Reloaded rounds wont chamber 7prc

[Tgrow503]

Tikka action , Proof prefit 7prc
ADG brass , eldm180gn , H4831sc

I have already sized and fired this brass once all 100 cases with 175gn eldx the first time I loaded them to 3.4 OAL and ran through them fine. Now I'm on my 2nd loading of them and using 180 eldm. I have resized all the brass and they chamber fine. I also have a hornady OAL gauge and checked with the 180s for touch to lands and came up with a 3.385 OAL . I loaded up 20 rounds for a ladder test at 3.381 and they will not chamber , not even close , bolt stops 1/4" from close. I measured my loaded neck dia at .315 spec is .317 . I have a round I loaded too deep at 3.28 same thing , bolt stops short wont close. I have measured the brass , neck, shoulder, bullet dia .284 etc and everything seems good , bolt drops on brass only. Its like I'm loading the bullets too long and there hitting the lands preventing the bolt to close , but how is this possible when the OAL gauge give me 3.385 to touch ? Hornady specs this load for a 3.32 OAl .The barrel and chamber are clean as far as I can see , the barrel has 100 rounds on it and has been scrubbed clean. I have also taken ogive measurements and everything seems good. What else could it be ? I do not have a boroscope handy . Anyone near Tualatin care to take a look ?

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[Bobbygun]

Puzzling. If it was me, I would take that round that is loaded too deep and set the bullet a little deeper to see if that helps. Maybe the shape of the bullet has something to do with it - longer point/shorter point. Just guessing. The last time I had an issue like this, it was the brass not quite being 100% sized, but you don't have that problem if the empty brass will chamber.

 

[P7M13]

Hornady brass?
Please post close-up pictures.
Check the shoulders very carefully. I found Hdy brass shoulders will deform when seating the bullet.
I de-load the bullet, powder & primer when this happens and toss the case.

 

[Koda]

I have resized all the brass and they chamber fine. I also have a hornady OAL gauge and checked with the 180s for touch to lands and came up with a 3.385 OAL . I loaded up 20 rounds for a ladder test at 3.381 and they will not chamber , not even close , bolt stops 1/4" from close. I measured my loaded neck dia at .315 spec is .317 . I have a round I loaded too deep at 3.28 same thing , bolt stops short wont close. I have measured the brass , neck, shoulder, bullet dia .284 etc and everything seems good , bolt drops on brass only.

The error is somewhere in your distance to lands (DTL) measurement is my guess. I have to question the accuracy of a .004" off the lands measurement.... one can squeeze +/- .002" from the calipers, and the Hornady gage isnt the most precise instrument for this...
Did you decap before using the gage?
Did you use a different bullet for each DTL measurement then average? ( you should...)

Sometimes the bullets ogive profile varies by as much as +/-.005". I often use the bullet comparator just to check a sample of bullet ogives to help give me a better idea of what kind of tolerance I can hold on my seating depth and my DTL.

 

[Tgrow503]

ADG brass. Yes I used the threaded Hornady case with the gauge so no primer. I agree .002 may not be enough. But the same thing happens when I try to chamber the short round loaded to 3.28 oal. I will check the bullets ogive again tonight . 3.28 is shorter than factory ammo and should chamber with plenty of room. But won't. I may order a boroscope to get a better look at the chamber.

 

[Koda]

Also double check your DTL... ive had some bullets not slide easy in the modified case neck and thought I was against the lands until 1 sample was way different. I use a light touch but if the bullet gives me issues then i use a heavy touch but have to remove the bullet with a cleaning rod. I usually measue 5 samples to average using a new bullet each time to account for ogive tolerances. Pick the average or the shortest measurent.

Also, be sure the nornady gage is attached on the correct side of the caliper blade because of its design it will offset the centerline of the measurement. Hard to explain.

 

[Tgrow503]

pressed one down to 3.2 oal still fighting it to chamber. I think I have a burr or something in the lands/ area. Need a boroscope or take it too a local smith to take a peek. Any recommendations?

 

[ActBlueDonor]

OAL isn't the problem.

What's your headspace at the datum?
Now, what's SAAMI headspace at Datum?

I bet an empty case won't chamber either. Has nothing to do with bullet depth. You can easily seat a bullet deeper when chambering.

What you're describing is a case not fully sized.

 

[Koda]

pressed one down to 3.2 oal still fighting it to chamber. I think I have a burr or something in the lands/ area. Need a boroscope or take it too a local smith to take a peek. Any recommendations?

You cant close on a 3.2" COAL but can measure the DTL with the hornady gage longer with the same bullet? If thats the case its not a burr or something. There is something inconsistent between the DTL measurements, sizing and actually seating bullets. Are you neck sizing or full length sizing?

 

[Pepe-lepew]

Isn't 7prc really tight in the throat?Have you checked run out to see if the bullet is seating crooked?

 

[Tgrow503]

Full length sizing . Yes DTL I get 3.385. Loaded one down to 3.3 and still fighting to close. Empty case is chambering fine. I just loaded it down to 3.27 and can get the bolt to close. I should be able to load these way longer. The factory ammo is 3.32 and my DTL is 3.8

 

[Tgrow503]

No. I haven't. I'm not sure how. I'm using a redding ultra with a sac bushing . I did load 100 rounds of eldx last go round and they all ran fine at 3.4 oal

 

[Koda]

The cases that the bolt will close, are those resized?
Are you shoulder bumping or sizing to saami spec?
And are you annealing before resizing?

 

[Bobbygun]

You don't happen to have any of those 175 grain bullets you used before? It would be interesting to seat one to your old 3.4 OAL and see if it will chamber.

 

[ActBlueDonor]

The cases that the bolt will close, are those resized?
Are you shoulder bumping or sizing to saami spec?

Ding ding ding

 

[Tgrow503]

Yes. I did anneal . All case are the same batch and I sized the shoulder to 1.82 sammi spec. I don't have anymore 175s shot them all. I was reading that Hornady 180g book specs are off and guys say the factory ammo is 3.28 oal but still doesn't explain the 3.885 DTL im getting with the same bullet same case.

 

[Koda]

All case are the same batch and I sized the shoulder to 1.82 sammi spec.

I believe the saami spec for the shoulder datum on the 7prc is 1.904" -.007"
How are you checking your shoulder datum? You should be using a .420dia comparator with the Hornady comparator.

 

[TTSX]

Crank down on the bolt real good and tight. It'll fit.






Not really

 

[Tgrow503]

I have sac headspace comparator 7mmx 30deg which they recommend for 7prc and I'm right at 1.82 .

 

[Koda]

I have sac headspace comparator and I'm right at 1.82 .

View attachment 2071452

Thats not to saami spec and thats not the shoulder datum. I dont know how SAC comparators work but you should be checking the shoulder datum to saami spec, 1.904" -.007" if you want to assure it will fit your chamber.

saami specs are free:

https://saami.org/wp-content/uploads/2025/04/SAAMI-Z299.4-CFR-2025-Centerfire-Rifle-Approved-2-10-2025.pdf