12.7 x 48mm (.510 whisper)

sjett

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Minuteman
Nov 28, 2013
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Chattanooga, TN
Need help on my build. Would like to use reamer design that uses 338 Lapua brass, Have talked to Pacific tool about a reamer, and resize reamer. will be using Remington 700 in a ACIS stock, Has any one used 338 Norma mag brass? and recommened barrel twist for Surplus bullets and 750 A Max. Thanks
 
I've got a 1:9 twist on mine. I just called up PTG and asked for a .510Whisper reamer and headspace gages - that simple. That's a good question on .338 Norma brass. My guess is that it'd be fine, though for me personally I just use .338LM cases with 2-5 firings that I've culled for various reasons (outside weight/headspace tolerance). Assuming you're shooting them subsonic, the 12.7x48mm loads are pretty easy on brass and you're dealing with the strongest portion of the case anyway. The only thing to watch out for with using older brass is that inner ring forming at the case web and it's quite obvious to the eye when you cut the brass in the first place. You can get dies from CH4D that include an expander die which is handy. Avoid making the brass with a neck turner if you can - it's serious lesson in frustration. After making about 10 myself, I paid my local smith to make the rest in his lathe.
 
Making the brass in a lathe is not a problem, as i have a Takisawa 14 x 30 that i do all my gun work on and a Bridgeport mill. I wonted to use the brass i had if i could. Ill cut one open tonight and measure case walls to see if possible. I will be making my own die as with any of my special calibers using PTG re size reamer. What brand Barrel did you use, Pacnor has one listed but have never used there barrels, I normally use Hart for my LR guns for the past 15yrs. Is there a good source for once fired brass in the group. Thanks
 
Looked into WSM brass and made a couple but I don't like not having a shoulder to head space on, and with low pressure cartridge action choice isnt as critical - will be using Remington 700 LA in Aics stock for mag feed, if it can handle the 338 Norma mag it can handle the .510


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I got my reamer from PTG and it works well. I've done about 10 barrels so far. I built a few guns using CZ 550 Safari Mag rifles that were 416 rigby. They work very well and the mag works with no mods when you use long bullets like the USGI BMG types. 3 rounds in the mag and one down the tube....
I've never tried using either the 338NM brass or the WSM but I can say that the likelyhood of WSM working is pretty low. The case head diameter is too small. 338LM is .585" where the WSM is .535" so you're missing a lot of room there. I've tried both turning the cases and using the neck turn method and so far the neck turning is the most accurate. You need to run the cases through a die to insure the interior is cylindrical prior to using either the lathe or neck turner. As the brass comes from the factory the inside is tapered and if you just turn the neck you'll find its a bit thin around the "shoulder" area of the neck. By running it through the die and expander you'll get a nice straight cylinder inside. I really like the CZ's because they're big enough to handle the round whether you're shooting super or subsonic. I'm not sure how the remmy will do. It seems small for the 338 LM or the 510. The bolt face seems to get a bit thin on the outer rim in the WSM cals so it must be really thin in the larger size.
In any case the round is pretty neat and works well. If the remington likes it you'll be set. . .

Frank
 
biffj said:
I got my reamer from PTG and it works well. I've done about 10 barrels so far. I built a few guns using CZ 550 Safari Mag rifles that were 416 rigby. They work very well and the mag works with no mods when you use long bullets like the USGI BMG types. 3 rounds in the mag and one down the tube....

This has some gears turning on my part as I just happen to have a brand spanking new CZ 550 in 416 Rigby taking up room in a safe, hmmmmmm. How much work to the action needs to be done and where to find a 1:9 .510" barrel?
 
This has some gears turning on my part as I just happen to have a brand spanking new CZ 550 in 416 Rigby taking up room in a safe, hmmmmmm. How much work to the action needs to be done and where to find a 1:9 .510" barrel?

