Plunk and spin gives very short OAL

[Wesquire]

Using the plunk and spin test I'm looking at 1.075 with BBI 147 FPs. Is this something I should be worried about?  Significantly shorter than the old lube groove version

Edited August 5, 2017 by Wesquire

[Sarge]

13 minutes ago, Wesquire said:

Using the plunk and spin test I'm looking at 1.075 with BBI 147 FPs. Is this something I should be worried about?

Not if it's the max your gun will take. Many guys get their barrels throated in CZ, tanfo, etc due to short chambers but if those feed 100% and shoot well out of your gun just go for it. Might drop the charge though then work your way back up with a chrono.

[kujo929]

Can't help you as I shoot 40 minor. But guessing that is why so many get their 9mm barrels reamed.


Sent from my iPhone using Tapatalk

[Wesquire]

If short works, why ream long? Making pf with less powder is a good thing. And I don't think pressure will be an issue on minor loads.

[Sarge]

2 hours ago, Wesquire said:

If short works, why ream long? Making pf with less powder is a good thing. And I don't think pressure will be an issue on minor loads.

Key is,"if short works". Often times ammo that is too short will not feed 100%. 

 Pressure can rear it's ugly head with any load. Even a mouse fart load if shortened too much

[Wesquire]

11 minutes ago, Sarge said:

Key is,"if short works". Often times ammo that is too short will not feed 100%. 

 Pressure can rear it's ugly head with any load. Even a mouse fart load if shortened too much

 

Hmm. I've always experienced short rounds feeding better.

[johnbu]

Pre-ream i ran 1.060" oal. Many thousands and they all ran flawlessly.

 

So....why ream?

 

Pressure spikes.  Even minor 147 at that oal is at the top of the pressure limit.  add a couple tenths more powder,  get bullet set back  from chamberin or any of a dozen things and pressure spikes. 

 

 

[haiedras]

Unless you've got a ton of BBI 147s, I'd also look at a different bullet profile if you don't want to ream your barrel, the ogive on the BBIs is pretty fat compared to the Acme 147 FPs 

[MemphisMechanic]

12 hours ago, Wesquire said:

If short works, why ream long? Making pf with less powder is a good thing. And I don't think pressure will be an issue on minor loads.

 

Obviously as stated, reduced case volume means higher pressures and less room for error with some of the really fast powders we like.

 

Additionally, the walls on 9mm brass begin to get thicker about .300" down into the case. Oftentimes,  loading long 147gr projectiles really short  requires so much bullet to be pushed down into the case... that it can cause a lot more failures to case gauge than you were seeing before.

 

I use a lot of BBIs since Chandler, the CEO, delivers to our local match - they're close by. Their 147 profile requires a short OAL like this in M&Ps, XDs, CZ, and Tanfos. It's a very chubby bullet profile.

 

If you have any interest in lighter bullets, their 124 TC is at the other end of the spectrum. I had my Tanfo reamed so I can't use that, but an M&P barrel that needed 1.080"-1.080" on the 147 RN will spin the 124 TC at 1.150".

 

I shot 2,500 147s through my Stock 3 and then switched to 124s. I actually prefer the way the lighter bullets shoot and feel, plus I wouldn't have had to get my Tanfo reamed to feed them. The increase in slide speed is actually a good thing in this platform, IMO.

 

Edited August 6, 2017 by MemphisMechanic

[Wesquire]

12 hours ago, haiedras said:

Unless you've got a ton of BBI 147s, I'd also look at a different bullet profile if you don't want to ream your barrel, the ogive on the BBIs is pretty fat compared to the Acme 147 FPs 

 

I've got many thousand

[haiedras]

1.075 isn't super super low for tanfos, but if you can do it, I'd just get the barrel reamed.