First custom rifle is here and i think its a keeper!!!!!

[MudRunner2005]

I was reading some really fine metric print! Could have been my eyes, or my metric to std. conversion At any rate, I haven't done the math but I think you would still end up with an acceptable shoulder?.....Rich

So Rich, how does my 7mm Malum look? Doable?

 

[MontanaRifleman]

This easy.....

Another one of my new designs that's destined to be a masterpiece... I call it, the 7mm Malum.

Nice looking cartridge. Some tips...

The taper is only .004 per inch which is probably lead to extraction issues. Ackley's tapers were in the .008-.009 per inch range.

It looks like you've blown out the web about .002 thou from spec. A lot of guys when they design a cartridge/reamer, will actually push the web in instead of out. This helps keep the primer pockets tight and longer brass life. Also, new brass from the factory will usually be 2-3 thou less than spec so designing your dies and reamer to this dimension is a good idea IMO.

My suggestion would be to go to a .520 web diameter and a .502 shoulder diameter.

I would also recommend sending your drawing to Dave Kiff at PTG and give him a call and talk through your idea with him before you lay out any $$$$. That will go a long way in getting this right the first time.

 

[elkaholic]

So Rich, how does my 7mm Malum look? Doable?

What is the parent dimension at the body/shoulder jct. in thousandths? If your measurements are correct; yes its doable. Your overall case length will likely shrink up to .020" when fireforming though. Did you take that into account?.......rich

 

[MudRunner2005]

What is the parent dimension at the body/shoulder jct. in thousandths? If your measurements are correct; yes its doable. Your overall case length will likely shrink up to .020" when fireforming though. Did you take that into account?.......rich

The case OAL is the same as factory 8x68s, but I shrunk the neck up to .300" from the shoulder side, so I could create the false shoulder for blowing the walls out during fire-forming.

 

[MudRunner2005]

Nice looking cartridge. Some tips...

The taper is only .004 per inch which is probably lead to extraction issues. Ackley's tapers were in the .008-.009 per inch range.

It looks like you've blown out the web about .002 thou from spec. A lot of guys when they design a cartridge/reamer, will actually push the web in instead of out. This helps keep the primer pockets tight and longer brass life. Also, new brass from the factory will usually be 2-3 thou less than spec so designing your dies and reamer to this dimension is a good idea IMO.

My suggestion would be to go to a .520 web diameter and a .502 shoulder diameter.

I would also recommend sending your drawing to Dave Kiff at PTG and give him a call and talk through your idea with him before you lay out any $$$$. That will go a long way in getting this right the first time.

My taper should be 0.010"... I will adjust the web down to .520", and adjust the taper accordingly. Thanks for that tip!

I will call Dave soon. I am really digging this design, and it's beltless and the brass is somewhat inexpensive...Especially compared to STW brass, which is rediculously expensive.

 

[elkaholic]

The case OAL is the same as factory 8x68s, but I shrunk the neck up to .300" from the shoulder side, so I could create the false shoulder for blowing the walls out during fire-forming.

No, what is the body/shoulder diameter of the parent?

 

[elkaholic]

My taper should be 0.010"... I will adjust the web down to .520", and adjust the taper accordingly. Thanks for that tip!

I will call Dave soon. I am really digging this design, and it's beltless and the brass is somewhat inexpensive...Especially compared to STW brass, which is rediculously expensive.

A taper of .011" from the web to the shoulder is fine for that case. That is about what I run and have no extraction problems. It helps keep the case from stretching as much as does the 40 degree shoulder. P.O. was a little conservative......rich

 

[MontanaRifleman]

No, what is the body/shoulder diameter of the parent?

Web, .522
Shoulder, .473

 

[MudRunner2005]

A taper of .011" from the web to the shoulder is fine for that case. That is about what I run and have no extraction problems. It helps keep the case from stretching as much as does the 40 degree shoulder. P.O. was a little conservative......rich

So, as long as I keep the body taper around .010" I should be fine with extraction. Good, that's what I've been going with on all the ones I've designed so far.

 

[bigngreen]

I would give the case head a few thou, a case will head will expand very easily the first firing then settles down if you don't allow it a touch of room you'll have issues getting it sized down. I know guys who will just pull a reamer at the end of chambering with a tight reamer to give the case head just a little breathing space at the back to avoid some issues. All the reamers I own, are set up like this from Kiff, the first time I saw how much room was at the base on a custom reamer compared to the new case I was surprised but after firing then sizing down it become clear. Kiff will know what it needs if you get it roughed out and make sure you can make the brass.

 

[elkaholic]

Web, .522
Shoulder, .473

Wow! that is plenty of room to improve. Like I previously stated though, he will get quite a bit of length shrinkage.........rich

 

[MontanaRifleman]

I would give the case head a few thou, a case will head will expand very easily the first firing then settles down if you don't allow it a touch of room you'll have issues getting it sized down. I know guys who will just pull a reamer at the end of chambering with a tight reamer to give the case head just a little breathing space at the back to avoid some issues. All the reamers I own, are set up like this from Kiff, the first time I saw how much room was at the base on a custom reamer compared to the new case I was surprised but after firing then sizing down it become clear. Kiff will know what it needs if you get it roughed out and make sure you can make the brass.

It was Kiff that suggested to me to me to push the web in for reasons mentioned. I got this advise while planning for the 270 Montana

 

[MontanaRifleman]

Wow! that is plenty of room to improve. Like I previously stated though, he will get quite a bit of length shrinkage.........rich

Yup, I'm thinking a good bit of shrinkage

 

[bigngreen]

It was Kiff that suggested to me to me to push the web in for reasons mentioned. I got this advise while planning for the 270 Montana

He's never advised me to go that route, but then our goal may have been different as well. My first custom reamer I was hell bent to get a tight one, but was talked out of it by a couple BR smiths before even talking to Dave and that advice has stuck with me So far served me well but the next one I may have wished to go tight!