Absolutely nothing needs to be done to the action. The .338 lapua was based on the 416 Rigby so the action is ready to go. The 510W is based on the .338 Lapua mag cut down and with a neck turned onto the front of the case. If you want to run short bullets supersonic you may need to add a spring to the front of the follower to insure it feeds right. With longer bullets like the BMG types you can fit 3rds in the mag and they'll feed fine as is.
The barrel blanks can be had from a number of makers. I've been buying PacNor blanks with 1-9 twist. They work well. I'd go with stainless because a suppressor can build up a lot of moisture in the bore and cause rust. I recommend to customers that they run an oily patch through the bore when they're done shooting whether the barrel is stainless or chrome/moly. The last 2 guns I built on these actions had 18" barrels. The round is mainly used for subsonics so why go longer? Customers have been very happy with the rifles. They are excellent quality.

Frank
 
Quick piggy back question. I'm looking to build a .510 Whisper as well. Can a regular long action 700 be used as a parent gun or do you need a magnum action? There's a local Rem700 chambered in 25-06 for sale for $400obo that i thought would make a good inexpensive base if it would work.
 
Its possible to use a regular 700 action but only with a number of mods. You have to open up the bolt face to handle the .585 rim diameter and it won't leave much of a ring on the bolt face. You will have to mod the magwell/receiver unless you plan on seating bullets deep. More likely you'll need to ignore the mag and single shot. If you do want to use the mag you also need to mod feedlips and the follower. I wouldn't fool with a regular 700 action to build one, I'd go with one of the custom actions like the defiance that is already set up for .338 LM. It may cost a bit more in parts but it will save a lot of time and effort and you'll get a better rifle in the end.

Frank
 
Its possible to use a regular 700 action but only with a number of mods. You have to open up the bolt face to handle the .585 rim diameter and it won't leave much of a ring on the bolt face. You will have to mod the magwell/receiver unless you plan on seating bullets deep. More likely you'll need to ignore the mag and single shot. If you do want to use the mag you also need to mod feedlips and the follower. I wouldn't fool with a regular 700 action to build one, I'd go with one of the custom actions like the defiance that is already set up for .338 LM. It may cost a bit more in parts but it will save a lot of time and effort and you'll get a better rifle in the end.

Frank

I have a machine shop (do mostly my own custom work and tight tolerance aluminum aerospace jobs) with an assortment of lathes and mills. Are the mods something a machinist (with not too much gunsmithing experience can handle? fairly straight forward? I'm not terribly interested in a very high level build (more of a budget build to see how i like the round and to play around with).
 
I have a machine shop (do mostly my own custom work and tight tolerance aluminum aerospace jobs) with an assortment of lathes and mills. Are the mods something a machinist (with not too much gunsmithing experience can handle? fairly straight forward? I'm not terribly interested in a very high level build (more of a budget build to see how i like the round and to play around with).

I did my first build on a Mauser 98 action and while it shoots well we still haven't gotten it to feed properly. I've got years of experience working on all sorts of guns. My suggestion to you is to start with something simple like a .338BR or a .300 blackout that won't require mods to the action. If you are trying to save money don't do it with stuff that can hurt you til you have some idea what you're doing. The machinery isn't the issue. Its knowledge about what needs done. With a lot of these situations there isn't a build program someone can give you. You have to work it out as you go and adapt things as you see they need to be done. The 510 isn't really a powerhouse round like the BMG by any means but it can be loaded up to the original capacity of the brass which is 60-62K psi. With the size of the case this can give you some pretty high bolt thrust and carving on the receiver isn't a good idea especially if you don't know what you're really doing. Most of us build these oddballs with the intent of loading subsonics at low pressure but we often drift into the what-if world of supersonics to see what they can do. Unless you destroy the rifle when you're done you'll never know what the next guy will try. In todays society where its always easier to hire a lawyer and blame someone else I'd be leery of taking shortcuts and using less than ideal parts. If you look at all the guys building rifles of this type you'll find few standard 700's in the mix. There is a reason for that. Guys have built some pretty hopped up magnums based on receivers that weren't really set up for them but it doesn't make it a good idea.....especially when there are good alternatives.

Having said all that you're obviously free to do as you wish. If saving a few bucks is more important than quality and safety have at it. Another thing to consider is the value of what you build after its done. My mauser based 510 wasn't worth much when done but the CZ550 Safari mag based guns sold for a premium. Use good quality parts that you don't have to carve on and you'll still have value when you're done. You can get your money back on the parts at least.....

Hope that helps

Frank
 
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