Chambering Changing OAL

Status
Not open for further replies.
peeplwtchr

peeplwtchr

Member
Joined
Sep 20, 2019
Messages
1,606
Hi All-

I was testing some Titegroup in 9mm today, and saw that when I chambered them in my PCC, they OAL went from 1.102 to 1.105. I'm pretty sure that won't change performance, but just curious why that happend. 1.02 OAL, .378-9 crimp.

Maybe my Lee sizing die?

Thanks
 
Momentum of chambering moving the bullet forward while the extractor holds the case rim?

Are all the rounds going longer?

BTW, I use maximum .378" taper crimp for .3555"-.356" diameter bullets (.377" for .355" sized bullets).
 
LiveLife said:
Momentum of chambering moving the bullet forward while the extractor holds the case rim?

Are all the rounds going longer?

I only did 3 so far, but they all changed.

BTW, I use maximum .378" taper crimp for .3555"-.356" diameter bullets (.377" for .355" sized bullets).
Click to expand...
 
peeplwtchr said:
LiveLife said:
Momentum of chambering moving the bullet forward while the extractor holds the case rim?

Are all the rounds going longer?
Click to expand...
I only did 3 so far, but they all changed.
Click to expand...
Then looks like it's the chambering action that's making the bullets move forward in case.

Walkalong said:
peeplwtchr said:
1.102 to 1.105.
Click to expand...
If they went from 1.102 to 1.105, I don't see an issue.
Click to expand...
As Walkalong posted, I don't think it will be much of an issue as if all the rounds are being chambered to 1.105" and "plunks" at 1.105", then your "chambered OAL" is all 1.105". ;)
 
LiveLife said:
Then looks like it's the chambering action that's making the bullets move forward in case.


As Walkalong posted, I don't think it will be much of an issue as if all the rounds are being chambered to 1.105" and "plunks" at 1.105", then your "chambered OAL" is all 1.105". ;)
Click to expand...

And 1.105 is the point where the .356 bullet meets the Lands, which is why it stops growing in length right?
 
LiveLife said:
Dang, really?

So if 1.103" your max OAL?

Mind if I ask what PCC/barrel and bullet you are using?
Click to expand...
Yeah, I just started reloading (9mm), not doing rifle until I get all the theory; following recipe. So yes to the bullet meeting the lands?

The PCC is an Extar EP9. The BCG is really heavy, and slams into battery with more force than an AR.
 
peeplwtchr said:
following recipe
Click to expand...
Are you loading to 1.103" just because published load data listed 1.100"?

Or is that the max OAL that will allow the round to freely drop in the barrel and spin without hitting the rifling?

peeplwtchr said:
The PCC is an Extar EP9. The BCG is really heavy, and slams into battery with more force than an AR.
Click to expand...
Blowback action PCC requires heavier combined BCG/buffer weight (19-22 oz) to hold case longer in the chamber before moving back from recoil - https://www.thehighroad.org/index.p...es-and-what-parts-did-you-use-and-why.825314/

I use around 20 oz combined weight for my Just Right/PSA/New Frontier PCC builds but some 3-gunners even go up to 23+ oz using stiffer .308 buffer spring instead of .223/5.56 buffer spring.

And according to Extar website, looks like they could be using stiffer recoil spring rate also, which would slam the BCG harder. You have any issues with last round bolt hold open (LRBHO)?
 
Last edited:
LiveLife said:
Are you loading to 1.103" just because published load data listed 1.100"?

.

Or is that the max OAL that will allow the round to freely drop in the barrel and spin without hitting the rifling?


Blowback action PCC requires heavier combined BCG/buffer weight (19-22 oz) to hold case longer in the chamber before moving back from recoil - https://www.thehighroad.org/index.p...es-and-what-parts-did-you-use-and-why.825314/

I use around 20 oz combined weight for my Just Right/PSA/New Frontier PCC builds but some 3-gunners even go up to 23+ oz using stiffer .308 buffer spring instead of .223/5.56 buffer spring.

And according to Extar website, looks like they could be using stiffer recoil spring rate also, which would slam the BCG harder. You have any issues with last round bolt hold open (LRBHO)?
Click to expand...

No, my target was 1.100, this round came out at 1.103.

The recoil spring does appear to be very stiff. No issues on LRBHO.

Good info. as usual, thanks!
 
peeplwtchr said:
And 1.105 is the point where the .356 bullet meets the Lands, which is why it stops growing in length right?
Click to expand...
peeplwtchr said:
So yes to the bullet meeting the lands?
Click to expand...
Are you familiar with the plunk test to determine the max OAL for that bullet in that gun? If so, great. If not, google it. Either way, plunk test that bullet in that gun and report back. Only then can we answer your question.
 
If you measure closely enough, semi-auto chambering almost always changes COAL. If you don't believe me, grab a box of factory premium ammo and your calipers, and go measure.

In the end, a couple thousandths doesn't make a whisker of difference. If can matter if your administrative handing results in full-speed rechambering of the same cartridge tens or hundreds of times.
 
Status
Not open for further replies.

Similar threads

G
  • Locked
9mm OAL
Replies
7
Views
2K
LiveLife
LiveLife
R
  • Locked
Lee factory crimp changes OAL
Replies
19
Views
3K
darwin-t
D
L
  • Locked
How much fudge factor allowed in OAL?
Replies
6
Views
480
1SOW
1
Captain Quack
This one isin't the memory...
Replies
19
Views
613
BC17A
BC17A
G
  • Locked
.308 case neck tension and crimping
Replies
11
Views
2K
Bart B.
B
Back
Top