pressure signs, ejector wipe, at just 42 gr of powder, which seems incredibly light. I’ve read about 45gr charges using same powder and bullet.

So my question is… Are having a tight chamber and easily seeing pressure signs related? Seems logical to me, but I’m also still rather new at this.

Seems to be lots of reports of Hornady ammo being oversized lately

Would be nice to KNOW the reamer specs. Could be a neck dimension is tight with insufficient bullet release clearance. This could show up with some pieces being so tight you have signs of pressure and sometimes with others working fine.

I encountered it once, a gunsmith told reamer maker to "tighten" up the specs so it would shoot its best. (later realized gunsmith didn't know squat about what he was asking for) Gunsmith and I had a deal for me to work up loads for his customer's rifle, a 6.5-284. I had no idea there was an issue with not enough clearance for bullet release. Some of the pieces of lapua brass worked fine and others showed signs of pressure. Happened to try fitting a bullet into a fired case and it was very tight. That had me asking what the neck dimension was....couldn't believe I was handed a rifle with tight chamber neck without being told. Had to neck turn the brass for proper release dimension.

As for not being able to close bolt on factory Hornady brass, IMO that is a headspace issue. Gunsmith might have made it on the tight side and Hornady brass shoulder is a few thousandths longer.

I would try to insert a bullet into the necks of fired cases. They should slide in easily. If not, then the neck of the chamber may be too tight--or the combination of chamber and case necks may be too tight.

I use a LOT of Hornady brass these days, and haven't found any "oversized" for the chamber. Have found a few cases with thicker brass "donuts" at the base of the neck, where it meets the shoulder. However, those have all been in cartridges where the necks are usually out-side turned for precision.

How short is the throat compared to SAAMI?

I have had several encounters with Hornady factory ammo being slightly "oversize" in some dimension.

I have had numerous .223 Varmint Express that would barely chamber in several different rifles, factory and custom. Other factory fits fine.

I have had several .270 WCF American Whitetail that chambered hard in several different rifles, factory and custom. Other factory fits fine.

I now have 25-06 American Whitetail that chambers hard in a brand new factory rifle. Other factory fits fine.

After firing, trimming, resizing and reloaded, it all fits just fine.

So a lil more info after hitting the range again today. At 42 gr H4350 and 127 LRX I get a light ejector mark or wipe every 3-5 pieces of ammo. Some pieces of fired brass are fine, then I get a light mark. 42.3 gr of powder puts ejector marks on the brass every time.

I also tried some 120gr TTSX. At 42 gr powder I got no pressure signs at all. At 42.3gr powder it acted like the above 127 LRX load at 42 gr. Got a light mark every few pieces.

I ordered some Lapua brass to try and will also try some factory ammo. Problem is, I’m almost scared to try factory ammo. Look at Barnes Vortx 120gr .260 specs. 2950 muzzle velocity! That MV is hotter by a good bit than ever their listed max load from their data sheets. So if I’m getting pressure signs without reaching max on their load data, their factory ammo appears to be even more high test! Should I be worried to give it a shot? Still scratching my head over this one. I don’t want to be limited to anemic ammo. I really hope I just got an odd batch of brass.

MD, a new bullet slides into a piece of fired brass fairly easily. Just some light finger pressure required.

No idea what the actual chamber measurements are other than they said it was cut to Saami specs.

I have 3 .308s, one is fitted with a Pac-Nor. Its chamber yields fired brass that has 1.4 grains less water capacity than the other two using the same brass. That will result in slightly more pressure with a given charge.

Another influence is a shorter throat.

With the Pac-Nor barrel, I reduced the load I was using in the other two by about .2 grains to get equal velocity.

What is the muzzle velocity of the 42g load?

??????????????

IMHO a bullet should slide in without any pressure as in fall by its own weight. Sounds like a tight neck/ thick necks from what has been said.

I don’t yet know. My local range doesn’t allow access beyond the firing line so I can’t set up my chrono. The range that does is an hour drive away. I realize that would tell me a lot I just haven’t had time to get there.

