450Bushmaster.net

The work with 185-grain bullets is on hold until some new equipment arrives. I decided to try the other end of the bullet-weight spectrum while waiting.


(Images of this Hornady bullet linked from Midway's and Hornady's web sites).

I have on hand some Hornady 300-gr XTP Mag bullets, which is one of the three bullets for which Hornady to date has furnished data for reloading.

The Hornady data shows a Cartridge Overall Length (COL) of 2.065. This length produces a bullet that is stuffed pretty far down into the case. What is Hornady's reason for specifying this length?

When I checked it, the length that would result in jamming the bullet into the lands of my rifle is about 2.220. Is the short length helpful in reducing case capacity, allowing pressure to build rapidly? Is the short length needed for clearance in the magazine or in the semi-auto mechanism?

I'll start with the specified length, but I'm curious about the underlying reason for having a cartridge shorter than seems necessary.

Thanks for any help.

--Bob
edited to update image url

Th Max oal is 2.260" for AR mag considerations and then I freebored the chamber .200" and Bushy kept that std. As you can only go 2.220" with no freeboring, I'd start somewhere near there, 2.210"?. The Hornady std is so the case mouth is at one of the cannellures, if memory serves. We need all the case capacity we can get and your chamber has some limitations. If you get froggy, you might want to get the chamber lengthened, to be able to pick up some more case capacity. My personal OAL is 2.250" allowing for dirt build up in an AR mag. For you guys that want a std LeMag/Hornady/saami spec chamber, with freeboring, contact Dave Manson Reamers and tell him I sent you..

T-
Thank you for the explanation. At Hornady's specified 2.065, both of the cannelures of the bullets are inside the case, the forward one just barely so.

As far as I know, my chamber conforms to SAAMI specs, since Manson ground the reamer and headspace gauge that produced it.

--Bob

PB,
I've been seating my 300 grain cast at 2.100, and I'm going to try 2.160 next. These are flat points so should correspond to XTPs. I shot a couple of hundred Nosler JHP 250 grainers seated to 2.10 and they pretty much will stay under 1.25 @ 100 yds once they're "dialed in".

Wildcatter, you mentioned freebore of the chamber? Are you referring to the throat? Personally, I'd rather have an extra .1 inch in the chamber, (case length), and I'd give up a tenth in the throat.

BD

BD1 wrote:PB,
I've been seating my 300 grain cast at 2.100, and I'm going to try 2.160 next. These are flat points so should correspond to XTPs. I shot a couple of hundred Nosler JHP 250 grainers seated to 2.10 and they pretty much will stay under 1.25 @ 100 yds once they're "dialed in".

Wildcatter, you mentioned freebore of the chamber? Are you referring to the throat? Personally, I'd rather have an extra .1 inch in the chamber, (case length), and I'd give up a tenth in the throat.

BD

If I understand correctly... Yes, the throat is .200 longer than the saami oal, aka, freebored. I myself liked the longer chamber, but Hornady wanted to use the pointed ftx bullets, so we had to shorten up the case some, .071. You guys seem to like a short oal, why not set the bullets out to pick up some powder? Other than the forward lube grove might be hanging out, if it's a problem and collecting dirt, etc, then leave the lube out of that grove...Just thinking here..

PB, if Dave made your reamer to saami spec, I don't understand why you are driving the bullet into the lands with that short oal, or am I missing something?

It's not so much that we "like" a shorter COAL, it's more that the RNFP designs, (like a JHP), are too short to seat out to a COAL of 2.250. The 293 grainer I'm using is only .762 long, to seat it to 2.250 would only leave 2 tenths of an inch in the case. I'm planning to try seating them out as far as practical, and if that works I'll look look at designing something with a longer nose. The objective with a cast boolit is to have the boolit chamber into the throat, and fit it exactly, so it gets it's start in near perfect alignment to the bore with a good gas seal. A gliding metal jacket gives a bullet a tougher hide, and they resist slugging up better, so they have a better chance of overcoming minor alignment discrepancies and finding the bore without the bullet becoming distorted in the process.

The cast boolits also have a much lower start pressure, so the freebore is not as useful for keeping pressures down as the velocities go up.

BD

The comments so far have been really helpful.

Here's a photo that may help.



On the left is a factory 250-gr FTX load. Next is my load with the 300-grain Hornady .452 XTP/Mag bullet seated to a COL of 2.065 inches, as described in the Hornady data sheet.

Third from the left is the same bullet seated to a length of 2.220, which is maximum in my chamber. On the right I've placed the bullet at the same height to help show how much of the bullet is in the case.

Even with the bullet seated deeply at the 2.065 COL, the case will hold more powder than the maximum load that Hornady has listed for this bullet.

Note of confusion: The 300-grain bullets shown here have been pulled out of a Hornady box labelled ".452 XTP/MAG #45235"; they have two cannelures. I purchased these in Sept 1999 from Graf's; they have a lot number of 98-335.

On Hornady's and Midway's current web sites, the bullet with this name and number is shown with a single cannelure.
On those sites, the 300-grain bullet with two cannelures is #45230, HP/XTP. In Hornady's reloading manual, 5th edition from 2000, bullet #45230 is shown with a single cannelure (page 758).

Did Hornady change from two to one cannelure on #45235, and from one to two cannelures on #45230 sometime in the last 10 years?

--Bob

I've never seen a "mag version" with two cannulers before. The last two boxes I bought from Midway back in April only have the one cannuler.

According to Hornady's website, the XTP/Mag has only one groove. The HP/XTP has two. The mag has a heavier jacket.