Sinclair Meplat trimmer chambers

[robinzon]

Hello all,

I recently got my hands on Sinclair Meplat trimmer (yes I know most don't like it but I have been looking into uniforming meplats on SMKs for some time and got this cheap). I got .22, 6.5mm and 6mm chambers to go with it but no .30 caliber chamber.

For those of you who may have the .30 caliber body (it says 30 on it) can you tell me the exact diameter of the hole for the bullet, I am not sure where at the ogive they are measuring.

Thanks much

 

[mikecr]

It's not a 'chamber' but merely some random datum. Could be 5thou under cal for instance.
Doesn't matter, because the resultant datum would be different for one shape of nose to another.

You just want to clean up the bulk of your bullet lot to the same meplat diameter. So where the tool takes datum doesn't matter, you set the trim to where you want it.
I'm compelled to recommend qualifying ogives from which your trim length to datum is based. You do this with a Bob Green Comparator (BGC).

 

[robinzon]

It's not a 'chamber' but merely some random datum. Could be 5thou under cal for instance.
Doesn't matter, because the resultant datum would be different for one shape of nose to another.

You just want to clean up the bulk of your bullet lot to the same meplat diameter. So where the tool takes datum doesn't matter, you set the trim to where you want it.
I'm compelled to recommend qualifying ogives from which your trim length to datum is based. You do this with a Bob Green Comparator (BGC).

Point well taken, I understand the concept and indeed I can use a specific bullet to set it to. However, I wanted to see what Sinclair originally opened it up to I am sure they have tried several lots to find a diameter that works. I could take an SMK and subtract 5-7 thousands.... I wonder if I need to get a finishing reamer or my smith has something with that precision.

 

[Pvt.Donut]

Having a stepped chamber would probably hold the bullet better than the original Sinclair design. Have it partiall opened to just over bullet diameter then the rest of it be several thou undersized should keep the bullet more concentric in the chamber.

 

[robinzon]

Having a stepped chamber would probably hold the bullet better than the original Sinclair design. Have it partiall opened to just over bullet diameter then the rest of it be several thou undersized should keep the bullet more concentric in the chamber.

Sounds reasonable, though it maybe more sensical to sell this and get a hoover trimmer.... there is also an interesting trimmer a South African company sells

https://sudamix-ring.co.za/product-category/meplat-trimmer-collet/

Sudami X-ring they also make a good press.

 

[PDS]

The 30cal hole on my Sinclair trimmer measures .296. It is a straight bored hole so only the edge of the hole touches the bullet. Also the tool is made of plastic so if you vary the pressure on the base of the bullet the depth the bullet goes into the hole will vary.

 

[robinzon]

The 30cal hole on my Sinclair trimmer measures .296. It is a straight bored hole so only the edge of the hole touches the bullet. Also the tool is made of plastic so if you vary the pressure on the base of the bullet the depth the bullet goes into the hole will vary.

Thanks so much that is what I was looking for.