Gunsmithing Question about reamers for .308

[jackinfl]

My question is this? What is the difference? Are they all for different bullet designs? What are the common ones on Tactical rifles or Sniper rifles where functioning 100% of the time is key. I know that my .308, that Moon at GAP built for me, has a 1995 Palma Match chamber. I told him I shoot 168 AMAX,175 SMK, or the 178 AMAX.

I'm just curious if the gunsmith chooses the chamber based on what the customer tells him he will be shooting, or is it based on an accuracy guarantee.

Also, I've seen references to chambered with this company's proprietary reamer. Can gunsmiths specify a reamer they want tweaked for certain dimensions?

Also, is this a trade secret kind of thing so others can't duplicate your builds?


This is a cut and paste from PT&G's site. For example of how many reamers there are.
308 1 ½ Inch
308 Bisley
308 Marlin
308 Match M-852
308 Norma Magnum (CIP)
308 Norma Magnum (Norma)
308 Palma Match (Throat Diameter .3085)
308 Winchester
308 Winchester Ackley Imp 40°
308 Winchester Davis Improved
308 Winchester Match


Thanks,
Jack

 

[wnroscoe]

Re: Question about reamers for .308

When I order chamber reamers I leave the case body and shoulder area at minimum SAAMI specs. I do how ever change the neck and free bore dimensions to my specs. On all of my reamers except one, a tight neck 6BR reamer, I strive for no more than .005" total clearance around the neck, that’s .0025" per side. Different brass manufacturers like Lapua, Win, Rem etc. will have different neck OD's so that has to be considered as well.

Free bore is another animal all together and is driven by bullet type and magazine type. For the 308 Win I find myself using the Bisley Reamer more and more.

It just flat out works great in an AI magazine with 168/175's and the accuracy results of the built rifles have been nothing short of impressive. I also have the 95 Palma but feel it's too short for the AI mag feed rifles but works great in a BDL or ADL type rifle. Free bore being the only real difference between the two reamers. My Bisley and 95 Palma reamers are un-modified as they came from PTG, my other reamers, especially my 260 reamers, are all modified to my standard. I even have a 260 reamer labeled "260 Roscoe" by the manufacturer.

Look at my WWW on the reamers page and you'll see several measurements listed like neck diameter and free bore. Chambers and reamers are another world all together. Everyone has their opinion, desires and taste.

 

[jackinfl]

Re: Question about reamers for .308

William,
Thanks so much. So,with the bisley you can load the bullet a little longer to take advantage on the mag length?
Jack

 

[wnroscoe]

Re: Question about reamers for .308

Yes

 

[Glen Seekins]

Re: Question about reamers for .308

I use the 308 Bisley reamer and it had worked perfectly. I dont know that i would have any reason to change.

 

[ranger1183]

Re: Question about reamers for .308

How difficult is it for a gunsmith to cut more freebore in a chamber?

I'm having to seat 175's SMK's, 178's A-Max's and 220 SMK's significantly short of the magazine length just to get them to allow the bolt to close.

I'd really like to use the max length that the modified AI mags will allow (2.955").

 

[biffj]

Re: Question about reamers for .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ranger1183</div><div class="ubbcode-body">How difficult is it for a gunsmith to cut more freebore in a chamber?

I'm having to seat 175's SMK's, 178's A-Max's and 220 SMK's significantly short of the magazine length just to get them to allow the bolt to close.

I'd really like to use the max length that the modified AI mags will allow (2.955").
</div></div>

It is quite simple to get a throating reamer to do exactly what you are looking for. As to whether that will work well is another question. The throater should be piloted and that will keep the front end concentric with the bore as long as your pilot fits properly. Using a removable pilot reamer will allow you to tailor that part. Now we come to the back end of the throating reamer which is not supported in the chamber. Unless all in the lathe, chuck and barrel are perfectly aligned you may have some runout in the the throating reamer which will open the freebore/throat up in a nonconcentric fashion. Thats not good. When the throater is part of the chamber reamer its always concentric with at least the chamber so this isn't a problem.....
You might have a chat with some of the reamer makers and get some experienced input from them. Dave Manson has been very helpful in explaining oddities like this and I'm sure others are as well....

Frank

 

[TT]

Re: Question about reamers for .308

PTG built my customer reamer which is very close the 95 Palma. I also ordered their uni-throater so I could lengthen the free bore as required.

After deciding to shoot heavier bullets than the 155 SMK I successfully used the uni-throater to add 0.020 more free bore with no degradation in accuracy. The rifle shoots in the low 4s before and after using the uni-throater...

 

[jackinfl]

Re: Question about reamers for .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: heatseekins</div><div class="ubbcode-body">I use the 308 Bisley reamer and it had worked perfectly. I dont know that i would have any reason to change. </div></div>

Heatseekins,
Can you share what round you are shooting and how long are you loading them.
Jack

 

[LRI]

Re: Question about reamers for .308

If you want a 308 with a long throat consider the 308 Gamboa. I have the reamer and it shoots well. Bob (Gamboa) is/was a dedicated Palma shooter who made the US team a few times. He's also a speed freak and is/was determined to break warp one with a 155 Sierra.

The chamber is essentially a 308 with a chromosome thrown in from Weatherby. It's got a longer throat to provide for increased powder charges while avoiding things like flat primers and black rings of death around primer pockets.

It works well. I've chambered a few Palma guns in it and they all seem to hold good elevation at 1k.

The Bisley reamer goes like this:

Take a min spec 308 and then make it "just big enough" so that if/when you shoot there (meaning Bisley, England) your gun passes the chamber gauge test. If it doesn't, they'll give you two options. sit it out or allow them to cram a reamer into your chamber to open the neck and/or throat area by hand. It's meant for the Radway Green machine gun ammo that they (and a few other countries) issue during world championships for the team events. (host countries provide the ammunition for the team events at all International Palma championships)

That's what the Bisley is all about.

 

[colchester]

Re: Question about reamers for .308

Has anybody tried a 308 reamer cut to the Obermyer print? I always wondered about this one.

 

[freddyp]

Re: Question about reamers for .308

Hi William,
So how far does the Sierra 175MK need to be seated out to touch the rifling in the Palma 95 and in the Bisley.

 

[Barney88PDC]

Re: Question about reamers for .308

My gun was built by William with the Bisley Reamer and a 175 SMK is kissing the lands at 2.091 base to ogive. Which IIRC is in the 2.810 OAL neighborhood but obviously varies some bullet to bullet.

 

[SDWhirlwind]

Re: Question about reamers for .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 73 fastback</div><div class="ubbcode-body">Has anybody tried a 308 reamer cut to the Obermyer print? I always wondered about this one. </div></div>

I am currently shooting a 308 cut with the Obermeyer spec. I load a 168SMK to 2.8" and it jumps about .040 IIRC. Shoots great with a 22 3/4" Rock 5R and easily runs 2720fps.

 

[freddyp]

Re: Question about reamers for .308

Well I presented my question to Dave Kiff at PTG. He told me to go with the 308 Palma Bisley (Bisley 150 Rule). He reset the throat to min spec (80 thou) and said the 175MK should be about 15 thou off the lands when seated at 2.800. The last gun that I had chambered this way, shot in the .3" all day long.