7PRC Partition wont chamber

[Lawnboi]

I see a bunch of Lumley stuff on there. If he installed their ejector and extractor that’s probably your issue. Just something to look at. Send us a picture of your bolt nose and I’ll tell you real quick.

Tikkas require some forward force, the bolt always just won’t drop because you do have to overcome that extractor and ejector.

 

[doc holiday13]

shouldn't be any forcing whatsoever. Your biggest help will be to show that you have factory ammo and see if it will chamber.. I don't see why the GS wanted to "custom cut" the chamber. It sounds like he didn't finishing chambering or has a jacked up reamer.

Take video of you attempting to chamber a factory loaded round. upload to youtube and send the link to the Gun Smith. He needs to finish the job properly. I don't think you could load a partition long enough to touch the lands in a 7mm. Box it up and send it back once he gets the link and you have a follow up conversation

 

[wind gypsy]

shouldn't be any forcing whatsoever. Your biggest help will be to show that you have factory ammo and see if it will chamber.. I don't see why the GS wanted to "custom cut" the chamber. It sounds like he didn't finishing chambering or has a jacked up reamer.

Take video of you attempting to chamber a factory loaded round. upload to youtube and send the link to the Gun Smith. He needs to finish the job properly. I don't think you could load a partition long enough to touch the lands in a 7mm. Box it up and send it back once he gets the link and you have a follow up conversation

Look at the partition in the OP. You'd need like a half inch of freebore for that choad to not jam in the lands.

 

[doc holiday13]

Look at the partition in the OP. You'd need like a half inch of freebore for that choad to not jam in the lands.

I did miss that photo. That said, you can still load pretty damn far with the 7prc before hitting lands. I don't have an partitians to compare to but I imagine if the case neck is 100% bullet contact for the full length of the neck; then I'd think it would chamber From a factory loaded 180ELDM to the lands on my Seekins is .125

Either way I think something is sideways on his chamber. I can't remember if the OP has tried to chamber factory loaded ammo?

 

[wind gypsy]

I did miss that photo. That said, you can still load pretty damn far with the 7prc before hitting lands. I don't have an partitians to compare to but I imagine if the case neck is 100% bullet contact for the full length of the neck; then I'd think it would chamber From a factory loaded 180ELDM to the lands on my Seekins is .125

Tiny boat tail, stubby nose, and 175 grains (with plenty of it being copper) = Long AF bearing surface. If the nose is 0.300"+ shorter than a 180 ELD, it's going to hit the lands at about that much shorter COAL. Not sure why people are confused on this.

Either way I think something is sideways on his chamber. I can't remember if the OP has tried to chamber factory loaded ammo?

He has, and it works.

Update. On the way home I stopped bought a factory loaded box of eldx. Their coal was measured at 3.291 and Chambered perfectly. Sat down with a partition at the press and did get it to chamber smoothly, at 3.009 unfortunately

 

[ChrisAU]

I bet if OP took a 7mm comparator and measured that factory load that will chamber and the "short" partition load it would start to make sense.

 

[streamerfish]

Tiny boat tail, stubby nose, and 175 grains (with plenty of it being copper) = Long AF bearing surface. If the nose is 0.300"+ shorter than a 180 ELD, it's going to hit the lands at about that much shorter COAL. Not sure why people are confused on this.

He has, and it works.

I'm not confused at all on the concept. I understand completely how it works....

However, if I have reloading manuals that have recipes for a 175gr partition at 3.260 OAL, then I would expect to be able to load them at 3.260, or close to that. Not having to go all the way down to 3.009 just to get it to fit.

Especially when Hornady also has book loads for the 175gr Interlock SP at a OAL of 3.265. Which is a very similar shaped and length bullet to the partition.

The thought process isn't why do partitions need to be loaded shorter potentially...Its more why does his chamber need the bullet loaded .250 shorter then multiple reloading manuals call for....That's not a little bit. That's a lot.