It doesn’t take much. Just a light touch and they drop right in.

I was asking (or attempting to) what his muzzle velocity was of the 127g LRX w/ 42g H4350 load.

This ^^^^^^

SDHUNTER,

No pressure (even "light finger pressure") should be needed to slide bullets into fired necks.

SDHNTR...after many, eight, PAC-NOR barrels in various cals, other than a 260, can tell you that I`ve learned to start at the low end of the powder charge with these barrels. We order pre-fit. They are tight.
As far as factory stuff goes, you may need to try more than one brand of ammo.

Can you inside neck ream?

Ok I dug out some more fired brass. Ttsx and gmx drop right in. The LRX seems to sometimes catch a bit on the cannelure rings but a light tap or shake and they drop.

I’m not familiar with “inside neck ream”. Please elaborate.

I understand starting light, I did that too. But got stopped short of max. Should I be spooked to shoot factory ammo? To follow my logic, Barnes 120 ttsx and H4350 max load on their data sheet is 2853fps, and I can’t reach it without pressure signs. Yet their Vortx factory ammo with the same bullet is published at 2950fps! See why I’m spooked?

So you are evidently saying that PacNor builds em tight as SOP? I assume for accuracy and I am getting good accuracy. Do I need to just resign myself to shooting anemic loads? Anything else I should try?

Try a new batch or brand of brass? Remember that this Hornady factory new brass wouldn’t chamber without a little force to push the bolt down. I had to full length size before they would chamber smoothly. I always full length resize anyway before shooting, but have never HAD to with other rifles to get new brass to chamber.

Should I throw caution to the wind and touch off some factory ammo? Think it’s safe given the load data concerns?

I’d also rather not pack this thing up and send it back as that’s a pain and deer season is close. I am excited to hunt this gun too. Im open to other ideas or things to try to narrow down the issue. Thanks for the feedback.

Do you have a headspace comparator? What does the headspace dimension measure?

new brass Vs. sized new brass Vs. fired brass

When sizing the new brass to chamber, what dimension(s) are changing? Just HS?

I don’t have a headspace comparator, just an ogive one. Trying to keep things simple. I’m kinda new at reloading but have not had these problems with a couple other rifles before.

I wouldn’t worry about shooting factory ammo, so long as it chambers.

You shouldn’t have to resize brass to chamber if it’s to spec. If the chamber is so tight that you can’t chamber factory ammo and/or new brass, ammo and brass that’s within SAAMI spec, I’d be fixing the chamber.

Did you verify throat jump—just to be sure you’re not headspacing off the bullet. Is the chamber and throat clear of chips/debris? Do you have a borescope?

You might be able to use your bullet comparator to compare HS dimensions on your brass, if you have the .416 insert.

I don’t. .358 is biggest I’ve got.

Yeah, there’s lots of throat. These loads were all .080”+ out. PacNor said they have an inspection process before shipping so I’d assume they scoped it.

I’ll get some new brass and some factory ammo and see if it chambers.

Look in the chamber real good with a flashlight and see if you’ve got a stray chip or bit of swarf swaged in there.

I did that, and cleaned and dried it well. Appears all clear. Nothing obvious.

No problem there, remember that neck has contracted after it released the bullet, from the sound of what you are say it is a nice neat chamber as one should expect in a custom barrel
You really need to do your load workup in conjunction with a good chronograph, the magnetospeed has worked really well for me

sdhuntr...I have a Forster case trimmer..I`m sure you have a simular tool, in which I can place a carbide cutting tool which is about 2 thous over bullet dia. What that does is uniform the necks on cases of various manufacture that may be a bit thick. So a bullet can be inserted into a fired case with no pressure at all. Whoever manufactures your trimmer should offer them. Get one.

I think you may be assuming your handloaded ammo is lacking in velocity, cause if I understand you, you can`t test this yet? Don`t jump to conclusions till your sure. All my PN barrels gave me the vels I wanted, below listed max in the books.

