PT&G uni throat bushing diameter

[Cal F]

I have a Remington 700 that I had rebarreled in 6.5 Grendel. It’s been a fun project, however, I have been wanting to lengthen the throat of the chamber to seat out my bullets farther. Due to it being an AR cartridge primarily, the chambers are cut with the AR mag length restrictions in mind I assume….

in my 700 I can have a much larger COAL and would like to take advantage of that but can’t due to starting to hit the jam point with about .5” of bullet still down in the case, soaking up my already tiny case capacity…

long story short, I came across the uni throater tool from PT&G and would like to give it a try on this rifle but am concerned that the bushing will have a larger diameter than the narrow Grendel chamber.
Does anyone have experience with these tools? Can anyone tell me what the diameter of the bushing is for a 6.5mm reamer?
Thanks for any help!

p.s. can anyone explain the possible tapered neck of the 6.5 Grendel chamber that Ive heard rumors in the dark of?

 

[Fast14riot]

Do you know what reamer was used on your barrel, or are you able to obtain a print for the reamer?

 

[Cal F]

Do you know what reamer was used on your barrel, or are you able to obtain a print for the reamer?

No I don’t have any of the reamer specs. The work was done by North West Action Works about 5 years ago. I wonder if they’d even still have the same reamer?

 

[Fast14riot]

The uni-throater is designed around a 30° shoulder, if less it contacts higher on the bushing, if more (40° Ackley chambers) it touches lower. You should be able to zero it on your current chamber by turning it backwards.

 

[DaveTooley]

SAAMI says it has a one diameter neck. Tapered necks aren't bad. Most cartridges have them.

 

[can1010]

mine are .429 bushing dia. you will just make it

 

[Cal F]

mine are .429 bushing dia. you will just make it

Thanks! I’ve tried to get the diameter from PT&G but haven’t heard back from them. I’m pretty excited to get that throat lengthened and re-work my loads.

 

[ronemus]

For added insurance, I used my cleaning rod guide to center the Uni-Throater. I used it to push the supplied bushing because I was working with an assembled rifle and couldn't push it directly. As stated above, it was easy to zero the adjustment by turning it backwards. It did a stellar job - very smooth, even cuts.

 

[Cal F]

For added insurance, I used my cleaning rod guide to center the Uni-Throater. I used it to push the supplied bushing because I was working with an assembled rifle and couldn't push it directly. As stated above, it was easy to zero the adjustment by turning it backwards. It did a stellar job - very smooth, even cuts.

I like that idea, I’ll try it when I get the tool. Just curious but what kind of change in load did you see after lengthening the throat? With my rifle I’m going to be adding quite a bit of OAL, So I’m expecting there to be some changes for sure.

 

[ronemus]

I hadn't done any load development prior to throating the barrel; I went to 0.400" freebore to work with 285-300 gr jacketed lead and 254-285 gr monolithic copper bullets in a .338 Lapua. I was surprised to find that the same throat was correct for all. The stock freebore was 0.200" so the longer throat allowed considerably larger powder charges. The 285-300 gr jacketed bullets work surprisingly well at magazine length with a 0.3" jump (~6gr less powder); velocities were ~200 fps slower.

 

[jbmarshtx]

I like that idea, I’ll try it when I get the tool. Just curious but what kind of change in load did you see after lengthening the throat? With my rifle I’m going to be adding quite a bit of OAL, So I’m expecting there to be some changes for sure.

What bullet and OAL are you trying? I shoot a 6.5 grendel for HP silhouette, and I've considered asking my smith to do the same thing for 130 grainers. I can load longer than the 2.60 AR magazine spec, but would like to squeeze a bit more without compressing powder.

 

[Cal F]

I would like to get an OAL of 2.45”, that’s with Hornady 130ELD-m. My rifle has always shot better with 130s especially the sierra 130 gamechanger but I haven’t been able to find those for over a year…so I gave in and started a new load work up with these ELD-Ms, that seem to be available from a few different stores currently. I have been getting good results but end up having to seat the Hornadys much deeper than the sierras cause of the different profiles. Lengthening the throat will benefit both bullets in the end I’m assuming.
my rifle has a 27” barrel and I’ve been getting really good velocity with the 130s

 

[jbmarshtx]

Thanks. I have a box of those to try. I was using the berger 130 ar, but they haven't been available either.