If you just look at the rough numbers......you have a 1.36" or so bullet, seating roughly .4" deep. It has roughly .8" bearing surface, about .4" left after seating...You "should" have roughly .4" before your on the lands. Generally run Partitions right up around .02 off the lands...at 3.260 OAL you "should" be right in the ball park.
If we were talking you know +- 20 thousandths or something...sure chambers vary, still within specs most likely. Bet we are talking 250 thousandths. I mean that's a mile short.....

Most of the info I could drag up seems to point towards around 3.24-3.26 OAL with a 175 Partition on various forums....A couple guys went down to 3.20 for a bigger jump.

Haven't seen anyone go clear down to 3.009 just to fit it. Its just out of spec.....

 

[Smithb9841]

Are there any partition factory loads you could purchase to see if factory loaded partitions work? And compare how deep those are seated?

 

[Choupique]

if I have reloading manuals that have recipes for a 175gr partition at 3.260 OAL, then I would expect to be able to load them at 3.260, or close to that.

I agree with this.

Sounds like an off spec ream job to me.

This is why I like factory rifles and book load data

 

[UnckleBob]

The smith is feeding you a line of bs about partitions and eld's; any of them will chamber in a SAAMI chamber. The 7PRC is designed with freebore for the long 7's, a partition will chamber with tons of room to spare; excessively so.

The 7PRC chamber was designed with the Eld's specifically in mind. They certainly didn't design that case for shooting InterLock bullets.

If his rifle cannot function with Elds, something is very wrong.

 

[UnckleBob]

Update. Got home this evening after borrowing a few 7mm bullets from a friend.
I loaded 162 gn Hornady sst @ 3.337 - wouldn’t chamber
I loaded 150 gn sierra matchking at 3.268- wouldn’t chamber
I loaded 140 gn Barnes ttsx - wouldn’t chamber
I loaded a 185 Nosler rdf at 3.439- wouldn’t chamber.

So then I decided to reload all these at their book length from their manufacturers book data.

So I loaded 162 Hornady sst at 3.070,
I loaded a 150 gn match king at 3.100
I loaded a 140gn Barnes ttsx at 3.110
And I loaded a 185 Nosler rdf at 3.320

I can get these to chamber if I force them. The rdf was so rough that it seated the bullet to 3.317.

Most importantly I’m noticing to chamber any of these bullets even a lil shorter than book length in order to get them to chamber when the bolt should rotate I’m having to force the bolt further I’m assuming jamming the bullets into the lands and I can feel the extractor snap over the case rim and then the bolt will rotate down. I have other tikkas and I went grab all of them and none of them have this phenomenon. Or feeling. What say you?

Will it chambers factory ammo? Maybe the way you are loading is the problem?

 

[Caseknife]

Will it chambers factory ammo? Maybe the way you are loading is the problem?

post #39, yes

 

[Choupique]

certainly didn't design that case for shooting InterLock bullets.

Yea but a book length load for a given bullet should chamber regardless of what that bullet looks like. The book length should account for the relationship between the bearing surface of the bullet and the leade geometry and all the tolerance stacking involved.

I dont know anything about 7 prc but I do agree with the earlier comment that the loaded round in the OP looks rediculous and sure doesnt look like it would chamber in anything. It looks like miniature a 30mm round.

No way to really determine whats up without a casting of the chamber to compare to the chamber drawing

 

[Walker6]

This thread started Wednesday, the 1st.

I’m calling April Fool’s, based solely on this photo:



OP, if I’m wrong then the best thing to do is buy one of these and get familiar with its use:

https://www.brownells.com/reloading/measuring-tools/bullet-comparators/sinclair-hex-style-bullet-comparators/

 

[Kimber7man]

This load chambers and fires easily in a SAAMI 7 PRC

 

[ckleeves]

This thread started Wednesday, the 1st.

I’m calling April Fool’s, based solely on this photo:

View attachment 1047356

OP, if I’m wrong then the best thing to do is buy one of these and get familiar with its use:

https://www.brownells.com/reloading/measuring-tools/bullet-comparators/sinclair-hex-style-bullet-comparators/

I think you’re right this has gotta be an April fools. You would need around .500 of freebore to chamber that bad boy! Or the OP is using a comparator measurement as COAL.