Your rifle is new....work with it till you understand what it`s telling you.

I would say yes..PN`s QC is SOP.

Good luck

Just a thought, don't know if it applies to sdhunter - I've seen fired cases sometimes that look like they have a little bit of crimp; i.e. the case mouth is tighter than the rest of the neck. That happens when case length is slightly long for the chamber, and it can raise pressure a bit.

I've also encountered a chamber or two that had shorter necks than standard spec, so cases trimmed to spec could still end up being too long. That can be hard to identify if you don't know to look for it.

Well the saga continues. Drove 30 miles out of town to the only decent gun shop around. Bought a new box of Lapua brass. Same thing, it won’t chamber. Bought a box of Barnes factory ammo. Guess what, it won’t chamber either. Man I was really hoping I just got a batch of bad brass at first. Now I’m really pissed! Now I have to take the scope off and ship back up there. Then sight in all over again! Arrghhh!

Yondering,

Have seen that as well, in fact my custom 6.5 SPC needs to have cases trimmed slightly shorter than SAAMI specs or there's some tightness inserting bullets into fired necks.

Don`t think anyone asked, did PN do the barrel job for you, install, or a local smith?

Either way, they should stand behind the work done.

That sucks..

Although a PIA in the short term, this is the right move.

I'm finding this thread to be very interesting. I have a custom rifle based on an FN commercial Mauser chambered to the 7x57 that has a very tight chamber. Like the OP, I get high pressure signs before reaching maximum published data. I haven't been able to set my chronograph up since the range changed the rules so I have no idea what the velocity is. Now that we're getting our summer thunderstorms on a fairly regular basis the range is a bit of a mud hole anyway with all the eater running into the 100 yard line and backing up to the berm.

To give an idea of what's happening, I loaded up some 170 gr. Sierra round nose bullets to duplicate the original 1893 load and then shot them over the chronograph. The Ruger #1A did 2310 FPS, the M70 FWT a bit faster at 2320 FPS and the custom Mauser 2450 FPS. I talked with my gunsmith and asked if he'd done a shorter than the usual throat and he said it had the long throat suited to 175 gr. round nose bullets. Twist is 1 in 8.5" BTW. Dunno for sure what the Ruger and Winchester have for barrel twist rates.

Guess I'll have to check if the bullet slides easily into the case next time out.
Paul B.

Will it chamber new brass without resizing?

take that rifle back to the gunsmith and all your different ammo, i bet the no go and go gauges don`t work either. sounds to me that gunsmith did a very poor job of machining that chamber on that barrel.

Yes, a chronograph. You do not know that your loads are anemic until you measure actual velocity.

All smiths I`ve had work done barreling a rifle, produced at least three fired cases for me after test firing the gun. You should have gotten the same.

That didn’t happen in my case. It’s frustrating, and an inconvenience to have to ship back, But we are all human beings. [bleep] happens. Pac nor has assured me they will make it right. I’m going to give them that opportunity before I badmouth them. Fingers crossed.

This^^^^^^. Having 3 rifles with minimum spec match chambers all 3 have exceeded book velocities for the stated charge, but the only way to know that is to chronograph the loads.

+3

Similarly, I have 6x55 Swede that's a nail driver. I assembled some ladder loads with my first accuracy experiments, and beginning at the low end made it less that 1/2 way through the set when pressure signs appeared. Still need to chronograph it, but I suspect it's running tight.

Look folks, I hear ya! I fully intend on getting to my chrono, but when 2 types of new brass, and factory ammo, won’t chamber, there’s obviously a bigger functional problem at work!

Once I ran the brass through my re sizing die it was fine.


Your words not mine. Just sounds tight and you don’t want to deal with the BS that goes with it. Oh well.

If you call not chambering factory ammo BS, you are right, I don’t want to deal with it!

Use a felt pen on new factory rounds, chamber in a safe area and check for rub marks. That should show where chamber is undersize, or brass is oversize.